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Staph Infections - B Cell Apoptosis 6/26/03 by Chaya Venkat Here is a little puzzle to get your little grey cells working. And there is a nice little "reward" at the end, if you read through this article. When a healthy person gets a bacterial infection for the first time, the body takes a little time to respond since the bacteria is a new antigen and the B-cells do not have any memory of it. But after that first time, the immune system retains a memory of that particular bacteria, its specific antigens, in terms of **memory B-cells**. The next time around, when the same bacteria strikes again, the body is able to mobilize its resources quickly. Antigen presenting cells ("APCs") such as dendritic cells carry bits and pieces of the bacteria to the lymph nodes, where they present the antigens to the B-cells. This means the memory B-cells are alerted immediately, and they go into overdrive. The required antibodies to attack that particular bacterial antigen are produced quickly, in large quantities, from plasma cells. Each of these antibodies is a perfect fit for the specific antigens displayed by the bacteria on its surface, and they lock on. Complement system is activated and the bacteria is quickly "opsonized", i.e., covered wit thousands of fragments of complement proteins. Some of the complement fragments kill directly by punching holes in the skin of the bacteria, others enlist the help of effector cells such as neutrophils, T-cells and macrophages. The net result of all this action is that the invading bacteria is killed off quickly, before it has a chance to establish a foothold in the body, before it has a chance to grow large armies of itself. This is the natural process we emulate in monoclonal therapy, what happens for example, when Rituxan (antibody) locks on to CD20 marker (antigen) on the surface of CLL cells. We have discussed in detail how complement, CDC, and ADCC mechanisms work, once the critical antigen-antibody pair is made. As you can see, the whole point of having memory B-cells is so that lessons learned the hard way the first time can help the body respond more quickly and efficiently the second time around. This is the basis of all immunizations and vaccinations. In some cases, the bacteria change their stripes subtly from one generation to the next. Immunizations given for one variety is not sufficient to generate fully effective memory cells for the newer version, and repeat immunizations may be necessary for the new version. This is why people need new flu-shots every year. OK. now for the puzzle. If the body is supposed to have this wonderful capacity to remember antigens it has seen before, how come people never have any immunity against staph infections? Staph infections are no joke, they cause major complications, including death, in many hospital patients. They are especially dangerous for immune compromised patients such as HIV patients, transplant patients, or cancer patients undergoing chemotherapy. Here is the answer. Just as our immune systems have developed over the millennia, finding better and quicker ways of dealing with attacking bacteria, viruses and the like, the little blighters have had just as long to figure out ways around our defenses. It is a cosmic chess game, played at the cellular level. Move, counter-move, each side trying to find holes in the defenses of the other side. As we mentioned above, some pathogens learn to survive by mutating, so that they are never quite the same from one batch to the next. This makes them hard to pin down, hard for our bodies to develop solid memory defenses against them. Staph infections go one better. Since our bodies develop "memory" by using B-cells, staph infections start by attacking the very B-cells. They generate a protein, called SpA, that is a deadly toxin to B-cells. This pre-emptive first strike capability of staph bacteria means that our bodies never get a good chance to develop any memory of this particular invader, our B-cells are killed off before they get a good look at what is killing them. This means we have just as hard a time dealing with staph infections for the umpteenth time, as we did the first time. Clever little blighters, right? Only reason why it does not kill us outright is that we have more than one cell line in our immune system, we have T-cells, neutrophils, macrophages etc which are pretty good at killing bacteria, as well as tools like broad-spectrum antibiotics. All staph bacteria succeed in doing is to make the game a little harder to win, since our bodies do not have the advantage of remembering the last attack, and being prepared for the next time around. How about situations where we may actually want all B-cells to die, as in the case of B-CLL patients? This may be one explanation for the rare cases of spontaneous remissions one hears about now and then. Invariably, the story goes like this: the lucky individual had a confirmed diagnosis of CLL, nothing out of the ordinary. Then he got some sort of a garden variety infection, which resolved itself in a week or so. Soon after, lo and behold, it was found he no longer had any traces of CLL, a case of spontaneous remission!! Could it be that the patient had a staph infection or something similar to it, which went after his B-cell population, killing them off with 100% efficiency, and in the process killing off all of his CLL cells as well? Remember, that is exactly what we are trying to do with Rituxan monotherapy, killing off all of the B-cells, except we have not yet learned how to do it with 100% efficiency. CLL patients get a nice remission with Rituxan, but generally speaking the disease returns in 6 months or so, when CLL cells left over after the therapy grow back their clonal population. Now if we can find a way of killing off each and every last one of the mature B-cells, which includes good B-cells but also all the CLL cells, we would have a cure for CLL. Eventually, the stem cells in the bone marrow will grow a nice new set of B-cells, good non-cancerous B-cells. All of the feverish activity in monoclonal antibody research for CLL is geared to this one point, how to improve the efficiency of B-cell kill, without killing any of the other cell line. Right now, the only way we seem to be able to kill off close to 100% of the CLL cells is by using combinations of chemotherapy drugs, such as the latest RFC combo therapy. Even here, I say "close to 100%" of the CLL cells are killed because even in "PCR negative" patients there is no guarantee that every single last CLL cell has been killed. "PCR negative" just says that the CLL cells, if any exist, are at concentrations lower than our ability to detect them. It is not yet certain that PCR negative remissions never relapse. It would be nice to be able to get PCR negative status, or even deeper remissions approaching a cure, with relatively non-toxic methods such as Rituxan, without needing to add more toxic Fludarabine and Cyclophosphamide components to the therapy. Perhaps some day we will be able to duplicate what the lowly staph bacteria does so well, kill B-cells with equally ruthless efficiency. Of course, we would like to do this with some control over the situation, without running into the pesky little problem of getting an actual staph infection. You would be happy to know that this is not a crazy idea thought up by yours truly, below is a press release that says they are actually going into clinical trials to try and do the same trick as staph bacteria, in this case in an effort to treat Lupus. (For those of you who may not know what this awful disease is, it is a type of autoimmune disease, where the culprits are B-cells). There seem to be more than one way of skinning the CLL cat. I am truly optimistic that the explosive growth in our understanding of immunology will make CLL a "manageable" if not "curable" disease in our life times. Press Release: Date: 28-Apr-2003 University of California - San Diego; Contact: Sue Pondrom 619-543-6163 Staph infection process leading to B cell suicide described by UCSD researchers The method that Staphylococcus aureus (staph) infection uses to inactivate the body's immune response and cause previously healthy B cells to commit suicide, is described for the first time by researchers at the University of California, San Diego (UCSD) School of Medicine in the May 5, 2024 issue of the Journal of Experimental Medicine. Normally, B cells mount an early defense against invading bacteria. From this immunologic experience, memory B cells are developed with the ability to quickly recognize these antigens and destroy the bacteria if they return in the future. When staph infections occur, however, this important process for immune defense can be corrupted. In studies with mice, the researchers found that a staph protein, called SpA, acts like a B cell toxin because it mounts a pre-emptive attack to target a specific region on the antigen receptors of B cells, which ultimately causes their death. Although the B cells begin to respond, they are quickly shut down, as the SpA de-activates these B cell antigen receptors, and there is also loss of other surface molecules such as CD19 and CD21, which are important for amplifying immune responses. Then, within a few hours, the SpA toxin induces B cells to turn on themselves in a programmed suicide process called apoptosis. As a direct consequence, the B cells never get a chance to develop the memory cells necessary to recognize and fight future staph infections. "This mechanism may explain why staph infections are so common and why many people get them recurrently," said Gregg Silverman, M.D., UCSD professor of medicine and senior author of the paper. He noted that apoptosis usually takes place on a regular basis in a small proportion of cells to control the size of lymphocyte populations and maintain homeostasis, to keep a balance in the internal equilibrium of body. However, SpA co-opts the normal apoptosis process, in effect killing the B cells too early, before they've had a chance to do their job. "Inappropriate mechanisms of induced apoptosis are not unique to many infections," Silverman said. "However, we should be able to use the same process induced by SpA, to treat the disease-causing B cells in autoimmune diseases and cancers like leukemia and lymphoma. These studies may also help us to make protective vaccines against staph."
