Analysis of molecular mechanism in endometrial cancer development.

我们之前报道过雌激素受体α(ERα)的转录激活增强有助于K-Ras介导的NIH3T3细胞转化[^<12> Val]。在活化的K-Ras 4B突变体存在的情况下，ERα显性负突变体（DNER）使ERα功能失活，使细胞周期阻滞在G0/G1，随后引发复制性细胞衰老，最终消除致瘤潜能。p53依赖性的p21上调与细胞衰老诱导有关。MDM2蛋白对DNER反应的改变解释了p21介导的细胞衰老诱导。一个致癌的K-Ras 4B突变体显著增加MDM2蛋白与p53共沉淀，抑制p53的转录活性。反过来，DNER发挥其功能，减少与p53共沉淀的MDM2蛋白，随后在致癌的K-Ras 4B突变体存在下刺激p53活性。此外，野生型ERα在NIH3T3细胞中过表达，导致MDM2蛋白水平显著升高，进而抑制p53转录活性。最后，我们证明了c-Jun的表达克服了p21蛋白水平在DNER反应中的抑制和增强。这些数据表明，致癌K-Ras 4B突变体激活的ERα-APl通路通过MDM2调节p53的转录活性，从而促进了NIH3T3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.