The endometrial lining of the uterine cavity is a highly dynamic tissue that is under the continuous control of the ovarian
steroid hormones,
estrogen and
progesterone. Endometrial
adenocarcinoma arises from the uncontrolled growth of the endometrial glands, which is typically associated with unopposed
estrogen action and frequently occurs in older postmenopausal women. The incidence of
endometrial cancer among younger women has been rising due to increasing rates of
obesity, a major risk factor for the disease. The
transforming growth factor β (TGFβ) family is a highly conserved group of
proteins with roles in cellular differentiation, proliferation, and
cancer. Inactivating mutations in the genes encoding the TGFβ
cell surface receptors (
TGFBR1/ALK5 and
TGFBR2) have been detected in various human
cancers, indicating that a functional TGFβ signaling pathway is required for evading
tumorigenesis. In this study, we present a mouse model with conditional inactivation of
activin receptor-like kinase 5 (ALK5) in the mouse uterus using
progesterone receptor cre ("Alk5 cKO") that develops endometrial
adenocarcinoma with
metastasis to the lungs. The
cancer and metastatic lung nodules are
estrogen dependent and retain
estrogen receptor α (ERα) reactivity, but have decreased levels of
progesterone receptor (PR)
protein. The endometrial
tumors develop only in Alk5 cKO mice that are mated to fertile males, indicating that TGFβ-mediated postpartum endometrial repair is critical for endometrial function. Overall, these studies indicate that TGFβ signaling through
TGFBR1/ALK5 in the endometrium is required for endometrial homeostasis,
tumor suppression, and postpartum endometrial regeneration.