Search

Follicle-stimulating hormone (FSH) and the FSH receptor contribute to tumor angiogenesis and are acknowledged risk factors for ovarian epithelial cancer (OEC). Accumulating evidence suggests that FSH can induce vascular endothelial growth factor (VEGF) and hypoxia inducible factor 1α (HIF1α) expression. We previously demonstrated that FSH induces reactive oxygen species (ROS) production and activates Nrf2 signaling. This study was performed to investigate whether FSH induces VEGF expression via a ROS-mediated Nrf2 signaling pathway. In the current study, OET cells were treated with FSH; dichlorofluorescein staining was used to determine ROS generation, western blotting was used to quantify Nrf2 expression and VEGF expression was measured using an ELISA. Nrf2 and HIF1α were knocked down using siRNAs to investigate the role of the Nrf2 and HIF1α signaling pathways in FSH-induced VEGF expression. The chromatin immunoprecipitation assay (ChIP) was used to determine HIF1α binding to the VEGF promoter. Finally, it was found that FSH induced ROS production and activated Nrf2 signaling; elimination of ROS or knockdown of Nrf2 blocked FSH-induced VEGF expression. Knockdown of Nrf2 impaired HIF1α signaling activation. Blockage of the FSH-ROS-Nrf2-HIF1α signaling pathway attenuated FSH-induced binding of HIF1α to the VEGF promoter. Collectively, this study indicates that ROS and aberrant expression of Nrf2 play an important role in FSH-induced angiogenesis in OEC, and provides insight into the mechanisms of FSH-induced VEGF expression. Elimination of ROS or inhibition of Nrf2 may represent potential therapeutic targets for the treatment of ovarian cancer.

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.

OCT4 plays a critical role in the maintenance of stem cell pluripotency and proliferation, and is overexpressed in multiple human tumors, including endometrial cancer. OCT4 expression can be modulated by miR-145 and the OCT4 pseudogene 5 (OCT4-pg5), which share similar binding sites in the OCT4 3'-untranslated region. The goal of the present study was to evaluate the interaction between miR-145 and OCT4‑pg5 on OCT4 expression in endometrial cancer. We assessed OCT4-pg5 expression in 14 benign endometrium and 29 endometrial carcinoma samples. Furthermore, miR-145 mimic transfection was performed to explore its effect on OCT4-pg5 and OCT4 expression, and small interfering RNA (siRNA)-mediated knockdown of OCT4 was conducted to determine whether the effect of OCT4-pg5 on cellular growth was OCT4-dependent. We observed that OCT4-pg5 was abnormally activated in the endometrial carcinomas, and that overexpression of OCT4-pg5 contributed to enhanced cell proliferation and OCT4-PI3K/AKT-cyclin D1 signaling. Moreover, the miR-145 mimic depleted OCT4 expression, whereas elevated OCT4-pg5 restored OCT4 expression and OCT4-PI3K/AKT-cyclin D1 signaling. In conclusion, these data indicate that OCT4-pg5 can act as an RNA sponge to protect OCT4 transcripts from being inhibited by miR-145, providing novel insight into the control of OCT4 expression.

High levels of gonadotropin are a risk factor for ovarian cancer development. Aberrant gonadotropin levels benefit tumor angiogenesis, but the detailed mechanism is not clear. Therefore, the aim of this study was to investigate the molecular mechanism of high levels of luteinizing hormone (LH) on the promotion of tumor angiogenesis and to outline a feasible therapeutic strategy. Western blotting and immunofluorescence staining were used to determine the effect of LH on VEGF and slit2 expression and examine the signaling pathway involved in regulating the expression of both molecules. Real-time PCR was used to investigate the effect of metformin on LH induction of VEGF and slit2 expression. It was found that 50 mIU/ml LH significantly upregulated VEGF and slit2 expression, and activated the PI3K/AKT-mTOR signaling pathway. However, metformin inhibited the mTOR signaling pathway and further blocked LH-induced VEGF and slit2 expression. In conclusion, high levels of LH promote angiogenesis in ovarian cancer via the PI3K/AKT-mTOR pathway. However, metformin could inhibit tumor angiogenesis by blocking the mTOR signaling pathway.

Aberrant nuclear factor-erythroid 2 (NRF2) expression correlates with tumor development. We investigated NRF2 expression in ovarian epithelial carcinoma (OEC), aiming to identify associations with clinicopathological factors, hormones and induced reactive oxygen species (ROS). Immunohistochemical staining for NRF2 expression was performed on 10 benign cystadenomas, 4 boderline tumors and 64 OECs. Western blotting was used to determine the effects of hormones on NRF2 expression in OEC. NRF2 protein was found to be overexpressed in OEC. Gonadotrophins and estrogen induced ROS production in OEC; these hormones also enhanced NRF2 expression. Therefore, aberrant expression may be induced by hormones through ROS signaling. Increased NRF2 expression may be a molecular event in OEC carcinogenesis.

