A new study in PLoS Genetics may explain why cancer cells seem "immortal," says Melissa Lee Phillips at the Nature News blog. While exploring the mitochondrial DNA of cancer cells, Jason Bielas and his colleagues at the Fred Hutchinson Cancer Research Center found that it was much less mutated than nuclear DNA. Since mitochondrial DNA contains genes necessary for the cell's metabolism, fewer mutations in the mitochondria may be beneficial to cancer cells' survival, Phillips says.
In previous research, Bielas and his colleagues found that there are 100 times as many de novo mutations in cancer cells as in healthy cells. But as this new study shows, "tumor cells contained an average of three times fewer new mutations than normal colon tissue," Phillips says. "The mutations found in healthy cells that seemed to be 'missing' from cancer cells were mainly C:G to T:A transitions — a type of mutation that results from oxidative damage." This made sense to the researchers because they say cancer cells shift from oxidative phosphorylation for their energy to anaerobic glycolysis, and this shift helps them avoid oxidative damage to their mitochondrial DNA. "The tumor mitochondria then function better than normal mitochondria, allowing the diseased cells to live indefinitely," Phillips says. Bielas tells her that this "may be a key factor in cancer cell immortality."