Analysis of molecular mechanism in endometrial cancer development.

我们以前报道过雌激素受体α（ERα）的转录激活增强有助于[^<12>瓦尔] K-Ras介导的NIH 3 T3细胞转化。在激活的K-Ras 4 B突变体存在下，ERα显性失活突变体（DNER）使ERα功能性失活，将细胞周期阻滞在G 0/G1期，随后引起复制性细胞衰老，最终消除致瘤潜力。p21的p53依赖性上调与该细胞衰老诱导有关。响应DNER的MDM 2蛋白的改变解释了这种p21介导的细胞衰老诱导。致癌性K-Ras 4 B突变体显著增加与p53共沉淀的MDM 2蛋白，并抑制p53转录活性。反过来，DNER发挥其功能，减少MDM 2蛋白与p53共沉淀，随后刺激p53活性的致癌K-Ras 4 B突变体的存在。此外，野生型ERα在NIH 3 T3细胞中的过表达导致MDM 2蛋白水平的显著增加，并导致p53转录活性的抑制。最后，我们证明了c-Jun表达克服了DNER对p21蛋白水平的抑制和由此产生的增强。提示K-Ras 4 B突变体激活的ERα-AP 1通路可能通过MDM 2调节p53转录活性而参与NIH 3 T3细胞的转化。

We previously reported that enhanced transcriptional activation of estrogen receptorα(ERα) contributed to [^<12> Val] K-Ras mediated NIH3T3 cell transformation. Functional inactivation of ERα by a dominant negative mutant of ERα (DNER) in the presence of activated K-Ras 4B mutant arrested the cell cycle at G0/G1, subsequently provoking replicative cell senescence, finally abrogating tumorigenic potential. p53-dependent up-regulation of p21 was implicated in this cell senescence induction. Alterations in the MDM2 protein in response to DNER accounted for this p21-mediated cell senescence induction. An oncogenic K-Ras 4B mutant significantly increased MDM2 proteins coprecipitated with p53, and suppressed p53 transcriptional activity. In turn, DNER exerted its function to decrease MDM2 proteins coprecipitated with p53, followed by the stimulation of p53 activity in the presence of the oncogenic K-Ras 4B mutant. In addition, overexpression of wild type ERα in NIH3T3 cells resulted in the significant increase in the MDM2 protein level and the resultant suppression of p53 transcriptional activity. Finally, we demonstrated that c-Jun expression overcame the suppression and resultant enhancement of p21 protein level in response to DNER. The data imply that the ERα-APl pathway activated by oncogenic K-Ras 4B mutant contributes to the NIH3T3 cells' transformation by modulating p53 transcriptional activity through MDM2.