In follow
up studies, the Silverman team will examine people with staph infections to
verify that the same process takes place and that it prevents individuals from
defending against staph infections. In addition, the investigators are planning
a clinical trial in one to two years to treat patients that have autoimmune
diseases such as lupus, that occur due to faulty B cells. Topic: Apoptosis
TRAIL - What is it and how does it work? 6/01/03 by Chaya Venkat One of our members expressed interest in TRAIL, here is what I have gathered thus far. Generally speaking, I think there are far too many acronyms, medical jargon to confuse the lay people like us. But here is one acronym that makes sense: **TRAIL** stands for "tumor necrosis factor-related apoptosis-inducing ligand". See what I mean? A little bit of background, before we discuss TRAIL and what it might mean to us down the road. In the natural order of things, as cells get old and decrepit, or have just plain outlived their usefulness, they are programmed to commit suicide when commanded to do so by the body sending them appropriate signals. This orderly process of cellular death is called "apoptosis". All hell breaks loose if the cells stop obeying the call to kill themselves, because that means useless and unwanted cells gradually accumulate in large numbers, eventually grinding the efficient running of the body to a halt. This is one aspect of cancer, the most important aspect of it from the perspective of CLL. "Tumor Necrosis Factor" or TNF is one of the death signals the body uses, and other members of the family includes Fas-ligand (FasL) and TRAIL. When a cell is targeted for death, members of the TNF family attach themselves to the appropriate docking stations ("receptors") on that cell, and the job gets done. We are now able to make many of these biologically active compounds in the lab. TNF-alpha was the first molecule to be tested for its anti-tumor activity, followed by Fas-ligand. These two molecules are efficient in killing a variety of tumor cells. However, they cause significant damage to normal tissues that result in life-threatening toxicities. A case of patient getting cured of cancer, but unfortunately dying in the process. Therefore, the search continued until the recently discovered new member of the TNF family, TRAIL. TRAIL has been shown to be selectively toxic, causing suicide of tumor cells and with minimal no toxicity against normal tissues, as demonstrated in cell studies, and animal studies using mice and monkeys. TRAIL is expressed in many human tissues, (although not in the liver and brain), which suggests that TRAIL does not have a toxic effect on normal cells. In fact, many normal primary cells such as epithelial cells, fibro-blasts, and skeletal muscle cells are resistant to TRAIL-induced apoptosis. TRAIL has two docking stations on cells, called death-receptors (DR4 and DR5). In addition, there are two 'decoy' receptors for TRAIL, called DcR1 and DcR2, which are there to fake out the TRAIL molecule, prevent it from killing normal cells. If TRAIL is to be a successful drug for selectively killing cancer cells, the hope is that these malignant cells have lots and lots of the correct death-receptors, DR4 and DR5, and not the decoy receptors DcR1 and DcR2. Recently, there is controversy that while most normal cells are not killed by TRAIL, liver cells could be an exception. This was not observed when TRAIL was tested with mice and monkeys, but here is a case where humans may be different from mice and monkeys. The first PubMed citation below draws a pretty blunt conclusion, "substantial liver toxicity might result if TRAIL were used in human cancer therapy". Just to keep us plain folk guessing, the second PubMed citation disagrees completely with the first one: these authors think TRAIL does not kill normal liver cells, only those that are already infected with hepatitis virus. Good thing too, these authors think, in fact TRAIL should be used not only for cancer, but also for treating hepatitis!! Go figure. TRAIL is expected to promotes apoptosis in cancer cells harboring death receptors, even in the presence of "oncogenes" Bcl-2 and Bcl-XL, which would otherwise protect the cancer cells from dying. In addition, in cell studies and mouse studies, TRAIL boosts the killing effects of chemotherapy drugs or radiation; therefore, the dose of chemotherapy drugs or radiation can be reduced, if they are combined with TRAIL in therapy protocols. The bottom line to the good news is that whereas most chemotherapy drugs and radiation are toxic to good cells as well as cancer cells, TRAIL kills cancer cells effectively, but it is non-toxic (barring the controversy about liver damage discussed above). If in one of your generous moments you might have sent money off to the Leukemia & Lymphoma Society, you might like to know part of your money went to support TRAIL research of two Canadian scientists. The press release is below, dated 2024. I tried to see if there were any updates from their research, but I was not able to locate any. Please write if you have additional information on this score. Two years is a long time in today's break-neck speed of biotechnology development. The only PubMed citation that I have found that directly connects TRAIL therapy in CLL is disappointing. It appears that B-cells from CLL are particularly resistant to TRAIL, because CLL cells express on their surface only low levels of the correct death-inducing TRAIL receptors, and high levels of the 'decoy' receptors. Same sort of a reason why Rituxan works better in follicular lymphoma than in CLL, because there are more CD20 markers for the Rituxan to latch on to in follicular lymphoma than there are in CLL. Scientists are now working to see how they can up-regulate the expression of the right death receptors in CLL cells, possibly by co-administering TRAIL along with more familiar chemotherapy drugs such as Cyclophosphamide. Somehow, that makes its appeal a lot less sexy to me. I have looked but found no references, yet, to clinical trials using TRAIL for CLL, or even for our kissing cousin NHL. While this technology is certainly interesting and worth watching, I do not expect there will be 'home runs' any time soon. These days, my definition of "soon" is determined by the median life expectancy of CLL patients. And the caveats I have seen thus far, especially the reference to the particular resistance of CLL cells to this drug, makes me pragmatic about its possible use for us. If I were to guess, my optimistic bet would be that TRAIL would become another very valuable drug in our fight against CLL, one that will have particularly good response in some CLL patients, but not all of us. Its best use is likely to be in combination with other chemotherapy drugs, and as salvage therapy for patients who are refractory to more conventional chemotherapy. In that sense, if the research pans out, TRAIL is likely to take its place alongside of Rituxan and Campath, in 5-10 year time frame. Abstracts: Nat Med 2024 May;6(5):564-7 Apoptosis induced in normal human hepatocytes by tumor necrosis factor-related apoptosis-inducing ligand. Jo M, Kim TH, Seol DW, Esplen JE, Dorko K, Billiar TR, Strom SC. Department of Pathology, School of Medicine, 200 Lothrop St. BST S-450, University of Pittsburgh, Pittsburgh, PA Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been reported to induce apoptosis in various tumor cells but not in nontransformed, normal cells. Preclinical studies in mice and nonhuman primates have shown that administration of TRAIL can induce apoptosis in human tumors, but that no cytotoxicity to normal organs or tissues is found. The susceptibility of tumor cells to TRAIL and an apparent lack of activity in normal cells has lead to a proposal to use TRAIL in cancer therapy. Here, we assessed the sensitivity of hepatocytes from rat, mouse, rhesus monkey and human livers to TRAIL-induced apoptosis. TRAIL induced apoptosis in normal human hepatocytes in culture but not in hepatocytes isolated from the other species. Human hepatocytes showed characteristic features of apoptosis, including cytoplasmic shrinkage, the activation of caspases and DNA fragmentation. Apoptosis and cell death in human hepatocytes was massive and rapid, occurring in more than 60% of the cells exposed to TRAIL within 10 hours. These results indicate that there are species differences in sensitivity to TRAIL, and that substantial liver toxicity might result if TRAIL were used in human cancer therapy.
