Objective To explore the potential relationship of the radiation-induced mitochondrial DNA A 977 base pairs(mtDNA A 977 bp) deletion and the radiosensitivity of tumor cell lines. Methods The surviving fraction(SF) and the ratio of mtDNA A 977 bp deletion were determined by clone forming assay and nested polymerase chain reaction(PCR) technique respectively after tumor cells of Hela, HepG2 ,EC-9706 and PC-3 were irradiated by various doses of X-ray radiation from 0 Gy to 8 Gy. Results The de-scending order of the four tumor cell lines radiosensitivities were the Hela, HepG2 ,EC9706 and PC-3 cells. The radiation-induced mtDNA A 977 bp deletion were detected after 1 Gy irradiated in Hela cells and 2 Gy irradiated in HepG2 ,EC-9706 and PC-3 cells. The deletion rate of the four tumor cell lines had no significant difference at 1 Gy(P>0. 05) ;but the deletion rate of Hela cells was significantly higher than that of the other tumor cell lines at 2 Gy(P<0. 01) ;at A Gy and 8 Gy,the deletion rate of Hela cells was significantly higher than that of the other tumor cell lines(P<0. 05) ,and the deletion rates of HepG2 and EC-9706 cells were high-er significantly than that of PC-3 cells(P<0. 01). There were negative corralations between the SF and the deletion rates in Hela, HepG2 and EC-9706 cells(r= - 0. 951,P<0. 05;r=-0. 976,P<0. 01;r= -0. 986,P<0. 01). Conclusion The ratio of mtDNA A 977 bp deletion may be an biological marker to predict the radiosensitivity of tumor cells.%目的 探讨肿瘤细胞经X线照射后线粒体DNA 4 977 bp缺失率与存活分数的潜在关系.方法 选用人宫颈癌细胞系(Hela细胞)、人肝癌细胞系(HepG2细胞)、人食管癌细胞系(EC-9706细胞)和人前列腺癌细胞系(PC-3细胞)4种肿瘤细胞系,经0 Gy到8 Gy X线照射后,采用克隆形成法测得存活分数,巢式PCR法检测线粒体DNA 4 977 bp缺失率.结果 肿瘤细胞放射敏感性由高到低依次是Hela细胞、HepG2细胞、EC-9706细胞和PC-3细胞.Hela细胞经1 Gy X线照射后,HepG2细胞、EC-9706细胞和PC-3细胞经2 Gy X线照射后均检测到线粒体DNA 4 977 bp缺失.1 Gy X线照射后,4种细胞线粒体DNA 4 977 bp缺失率比较,差异无统计学意义(P>0.05);2 Gy X线照射后,Hela细胞线粒体DNA 4 977 bp缺失率高于其余3种细胞(P<0.01);4 Gy和8 Gy X线照射后,Hela细胞线粒体DNA 4 977 bp缺失率高于其余3种细胞(P<0.05),HepG2细胞和EC-9706细胞线粒体DNA 4 977 bp缺失率高于PC-3细胞(P<0.01).Hela细胞、HepG2细胞和EC-9706细胞的存活分数和缺失率之间呈负相关(r=―0.951,P<0.05;r=―0.976,P<0.01;r=―0.986,P<0.01).结论线粒体DNA 4 977 bp缺失可能是一个反映肿瘤细胞放射敏感性的生物标记.
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