Uterine Pgrmc2 Deficiency Attenuates Endometrial Hyperplasia and Cancer and Prolongs Lifespan in a Pten Loss-of-Function-Induced Cancer Model

Abstract

The expression of members of the progesterone receptor membrane component (PGRMC) family, particularly PGRMC1, is elevated in diverse types of cancers, particularly those of the female reproductive system. While xenograft tumor studies using human transformed cell lines in immunocompromised mice have suggested that PGRMC1 enhances tumor growth and chemoresistance, the exact role of members of the PGRMC family in cancer development in vivo remains unclear. In this study, we examined the effect of deleting Pgrmc2 on the development of endometrial hyperplasia and cancer using a murine phosphatase and tensin homologue (Pten) conditional loss-of-function model. We previously established that PGRMCs are cell survival factors that are required for normal estrogen-induced uterine epithelial cell proliferation and normal female fertility. The deletion of Pgrmc2 reduced the incidence and severity of endometrial hyperplasia and cancer in mice with conditional Pten-heterozygous uteri and increased lifespan in mice with conditional Pten-knockout uteri. Mechanistically, the deletion of Pgrmc2 decreased uterine glandular epithelial cell proliferation. Pten loss-of-function-induced endometrial hyperplasia and cancer elevated uterine inflammation, but this was not impacted by PGRMC2 deficiency. This study identifies PGRMC2 as a potential therapeutic target to be inhibited in the treatment of endometrial hyperplasia and cancer, particularly where PTEN activity is reduced due to gene mutation or loss.

Keywords: PGRMC1; PGRMC2; PTEN; cancer; endometrial; hyperplasia; progesterone; uterus.

Figure 1

Human endometrial PGRMC2 protein levels during the menstrual cycle and in endometrial cancer. (A) Localization of PGRMC2 (brown stain) in human endometrial stroma (black arrows) and epithelia (red arrows) collected during the proliferative and secretory phases of the menstrual cycle and endometrial (endo) cancer detected by immunohistochemistry. Lower panels show sections stained without primary antibody as a negative control. (B) Contingency plots comparing semi-quantitative h-score values for PGRMC2 in endometrial epithelial and stromal tissues. The h-score index ranges from low (blue) to high (orange). N = 10, scale bar = 100 µm.

Figure 2

Gross anatomy of female reproductive tracts and uterine histology. (A) Gross reproductive tract anatomy from Pten^+/fl; Pgrmc2^fl/fl (control), Pten^+/d, Pten^+/d; Pgrmc2^d/d, Pten^d/d, Pten^d/d, and Pten^d/d; Pgrmc2^d/d mice at one week after ovariectomy at 9 months of age. H&E-stained uterine cross-sections from (B) Pten^+/fl; Pgrmc2^fl/fl (control), (C) Pgrmc2^d/d, (D) Pten^+/d; Pgrmc2^d/d, and (E) Pten^d/d mice. N = 3–28. scale bar = 100 µm.

Figure 3

Endometrial hyperplasia and cancer in Pten^+/d and Pten^+/d; Pgrmc2^d/d mice. Uterine wet weight (A), incidence of hyperplasia (B), and incidence of endometrial cancer (C) are compared between Pten^+/d and Pten^+/d; Pgrmc2^d/d mice. n = 9 or 28.

Figure 4

Impact of Pgrmc2 ablation on Pten loss-of-function-induced cancer and lethality. (A) Comparison of normalized reproductive tract weight from Pten^d/d and Pten^d/dPgrmc2^d/d mice (p > 0.05). (B) Kaplan–Meier survival analysis comparing lethality of endometrial carcinoma in Pten^d/d and Pten^d/dPgrmc2^d/d mice. p ≤ 0.0001, n = 8–9.

Figure 5

Messenger RNA levels of the classical progesterone receptor (Pgr) and estrogen receptor alpha (Esr1) were measured by qPCR in Pten^+/fl; Pgrmc2^fl/fl, Pten^+/d, and Pten^+/d; Pgrmc2^d/d mice. n = 5.

Figure 6

Effect of Pten heterozygosity and Pgrmc2 ablation on endometrial epithelial cell mitosis in young and aged Pten^+/fl; Pgrmc2^fl/fl, Pten^+/d, and Pten^+/d; Pgrmc2^d/d mice. The marker phospho-histone H3 (phH3) was used to quantify mitosis in endometrial luminal and glandular epithelia in young ovariectomized sexually mature Pten^+/fl; Pgrmc2^fl/fl, Pten^+/d, and Pten^+/d; Pgrmc2^d/d mice treated with vehicle (veh, sesame oil) (A) or E2 (100 ng E2 for 2 days, 5 days without treatment, 50 ng E2, and tissue collection 18 h later) (B). (C) Quantification of basal mitosis in ovariectomized aged (i.e., 9 months) Pten^+/fl; Pgrmc2^fl/fl, Pgrmc2^d/d, Pten^+/d, and Pten^+/d; Pgrmc2^d/d mice. N = 3–4 per group, * p ≤ 0.05, ^# p = 0.07.

Figure 7

Uterine mast cell infiltration and degranulation in Pten^+/fl; Pgrmc2^fl/fl, Pten^+/d, and Pten^+/d; Pgrmc2^d/d mice. The total number of toluidine-stained mast cells (A) and degranulated mast cells (B) was determined in uterine histological sections from 9-month-old ovariectomized Pten^+/fl; Pgrmc2^fl/fl, Pten^+/d, and Pten^+/d; Pgrmc2^d/d mice. * p ≤ 0.05, n = 3.