The response of human glioma cell lines to low-dose radiation exposure

Purpose: To examine the low-dose radiation response of a series of radioresistant human glioma cell lines and determine if low-dose hypersensitivity is a characteristic of these cells. Materials and methods: The clonogenic survival of six radioresistant human glioma cell lines was measured following exposure to graded, single, very low doses of X-rays in vitro. High resolution was achieved using either a Dynamic Microscopic Image Processing Scanner (DMIPS) or a cell sorter (CS). Results: In five of the six cell lines tested, low-dose hypersensitivity (HRS) was demonstrated although in the sixth, a grade III astrocytoma line, it was not. These results are consistent with previous data indicating that low-dose hypersensitivity is more marked in more radioresistant cell lines although the difference between the glioblastoma cell lines with differing SF2 is not marked. Conclusion: Low-dose hypersensitivity is common in radioresistant glioma cell lines. This may have implications for the treatment of these rumours if further studies confirm that HRS translates to increased effectiveness per gray in vivo when very low doses per fraction are used.