非p53依赖途径c-myc对乳腺癌细胞p21Cipl基因调控及细胞凋亡的影响

Effect of c-myc on p21Cipl and apoptosis of breast cancer cells via a p53,independent manner

目的观察非P53依赖途径突变型（T58A）与野生型c-myc（WT）对乳腺癌细胞P21cip1基因调控及细胞凋亡的影响。方法携带c-myc T58A与WT基因慢病毒表达载体分别感染乳腺癌细胞株HCC1937（细胞感染率为85% ）,未感染者及仅感染慢病毒者为A组（空白对照组）、B组（感染对照组），感染c-myc T58A及WT者为实验组C、D组。慢病毒P21cipl/SiRNA载体感染以上各组细胞，逆转录-聚合酶链反应（RT-PCR）和Western blot检测感染前后各组c-myc、P21cip1的mRNA和蛋白表达,原位末端转移酶标记（TUNEL）检测细胞凋亡。结果与A、B组比较，C组和D组c-myc过表达（P 〈0. 001）。感染前，C组P21CipI含量显著高于A、B、D组（P 〈 0. 001），D组P21Cipl含量最低（p〈0.01），C组细胞凋亡率显著低于A、B、D组,D组凋亡率最高，凋亡率：A组为（5.5 ±0.5）%、B 组为（5. 8 ±0.3）%、C 组为（2. 8 ±0.3）%、D 组为（9. 8 ±0.8）% （P 〈0.01）;感染后，各自组内凋亡率较前明显提高（P〈0.05）。结论非P53依赖途径中，野生型c-myc可通过下调P21eipl基因表达促进细胞凋亡，突变后（T58A）此功能减弱，诱导细胞凋亡能力降低。

Objective To investigate the effect of mutant （T58A） and wild type （ WT） c-myc onp21Clpl and apoptosis of breast cancer cells in a p53-independent way. Methods Lentiviral vectors contai-ning c-myc T58A and WT were transfected into breast cancer cells HCC1937 （ cell transfection rate exceeds85% ） . Untreated cells （ group A） and cells transfected by lentivirus without c-myc gene （group B） servedas blank control group and transfection control group respectively. Cells stably expressing c-myc T58A（group C） and WT （group D） served as experiment groups. All the cells were then transfected by p21Cipi/siRNA. RT-PCR and Western blotting were used to detect the mRNA and protein levels of c-myc andp21Cipl,and the apoptosis was examined by using TdT-mediated dUTP nick end labeling （TUNEL） . Re-sults As compared with groups A and B,the c-myc was overexpressed in groups C and D （ all p 〈0. 01 ） . Before transfection, the p21c,pl in group C was highest （P 〈0. 01 ）,while group D had the lowestexpression of p21Cipl （p 〈0. 01 ） ; the apoptosis rate in group C was lower than in other groups, and that ingroup D was the highest： （5. 5 ±0. 5）% , （5. 8 ±0. 3）% , （2. 8 ±0. 3）% and （9. 8 ±0. 8）% in groupsA,B,C and D, respectively （p 〈0.01）. After transfection, the apoptosis rate in all groups were im-proved obviously （P 〈0.05）. Conclusion Normally,in a non-p53 background,c-myc WT can suppressthe expression of p21c,pI,resulting in the increased apoptosis rate, but after mutation （T58A）,the abilityof c-myc to induce apoptosis is decreased.