Correlation between residual level of DNA double-strand breaks and the radiosensitivity of cancer cells / 中华放射医学与防护杂志

Objective To understand the variation of the DNA double-strand break rejoining capacity among different cultured cancer cell lines and the primary cancer cells from brain cancer patients,and to explore the predictor of radiotherapy responses of cancers. Methods DNA double-strand breaks (DSBs) were induced by 60Co γ-irradiation. Pulsed-field gel electrophoresis was used to analyze the initial production and rejoining of DNA DSBs. Radiosensitivity was determined by in vitro assay of clonogenic-forming capacity. Results A wide variation of radiosensitivity, e.g. The survival parameter of D0 varied from 0.65 to 2.15 Gy, was displayed among the eight cell lines derived from different type of cancers. Although differential level of initial DNA DSBs induced by 20 Gy γ-rays was observed among various cell lines, it was not correlated with the radiosensitivity. The deficiency of DNA DSB rejoining in radiosensitive cell lines was shown either in the early rapid-rejoining phase (SX-10 cells) or in the late slow-rejoining phase (A2780 cells). A significant relationship was observed between the residual level of DNA DSBs measured at 2 h post-20 Gy irradiation and the cellular radioseusitivity (D0 or SF2). The kinetic curves of rejoining DNA DSBs in the primary human brain tumor cells indicated a variation on DSB rejoining capacity among different individual tumor. The residual level of DNA DSBs after 2 h of rejoining post 20 Gy irradiation in primary human brain tumor cells is compatible to the results obtained in vitro culture cancer cell lines. Conclusions The residual level of DNA DSBs is correlated with radioresistance of cancer cells, and the residual DNA damage is a useful parameter in predicting the response of tumor tissue to radiotherapy.

Cell Senescence and the Enzyme System for Surveillanceand Repair of DNA Damage / 生物化学与生物物理进展

Senescence is one of the most important phenomena in cells' life. It is hold by one of hypothesis for cell senescence that residue DNA damages of a cell will accelerate its senescence.The normal function of surveillance and repair system for DNA damage is highly related with the senescence regulation of a cell. As a result, research of senescence regulation role of enzymes related for surveillance and repair of DNA damage, such as PARP, DNA-PK, ATM, p53, etc., will discover the inner relation between stress response of cell to DNA damage, regulation of DNA damage repair and cell senescence. That may be helpful for research of anti-aging and treatment of tumor by regulation of senescence of tumor cells.

Chromosome Location and Elongation of Radiation-induced Expressed Sequence Tag by the Aid of Bioinformatics / 生物化学与生物物理进展

Regulation of gene expression is one of the most importa nt responses of cells to DNA damage induced by radiation. A novel expressed seq u ence tag (EST) fragment had been cloned from human embryo lung cells induced by 50cGy radiation and named RIG1. To clone the full-length cDNA of RIG1, a non-c loned cDNA library of human embryo lung cells induced by low dose irradiation ha d been established. This library was used as template in enchanced nest RACE PCR and biotin-labeled probe was used for further purification. The 3′ flanking s equence of this EST was cloned and sequenced with this set of technology. It was illuminated by homology analysis that this 3′ flanking sequence and the origin al EST are well aligned with a BAC clone of 20th chromosome and the predic ted exons sequence of this chromosome is well consisten ce with the real EST. Thus the RIG1 can be roughly located in 20th chromos ome. By use of the exons sequence predicted from chromosome sequence by GENSCA N, full-length of RIG1 gene has been cloned. Chromosome location of RIG1 gene i s further determined by this successful verification of Bioinformatics predictio n by experiment. By the same step, genome sequence of RIG1 has been determined. Therefore,by the combined use of Bioinformatics analysis，the full-length cDNA sequence and genome sequence of RIG1 gene are obtained and the predicted protei n sequence is determined.

Effects of recombinant epidermal growth factor receptor antisense adenovirus combined with irradiation on breast cnacer cells / 中华放射肿瘤学杂志

Objective To investigate the effects of a recombinant antisense adeno virus for epidermal growth factor receptor (EGFR) combined with irradiation on b reast cancer cells.Methods Human EGFR cDNA fragment was subcloned in the oppos ite orientation to the cytomegaloviral promoter and inserted into a E1/E3-delet e d type 5 adenoviral vector to obtain AdE5 construct which expresses EGFR antisen se RNA. Combined with ?-ray irradiation, its effects on clonogenicity and cell cycle phase distribution were studied in a human breast cancer line MDA-MB-231 . Results EGFR protein expression was dramatically inhibited in MDA-MB-231 cell s after AdE5 infection. The post-irradiation clonogenicity was reduced by AdE5 in a viral and irradiation dose-dependent manner. Further cytometric analysis show e d that AdE5 infection at a?MOI of 300?pfu/cell induced a cell cycle progre ssion from radio-resistant G 0+G 1 phases to radiosensitive G 2+M phases, resultin g in a synergistic effect after combination of these two treatments. Conclusions The t ransduction of EGFR antisense RNA by adenoviral vector is effective for antisens e strategy targeting EGFR, and increases the cell-killing effect of ionizing radiation on breast cancer cells.