A team of Harvard Medical School researchers has identified a protein that 10 percent of tumor cells use to attain an immortal state. By blocking the molecule, it may be possible to stop these cancer cells from proliferating. The approach might also be used as part of a two-pronged strategy to combat the remaining 90 percent of tumors, the researchers say. “This gives us a new drug target for cancer,” said David Sinclair, Harvard Medical School assistant professor of pathology. He and Haim Cohen, HMS research fellow in pathology, published their findings in March 2001.