苯巴比妥促癌过程中细胞凋亡与bcl-2和bax mRNA表达的变化

APOPTOSIS AND EXPRESSION OF bcl-2 AND bax mRNA OF RAT LIVER DURING CANCER PROMOTION BY PHENOBARBITAL

目的研究苯巴比妥(PB)促肝癌过程中细胞凋亡与相关基因bcl-2和bax mRNA表达,探讨PB促肝癌的分子机制。方法建立大鼠肝癌启动/促进模型,采用TUNEL法检测促癌过程中肝细胞凋亡,提取总RNA用RT-PCR检测bcl-2和bax mRNA在促癌过程中的表达。结果经DEN启动诱发的大鼠肝癌前病灶细胞凋亡率显著高于正常组。高、低剂量PB组和启动组随时相点延长细胞凋亡率降低,且各时相点间凋亡率差异显著(P<0.05)。经DEN启动的各组(高、低剂量组和启动对照组)bcl-2 mRNA表达显著高于正常对照组,高剂量组随时相点延长bcl-2 mRNA表达呈增高趋势。经启动处理的各组bax mRNA表达高于正常对照,高剂量组baxmRNA表达随时间延长而降低。结论在促癌阶段,促癌物PB能抑制凋亡,诱导抗凋亡基因bcl-2 mRNA表达上调和促凋亡基因bax mRNA表达下调,提示凋亡抑制可能是促癌的机制之一。

Objective To study the apoptosis and expressions of apoptosis - related genes bcl - 2, and bax mRNA of rat liver during cancer promotion by phenobarbital（PB）, and to explore the molecular mechanism of cancer promotion. Methods The rat liver initiating - promotion model was established. Apoptosis was detected by terminal - deoxynucleotidyl- transferase- mediated nick end labeling （TUNEL）. Total RNA was extracted and the expression of bcl - 2, and bax mRNA were measured using RT - PCR. Results The rate of apoptosis of rat liver precancerous hyperplastic foci followed by diethyl nitrosamine （DEN） treatment was significantly higher than that of normal control group. As time increased, the apoptosis rate was significantly decreased in both high and low dose groups treated with PB （ P 〈 0.05, P 〈 0.01）. The expression of bcl - 2 mRNA, and bax mRNA in all initated groups（including high - dose, low- dose, single - initiation group） were significantly higher than in normal control group. The expression of bcl - 2 mRNA in high - dose group tended to increase as time point increased. The expression of bax mRNA in high - dose group was decreased as time point increased. Conclusion Phenobarbital might suppress apoptosis by inducing bcl - 2 mRNA up - regulation, and bax mRNA down - regulation suggesting that suppression of apoptosis may be one of the mechanism of cancer promotion.