| The latest medical advances from Johns Hopkins Medicine |
| GERM - CHEMO COMBO FIGHTS CANCER |
 Bacteria that can cause deadly infections in humans and animals have shown promise in
treating cancer by "eating" tumors from the inside out. Now, two new studies at the Johns Hopkins Kimmel Cancer Center have demonstrated that, combined with specially packaged anti-cancer drugs, the bacterial therapy's prospects for
cancer eradication have dramatically improved.
In mouse experiments reported in the Nov. 24 issue of Science, the Johns Hopkins researchers demonstrated that genetically modified bacteria called Clostridium novyi-NT (C.novy-NT) have a special taste for oxygen-starved environments much like those found in the core of cancer cell clusters. The modified bacteria themselves are relatively harmless, but their unmodified counterparts produce poisons that have killed some humans and cattle when introduced into the bloodstream. "It is not difficult to kill cancer cells. The challenge is killing them while sparing normal cells," says Bert Vogelstein, M.D., professor and co-director of the Ludwig Center and Howard Hughes Medical Institute at the Johns Hopkins Kimmel Cancer Center. The bacteria's cancer-killing effects were first discovered five years ago by the Johns Hopkins team who noticed the germ's ability to grow and spread in the oxygen-poor core of mouse tumors and the blackened scars signaling that most of the cancer cells had been destroyed. Normal surrounding cells were largely unaffected. But the bacteria failed to kill cancer cells at the still oxygen-rich edge of the tumors. In response, the Johns Hopkins team added specially packaged chemotherapy to the bacterial attack speculating that certain properties of the bacteria would improve the drug's effectiveness, according to Shibin Zhou, M.D., Ph.D., assistant professor of oncology at the Johns Hopkins Kimmel Cancer Center. The combo approach temporarily wiped out both large and small tumors in almost 100 mice and permanently cured more than two-thirds of them. The likely explanation for the greater cancer cell kill by the combination treatment is that the bacteria expose the tumors to six times the amount of chemotherapy than is usually the case by improving the breakdown and dispersal of the chemotherapy's fatty package at the tumor site. The investigators repeated experiments using two packaged chemotherapy drugs -- doxorubicin and irinotecan -- and observed similar tumor-killing effects of both when used in combination with the bacteria. "Packaged" cancer drugs currently are available in microscopic fatty capsules called liposomes which gravitate to tumors because they are too large to fit through the skins of tightly woven blood vessels surrounding normal tissue and small enough to get through tumor vasculature. Combining C.novyi-NT and liposomes filled with chemotherapy seems to have its synergistic effect on tumors owing to the presence of an enzyme found lurking in C. novyi-NT cultures, which Ian Cheong, Ph.D., in the Vogelstein lab dubbed liposomase. It destroys fatty membranes and may disrupt the outer layer of liposomes releasing their drug contents. "Drugs contained in these ‘Trojan horse' compartments are specifically released at the tumor site by the C-novyi-NT bacteria which may improve the effectiveness and safety of the therapy," says Cheong, who is the lead author of the study. The scientists note that liposomase could be used in a variety of other targeted therapies besides the bacteria combination. Such approaches could include attaching liposomase to antibodies that have an affinity for specific tumors or adding its DNA code to gene therapy. As many drugs can be packaged within liposomes, the investigators say the approach could have general utility. In a companion study published in the Nov. 19 online issue of Nature Biotechnology, the Johns Hopkins team decoded the entire C.novyi-NT genome, which Zhou says "was instrumental in identifying liposomase and will help improve our bacterial-based therapies." Preliminary safety tests of injected C. novyi-NT alone are under way in a small number of cancer patients.The research was funded the Virginia and D.K. Ludwig Fund for Cancer Research, the Commonwealth Foundation, Miracle Foundation, and the National Institutes of Health. Co-authors include Xin Huang, Chetan Bettegowda, Luis A. Diaz., Jr., and Kenneth W. Kinzler at the Johns Hopkins Kimmel Cancer Center. 1 Cheong, I., et al. A C.novyi Protein Enhances the Release and Efficacy of Liposomal Cancer Drugs. Science online, November 24, 2006. 2 Bettegowda, C., et al. The Genome and Transcriptomes of the Anti-Tumor Agent Clostridium novyi-NT. Nature Biotechnology online, Nov 17, 2006. |
| HOPKINS PERFORMS HISTORIC "DOMINO DONOR" "QUINTUPLE" KIDNEY TRANSPLANT |
 Surgical teams at Johns Hopkins have successfully completed the first five-way donor
kidney swap among 10 individuals. All five organ recipients -- three men and two women -- are fine, as are the five donors, all of whom are women. The marathon, 10-hour surgeries that began at 7 a.m. Nov. 14 occupied six operating rooms
staffed by twelve surgeons, eleven anesthesiologists and eighteen nurses at The Johns Hopkins Hospital.
