Cell killing, nuclear damage and apoptosis in Chinese hamster V79 cells after irradiation with heavy-ion beams of 16O, 12C and 7Li

Chinese hamster V79 cells were exposed to high LET (linear energy transfer) 16O-beam (625 keV/μm) radiation in the dose range of 0–9.83 Gy. Cell survival, micronuclei (MN), chromosomal aberrations (CA) and induction of apoptosis were studied as a follow up of our earlier study on high LET radiations (7Li-beam of 60 keV/μm and 12C-beam of 295 keV/μm) as well as 60Co γ-rays. Dose dependent decline in surviving fraction was noticed along with the increase of MN frequency, CA frequency as well as percentage of apoptosis as detected by nuclear fragmentation assay. The relative intensity of DNA ladder, which is a useful marker for the determination of the extent of apoptosis induction, was also increased in a dose dependent manner. Additionally, expression of tyrosine kinase lck-1 gene, which plays an important role in response to ionizing radiation induced apoptosis, was increased with the increase of radiation doses and also with incubation time. The present study showed that all the high LET radiations were generally more effective in cell killing and inflicting other cytogenetic damages than that of low LET γ-rays. The dose response curves revealed that 7Li-beam was most effective in cell killing as well as inducing other nuclear damages followed by 12C, 16O and 60Co γ-rays, in that order. The result of this study may have some application in biological dosimetry for assessment of genotoxicity in heavy ion exposed subjects and in determining suitable doses for radiotherapy in cancer patients where various species of heavy ions are now being generally used.