Protein Kinase C α Modulates Estrogen-Receptor-Dependent Transcription and Proliferation in Endometrial Cancer Cells

Roles of estrogen receptor α in endometrial carcinoma (Review)

Endometrial carcinoma (EC) is a group of endometrial epithelial malignancies, most of which are adenocarcinomas and occur in perimenopausal and postmenopausal women. It is one of the most common carcinomas of the female reproductive system. It has been shown that the occurrence and development of EC is closely associated with the interaction between estrogen (estradiol, E2) and estrogen receptors (ERs), particularly ERα. As a key nuclear transcription factor, ERα is a carcinogenic factor in EC. Its interactions with upstream and downstream effectors and co-regulators have important implications for the proliferation, metastasis, invasion and inhibition of apoptosis of EC. In the present review, the structure of ERα and the regulation of ERα in multiple dimensions are described. In addition, the classical E2/ERα signaling pathway and the crosstalk between ERα and other EC regulators are elucidated, as well as the therapeutic targeting of ERα, which may provide a new direction for clinical applications of ERα in the future.

The complexities of PKCα signaling in cancer

Protein kinase C α (PKCα) is a ubiquitously expressed member of the PKC family of serine/threonine kinases with diverse functions in normal and neoplastic cells. Early studies identified anti-proliferative and differentiation-inducing functions for PKCα in some normal tissues (e.g., regenerating epithelia) and pro-proliferative effects in others (e.g., cells of the hematopoietic system, smooth muscle cells). Additional well documented roles of PKCα signaling in normal cells include regulation of the cytoskeleton, cell adhesion, and cell migration, and PKCα can function as a survival factor in many contexts. While a majority of tumors lose expression of PKCα, others display aberrant overexpression of the enzyme. Cancer-related mutations in PKCα are uncommon, but rare examples of driver mutations have been detected in certain cancer types (e. g., choroid gliomas). Here we review the role of PKCα in various cancers, describe mechanisms by which PKCα affects cancer-related cell functions, and discuss how the diverse functions of PKCα contribute to tumor suppressive and tumor promoting activities of the enzyme. We end the discussion by addressing mutations and expression of PKCα in tumors and the clinical relevance of these findings.

Estrogen Enhances Endometrial Cancer Cells Proliferation by Upregulation of Prohibitin

Estrogen plays an essential role in type I endometrial cancer cell proliferation. Despite great progresses in the etiology has been obtained in the past, however, the molecular mechanisms remain to be fully clarified. Prohibitin has been demonstrated involvement in multiple cancers' development. If it also contributes to estrogen-driven endometrial cancer proliferation is not clear. IHC assay result display that prohibitin overexpressed in endometrial cancer tissue and associated with the poor prognosis; Western blot assay detect that upregulated prohibitin expression with dose- and time-dependent manners. The cellular growth was monitored with SRB assay which demonstrate that knockdown prohibitin attenuated estrogen-induced proliferation. Ubiquitination assay finds estrogen increased prohibitin level through stabilizing prohibitin protein via inhibition of ubiquitination, while estrogen-induced protein expression was mediated by estrogen receptor. Our findings provide a new insight on the mechanism of estrogen-induced proliferation, implying the possibility of using prohibitin as a potential therapeutic target for the treatment of endometrial cancer.

Estrogen promotes fat mass and obesity-associated protein nuclear localization and enhances endometrial cancer cell proliferation via the mTOR signaling pathway

Extensive exposure to estrogen is generally acknowledged as a risk factor for endometrial cancer. Given that the accumulation of adipocytes also contributes to the increased production of estrogen, in the present study, we evaluated the expression of the fat mass and obesity-associated (FTO) gene in endometrial tumor tissues and further explored the mechanism of how estrogen facilitates FTO nuclear localization and promotes endometrial cancer cell proliferation. Immunohistochemical (IHC) staining assay was used to detect the FTO expression in endometrial tumor samples. Western blotting was performed to investigate the mechanism of estrogen-induced FTO nuclear localization. siRNA was used to knock down ERα and further explore its role in FTO nuclear localization. MTT assay was carried out to determine cell proliferation. We found that FTO was overexpressed in endometrial carcinoma tissues and served as a poor prognostic marker. Additionally, estrogen induced FTO nuclear accumulation via the mTOR signaling pathway and the nuclear localization was ERα-dependent, which contributed to enhanced proliferative activity. Therefore, the present study provides new insight into the mechanisms of estrogen-induced proliferation, implying the possibility of using FTO as a potential therapeutic target for the treatment of endometrial cancer.