Four transplant candidates had come to Johns Hopkins separately for evaluation, each with a willing donor whose blood and tissue types were incompatible with the intended recipient and who therefore could not donate to their loved one. Using a previously developed living donor matching system, the Johns Hopkins transplant team included a so-called altruistic donor in the mix and were able to arrange a five-way swap, in which all four original candidates received compatible kidneys from someone they had never met, and the remaining kidney went to a patient who was next on the United Network for Organ Sharing (UNOS) organ recipient list. An altruistic donor is a person who, for personal reasons, has a generous desire to donate a kidney to no particular recipient. The Johns Hopkins transplant team is a pioneer in the exchange of kidneys between incompatible donor-recipient pairs -- a procedure called kidney paired donation (KPD). Johns Hopkins performed the first non-domino KPD transplant in the United States in 2001, the first non-domino KPD triple transplant in 2003 and the first triple domino transplant in 2005. To date, its surgeons have transplanted 41 patients in KPD operations. In Tuesday's operations, surgical teams took kidneys from five unrelated female donors and transplanted them into the five unrelated recipients, whose ages range from 40 to 77 years. Donors and recipients hail from California, West Virginia, Florida, Maine, Maryland and Ontario, Canada. The one "altruistic" donor, Honore Rothstein, is a healthy 48-year-old computer programmer who says she was motivated to donate a kidney after losing both her husband and her daughter in separate accidents or illnesses. "It has been a privilege to help Ms. Rothstein fully realize her altruism by placing her into a domino transplant where her gift has made five transplants possible that would not have occurred," says Robert Montgomery, director of the Incompatible Kidney Transplant Program, chief of the Division of Transplantation, and director of the Comprehensive Transplant Center at Hopkins. In a paper published last August in the British journal Lancet, Montgomery laid out the blueprint for a wider system of pairing altruistic donors and incompatible recipient pairs to greatly increase the number of available organs and better serve the interests of both transplant donors and recipients. Without a universal system of this kind in place, Montgomery says altruistic donors often end up on an Internet donation site or are subject to inconsistent allocation systems in which only a single patient benefits. For example, in some cases, the kidney goes to a patient deemed to have the best chance for long-term survival, while in others, the organ is given to a patient in greatest need or to someone at the top of the UNOS waiting list regardless of predicted outcome or need. "With domino paired donation, all three of these ethical tenets are satisfied," says Montgomery. "The likelihood of a good outcome is increased by spreading the risk of recipient graft loss across more people. The neediest are served, since in many cases incompatible donor-recipient pools have a high proportion of patients who are hard to match. And fairness is served because the last paired donor's kidney in the chain is allocated to the next compatible patient on the deceased donor waiting list." All five donor surgeries began simultaneously at 7:15 a.m. and were finished at 11 a.m. Four donor kidneys remained in the same operating rooms, which were cleaned and readied for the intended recipients. One kidney was taken to another room. The recipients' procedures began at 1 p.m. and were finished at 5:15 p.m. All the donors were released from the hospital by Nov. 17, and the recipients should be released by Nov. 20. Each of the donors will be monitored for the remainder of their lives to make sure their remaining kidney continues to function properly. The recipients have been placed on medications that will help ensure that they won't reject the kidney. They will be evaluated weekly for the first six weeks, then monthly, with the frequency of hospital visits slowly tapering off over time. The average expected life of a live donor kidney is 18 to 20 years. The recipients had lost the use of their kidneys for a variety of reasons, including blood clots, end-stage renal disease and a motor vehicle accident. Nearly 100 medical professionals were instrumental in making this complex series of transplants possible, including immunogeneticists, anesthesiologists, operating room nurses, nephrologists, transfusion medicine physicians, critical care doctors, nurse coordinators, technicians, social workers, psychologists, pharmacists, financial coordinators and administrative support people. |
| RESEARCHERS FIND GENE LINKED TO CROHN'S DISEASE |
 An international team of researchers has identified another gene mutation linked to the
inflammatory bowel diseases (IBD) Crohn's disease and ulcerative colitis.
