Abstract
It is well known that the gene status of tumor suppressor p53 can determine the cell's fate. In fact, wild-type (wt) p53 cells were more sensitive to low-linear energy transfer (LET) radiation such as X-rays than mutated (m) p53 cells due to p53-dependent apoptosis. However, there is little information available on p53-dependent and -independent apoptosis following exposure to high-LET radiation from different types of heavy-ion beams. Therefore, we examined radiation-induced apoptosis in response to high-LET radiation in a human lung cancer cell line. The wtp53 or mp53 gene was transfected to the p53-null parental cells. The cells were exposed to X-rays or high-LET radiation using different nuclei ion-beams (C-beams, 13 KeV/µm; Ne-beams, 35 KeV/µm; Si-beams, 55 KeV/µm; Ar-beams, 85 KeV/µm; Fe-beams, 200 KeV/µm). We found that (i) there was no significant difference in cellular sensitivity to high-LET radiations (> 85 KeV/µm) among these cells, although the sensitivity of wtp53 cells to X-rays was higher than that of mp53 or p53-null cells; (ii) X-ray-induced apoptosis at higher frequencies in wtp53 cells when compared to mp53 and p53-null cells; (iii) Fe-beams induced efficiently apoptosis in a p53-independent manner. The present results indicate that high-LET radiation induces apoptosis in a p53-independent manner, and suggest that this radiation is useful to any types of p53-pacients in cancer therapy.
