The Myc oncogene can disrupt the 24-hour internal rhythm in cancer cells. Timing of the body's molecular clock in normal cells synchronizes the cellular need for energy with food intake during our sleep-wake cycle. Timing matters to the study of cancer in two ways. First, toxicity to some chemotherapy drugs is related to time of day. For example, a cancer drug called 5-flourouracil is less toxic if given to a patient at night because the liver enzymes that detoxify it are more abundant at night. Second, several circadian rhythm genes have been implicated as tumor suppressors, although those exact connections are as yet unclear. Other researchers have also observed that many, but not all, cancer cell cultures lack proper circadian rhythm. “Our hypothesis is that disrupting circadian rhythm benefits cancer cells by unleashing their metabolism from the constraints of the molecular clock,” says Altman. “In this regard, cancers don't sleep; they don't rest.” The Penn study deals with the relationship of clock proteins in peripheral tissues associated with three types of cancer cells. The researchers surmise that Myc may affect circadian rhythm by promiscuously binding to promoter regions in key genes for maintaining circadian rhythm. In fact, using a well known genome browser they confirmed that Myc binds to circadian genes.
…”This work ties together the study of cell metabolism and cancer chronotherapy – If cells don't have to 'rest,” they may replicate all the time, with no breaks at all. ” “The understanding of these basic mechanisms from our work should lead to better cancer treatment strategies that reduce side effects and increase effectiveness” says Hsieh.