Simulated galactic cosmic radiation-induced cancer progression in mice

Prolonged manned space flight exposure risks to galactic comic radiation, has led to uncertainties in a variety of health risks. Our previous work, utilizing either single ion or multiple ion radiation exposure conducted at the NSRL (NASA Space Radiation Laboratory, Brookhaven, NY) demonstrated that HZE ion components of the GCR result in persistent inflammatory signaling, increased mutations, and higher rates of cancer initiation and progression. With the development of the 33-beam galactic cosmic radiation simulations (GCRsim) at the NSRL, we can more closely test on earth the radiation environment found in space. With a previously used lung cancer susceptible mouse model (K-ras^LA-1), we performed acute exposure experiments lasting 1-2 h, and chronic exposure experiments lasting 2-6 weeks with a total dose of 50 cGy and 75 cGy. We obtained histological samples from a subset of mice 100 days post-irradiation, and the remaining mice were monitored for overall survival up to 1-year post-irradiation. When we compared acute exposures (1-2 hrs.) and chronic exposure (2-6 weeks), we found a trend in the increase of lung adenocarcinoma respectively for a total dose of 50 cGy and 75 cGy. Furthermore, when we added neutron exposure to the 75 cGy of GCRsim, we saw a further increase in the incidence of adenocarcinoma. We interpret these findings to suggest that the risks of carcinogenesis are heightened with doses anticipated during a round trip to Mars, and this risk is magnified when coupled with extra neutron exposure that are expected on the Martian surface. We also observed that risks are reduced when the NASA official 33-beam GCR simulations are provided at high dose rates compared to low dose rates.