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Archive - Mar 21, 2010

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Scientists Identify Gene for Lung Cancer in Never-Smokers

Variations in a gene called GPC5 have been identified which might contribute to a significantly higher risk of developing lung cancer in people who have never smoked. The findings, from genome-wide association studies to outline the genetic changes involved in lung cancer in never smokers, suggest that GPC5 might be a new target for investigation and drug development, and could be used to identify high-risk individuals. Lung cancer in people who have never smoked (defined as those who have smoked fewer than 100 cigarettes in their lifetimes) is an increasing public-health problem, responsible for 25 percent of all lung cancer cases worldwide. Despite attempts to identify the specific genetic mechanisms responsible, the causes of lung cancer in never-smokers have remained poorly understood. Recent studies have identified several candidate genes that have a moderate effect on the risk of lung cancer, but no study has identified the genetic basis of lung cancer in never smokers. "This is the first gene that has been found that is specifically associated with lung cancer in people who have never smoked," said the study's senior author, Mayo Clinic genetic epidemiologist Dr. Ping Yang. "What's more, our findings suggest GPC5 may be a critical gene in lung cancer development and genetic variations of this gene may significantly contribute to increased risk of lung cancer," she said. "This is very exciting. Findings from this study concern pure lung cancer that is not caused by smoking, and it gives us some wonderful new avenues to explore. Our suspicion all along is that this is a distinct disease, and that is why we undertook this study," Dr. Yang said.

New Ways to Kill Tuberculos Organism Discovered

Two novel ways to kill the bacterium (Mycobacterium tuberculosis) that causes tuberculoisis (TB) have been discovered by researchers at the Albert Einstein College of Medicine, together with collaborators. TB still kills an estimated 2 million people each year and the scientists believe that their findings could lead to a potent TB therapy and would also prevent resistant TB strains from developing. "This approach is totally different from the way any other anti-TB drug works," said Dr. William R. Jacobs, Jr., the study's senior author and professor of microbiology & immunology and of genetics at Einstein. "In the past few years, extremely drug-resistant strains of TB have arisen that can't be eliminated by any drugs, so new strategies for attacking TB are urgently needed." In searching for a new Achilles' heel for M. tuberculosis, Dr. Jacobs and colleagues focused on an enzyme called GlgE. Previous research had suggested that GlgE might be essential for the growth of TB bacteria. GlgE would also be an excellent drug target because there are no enzymes similar to it in humans or in the bacteria of the human gut. The GlgE research revealed a previously unknown enzymatic pathway by which TB bacteria convert the sugar trehalose (consisting of two glucose molecules) into longer sugar molecules known as alpha glucans, building blocks that are essential for maintaining bacterial structure and for making new microbes through cell division. GlgE was the third of four enzymes involved in this pathway leading to alpha glucans molecules. Sure enough, when the researchers inhibited GlgE, the bacteria underwent "suicidal self-poisoning"--a sugar called maltose 1-phosphate accumulated to toxic levels that damaged bacterial DNA, causing the death of TB bacteria grown in Petri dishes as well as in infected mice.

Nanoparticles Deliver Effective siRNAs to Tumor Cells

A California Institute of Technology (Caltech)-led team of researchers and clinicians has published the first proof that a targeted nanoparticle—used as an experimental therapeutic and injected directly into a patient's bloodstream—can traffic into tumors, deliver double-stranded small interfering RNAs (siRNAs), and turn off an important cancer gene using a mechanism known as RNA interference (RNAi). Moreover, the team provided the first demonstration that this new type of therapy, infused into the bloodstream, can make its way to human tumors in a dose-dependent fashion—i.e., a higher number of nanoparticles sent into the body leads to a higher number of nanoparticles in the tumor cells. These results demonstrate the feasibility of using both nanoparticles and RNAi-based therapeutics in patients, and open the door for future "game-changing" therapeutics that attack cancer and other diseases at the genetic level, said lead author Dr. Mark Davis, the Warren and Katharine Schlinger Professor of Chemical Engineering at Caltech. The scientific results are from an ongoing phase 1 clinical trial of these nanoparticles (image, Caltech/Derek Bartlett) that began treating patients in May 2008. Phase 1 trials are, by definition, safety trials; the idea is to see if and at what level the drug or other therapy turns harmful or toxic. These trials can also provide an in-human scientific proof of concept—which is exactly what is being reported in the current article. The current results were published online on March 21, 2010 in Nature. [Press release] [Nature abstract]

Study of Rare Genetic Disorder Suggests Role for Fibrillin-1 in Scleroderma

By studying the genetics of an autosomal dominant disorder called “stiff skin syndrome,” a rare congenital form of scleroderma, researchers at the Johns Hopkins University School of Medicine and collaborating institutions have learned more about the much more common acquired form of scleroderma, also called systemic sclerosis. Systemic sclerosis affects approximately one in 5,000 people and leads to hardening of the skin, as well as to other debilitating and often life-threatening problems. “[Acquired] scleroderma is a common and often devastating condition, yet its cause remains mysterious. My greatest hope is that this work will facilitate the development of new and better treatments,” said senior author Dr. Harry C Dietz, the Victor A. McKusick Professor of Genetics and Director of the Johns Hopkins William S. Smilow Center for Marfan Syndrome Research. Acquired scleroderma generally affects previously healthy young adults, causing scarring of skin and internal organs that can lead to heart and lung failure. “Most often individuals with [acquired] scleroderma do not have other affected family members, precluding use of genetic techniques to map the underlying genes. Instead, we turned to a rare but inherited form of isolated skin fibrosis called “stiff skin syndrome,” hoping to gain a foothold regarding cellular mechanisms that might prove relevant to both conditions,” said Dr. Dietz. A number of clues led Dr. Dietz and his team to strongly suspect a role for the connective tissue protein fibrillin-1 in these skin conditions. First, excess collagen is a hallmark feature of both stiff skin syndrome and acquired scleroderma.