沉默BMI-1基因对食管癌细胞裸鼠移植瘤体内放射增敏效应的影响

Effect of silencing BMI-1 gene on radiosensitization in transplanted tumors of nude mice with esophageal carcinoma in vivo

目的探讨沉默食管癌细胞BMI-1基因对裸鼠移植瘤放射敏感性的影响。方法将36只BALB/c/nu裸鼠随机分为6组:空白对照组、空白对照+照射组、空载组、空载+照射组、沉默BMI-1组、沉默BMI-1+照射组,每组6只。于裸鼠皮下接种ECA109食管癌细胞,构建裸鼠移植瘤模型,给予放射线照射1次3Gy,共5次。自接种后第14天开始,每2~3d测量1次移植瘤的最大径(a)和最短径(b),记录成瘤时间,计算肿瘤体积(ab2/2)。自首次照射24h后每组处死3只,qRT-PCR和免疫组织化学法分别检测各组裸鼠移植瘤组织中BMI-1、bcl-2、baxmRNA和蛋白表达,采用TUNEL法检测各组裸鼠移植瘤组织的凋亡情况;观察各组剩余裸鼠移植瘤照射后的生长情况和肿瘤体积变化。结果空白对照组与空载组裸鼠移植瘤生长速度最快,沉默BMI-1后移植瘤生长速度减慢,沉默BMI-1+照射组移植瘤生长速度最慢(P均<0.05)。照射后各组移植瘤的凋亡水平高于照射前(P均<0.01),照射前、照射后BMI-1沉默组移植瘤凋亡水平均高于空白对照组、空载组(P均<0.01)。照射前BMI-1沉默组细胞中BMI-1mRNA和蛋白的表达水平均低于空白对照组、空载组(P均<0.01),照射后这种趋势更明显。与空白对照组、空载组相比,照射前后BMI-1沉默组bcl-2mRNA和蛋白表达水平均下降,baxmRNA和蛋白表达水平均上调(P均<0.01)。结论沉默BMI-1基因有效增加了食管癌裸鼠移植瘤组织的放射敏感性,此与诱导细胞凋亡密切相关。

Objective To explore the effect of silencing BMI-1 on the radiosensitivity of esophageal cancer xenografts in nude mice.Methods Thirty-six male BALB/c/nu nude mice were randomly divided into 6 groups:the control group,control+irradiationgroup,NC group,NC+irradiationgroup,BMI-1 shRNA group,BMI-1 shRNA+irradiationgroup,with 6 in each.The esophagus cancer ECA109 cells were subcutaneously inoculated into the paw pads of mice in order to set up transplantation tumor models.The irradiated mice were given 3Gy irradiationeach time,for 5 times.The longest diameter and shortest diameter of transplanted tumor were measured every 2 to 3 days since the fourteenth day after inoculation,and we recorded and then calculated the tumor volume according to the formula.Three nude mice in each group were sacrificed at 24 h after irradiation,and the mRNA and protein expression of BMI-1,bcl-2,and bax in transplantation tumor tissues was measured by real-time quantitative PCR and immunohistochemical assay,respectively.Additionally,the apoptosis of transplantation tumor tissues was detected by TUNEL assay.The growth and tumor volume of the other nude mice in each group were observed.Results The tumor growth rate was the highest in the control group and NC group.Down-regulation of BMI-1 reduced the growth rate of xenografts and the tumor growth rate was the slowest after irradiation(all P<0.05).TUNEL assay revealed that the apoptosis rates in each group increased significantly after irradiation compared with that in the corresponding unirradiated groups(all P<0.01).Additionally,the apoptosis rates of tumor tissues in BMI-1 shRNA group were higher before and after irradiation than those of the control and NC groups(all P<0.01).In addition,the mRNA and protein expression of BMI-1 was significantly lower in the BMI-1 shRNA group than in the control and NC groups before irradiation(both P<0.01),and the tendency became more significant after irradiation.Compared with the control and NC groups,the mRNA and protein expression levels of bcl-2 were down-regulated in the BMI-1 shRNA group,whereas the bax mRNA and protein expression levels were up-regulated before and after irradiation(all P<0.01).Conclusion Silencing BMI-1 effectively increases the radiosensitivity of esophageal cancer xenografts in nude mice,which is closely related to inducing apoptosis of tumor cells.