EukekAlert! reports on a mechanism that may reverse half of all cancers - assuming that the cancer cells don't promptly evolve their way around it, that is. "Researchers identified a precise threshold level of the signaling molecule Myc that determined the fate of tumor cells in a cancer of the immune system in mice. Above the threshold, high levels of Myc drove immune cells to grow too large and multiply uncontrollably. When the researchers lowered Myc levels below the threshold, the same cells shrank to normal size, stopped multiplying and began dying normally. ... But Myc is essential, at lower levels, for normal cell function. So, switching Myc all the way off is not an option for treating cancer. ... In the past, scientists have shown that cancer signals such as Myc are 'like light switches' [and the] idea that this is a threshold is really not the way we were all thinking ... We were able to experimentally prove that we can turn Myc off a little bit, or for a little time, and that's enough to have a profound effect on cancer."