The team, including Johns Hopkins gastroenterologists and geneticists, says the novel mutation is in the interleukin-23 (IL-23) gene receptor present in healthy people without Crohn's disease but rare in those with the disease. IL-23 is a protein that regulates chronic inflammation and helps the body fight bacterial infections. Its receptor, IL23R, is present on lymphocytes and macrophages, white blood cells responsible for mounting immune response to infections. IL-23 has long been linked to IBD and autoimmune psoriasis, but this new genetic variation in the protein's receptor offers a novel pathway for tracking the disease process and for potential drug treatments. Results of the study, by a consortium of researchers from Johns Hopkins and six other American and Canadian institutions, appears in Science Express, an online publication of the journal Science, on Oct. 26. "The IL-23 receptor variation we discovered appears to affect the IL-23 pathway, altering the body's response to chronic inflammation, which may trigger autoimmune disease," says study co-author Steven R. Brant, M.D., associate professor of medicine and director of research and the genetics laboratories of Johns Hopkins' Harvey M. and Lyn P. Meyerhoff Inflammatory Bowel Disease Center. "The fact that this gene has already been implicated in other autoimmune disease like psoriasis offers strong evidence that we are on the right track. In the Crohn's study, researchers located the IL23R disease-associated protein variant by scanning nearly all of the 22,000 genes that make up the human genome. The study looked at 547 test subjects with Crohn's disease and 548 healthy controls. Patients were recruited from six of the seven centers in the consortium. Researchers examined more than 300,000 variations in the genetic code, known as single nucleotide polymorphisms or SNPs, to identify which of the variations among these 22,000 genes can explain the genetic predisposition to developing Crohn's disease. SNPs are commonly occurring variations in our DNA code that are routinely used as a method for finding genetic links to diseases. Researchers scanned the genomes using a relatively new technology that allows researchers to study variations found in nearly all human genes for association with diseases. Researchers found that test subjects with Crohn's disease were roughly fourfold less likely to have an SNP variation that alters an important amino acid of the IL-23 receptor gene. More than 1 million Americans have Crohn's disease or ulcerative colitis. Because IBD tends to run in families and is more prevalent in certain ethnic populations, scientists have long suspected that there is a significant genetic component. A previous study, conducted in part at Hopkins, identified another gene mutation on the CARD15/NOD2 gene, common in people with Crohn's disease, but Brant says the new gene is a better candidate for drug treatments. "IL-23 is directly linked to an inflammatory pathway, making it a better candidate for drug therapies than CARD15/NOD2," he says. Brant says the team has identified additional gene variations potentially related to Crohn's disease, and the consortium will investigate these as well. "As more genes associated with Crohn's disease are discovered, we envision a time when gene testing may provide important guidance regarding the prognosis and treatment of each patient," says co-author Themistocles Dassopoulos, M.D., an assistant professor of medicine at the Meyerhoff Inflammatory Bowel Disease Center. The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases. |
| HOPKINS RESEARCHERS DISCOVER HOW BRAIN PROTEIN MIGHT CONTROL MEMORY |
 Researchers at Johns Hopkins have figured out how one particular protein contributes to
long term memory and helps the brain remember things longer than an hour or two. The findings are reported in two papers in the Nov. 9 issue of Neuron.
