The synergistic effect of Mig-6 and Pten ablation on endometrial cancer development and progression

Ablation of Mig-6 in the murine uterus leads to the development of endometrial hyperplasia and estrogen-induced endometrial cancer. An additional endometrial cancer mouse model is generated by ablation of Pten (either as heterozygotes or by conditional uterine ablation). To determine the interplay between Mig-6 and the PTEN/PI3K signaling pathway during endometrial tumorigenesis, we have generated mice with Mig-6 and Pten conditionally ablated in progesterone receptor positive cells (PR(cre/+)Mig-6(f/f)Pten(f/f) ; Mig-6(d/d)Pten(d/d)). The ablation of both Mig-6 and Pten dramatically accelerated the development of endometrial cancer compared to single ablation of either gene. The epithelium of Mig-6(d/d)Pten(d/d) mice showed a significant decrease in the number of apoptotic cells compared to Pten(d/d) mice. The expression of the estrogen-induced apoptotic inhibitors Birc1 was significantly increased in the Mig-6(d/d)Pten(d/d) mice. We identified ERK2 as a MIG-6 interacting protein by co-immunoprecipitation and demonstrated that the level of ERK2 phosphorylation was increased upon Mig-6 ablation either singly or in combination with Pten ablation. These results suggest that Mig-6 exerts a tumor suppressor function in endometrial cancer by promoting epithelial cell apoptosis through the down-regulation of the estrogen-induced apoptosis inhibitors Birc1 and the inhibition of ERK2 phosphorylation.