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Split-dose exposures versus dual ion exposure in human cell neoplastic transformation
Paula V Bennett1, Noelle C Cutter, Betsy M Sutherland
1Biology Department, Bldg 463, Brookhaven National Laboratory, Upton, NY 11973-5000, USA.
Radiation and Environmental Biophysics
|January 27, 2007
Summary
Space radiation, dominated by protons, significantly impacts human cell transformation. Low-dose proton exposure before high-energy particle exposure dramatically increases cancer induction risk in astronauts.
Area of Science:
- Space radiation biology
- Astrobiology
- Radiation oncology
Background:
- Space radiation comprises numerous protons and fewer high atomic number, high energy (HZE) particles.
- Astronauts are exposed to multiple proton hits before encountering HZE particles.
- Neoplastic transformation of human cells is a key early step in cancer induction.
Purpose of the Study:
- To investigate the impact of proton exposure preceding HZE particle exposure on human cell transformation.
- To differentiate between fractionated doses and mixed-beam irradiation effects.
- To determine if low-dose proton priming enhances HZE-induced transformation.
Main Methods:
- Human primary cells were irradiated with fractionated doses of protons or HZE particles.
- Clonogenic survival and neoplastic transformation (anchorage-independent growth) were measured.
- Cells were exposed to varying proton doses followed by HZE ions with a 15-minute interval.
Main Results:
- Fractionated doses (20 cGy + 20 cGy) of protons or HZE ions showed similar effects to a single 40 cGy dose, differing from mixed-beam irradiation.
- Proton doses as low as 1 cGy, followed by HZE ions, resulted in significantly greater than additive transformation frequencies.
- These findings highlight the critical role of protons in modulating HZE particle effects on human cells.
Conclusions:
- Proton priming is a critical factor in space radiation's effect on human cells.
- Even minimal proton exposure can substantially increase cancer induction risk when followed by HZE particle exposure.
- Understanding these interactions is vital for astronaut radiation protection strategies.
