Genotoxic effects in M5 cells and Chinese hamster V79 cells after exposure to 7Li-beam (LET=60 keV/microm) and correlation of their survival dynamics to nuclear damages and cell death

Chinese hamster V79 cell and a cell strain M5, derived from V79 cells and reported to be relatively resistant to gamma-ray, hydrogen peroxide, and N-methyl-N-nitro-N-nitrosoguanidine (MNNG; a potent human carcinogen), were exposed to high LET (7)Li-beam (LET=60 keV/microm) at approximately 90% confluent state in the dose range of 0-1 Gy. Effects of (7)Li-beam exposure on cell survival, micronuclei induction (MN), chromosomal aberrations (CA) and apoptosis were compared in both the cell lines. A dose-dependent decline in survival for both the cell lines was noted, relatively less in M5 cells (mostly p<0.01) indicating greater radio-resistance in this strain. The MN, CA and apoptosis increased in a dose-dependent manner in both V79 and M5 cells. Significant differences in various other parameters between these two cell lines were also noted. The relative intensity of DNA ladder, which is a useful marker for the determination of the extent of apoptosis induction, was much higher in V79 cells. A good correlation between the reduction of the surviving fractions and the increase in frequencies of MN or CA or apoptosis was noted for both the cell lines.