The protein, called Arc, has been implicated in memory-linked behaviors ranging from song learning in birds to rodents being aware of 3 D space. In people, Arc may be one culprit behind certain long term memory-based behaviors like drug addiction, the researchers say. "We think Arc controls how brain cells learn and associate behaviors and remember them over a long period of time," says Paul F. Worley, M.D., professor of neuroscience and neurology at Hopkins and director of both studies. "For example, the person who quits smoking can wean himself from cravings at home, at work or outside. But if you put him in a bar with a drink in his hand, his brain remembers that former association and suddenly the craving returns. These types of long term associations are memories wired in your brain." Years ago, Worley and his colleagues, studying laboratory rats, found that their brains made lots of Arc protein while the animals were awake and active. In fact, it has been long known that stimulating individual nerve cells-- by an act as simple as exploring new environs, for example--causes the cells to make more Arc protein almost immediately. "Arc is an instant and reliable readout for active cells in the brain," says Worley. But although scientists knew that active cells were making copious amounts of Arc, no one knew exactly what Arc was doing in those cells until now. To figure out what Arc was doing, the Hopkins team looked for what other proteins Arc "plays" with. Using Arc protein as bait, they went on a molecular fishing expedition in a pond filled with other proteins normally found in the brain and hooked two known to be involved in transporting materials into and out of cells. "Moving things in and out of cells is critical for normal brain cell function. We were extremely excited that Arc might somehow be involved in this transport because it links transport to memory formation," says Worley. "This brings us one step closer to understanding how the brain saves memories." According to Worley, memories form when nerve cells connect and "talk" to other nerve cells. It-s thought that the stronger these connections are, the stronger the memory. Like the childhood game called Telephone, where one person taps her neighbor and whispers a message that is passed on in similar fashion to the next person in line, nerve cells connect and "talk" to each other by relaying messages -- usually by passing small chemicals -- from cell to cell. When nerve cells connect with each other in the brain, one cell releases chemicals into the space between it and its neighbor. The neighboring cell has protein receptors on its surface that capture the released chemicals. The cell that captures these chemicals then swallows up the receptor chemical complexes, removing the receptors from the cell's surface. The more receptors present, according to Worley, the stronger the connection between the two cells. New receptors constantly replace the swallowed up ones. The two proteins that came out of the Arc fishing expedition -- known as dynamin and endophilin -- previously were known to be critical for this swallowing action. And, it turns out that Arc controls these two proteins and therefore controls how often cells swallow receptors from their surfaces. When the researchers altered Arc so that it was unable to bind these two proteins, cells were unable to "swallow" and wound up with more receptors than normal on their surfaces. Adding more Arc to cells caused the opposite to happen; the cells hyperactively swallowed up too many receptors, leaving few at the surface. Unfortunately, it's possible to over excite a cell to death, says Worley, and if the excitation controls come off, the strength of long term memory is altered. So what does Arc's control over brain cell receptors mean for our ability to remember where we put the car keys? "We know that animals lacking Arc live only in the here and now. They learn fine in the short term, but tomorrow they will need to relearn everything," says Worley. And in the case of long term memories that are better forgotten, such as that cigarette craving while sitting in a bar, a better understanding of how these memories form promises hope that there might be a way in the future to forget them entirely. Researchers were supported by grants from the National Institute of Mental Health, the National Institute of Deafness and Other Communication Disorders, the Howard Hughes Medical Institute and the Human Frontier Science Program Organization. Authors of the two papers are Shoaib Chowdhury, Jason Shepherd, Gavin Rumbaugh, Hiroyuki Okuno, Gregory Lyford, Jing Wu, Richard Huganir and Worley of Hopkins; Ronald Petralia of National Institute on Deafness and Other Communication Disorders at the National Institutes of Health; and Niels Plath and Dietmar Kuhl of Freie Universitat Berlin in Germany. |
| CHOCOLATE "OFFENDERS" TEACH SCIENCE A SWEET LESSON |
