New research out of UCSD indicates that radiation therapy and many forms of chemotherapy actually may be promoting the progression of some cancers rather than halting or reversing the disease’s progression. The study, led by Yang Xu, an associate professor of biology, examined the p53 gene that is critical in suppressing cancer. When the gene was mutated, which it is in about half of all tumors, the cancer cell could lose the ability to “know” that its DNA has been damaged by a cancer treatment and therefore should die.

Xu says many cancer treatments kill cancer cells by inducing DNA breaks — cause enough breaks and the cells die. But 50 percent of human cancers carry the mutant version of the p53 gene, which blocks the sensation within the cell of the breaks. “Cancer treatments can potentially promote mutations,” says Xu, “and make the tumor harder to treat later on. More mutations within the cancer cell would allow them to grow faster and become more metastatic.”

As an outgrowth of his research, Xu expects doctors who treat cancer will be more careful with those that contain the mutant version of the p53 gene. “In the long run, maybe we can figure out a way to prevent the p53 mutant from blocking the sensing of the DNA damage,” he says.

The research originally was published online in early April in Nature Cell Biology and appears in the May print edition along with a commentary by an expert on the subject, Dr. Michael Kastan of St. Jude Children’s Hospital in Memphis. Kastan does not believe the newly discovered properties of p53 would lead to radiation resistance.

Along with Xu, other members of the research team included Hoseok Song, a postdoctoral fellow at UCSD, and Monica Hollstein, a collaborator at England’s University of Leeds.

— Tim McClain