PMID:
10802713 FASEB J 2003 Jan;17(1):94-6 Involvement of TRAIL and its receptors in viral hepatitis. Mundt B, Kuhnel F, Zender L, Paul Y, Tillmann H, Trautwein C, Manns MP, Kubicka S. Department of Gastroenterology and Hepatology, Medizinische Hochschule Hannover, Germany. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is able to kill a broad spectrum of tumor cells but appears to be nontoxic to most normal cells. Because there are conflicting data about the hepatotoxicity of TRAIL, we investigated the physiological function of TRAIL and its receptors in the liver. Hepatocytes are sensitive for FasL- and TRAIL-mediated apoptosis in vitro, but TRAIL induces no apoptosis in healthy livers in vivo. Using mouse models of adenoviral hepatitis and livers of patients with hepatitis infection, we could demonstrate that apoptosis in virally infected hepatocytes is mediated by TRAIL receptor DR5 and TRAIL. In contrast to FasL, TRAIL-mediated apoptosis of hepatocytes in vivo is triggered through viral infection. The TRAIL receptor/ligand system enables the organisms to specifically kill virus-infected hepatocytes, whereas normal uninfected hepatocytes in vivo are resistant to TRAIL-mediated apoptosis. Overexpression of TRAIL in the liver after viral infection is not dependent on lymphocytes, natural killer, or Kupffer cells, which indicates that the TRAIL receptor/ligand system is a paracrine mechanism of hepatocytes against virally infected cells. Our results suggest that TRAIL might be used not only for cancer therapy but also for therapy of patients with viral hepatitis to selectively eliminate infected hepatocytes and limit viral replication.
PMID:
12475902 Press Release: Sept 28, 2024 Manitobans receive prestigious international award Research may lead to new treatment, eventual cure for adult leukemia (Winnipeg) Two researchers from the Manitoba Institute of Cell Biology (MICB) at CancerCare Manitoba received a prestigious international award this month to further research that may lead to new treatments and the possible eventual cure for what can be a terminal form of cancer. Chronic Lymphocytic Leukemia (CLL) is an incurable leukemia that mainly affects older adults. Therapy is designed to lengthen and improve the quality of life for patients and is required in about half of all cases. Dr. Spencer Gibson and Dr. James Johnston received a prestigious award from an American non-profit organization, the Leukemia & Lymphoma Society, to study the role of a naturally occurring protein, TRAIL in treating CLL. TRAIL effectively kills cancer cells while leaving normal cells alone. Initial findings by these researchers in the laboratory indicated the patient’s CLL cells die following treatments with TRAIL while normal blood cells remain healthy. “The Society’s Translational Research Program provides support for new and novel research that takes the discoveries of the laboratory bench and translates them into new treatments for blood-related cancers,” explains Alan Kinniburgh, Ph.D., vice president for research at The Leukemia & Lymphoma Society. “Dr. Gibson and Dr. Johnston are our first Manitoba-based researchers. We're thrilled to welcome them to our worldwide team of researchers who are focused on finding clinical applications for their work, which will hopefully lead to cures for these devastating blood-related cancers.” “This is a prime example of basic research being translated into the development of new treatments for cancer right here in Manitoba,” said Dr. Spencer Gibson, researcher. “It also demonstrates the enhanced insight gained when researchers work side-by-side with clinicians.”
MICB will
receive $100,000 U.S. annually for the next three years to help fund the
research. MICB is dedicated to fundamental research in biology and its relation
to health, with a primary emphasis on cancer and related diseases. The MICB was
founded jointly by CancerCare Manitoba and the University of Manitoba in
1969. Oncogene 2002 Oct 3;21(44):6809-18 Mechanisms of resistance to TRAIL-induced apoptosis in primary B cell chronic lymphocytic leukaemia. MacFarlane M, Harper N, Snowden RT, Dyer MJ, Barnett GA, Pringle JH, Cohen GM. MRC Toxicology Unit, Hodgkin Building, University of Leicester, PO Box 138, Lancaster Road, Leicester LE1 9HN, UK. Primary B cells from B cell chronic lymphocytic leukaemia (B-CLL) were resistant to the novel selective cytotoxic agent, TNF-related apoptosis-inducing ligand (TRAIL). Low levels of the death-inducing TRAIL receptors, TRAIL-R1 and TRAIL-R2 but not the putative 'decoy' receptors, TRAIL-R3 and TRAIL-R4, were expressed on the surface of B-CLL cells. Resistance to TRAIL was upstream of caspase-8 activation, as little or no caspase-8 was processed in TRAIL-treated B-CLL cells. Low levels of a TRAIL death-inducing signalling complex (DISC) were formed in these cells, accompanied by the recruitment of endogenous FADD, caspase-8 and c-FLIP(L) but not c-FLIP(S). Both caspase-8 and c-FLIP(L) were cleaved to form two stable intermediates of approximately 43 kDa, which remained associated with the DISC. Caspase-8 was not further processed to its active heterotetramer. Thus the resistance of B-CLL cells to TRAIL may be due partly to low surface expression of the death receptors resulting in low levels of DISC formation and also to the high ratio of c-FLIP(L) to caspase-8 within the DISC, which would prevent further activation of caspase-8. Our results highlight the possibility of sensitising B-CLL cells to TRAIL by modulation of c-FLIP levels or by upregulation of surface expression of death receptors.
