Effect of dose-rate on induction of neoplastic transformation in vitro by low doses of 232 MeV protons

Abstract

Purpose: To determine the effect of dose-rate on induction of neoplastic transformation in vitro by low doses of 232 MeV protons.

Materials and methods: The experimental system used was the human hybrid cell assay. The dose-rates examined were 50 cGy/min and 20 cGy/h. The dose-rate 20 cGy/h was chosen as this is in the range of the maximum dose-rate that can be experienced in an unshielded space environment following a solar flare. At low dose-rate (LDR), doses from 0.5–100 cGy were studied. At high dose rate (HDR), the dose range was 0.5–200 cGy.

Results: The data indicated no significant differences between the two dose-rates at doses up to 100 cGy.

Conclusion: For the endpoint of neoplastic transformation in vitro, high dose-rate data may be sufficient to estimate low dose-rate effects (20 cGy/h) in the dose range up to 100 cGy from 232 MeV protons. The data are of relevance to risk estimation for space travel.

Keywords:

• adaptive response
• carcinogenesis
• dose-response curve

Acknowledgements

This research was supported by NASA Grant No. NNJ06HD90G and by the Phi Beta Psi Sorority. We thank Steven Rightnar and Peter Koss from the Loma Linda University High Energy Proton Facility for their vital support in providing dosimetry and beam delivery.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.