Some "chocoholics" who just couldn't give up their favorite treat to comply with a study to test blood stickiness have inadvertently done their fellow chocolate lovers - and science - a big favor. Their "offense," say researchers at Johns Hopkins led to what is believed to be the first biochemical analysis to explain why just a few squares of chocolate a day can almost halve the risk of heart attack death in some men and women by decreasing the tendency of platelets to clot in narrow blood vessels. "What these chocolate 'offenders' taught us is that the chemical in cocoa beans has a biochemical effect similar to aspirin in reducing platelet clumping, which can be fatal if a clot forms and blocks a blood vessel, causing a heart attack," says Diane Becker, M.P.H., Sc.D., a professor at the Johns Hopkins University's School of Medicine and Bloomberg School of Public Health. Becker cautions that her work is not intended as a prescription to gobble up large amounts of chocolate candy, which often contains diet-busting amounts of sugar, butter and cream. But as little as 2 tablespoons a day of dark chocolate - the purest form of the candy, made from the dried extract of roasted cocoa beans - may be just what the doctor ordered. Researchers have known for nearly two decades that dark chocolate, rich in chemicals called flavonoids, lowers blood pressure and has other beneficial effects on blood flow. The latest Johns Hopkins findings, to be presented Nov. 14 at the American Heart Association's annual Scientific Sessions in Chicago, identified the effect of normal, everyday doses of chocolate found in ordinary foods, unlike previous studies that found decreased platelet activity only at impractically high doses of flavonoids equivalent to eating several pounds of chocolate a day. "Eating a little bit of chocolate or having a drink of hot cocoa as part of a regular diet is probably good for personal health, so long as people don't eat too much of it, and too much of the kind with lots of butter and sugar," says Becker. In the study, 139 people Becker - whom Becker somewhat tongue in cheek calls "chocolate offenders" - were disqualified from a much larger study looking at the effects of aspirin on blood platelets. The Genetic Study of Aspirin Responsiveness (GeneSTAR) was conducted at johnd Hopkins from June 2004 to November 2005 and enrolled more than 500 men and 700 women participants nationwide. Shortly before aspirin dosing began for the subjects, they were told to stay on a strict regimen of exercise and to refrain from smoking or using foods and drinks known to affect platelet activity. These included caffeinated drinks, wine, grapefruit juice - and chocolate. The non-compliers - who admitted to eating chocolate - were a diverse group who got their flavonoid "fix" from a variety of sources, including chocolate bars, cups of hot cocoa, grapes, black or green tea, and strawberries. And while they were excluded from the aspirin study, Becker and her team scoured their blood results for chocolate's effect on blood platelets, which the body recycles on a daily basis. When platelet samples from both groups were run through a mechanical blood vessel system designed to time how long it takes for the platelets to clump together in a hair-thin plastic tube, the chocolate lovers were found to be less reactive, on average taking 130 seconds to occlude the system. Platelets from those who stayed away from chocolate as instructed clotted faster, at 123 seconds. In another key test of urine for waste products of platelet activity, primarily urinary thromboxane (11-dehydro-thromboxane B2), scientists found that chocolate eaters showed less activity and waste products on average, at 177 nanograms per millimol of creatinine, versus an average of 287 nanograms per millimol of creatinine in the group that abstained. Participants ranged in age from 21 to 80; 31 percent were black and the rest were white. In total, more than 200 different tests of platelet reactivity were performed and analyzed in the study. Because whole blood contains other cells that affect platelet aggregation, testing was repeated using a purified version of test samples made up of strictly platelet-rich plasma. None of the "offenders" had previous histories of heart problems, such as a heart attack, but all were considered to be at slightly increased risk of heart disease because of family history. Fifty percent of women participants were postmenopausal. "These results really bring home the point that a modest dietary practice can have a huge impact on blood and potentially on the health of people at a mildly elevated risk of heart disease," says study co-author Nauder Faraday, M.D., an associate professor at Johns Hopkins. "But we have to careful to emphasize that one single healthy dietary practice cannot be taken alone, but must be balanced with exercise and other healthy lifestyle practices that impact the heart." Besides Becker and Faraday, other investigators in this research were Lisa Yanek, M.P.H.; Taryn Moy, M.S.; and Lewis Becker, M.D. |
