Abstract
BackgroundAberrant hyperactivation of epithelial proliferation, AKT signaling, and association with unopposed estrogen (E2) exposure is the most common endometrial cancer dysfunction. In the normal uterus, progesterone (P4) inhibits proliferation by coordinating stromal-epithelial cross-talk, which we previously showed is mediated by the function of Mitogen-inducible gene 6 (Mig-6). Despite their attractive characteristics, non-surgical conservative therapies based on progesterone alone have not been universally successful. One barrier to this success has been the lack of understanding of the P4 effect on endometrial cells.MethodTo further understand the role of Mig-6 and P4 in controlling uterine proliferation, we developed a Sprr2f-cre driven mouse model where Mig-6 is specifically ablated only in the epithelial cells of the uterus (Sprr2fcre+Mig-6f/f). We examined P4 effect and regulation of AKT signaling in the endometrium of mutant mice.ResultsSprr2fcre+Mig-6f/f mice developed endometrial hyperplasia. P4 treatment abated the development of endometrial hyperplasia and restored morphological and histological characteristics of the uterus. P4 treatment reduced cell proliferation which was accompanied by decreased AKT signaling and the restoration of stromal PGR and ESR1 expression. Furthermore, our in vitro studies revealed an inhibitory effect of MIG-6 on AKT phosphorylation as well as MIG-6 and AKT protein interactions.ConclusionsThese data suggest that endometrial epithelial cell proliferation is regulated by P4 mediated Mig-6 inhibition of AKT phosphorylation, uncovering new mechanisms of P4 action. This information may help guide more effective non-surgical interventions in the future.
Highlights
Aberrant hyperactivation of epithelial proliferation, AKT signaling, and association with unopposed estrogen (E2) exposure is the most common endometrial cancer dysfunction
These data suggest that endometrial epithelial cell proliferation is regulated by P4 mediated Mitogen-inducible gene 6 (Mig-6) inhibition of AKT phosphorylation, uncovering new mechanisms of P4 action
A decrease of stromal progesterone receptor (PGR) and Estrogen receptor α (ESR1) expression in Sprr2fcre+Mig-6f/f mice Previously, we reported that the hyperplastic phenotype of endometrial epithelial cell specific Mig-6 knockout (Sprr2fcre+Mig-6f/f; Mig-6d/d) mice were observed at 10 weeks of age [43]
Summary
Aberrant hyperactivation of epithelial proliferation, AKT signaling, and association with unopposed estrogen (E2) exposure is the most common endometrial cancer dysfunction. Progesterone (P4) inhibits proliferation by coordinating stromal-epithelial cross-talk, which we previously showed is mediated by the function of Mitogen-inducible gene 6 (Mig-6). Despite their attractive characteristics, non-surgical conservative therapies based on progesterone alone have not been universally successful. Progestin therapies used in the clinic are effective for some patients but not all cases of endometrial hyperplasia and well-differentiated endometrioid endometrial cancer Another major limitation of progestin therapy is the lack of a clinical standard protocol for the type, dose, and duration of treatment [11,12,13]. The molecular mechanisms underlying progesterone (P4) resistance in endometrial cancer have not been fully understood
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