Genes & Cells

Why mosquitoes don’t get malaria, plus brain stem cells and hot cancer treatment in this week’s news

Gut bacteria: 1, malaria: 0 Malaria, meet your natural nemesis. Friendly bacteria living in mosquito abdomens kill off the parasites that cause malaria, a finding that may explain why pathogen-infected mosquitoes don’t get sick, U.S. and African researchers report in the May 13 Science . Malaria-causing Plasmodium parasites mature and grow in the guts of live mosquitoes. But microscopic helpers in the mosquitoes’ gut don’t let the parasites get too far. In lab studies, one type of Enterobacter impeded the disease-causing organisms’ development by close to 90 percent. The helpful bacteria secrete nasty juices that seem to break down the pathogen’s cellular machinery, researchers say. — Daniel Strain Disposable brain stem cells Brain stem cells subscribe to a philosophy of use it and lose it. Most stem cells can divide seemingly forever. But in the brain, stem cells divide only a few times before turning into star-shaped cells called astrocytes, a team of researchers from three universities reports in the May 6 Cell Stem Cell . So as a person or animal ages, there are fewer stem cells to replenish brain cells. Exercise and drugs such as Prozac stimulate new brain cell production without dipping into the stem cell pool. Harnessing that ability may help preserve stem cell reserves. — Tina Hesman Saey Warm tumor, hot mess Heating up tumors makes them more susceptible to some chemotherapy drugs. Now a team of researchers in the Netherlands and England show that heat helps disable tumor cells by throwing a wrench into the system cancer cells use to repair broken DNA. Warming mouse cells to a feverish 41 degrees Celsius (105.8 Fahrenheit) leads a repair protein called BRCA2 to degrade, the team reported online May 9 in the Proceedings of the National Academy of Sciences . Combining heat with a cocktail of chemotherapy drugs killed cancer more effectively in mice and rats than any of the treatments alone. — Tina Hesman Saey Exhaustion plagues immune cells in melanoma People with melanoma often have plenty of cancer-fighting white blood cells known as T cells, but their immune systems still fail to keep the deadly skin cancer in check. Now researchers in Lausanne, Switzerland, think they know why. T cells circulating in melanoma patients’ blood are raring to go, but ones in tumor cells that have spread around the body show chemical signs of exhaustion, the researchers report online May 9 in the Journal of Clinical Investigation . The finding may suggest ways to get T cells back in the fight. — Tina Hesman Saey

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