Two common dietary molecules found in legumes and bran could protect DNA from the harmful effects of radiation, researchers from the University of Maryland report.
Inositol and inositol hexaphosphate (IP6) protected both human skin cells and a skin cancer-prone mouse from exposure to ultraviolet B (UVB) radiation, the damaging radiation found in sunlight, the team reported today at the American Association for Cancer Research Centennial Conference on Translational Cancer Medicine.
According to the researchers, inositol and IP6 could decrease the severity of side effects from radiation therapy, saving healthy cells while simultaneously increasing the potency of the treatment against cancer cells. Both molecules are potent antioxidants, the Maryland researchers say, capable of preventing reactive molecules from injuring DNA and turning cells cancerous.
“Both of these potent antioxidants have been shown to have broad-spectrum anti-tumor capabilities, and now our studies confirm the degree to which these molecules protect against the DNA-damaging effects of ionizing radiation,” said Abulkalam M. Shamsuddin, M.D., professor of pathology at the University of Maryland School of Medicine. “Radiation damage is radiation damage, regardless of the source, so there could also be a protective role for IP6 in any form of radiation exposure, whether it is from a therapeutic dose or from solar, cosmic or nuclear sources.”
While both inositol and IP6 are related to B vitamins, they are not considered essential dietary nutrients. In the 1980s, however, researchers discovered that these molecules, abundant within the hulls of seeds and grains, had definitive protective effects against colorectal cancer.
Inspired by reports of a clinical trial begun in 2001 at Clinical Hospital in Split, Croatia, which suggested IP6 enhanced the effectiveness of radiotherapy while lessening the side effects, Shamsuddin and his colleagues sought to investigate the extent of the protective properties of these molecules. With funding from IP-6 Research, Inc., a company formed by Shamsuddin, the researchers began a study to determine how human skin cells responded to UVB radiation when dosed with IP6.
Normally, cells permanently damaged by radiation undergo a genetically programmed process of cell suicide, called apoptosis. Shamsuddin reports that UVB-irradiated human keratinocytes, when treated with IP6, were more likely to survive. Untreated skin cells were more likely to undergo apoptosis, indicating that the DNA in those cells was damaged irreparably and fatally. According to Shamsuddin, the treated cells take an extended pause at the point in the cellular life cycle where innate mechanisms repair DNA before the cell divides.
“IP6 certainly has some interactivity with DNA, but how exactly it works to repair DNA is still something of a mystery. There are reports that IP6 binds with DNA repair molecule Ku to bring about the repair process,” Shamsuddin said. “More importantly, we still don't know how IP6 can appear to help healthy cells live while also enhancing the ability of radiation to kill cancer cells.”