'Space travel may up colon cancer risk'

Space travel may increase the risk of colon cancer, a new study led by Indian-origin scientists has warned.

Researchers, from Georgetown Lombardi Comprehensive Cancer Center, found that cosmic radiation impairs the ability of cells in the intestines of mice to eliminate oncogenic proteins, thus substantially increasing development of colorectal tumours.

The study funded by NASA is important because it might provide a direction for researchers in designing strategies to protect space travellers against increased cancer risk, said the scientists, Shubhankar Suman and Kamal Datta.

"While there is no reliable estimate of colorectal cancer risk from space radiation exposure, we have shown that exposure to cosmic radiation causes markedly increased intestinal tumours in mice," said Datta, an assistant professor in the department of biochemistry and molecular and cellular biology.

"These findings have implications for the health of astronauts undertaking exploratory missions into outer space and for future space tourists," he said in a statement.

"Our objective is to develop a risk estimate based on mouse model studies and to identify molecular mechanisms contributing to it, so that we can develop strategies to protect astronauts during long duration space missions, such as one to Mars," said Lombardi Fornace, director of the NASA programme at Georgetown.

Both researchers used specialised mutant mice to study the effects of 56Fe radiation, a highly ionising radiation prevalent in space.

"This radiation is considered the greatest challenge for space exploration. It deposits higher amount of energy in the body than does the gamma-/x-rays causing relatively higher DNA damage. This is believed to increase carcinogenic risk in astronauts, although accurate risk estimates are not yet available," said Datta.

Researchers also report that 56Fe radiation significantly increased colorectal cancer risk in mouse models of colorectal cancer through enhanced activity of beta-catenin, an oncogene that activates expression of pro-growth genes in the colon.

In his study, Datta reports that tumour formation in mouse intestines after exposure to cosmic radiation, unlike after exposure to gamma radiation, was dose dependent.

"Sustained exposure during prolonged space missions such as a mission to Mars and lengthy stays at the International Space Station may cause significant cosmic radiation dose accumulation in astronauts and thus remains a long-term health concern of space exploration," said Datta.