摘要目的 研究抑制MDC1基因的蛋白表达对裸鼠移植瘤的影响,观察裸鼠肿瘤病理组织学和细胞生物学特征的变化.方法 根据MDC1 mRNA序列,设计合成3对有效的干扰序列和阴性对照序列,并与载体pSIH1-H1-copGFP形成重组质粒,RT-PCR和蛋白印迹法测定MDC1 mRNA和蛋白表达水平,筛选出阴性转染组(ECA109-N)、MDC1转染组(ECA109-M)细胞,将其接种裸鼠分为ECA109-M、ECA109-N、ECA109组,上述各组又分为60C0 γ射线照射组和未照射组.观察各组裸鼠移植瘤照射后体积变化,蛋白印迹法检测移植瘤组织中CHK1、CHK2、CHK2T68表达水平,流式细胞仪分析裸鼠肿瘤组织中细胞周期分布和细胞凋亡情况.多组样本均数间的比较采用方差分析,组间两两比较采用SNK-q检验.结果 成功构建pMDC1-shRNA质粒并转染ECA109细胞,获得稳定转染细胞ECA109-M.所有接种裸鼠均成活并在接种后1周左右可见裸鼠爪下形成移植瘤,各组之间肿瘤大小相近(P＞0.05).15Gy照射后单纯照射组和空载照射组裸鼠的肿瘤生长速度慢于未照射组(P＜0.05),其中MDC1转染联合照射组较阴性对照组和空白组肿瘤相对生长速率降低(P＜0.05),生长抑制率升高(P＜0.05).MDC1转染联合照射组q值为1.36.MDC1转染联合照射组裸鼠体内CHK1和CHK2的蛋白表达水平相近(P＞0.05),但CHK2T68磷酸化水平明显降低(P＜0.05),各组裸鼠肿瘤组织中细胞周期分布和凋亡细胞比例也相近(P＞0.05).结论 RNA干扰降低MDC1蛋白表达后可有效增强细胞的放射敏感性,表现为抑制了60Co γ射线照射后裸鼠移植瘤的生长速度.

abstractsObjective To investigate the effects of inhibition of MDC1 protein expression on xenografted tumors in nude mice,and to observe the histopathological and cellular changes in nude mice.Methods Three pairs of effective and control short hairpin RNA targeting MDC1 mRNA were designed and cloned into the pSIH1-H1-copGFP vector.Real-time PCR and Western blot were used to determine the mRNA and protein expression of MDC1.After selection by copGFP reporter gene,cells were divided into negative transfection group (ECA109-N) and MDC1 transfection group (ECA109-M).The transfected cells were injected into nude mice.The mice were divided into ECA109 group,ECA109-N group,and ECA109-M group.Each group was divided into irradiation subgroup and non-irradiation subgroup.The changes in tumor size after irradiation were evaluated in each group.Western blot was used to measure the expression of CHK1,CHK2,and CHK2T68 in xenografted tumors.Flow cytometry was used to analyze the cell cycle distribution and apoptosis of tumor cells in nude mice.The variance analysis was used to compare the mean of multiple groups,and the SNK-q test was used in the two two groups.Results The pMDC1-shRNA plasmid was successfully constructed and used to transfect ECA109 cells.ECA109-M cells were obtained by stable transfection with the recombinant plasmid.All inoculated nude mice survived with visible xenografted tumors at the underside of the paw in about one week.There was no swelling and wound in inoculation sites.There was no significant difference in tumor size between different groups (P＞0.05).The tumor growth in the ECA109 group and the ECA109-N group significantly slowed down after irradiation with a dose of 15 Gy (P＜0.05).Compared with the other two groups,the ECA109-M group had a significant smaller tumor size,significantly slower relative tumor growth,and significantly higher growth inhibition (all P＜0.05).The q value of the ECA109-M group was 1.36.In the ECA109-M group,there were no significant changes in the protein expression of CHK1 and CHK2 after irradiation (P＞ 0.05);however,the phosphorylation of CHK2T68 protein was significantly reduced after irradiation (P＜0.05).There were no significant differences in cell cycle distribution or the proportion of apoptotic cells in tumor tissue between the three groups (P＞0.05).Conclusions Inhibition of MDC1 protein expression by RNA interference can effectively inhibit the growth of xenografted tumors after irradiation in the nude mice by increasing their radiosensitivity.