PMID:
12360407 (Chaya's note: these authors use a slightly different naming system: They call the death receptors DR4 and DR5 as R1 and R2, and the two 'decoy' receptors DcR1 and DcR2 are called R3 and R4. If all these guys were on the same page, used the same names for stuff, it would make our job of trying to figure these things out a little easier). Topic: Apoptosis
Velcade (Bortezomib - PS341) Update 5/20/03 by Chaya Venkat I have written before on the drug PS-341 (also MLN341, also bortezomib, also "Velcade", Millennium Pharmaceutical's trade name). URLs to some of the articles on CLL Topics are given below. Combination
of proteasome inhibitor PS-341 with local radiation To summarize, Velcade is a proteasome inhibitor. Proteasome are enzyme complexes in the cell responsible for breaking down a variety of proteins, including many that regulate cell division. One of the mechanisms by which PS-341 acts is interfering with the regulation of anti-apoptotic survival genes such as the bcl2 gene, and thereby causing the cancer cells to cause suicide (apoptosis). Studies in the lab have suggested that cancer cells are especially vulnerable to drug therapy that temporarily switches off proteasome function for 1 or 2 days. Proteasomes are enzymes that also act as roving 'garbage disposals' for cells--targeting, absorbing and breaking down unwanted proteins that could accumulate and interfere with normal cellular function. Cancer cells appear to be less well mannered than normal cells, and generate a lot more "garbage" than normal cells, and therefore they seem to be a lot more sensitive to a strike by garbage collection workers. In one study, lymphoma cells exposed to a proteasome inhibitor died at rates 40 to 50 times higher than those of normal, healthy cells. Based on this exciting and elegant science, I was looking forward to reports of good clinical response. I have not seen too many officially reported results yet, but the rumor on the street is that PS-341 did not do so well against CLL in some early phase clinical trials done at M. D. Anderson. I would appreciate any information to the contrary, if you are aware of it. I thought there were going to be more clinical trials for CLL using MLN-341, but I have not come across any reports of the results, and I am not even sure whether these trials are underway. Apparently it did a lot better against some other forms of hematological cancers, especially multiple myeloma. The FDA has just approved the use of Velcade for multiple myeloma, in record time. See the article below from ACS. While only a quarter of the patients in the multiple myeloma clinical trials responded (we are not talking of complete responses (CR), but any kind of a response at all), this must be seen in the light of the nature of the disease and the patient population: multiple myeloma is a tough adversary, and all of these patients were heavily pre-treated. There are some indications that Velcade may work better as an adjunct to other chemotherapy or radiotherapy regimes, rather than as a solo act. Proteasome inhibition may make the cancer cells easier to kill, and thereby make combinations of Velcade with other drugs more effective than either by itself. I wonder if anyone is considering a Velcade plus Rituxan combination for CLL... News Report: ACS News Center The Food and Drug Administration has approved the drug Velcade (bortezomib) for patients with multiple myeloma that has not responded to other treatments.FDA Approves New Drug For Multiple Myeloma, Velcade For Use When Other Treatments Fail Article date: 2024/05/16 The Food and Drug Administration has approved the drug Velcade (bortezomib) for patients with multiple myeloma that has not responded to other treatments. The drug is the first in a new class of anticancer medicines called proteasome inhibitors. “The FDA approval of Velcade represents a major advance,” said Ken Anderson, MD, director of the Jerome Lipper Multiple Myeloma Center at the Dana-Farber Cancer Institute, and a lead investigator in trials of the drug.
Multiple
myeloma is a cancer of the blood plasma cells that causes tumors to form in bone
marrow. The American Cancer Society estimates that about 14,600 More Studies Needed The FDA approved the drug on an accelerated schedule, meaning it has not gone through the full battery of clinical trials normally required to bring a drug to market. The approval was based on a study of 202 patients whose disease had not responded to two previous therapies. About 28% of patients who received Velcade showed a response, which lasted about a year. A response means that blood levels of the abnormal protein typically secreted by myeloma cells had decreased. “The drug shows a significant effect on patients with multiple myeloma that have not responded to other treatments – a response that is likely to result in significant clinical benefit,” FDA Commissioner Mark McClellan, MD, PhD, said in a statement.
However,
no clinical trials have yet proven that Velcade actually increases survival, and
Millennium is required to continue studies to determine how helpful the drug is,
and to compare it to standard treatments for myeloma. Velcade is also being
studied for patients with metastatic colorectal cancer, and people with advanced
non-small-cell lung cancer. Velcade can cause side effects including nausea,
vomiting, fatigue, diarrhea, decreased blood platelets and red blood cells, and
numbness or tingling in the extremities. The manufacturer said these side
effects were generally manageable in the patients studied. Topic: Apoptosis
4/10/03 by Chaya Venkat We recently examined an interesting report on the Geron Corporation's Phase - I clinical trial results for prostate cancer using an anti-telomerase vaccine approach. This is clearly an important approach to what could potentially be termed "universal cancer vaccine" that would hopefully work for a variety of cancer types. Before we can discuss how anti-telomerase cancer vaccines may work, it might help to have an overview of "telomeres", our internal clocks that control how our very cells age and die. Overview of Telomeres / Telomerase Each cell in your body has 46 chromosomes, 23 of them come from your mother and 23 from your father. In the normal process of living, cells die and are replaced by new cells. Every time a cell divides in two to make two new cells, the 46 chromosomes in the original "mother" cell are exactly duplicated in the new daughter cells. Well, not exactly, the problem is that when a chromosome is duplicated, the Xeroxing process does not happen exactly right to the very tips. This is where the "telomeres" come in: these are little caps at the ends of each strand of chromosomes. 46 chromosomes per cell, which means there are 92 telomeres, two each per chromosome, to cap the two ends of the chromosome, keep a lid on things as it were. Think of it this way: each of the laces on your sneakers is a chromosome, and the little plastic tips at each end is a telomere. Those plastic tips are important, without these tips to protect them, the laces will soon fray and decay. The telomeres keep the genetic information of the chromosomes intact, without getting frayed and corrupted from one generation of mother cells to the next generation of daughter cells. Since the telomeres themselves carry no genetic information, the fact that the very tips are not duplicated exactly makes no difference. In fact, the length of the telomere gets shortened with each duplication. In every generation, the daughter cells have slightly shorter telomeres than their mother cells had, because a little bit of the telomere at the very tip does not get duplicated. When the telomere gets worn down to a nub and finally disappears after a defined number of cell divisions, it is no longer possible for that cell to divide properly any more. The cell has aged to a point where it is no longer viable, and dies. Think of this as an aging process, at the very cellular level, a built-in mechanism for getting rid of old cells that have been through too many cell divisions and no good any more. This is actually an important mechanism that the body has developed, to avoid premature