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| ADULT PIG STEM CELLS SHOW PROMISE IN REPAIRING ANIMALS' HEART ATTACK DAMAGE |
Johns Hopkins scientists have successfully grown large numbers of stem cells taken from adult pigs' healthy heart tissue and used the cells to repair some of the tissue damage done to those organs by lab-induced heart attacks. Pigs' hearts closely resemble those in humans, making them a useful model in such research. Following up on previous studies, Johns Hopkins cardiologists used a thin tube to extract samples of heart tissue no bigger than a grain of rice within hours of the animals' heart attacks, then grew large numbers of cardiac stem cells in the lab from tissue obtained through biopsy, and within a month implanted the cells into the pigs' hearts. With help from a blue-dye tracking system, the scientists have shown that within two months the cells had developed into mature heart cells and vessel-forming endothelial cells. "This is a relatively simple method of stem cell extraction that can be used in any community-based clinic, and if further studies show the same kind of organ repair that we see in pigs, it could be performed on an outpatient basis," says Eduardo Marbán, M.D., Ph.D., senior study author and professor and chief of cardiology at the Johns Hopkins University School of Medicine and its Heart Institute. "Starting with just a small amount of tissue, we demonstrated that it was possible, very soon after a heart attack, to use the healthy parts of the heart to regenerate some of the damaged parts." Marbán cautions that no overall improvements in heart function have yet been shown in these studies, which were not designed to establish such changes and used relatively low numbers of infused cells (10 million or less). "But we have proof of principle, and we are planning to use larger numbers of cells implanted in different sites of the heart to test whether we can restore function as well," he says. "If the answer is yes, we could see the first phase of studies in people in late 2007." The latest Johns Hopkins findings are scheduled to be presented Nov. 13 at the American Heart Association's annual Scientific Sessions in Chicago. They are believed to be the first results in animal studies to show that so-called cardiac stem cell therapy can be successfully applied with minimally invasive methods to circumstances closely resembling those in humans. Scientists say the results build on earlier studies with cardiac stem cells in mice and humans that demonstrated success in regenerating infarcted heart muscle and restoring heart cell function post-infarct. For the study, cardiac stem cells were extracted by tissue biopsy from eight pigs whose main arterial blood supply was tightened for more than two hours, duplicating the effects and damage caused by heart attack. Using techniques developed in Marbán's lab, researchers extracted about a million cardiac stem cells from undamaged heart tissue, growing them without the use of potentially dangerous chemical stimulators. After three weeks, the stem cells turned into spherical balls of cells that mimicked the electrical properties of heart muscle cells. The so-called cardiospheres yielded on average more than 14 million cells. Within a month after the initial heart attack, a catheter tube was inserted into an artery in the pig leg for infusing the cardiospheres. Previous research had shown that they would on their own migrate to the damaged zones of the heart. Marbán's team was able to confirm this because they had labeled the stem cells with a gene that codes for an enzyme producing a blue dye, which could be seen under a microscope. Months later, when researchers examined the hearts to see if any damaged tissue had been repaired, they found blue spots indicating where the stem cells had taken root. Closer examination of results revealed that stem cells had matured and grown in the border zones of the damaged area, where researchers suspect both dead and living tissue mingle and some blood supply remains. "The goal is to repair heart muscle weakened not only by heart attack but by heart failure, perhaps averting the need for heart transplants," says Peter Johnston, M.D., study author and a Reynolds Foundation postdoctoral cardiology research fellow at Johns Hopkins' Heart Institute. "By using a patient's own adult stem cells rather than a donor's, there would be no risk of triggering an immune response that could cause rejection." The studies were supported by the Donald W. Reynolds Foundation. Coauthors were Tetsuo Sasano, M.D.; Kevin Mills; Amr Youssef, M.B.B.Ch., M.Sc.; Mark Pittenger, Ph.D.; and Richard Lange, M.D. Marbán is also the Michel Mirowski, M.D., Professor of Medicine at Johns Hopkins and director of its Donald W. Reynolds Cardiovascular Clinical Research Center and the Institute of Molecular Cardiobiology. Johnston's work on this study was recently recognized at Johns Hopkins, on Oct. 26, with one of three Stanley L. Blumenthal Cardiology Research Awards. |
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