Steroid hormone intervenes in the endometrial tumorigenesis of pten ablation

Abstract

Background: Endometrial cancer, the most common gynecological cancer, is closely associated with endometrial hyperplasia, unopposed estrogen exposure, and genetic alterations. Phosphatase and tensin homologue (PTEN) is a tumor suppressor genes completely lost or mutated in >50% of primary endometrioid endometrial cancers. Estrogen-dependent endometrioid carcinoma is the most common type of endometrial cancer. Progesterone is a hormone that antagonizes the growth-promoting properties of estrogen in the uterus. Progestin is used as a conservative endocrine treatment of early endometrial cancer in order to preserve fertility as well as a palliative measure for advanced-stage patients. Progesterone therapy has been shown to be effective in preventing endometrial cancer as well as controlling growth of the endometrium. However, the effectiveness of progestin for women with endometrial cancer is less clear.

Methods: In order to understand the effect of steroid hormone on endometrial cancer progression, we used a mouse endometrial cancer model with conditional loss of Pten in the mouse uterus (PR (cre/+) Pten (f/f) , Pten(d/d) ). To assess the effect of steroid hormones, ovariectomized Pten(f/f) and Pten(d/d) mice were treated with estrogen or progesterone over a period of three month.

Results: Uterine weight gain was significantly decreased in ovariectomized PR (cre/+) Pten(f/f) mice compared to intact PR (cre/+) Pten(f/f) mice. Ovariectomized PR (cre/+) Pten(f/f) mice treated with P4 or vehicle also exhibited decreased uterine cancer size compared with intact PR (cre/+) Pten(f/f) mice. Proliferation of ovariectomized PR (cre/+) Pten(f/f) mice treated with P4 is highly decreased compared to other groups. The levels of stromal progesterone receptor were highly increased in ovariectomized PR (cre/+) Pten(f/f) mice treated with P4 which resulted in decreased epithelial proliferation.

Conclusions: These results suggest that P4 treatment significantly reduces tumor mass but does not affect cancer progression in PR (cre/+) Pten(f/f) mice.

Keywords: Endometrial cancer; Estrogen; PTEN; Progesterone; Progesterone receptor.

Fig. 1.

Estrogen dependent formation of endometrial cancer in PR^cre+ Pten^f/f mice. (A) The ratio of uterine weight to body weight in intact and ovariectomized E2 treated PR^cre+ Pten^f/f mice (OVX E2). The results represent the mean±SEM. *P< 0.05, ^***P<0.001. (B) The uterine gross morphology of intact and ovariectomized E2 treated Pten^f/f mice (OVX E2) (a, b) and PR^cre+ Pten^f/f mice (c, d). (C) Estrogen (E2) treatment induces endometrial cancer development in Pten ablated mice uterus. Hematoxylin and eosin staining of intact and ovariectomized E2 treated Pten^f/f mice (OVX E2) (a, b) and PR^cre+ Pten^f/f mice (c, d).

Fig. 2.

Ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4) show a decrease uterine weight compared with intact. (A) The ratio of uterine weight to body weight in intact, ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4). The results represent the mean±SEM. **P<0.01, ^***P<0.001. (B) The uterine gross morphology of intact, ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4) (a–c) and PR^cre+ Pten^f/f mice (d–f). (C) Hematoxylin and eosin staining of intact, ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4) (a–c) and PR^cre+ Pten^f/f mice (d, e and f for low magnification; g, h and i for high magnification).

Fig. 3.

The regulation of proliferation and apoptosis in Pten ablated mice uterus after P4 treatment. (A) Immunostaining for phospho-histone H3 in intact, ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4) (a–c) and PR^cre+ Pten^f/f mice (d–f). (B) Quantification of phospho-histone H3 positive cells in epithelial cells. The results represent the mean±SEM. ^*P< 0.05, ^***P<0.001.

Fig. 4.

The expression of PR is recovered in PR^cre+ Pten^f/f mice after P4 treatment. (A) Immunohistochemical analysis of PR in the uteri of intact, ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4) (a–c) and PR^cre+ Pten^f/f mice (d–f). (B) Quantification of PR positive cells in stromal cells. The results represent the mean±SEM. *P<0.05, **P<0.01. (C) Immunohistochemical analysis of ERα in the uteri of intact, ovariectomized vehicle (OVX Veh) and P4 treated PR^cre+ Pten^f/f mice (OVX P4) (a–c) and PR^cre+ Pten^f/f mice (d–f). (D) Quantification of PR positive cells in stromal cells.