Analysis Of DNA Cluster Damage Repair In Glioblastoma Cells Induced By Ionizing Radiation

Malignant gliomas include glioblastoma multiforme and anaplastic astrocytoma,of which glioblastoma（GBM,grade IV）is the most common and most malignant primary brain tumor in humans.GBM is characterized by rapid progression and diffuse invasion,so surgery can not be completely removed,and combined with high-dose conventional radiotherapy cannot also effectively prevent recurrence.At the same time,glioblastoma has a very strong DNA repair property,which makes it less beneficial to rely on DNA-induced death treatment,such as conventional radiation or temozolomide chemotherapy.As one of the most advanced therapeutic rays in particle radiotherapy,carbon ions can produce accurate ray energy deposition,lead to DNA cluster damage repair and induce large radiobiology damage,so it has potential therapeutic benefits.In this paper,the repair behavior of DNA cluster damage in glioblastoma cells induced by ionizing radiation was studied.In this study,U87 cells were divided into control group,X-ray and carbon ion irradiation group.U87 cells were irradiated with carbon ions of 2 Gy,4 Gy,6 Gy or X rays of 1 Gy,2 Gy,4 Gy,8 Gy and 16 Gy.Firstly,Monte Carlo damage simulation software（MCDS）was used to calculate the DNA damage induced by carbon ions.Then the proliferation and activity of the cells were detected by Brd U labeling method.DNA damage was analyzed by pulse field gel electrophoresis.Immunofluorescence assay was used to detect the dynamic recruitment levels of γH2AX and 53BP1 in the nucleus.Western Blot was used to detect the expression of key proteins in DNA damage repair.The results showed that carbon ions inhibited the proliferation and activity of U87 cells more than X-ray,and the mechanism might be related to the fact that the DNA cluster damage induced by carbon ions was mainly repaired by non-homologous terminal link（NHEJ）pathway.DNA damage caused by X-ray is repaired by homologous recombination（HR）and base excision repair（BER）.The changes of HR and BER repair proteins may be related to non-DSB clustered injury repair.This study elucidates the molecular mechanism of heavy ions irradiation overcoming the biological effects of radio-resistant of glioblastoma,it provides experimental basis for improving the radiation sensitivity of glioblastoma.