cancer. Using an analogy that is more or less accurate, if you Xerox a document, then Xerox the copy once more, keep doing this for many times, each time copying the prior generation copy, you can imagine that after a while the copies will start looking blurred, smudged and no where as clean and clear as the original document. There will be a gradual accumulation of spots, smudges and errors, to the point where the document is no longer readable. Same thing with cells. As time goes one, there is a gradual process of accumulation of genetic misinformation in the chromosomes, and particular errors in a given chromosome in a given cell are dutifully passed on to its daughters. As in our Xerox analogy, errors continue to accumulate over many generations, to the point where the cell is no longer a well functioning cell. It is no longer desirable for this defective cell to reproduce and make more daughters and grand daughters of itself. This is where the gradually shortening telomeres come in, to deliver the kiss of death, and the cell dies with no further reproduction. It is believed that shortened telomeres and eventual death of cells that have gone through their ordained number of divisions may be responsible for some of the changes we associate with normal aging. There are one particular bunch of cells in your body, that are exempt from the telomere control of how many times they can divide: these are the reproductive cells, the eggs and the sperm. Makes sense, if the species is to continue, babies must get born based on a single fertilized egg, and this single cell then goes on to make a whole human being. There is a particular enzyme, called "telomerase" that has been called an immortalizing enzyme. It has the capability of adding to the length of the telomere tips after each cell division, keeping intact the length of the tips, compensating for the erosion of the tips that would happen with each cell division, in the absence of the activity of this enzyme. Without telomerase activity to counteract the effect of the shrinking lengths of telomeres on reproductive cells, the human race will become extinct very soon. Besides the reproductive cells, the enzyme telomerase is expressed also in proliferative cells of renewal tissues (e.g. bone marrow cells, basal cells of the epidermis, proliferative endometrium, and intestinal crypt cells). It is not expressed and it is undetectable in normal cells. Now comes the punch line, it has been found that most human tumors have high telomerase activity while most normal human cells do not, with the exceptions noted above. Telomerase activity in cancer cells means that the "immortalizing enzyme" is working in these malignant cells, keeping the telomeres from getting shorter with each generation. Such malignant cells can keep dividing indefinitely, producing more and more corrupt copies of themselves. It has been proposed that up-regulation of telomerase and its activity may be a critical event responsible for continuous tumor cell growth. Most, but not necessarily all, malignant tumors may need telomerase to sustain their growth. This up-regulation of telomerase activity may be a necessary step required for the continuing proliferation of advanced cancers. There is experimental evidence from many researchers that telomerase activity is present in almost all human tumors but not in normal cells that may be right next to the tumor. Telomerase researchers are working on using this fact to develop ac curate and quick methods for detecting cancer in the first place, by looking for the tell-tale signals of telomerase activity; and next step, control the explosive proliferative growth of cancer cells by taking away their immortalizing enzyme. There is a lot of information available on this subject, I have sampled a few abstracts below to give you a sense of the type of work that is going on, specially in the context of CLL. The first two PubMed citations below discuss telomere length and telomerase activity in the context of CLL patient survival prognosis. The authors conclude, "telomerase activity was the most significant prognostic factor for overall survival in B-CLL". Both of these papers link short telomeres with increased telomerase activity, and poorer prognosis. Once we start discussing CLL prognostic indicators, can IgVH gene mutation status be far behind? The third PubMed citation connects the dots: short telomeres, high telomerase activity and unmutated IgVH gene status all go together, and this may explain why the patients with unmutated IgVH gene have a poorer prognosis, they are also the ones with high telomerase activity in their CLL cells, making them "immortal". So much for understanding telomeres and telomerase activity, and how this can possibly be a good prognostic tool for cancers of all kinds, including CLL. So what can be done about it? This is where the Geron technology comes in. Researchers at Duke and Geron came up with a technique where by bits of telomerase are fed to mature dendritic cells obtained from the patient, by leukapheresis of blood. This brew is then injected back into the patient as a vaccine. As you know by now, dendritic cells are very good at presenting bits of proteins to "effector" cells such as T-cells. When snippets of telomerase are presented as antigens by these professional antigen presenting cells (APCs), T-cells are activated to become killers, going after any cell that displays the protein fragments that had been defined as antigens by the APCs. The Duke clinical trial showed that in the vast majority of patients, after vaccination with appropriately indoctrinated dendritic cells, such an activation of T-cells to become Cytotoxic T-Lymphocytes (CTLs) did indeed happen, and there was a decrease in circulating prostate cancer cells in the blood. They also observed no toxicity or side effects attributable to the vaccination. So far, so good. I guess the big question for us folks is how long it is going to take from Phase-I clinical trials for prostate cancer to go to late stage trials for CLL. This waiting game can be hard on patients' nerves, especially those facing therapy decisions in real time. Reference: Geron Corp publications on telomeres and telomerase - Link to product development pages at Geron Corp. Abstracts: Cancer Res 1998 Nov 1;58(21):4918-22 Telomere length and telomerase activity predict survival in patients with B cell chronic lymphocytic leukemia. Bechter OE, Eisterer W, Pall G, Hilbe W, Kuhr T, Thaler J. Department of General Internal Medicine, Innsbruck University Hospital, Austria. The telomere-telomerase hypothesis states that the vast majority of human tumors have a prolonged replicative life span throughout expressing telomerase, which compensates the cell division-associated loss of telomere DNA. The use of telomere length and telomerase expression as new biological markers in cancer patients requires their correlation with disease prognosis. We, therefore, correlated the mean telomere length based on a telomere restriction fragment assay and the activity of telomerase measured with a telomeric repeat amplification protocol with clinical data and overall survival in 58 patients with B cell chronic lymphocytic leukemia (B-CLL). Telomere length showed a highly inverse correlation to telomerase activity. Patients with telomeres below 6.0 kb were associated with high telomerase activity, whereas patients with a telomere length >6.0 kb generally showed low enzyme activity (P <0.001). Patients in Binet A exhibited significantly longer telomeres and had less telomerase activity than did patients in Binet B or Binet C, where significantly shorter telomeres and higher telomerase activity were observed (P=0.031). Short telomere length and high telomerase activity were significantly associated with a shorter median survival (P=0.02 and P <0.001), and telomerase activity was the most significant prognostic factor for overall survival in B-CLL (P <0.001). Our data provide evidence that telomere length, as well telomerase activity, exerts a strong impact on the survival of B-CLL patients and that telomerase activity can be used as a new prognostic marker in this disease.
