Radiation-induced Delayed Microsatellite Instability in Human Normal Liver HL-7702 Cells

Key words: 
• heavy ion /
• radiotherapy /
• delayed effect /
• microsatellite instability /
• loss of heterozygosity

Abstract: Human normal liver cell line HL-7702 cells were irradiated with high linear energy transfer (LET) ¹²C⁶⁺ ions and low-LET X-rays, respectively. Delayed effect in terms of microsatellite instability (MSI) in progenies of the directly irradiated cells and bystander cells, obtained in the way of medium transfer at the 8th passage postirradiation,were examined. The delayed effect induced by the high-LET 12C6+ ions was different from that induced by the low-LET X-rays, and a higher incidence of MSI was observed in the progenies of the cells after exposure to the X-rays than to the ¹²C⁶⁺ ions. We also found that the delayed effect in the progenies of the bystander cells was much more severe than those
of directly irradiated cells. Furthermore, the events of MSI and loss of heterozygosity (LOH) induced by the ionizing radiations were not randomly distributed throughout the genome and specific loci existed indeed. These results imply that the radiation risk to normal tissues is lower in heavy ion therapy than in conventional X-ray radiotherapy, and the analysis of microsatellite loci with MSI high frequency occurrence can be applied to access long-term survival condition and second cancer risk for the patients after radiotherapy.