PMID:
9810000 Br J Haematol 1999 Sep;106(3):662-8 Telomerase activity in chronic lymphoproliferative disorders of B-cell lineage. Trentin L, Ballon G, Ometto L, Perin A, Basso U, Chieco-Bianchi L, Semenzato G, De Rossi A. Department of Clinical and Experimental Medicine, Clinical Immunology Branch, University School of Medicine, Padova, Italy. The progressive shortening of telomeres at each cell division is a key mechanism in controlling cell proliferative capacity. The activation of telomerase, a reverse transcriptase that extends telomere length, potentially leads to unlimited cell proliferation, and is believed to play a critical role in the neoplastic process. High levels of telomerase activity have been demonstrated in almost all solid tumours; however, little data is available concerning its expression in chronic B-cell neoplasms. By using a quantitative polymerase chain reaction-based method we quantified telomerase activity in normal B lymphocytes, and in various B-cell malignancies, including chronic lymphocytic leukaemia (CLL), mantle cell lymphoma (MCL) and hairy cell leukaemia (HCL). Compared to normal B cells, which expressed very low levels of telomerase activity, malignant cells from most of the patients showed a significant increase in telomerase activity, with highest values observed in HCL samples. Moreover, among the CLL and HCL cases, significantly higher levels of telomerase activity were found in patients with progressive disease at 1 year follow-up versus patients with stable disease. These data suggest that telomerase activity might correlate with disease progression.
PMID:
10468854 Br J Cancer 2024 Feb 24;88(4):593-8 Association between telomere length and V(H) gene mutation status in chronic lymphocytic leukaemia: clinical and biological implications. Hultdin M, Rosenquist R, Thunberg U, Tobin G, Norrback KF, Johnson A, Sundstrom C, Roos G. Department of Medical Biosciences, Pathology, Umea University, Sweden. The immunoglobulin V(H) gene mutation status can divide B-cell chronic lymphocytic leukaemia (CLL) into two entities with a different clinical course. Cases with unmutated V(H) genes, considered to evolve from pregerminal centre (GC) cells, have a worse outcome compared to cases showing mutated V(H) genes, that is, post-GC derived. Also, telomere length has been reported to be of prognostic s ignificance in CLL. Interestingly, telomerase becomes activated during the GC reaction and an elongation of the telomeres occurs in GC B cells. We performed telomere length and V(H) gene analysis in a series of 61 CLL cases, in order to investigate if the unique telomere lengthening shown in GC B cells could reflect the telomere status in the two subsets of mutated and unmutated CLL. A novel association was found between V(H) gene mutation status and telomere length, since significantly shorter telomeres were demonstrated in the unmutated group compared to the mutated group (mean length 4.3 vs 6.3 kbp). Shorter telomeres also constituted a subgroup with a worse prognosis than cases with longer telomeres (median survival 59 vs 159 months). Furthermore, the Ig gene sequence data revealed that samples with high mutations frequency (>6%) had long telomeres ( approximately 8 kbp). Thus, both the telomere and V(H) gene mutation status in CLL appear linked, which may reflect the proliferative history of the clonal cells with regard to the GC reaction.
PMID:
12592375 Topic: Apoptosis
Combination of Proteasome Inhibitor PS-341 with Local Radiation 3/28/03 by Chaya Venkat Here is the link to a Reuters Health article that talks about good results obtained (in mouse studies) by combining PS-341, a proteasome inhibitor, with local radiation to tumors. Interesting reading: Study raises hope of 'self-vaccine' against cancer. I have written before on the drug PS-341: please see articles dated Sept 25, 2002 and Sept 30, 2024. To summarize, this new drug called PS-341 (also MLN341, also bortezomib, also "Velcade", Millennium Pharmaceutical's trade name) is a proteasome inhibitor. Proteasome are enzyme complexes in the cell responsible for breaking down a variety of proteins, including many that regulate cell division. One of the mechanisms by which PS-341 acts is interfering with the regulation of anti-apoptotic survival genes such as the bcl2 gene, and thereby causing the cancer cells to cause suicide (apoptosis). Studies in the lab have suggested that cancer cells are especially vulnerable to drug therapy that temporarily switches off proteasome function for 1 or 2 days. Proteasomes are enzymes that also act as roving 'garbage disposals' for cells--targeting, absorbing and breaking down unwanted proteins that could accumulate and interfere with normal cellular function. Cancer cells appear to be less well mannered than normal cells, and generate a lot more "garbage" than normal cells, and therefore they seem to be a lot more sensitive to a strike by garbage collection workers. In one study, lymphoma cells exposed to a proteasome inhibitor died at rates 40 to 50 times higher than those of normal, healthy cells. Based on this exciting and elegant science, I was looking forward to reports of good clinical response. I have not seen too many officially reported results yet, but the rumor on the street is that PS-341 did **not** do so well against CLL in some early phase clinical trials done at M. D. Anderson. Apparently it did better against some other forms of hematological cancers. Disappointing. Now comes this new twist on use of PS-341. A little background to make it easier to understand the new approach reported in the Reuters' article. Much of this is from a previous article dated July 3, 2024 on Apoptosis versus Necrosis. There are two types of cell death, apoptosis and necrosis. I read somewhere, necrosis can be thought of as murder, where the cell is killed by some external factor. Examples of necrosis are skin cells that are killed, and undergo necrosis, when burned beyond repair; or tumor cells that are mashed beyond hope of repair, say due to a burst of locally directed radiation. Apoptosis can be thought of as suicide, where the cell obediently kills itself upon receiving the right signals to do so. All normal cells have a defined role to play, and a time comes in the life of every cell when there is no further role to play. When that time comes, all good cells die obediently on receiving the death signal from the body, the individual cell dying to benefit the larger community. In some cases, as in cancer, the cell develops a case of not listening very well, and refuses to die on command. As in the case of CLL, they then proliferate out of control, not so much because they are multiplying too fast, but because they are not dying fast enough. A little persuasion is needed, to get the message across. Another big difference between the two pathways of cell death: in necrosis the end is messy, the cell's membrane bursts open spewing forth all sorts of fragments of the contents of the cell that has just been killed. If this cell had been an infected cell, or a tumor cell, these fragments may be interesting enough to trigger an immune response, sometimes giving rise to inflammation. Apoptosis on the other hand is characterized by nice packaging of the cell into little packages that can be easily phagocytized (gobbled up) by other cells. Apoptosis therefore does not have the mess and fuss associated with necrosis, and therefore does not cause an immune response or inflammation. Makes sense, does it not, apoptosis is one of the regular, routine and necessary functions of the body. It would not do to have the immune system getting riled up every time a cell does its appointed task of killing itself on command. The police force (Immune system) needs to come out only for murder cases (necrosis), not death due to natural causes (apoptosis). Bottom line, necrosis may trigger an immune response, if the fragments of the murdered cell are appropriately presented to the immune system, by a professional antigen presenting cell (APC) such as a dendritic cell. In other words, necrotic tumor cell fragments are a necessary component if one were to hope for the immune system getting activated and respond as if the patient had been vaccinated. This is oversimplified, as usual, but it may help get across some of these concepts. So, this new approach with PS-341 seems to be this, and they would like to try this out with breast cancer patients: treat patients with GM-CSF ahead of time to increase production of dendritic cells (see above, these are the professional antigen presenting cells). Then use local radiation to cause **necrosis** of tumor cells in one location, possibly targeting a tumor that is easily accessed and close to the surface. The necrosis cell fragments become good antigens for the dendritic cells to latch on to, and the correct presentation of these fragments to the immune system will hopefully trigger an immune response, causing the immune system cells to go out and attack all other cells that carry similar fragments, namely tumor cells at other locations. Immune response in cancer patients is not very strong, I get the sense that the PS-341 is there to make the cancer cells sufficiently under stress to begin with, so that even a weak immune response is enough to kill the tumor cell. Neat idea. The immune system is much more complex, can do a better job of hunting down and locating the tumor cells through out the body, and the PS-341 gives an assist in the cell kill once they have been identified. This approach, if it works, would be of great interest to CLL patients. We have had quite a bit of discussion recently on bulky lymph nodes, and how they are harder to clean out with monoclonals like Rituxan. Also, for many of us, the swollen lymph nodes are close to the surface and accessible to local radiation. On my wish list would be results that show that radiation at one nodal site, in combination with PS-341, eliminates all other nodes at all other sites. This makes possible the concept of limited radiation at a limited and carefully chosen site doing the job of cleaning out other nodes, perhaps these nodes are at more inaccessible locations, perhaps too close to other important organs and where you may not want to hit them with a dose of radiation. Topic: Apoptosis
9/30/02 by Chaya Venkat The Reuters article below is sufficiently readable that I will not try to annotate it further. Please look up my previous article on proteasome inhibitors. This drug is now in phase-2 trials, sponsored by the NCI, for CLL. The link to the clinical trial is given in my previous article. There is quiet but impressive excitement building about this drug. It could be in your future. Article: Proteasome inhibitors: PS-341 (MLN-341) CHICAGO (Reuters Health) - Early results from human trials suggest that cancer cells may be especially vulnerable to newly developed drugs that switch off their ability to rid themselves of excess proteins. One drug, called PS-341, showed ``hugely impressive'' results in either slowing or--in one case--stopping progression of multiple myeloma, an often-lethal blood cancer, according to researcher Dr. Robert Orlowski of the University of North Carolina, Chapel Hill. He presented the findings here Monday at the annual meeting of the American Chemical Society. Studies in the lab have suggested that cancer cells are especially vulnerable to drug therapy that temporarily switches off proteasome function for 1 or 2 days, Orlowski said. Proteasomes are enzymes that act, in large part, as roving 'garbage disposals' for cells-- targeting, absorbing and breaking down unwanted proteins that could accumulate and interfere with normal cellular function. Because proteasomes are "absolutely necessary for cellular survival", shutting them down over the long term inevitably leads to cell death, Orlowski explained. In one such study, lymphoma cells exposed to a proteasome inhibitor died at rates 40 to 50 times higher than those of normal, healthy cells. After observing significant tumor suppression in mice treated with the proteasome inhibitor PS-341, Orlowski and colleague Dr. Julian Adams of Millennium Pharmaceuticals, Cambridge, Massachusetts, began a phase I study of the drug in nine patients with multiple myeloma, in which blood plasma cells undergo abnormal explosive growth. The study was supported by a grant from The Leukemia and Lymphoma Society. All of the patients had already shown poor progress with current chemotherapies--not surprising, since, in a majority of cases, myeloma cells quickly gain resistance to available drugs. A phase I trial is conducted to evaluate the safety of a drug therapy, not its effectiveness. However, during just one month of PS-341 therapy, all but one of the patients in the study experienced a significant, positive response to the drug. In one patient, a 42-year-old woman previously resistant to all available medications, the bone marrow plasma cell count has declined from 41% before treatment to a normal, healthy 1% after just one month of treatment. Her disease has since stabilized to the point that she "has not required any therapy for one year,'' according to Orlowski. He told delegates that studies in a similar group of patients with non-Hodgkin's lymphoma has produced similarly impressive results. Phase II trials are currently under way, Orlowski said, and include patients with solid tumors as well as blood cancers. In the phase I study, PS-341 was generally well tolerated, with patients experiencing only mild to moderate levels of side effects such as anemia or fatigue. The North Carolina researcher said the "best role'' for PS-341 and other proteasome inhibitors may be as a booster for current chemotherapy. Previous studies have shown, he explained, that these types of drugs work to re-establish the vulnerability of cancer cells "to other types of (drugs) that are currently available and to which they would normally be resistant.''
In one
study, for example, cancer cell lines normally resistant to the chemotherapy
drug dexamethasone lost that resistance when researchers added PS-341 to the
mix. Another article apparently covering the same study and results appeared in an ASCO (American Society of Clinical Oncology) news release dated 11/15/2002. Here is a link to the article: Targeted Therapy Generates Anti-Tumor Activity. Topic: Apoptosis
PS-341 (Proteasome Inhibitor) for CLL and MCL 9/25/02 by Chaya Venkat There seems to be interest building in a new drug called PS-341 (also MLN341, also bortezomib, also "Velcade", Millennium Pharmaceutical's trade name). This is a proteasome inhibitor. Proteasomes are enzyme complexes in the cell responsible for breaking down a variety of proteins, including many that regulate cell division. One of the mechanisms by which PS-341 acts is interfering with the regulation of anti-apoptotic survival genes such as the bcl2 gene, and thereby causing the cancer cells to cause suicide (apoptosis). Dr. Kanti Rai had encouraging things to say about this drug on a recent HealthTalk interview, he is apparently participating in testing of this drug. Any of you who have contact with Dr. Rai, do us all a favor and see if you can find out more about this drug. The URL for the HealthTalk interview is below: http://www.healthtalk.com/oncology/horiz/rai/05.html. Of particular interest to one member that may in fact have MCL would be an ASH 2024 abstract I came across, that specifically talks about use of PS-341 for Mantle Cell Lymphoma. Abstract: [1945] Anti-Tumor Activity of the Proteasome Inhibitor PS-341 in Mantle Cell Lymphoma B Cells. Lan Pham, Archito Tamayo, Piao Lo, Linda Yoshimura, Richard J. Ford. Hematopathology, MD Anderson Cancer Center, Houston, TX, USA
Mantle
Cell Lymphoma (MCL) remains the most therapeutically resistant neoplastic
disease among the non-Hodgkin's lymphomas (NHL), a group of human lymphoid
neoplasms that is showing a continual increase in incidence in the US. The
reason for the resistence of MCL to current therapeutic modalities is not clear,
indicating that new therapeutic approaches to MCL are clearly needed. In
preclinical studies, bortezomib and other proteasome inhibitors have shown
activity against a variety of B-cell malignancies, including multiple myeloma,
diffuse large B-cell lymphoma, mantle cell lymphoma, and Hodgkin's lymphoma.
These agents can induce apoptosis and sensitize tumor cells to radiation or
chemotherapy. Based on these findings, phase I clinical trials were conducted
with bortezomib in various solid and hematologic malignancies. In these studies,
bortezomib was generally well tolerated with manageable toxicities. Phase II
trials have been initiated for relapsed and refractory multiple myeloma,
refractory chronic lymphocytic leukemia, and non-Hodgkin's lymphoma. Preliminary
data from the multiple myeloma phase II study indicate that a significant number
of patients responded to therapy or exhibited stable disease and that the drug
had manageable toxicities. These findings, along with extensive preclinical
data, suggest that bortezomib and other proteasome inhibitors may have
far-reaching potential in the treatment of various cancers, including B-cell
malignancies." PS-341 is in trials for just about every type of solid tumor you can think of. The URL link to the phase-II clinical trial for b-cell cancers (including CLL and MCL) is http://clinicaltrials.gov/show/NCT00023764. It is being sponsored by the NCI and Memorial Sloan Kettering. Might be worth checking out, but at this time they seem to be recruiting only refractory cases. We will be on the lookout for more information on this promising approach. Topic: Apoptosis
Combination Therapy with Genasense and Rituxan 7/10/02 by Chaya Venkat I have written earlier on the subject of Genasense, Genta's drug that blocks and down regulates formation of bcl-2, the protein that otherwise protects cancer cells from dying a natural death. You can look up the clinical trial information re Genasense on this website. Incidentally, CLL is one of the cancers that has very high expression of bcl-2, and therefore a good candidate for Genasense. There were infusion related problems with the first of the clinical trials at M D Anderson, seems to be the norm for any new drug. (One reason why you should be extra careful in signing up for phase-1 clinical trials. There does seem to be a significant learning curve while the experts figure out how to administer the new drug). But more recent trials seem to have worked out the kinks. You can look up more of the science behind Genasense at www.genta.com Now comes a recent press release from Genta corporation (April 2024) that says the combination of Genasense and Rituxan could be synergistic, with a one-two punch that is greater than the sum of the two. Genasense down regulates bcl-2, making the cancer cells much more susceptible to attack by Rituxan. Down the road, if this sort of combination continues to look good in clinical trials, standard chemotherapy regimes may become a thing of the past. Remember though, these results are pre-clinical, in CLL mice. Long road from mice to men. Press Release: New Studies Show Genasense(TM) Potentiates Anticancer Actions of Taxotere(R) and Rituxan(R) BERKELEY HEIGHTS, N.J., April 8 /PRNewswire-FirstCall/ -- Genta Incorporated (Nasdaq: GNTA - news) announced today that two new studies have shown that Genasense(TM), the Company's lead anticancer compound, strongly enhanced the anticancer activity of two leading anticancer agents, Taxotere® (docetaxel; Aventis Pharma, SA) and Rituxan® (rituximab; Genentech, Inc.). Results from these separate preclinical studies were presented at the annual meeting of the American Association of Cancer Research (AACR) in San Francisco. Dr. Jill Lacy and colleagues from Yale University tested the effects of Genasense and Rituxan in mice with human lymphoma. Previous studies by this group had shown that Genasense used alone down-regulated Bcl-2, the protein target of Genasense treatment, and stimulated apoptosis (programmed cell death). While Genasense significantly prolonged survival, it was not curative when used alone (Cancer Research 60:5354, 2000; http://cancerres.aacrjournals.org/cgi/content/full/60/19/5354 ). In the current study, untreated animals with lymphoma expired at a median time of 44 days. Rituxan alone increased survival to 59 days, whereas Genasense alone increased survival to 71 days. However, neither agent was curative when used by itself. In the combination study, Genasense plus Rituxan increased survival to 150+ days, and 5 of 7 animals were ultimately proven to be free of disease. "In addition to previous
studies that showed synergy between Genasense and Taxotere in prostate cancer,
we are very excited by the new data for this combination in non-small cell lung
cancer (NSCLC),'' said Dr. Loretta M. Itri, Executive Vice-President and Chief
Medical Officer. "In addition to having advanced this combination into a
randomized clinical trial in patients with NSCLC, Genta plans to quickly explore
the Genasense/Rituxan synergy in several new trials this year. Clinical
confirmation of the documented synergy between Genasense and these two agents is
a key feature of our future development programs.'' Topic: Apoptosis
7/3/02 by Chaya Venkat There are two types of cell death, apoptosis and necrosis. I read somewhere, necrosis can be thought of as murder, where the cell is killed by some external factor. Examples of necrosis are skin cells that are killed, undergo necrosis, when burned beyond repair; or tumor cells that are mashed beyond hope of repair due to an ultrasound burst that is powerful enough to do so. Apoptosis can be thought of as suicide, where the cell obediently kills itself upon receiving the right signals to do so. All normal cells have a defined role to play, and a time comes in the life of every cell when there is no further role to play. When that time comes, all good cells die obediently on receiving the death signal from the body. In some cases, as in cancer, the cell develops a case of not listening very well, and refuses to die on cue. As in the case of CLL, they then proliferate out of control, not so much because they are multiplying too fast, but because they are not dying fast enough. A little persuasion is needed, to get the message across, and this is where a lot of the chemotherapy drugs come in, getting through the death signal to cells that had somehow evaded responding to the message to commit suicide. Another big difference between the two pathways of cell death, in necrosis the end is messy, the cell's membrane bursts open spewing forth all sorts of fragments of the contents of the cell that has just been killed. If this cell had been an infected cell, or a tumor cell, these fragments may be interesting enough to trigger an immune response, sometimes giving rise to inflammation. Apoptosis on the other hand is characterized by nice packaging of the cell into little packages that can be easily phagocytized (gobbled up) by other cells. Apoptosis therefore does not have the mess and fuss associated with necrosis, and therefore does not cause an immune response or inflammation. Makes sense, does it not, apoptosis is one of the regular, routine and necessary functions of the body. It would not do to have the immune system getting riled up every time a cell does its appointed task of killing itself on command. The police force (Immune system) needs to come out only for murder cases (necrosis), not death due to natural causes (apoptosis). Bottom line, necrosis may trigger an immune response, if the fragments of the murdered cell are appropriately presented to the immune system, by a professional antigen presenting cell (APC) such as a dendritic cell, and the presentation is accompanied by all the necessary co-stimulatory signals. In other words, necrotic tumor cell fragments are a necessary component of vaccines of the heat shock variety we discussed in previous articles. If the tumor cells are dead via apoptosis pathways, there is no necrotic peptide fragments, cell death is nice and tidy, nothing for the immune system to respond to, hence no vaccine effect is possible. This is oversimplified, as usual, but it may help get across some of these concepts. Topic: Apoptosis
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