To elucidate the mechanisms of nuclear estrogen receptor (ER)-mediated and G protein-coupled receptor 30 (GPR30)-mediated signaling in the regulation of proliferation in ER-positive and ER-negative endometrial cancer cells, two human endometrial carcinoma cell lines, Ishikawa (ER-positive) and KLE (ER-negative), were used. PCR and Western blot analyses were used to determine the effects of estrogen stimulation on the activation of Notch and GPR30-PI3K/AKT signaling. Cell growth was investigated using MTT assays. Overexpression of ER in ER-negative cells was achieved by plasmid transfection and was used to investigate the effects on cellular growth and Notch signaling. GPR30-mediated signaling was evaluated using siRNA interference. Estrogen stimulated cell proliferation in both cell lines, it activated Notch signaling in ER-positive Ishikawa cells, but not in ER-negative KLE cells. Blockade of this signaling by a Notch inhibitor resulted in partial arrest of estrogen-induced cell proliferation in Ishikawa cells. Overexpression of ER in KLE cells restored estrogen-enhanced Notch signaling and further promoted cell growth. GPR30, as a new G-protein-coupled estrogen receptor, was detected in both cell lines, but was stronger in ER-negative KLE cells. Depletion of GPR30 in KLE cells abolished estrogen-induced PI3K/AKT signaling activation and resulted in inhibition of cell proliferation. Conclusively, regulation of proliferation in nuclear ER-positive endometrial cancer cells is mediated by both ER-Notch signaling and GPR30-PI3K/AKT signaling, whereas only the latter pathway is involved in the regulation of growth in nuclear ER-negative endometrial cancer cells.

Ovarian clear cell adenocarcinoma (OCCA) is an aggressive ovarian malignancy with a poor prognosis. The role of estrogen receptor β (ERβ) in the development of OCCA remains to be clarified. To investigate the action of ERβ in the proliferation and invasion of OCCA cells, the ES-2 cell line was stably transfected with full-length human ERβ cDNA, and clones were screened and identified using RT-PCR and western blot assay. ERβ stable transfectants, referred to as ESβ1 and ESβ2 cells, were compared with mock transfectant ESVE and parental ES-2 cells with respect to their growth, motility and ability to activate target genes. ESβ1 and ESβ2 cells expressed ERβ mRNA and protein, whereas ES-2 and ESVE cells were ERβ negative. ERβ transfectants exhibited distinct characteristics from ES-2 and ESVE cells including proliferative properties and the ability to express cyclin D1 in the presence of 17β-estradiol (E2). ERβ inhibited ES-2 cell proliferation, which was determined using the MTT assay, BrdU labeling method and by the down-regulation of cyclin D1 gene expression. Moreover, exogenous ERβ expression resulted in a significant inhibition of ES-2 cell motility in an in vitro invasion assay. ERβ reduced the expression of MMP2 mRNA and the activity of MMP2 enzymatic activity in a ligand-dependent manner. In summary, ERβ may inhibit the proliferation and invasion of ES-2 cells and may be an important regulator in OCCA carcinogenesis.

Our previous study revealed that estrogen regulates nm23-H1 expression thus promoting cell migration-invasion via activating PIK3/Akt pathway. In this study, we explored the effect of hormone on hypoxia-inducible factor-1 (HIF-1alpha), a key factor in cancer invasion and metastasis, via activation of Akt signaling transduction pathway. We treated two ovarian cancer cell lines ES-2 and SKOV3 with 17beta-estradiol, methoxyprogesterone acetate (MPA) only, or hormone combined with and Akt, MAPK pathway inhibitor, or transefected with siRNA targeting Akt sequenced with hormone. Expression of HIF-1alpha was measured by Western blotting. We observed the effect of hormone on nm23-H1 expression after the cells were transfected by siRNA targeting HIF-1alpha or treated with CoCl2 to induce HIF-1alpha overexpression. The 17beta-estradiol increased HIF-1alpha expression in ovarian cancer cells, and this upregulatory effect was abrogated by Akt inhibitor LY294002 (P0.05) and Akt siRNA interference (P0.05), but not affected by MAPK inhibitor PD980059 (P0.05). MPA had the opposite effect. Nm23-H1 protein expression in ES-2 and SKOV3 cells were decreased after treatment with 17beta-estradiol (P0.05), whereas MPA had the opposite effect. The effect was attenuated by HIF-1alpha siRNA (P0.05) and enhanced by HIF-1alpha overexpression after CoCl2 treatment (P0.05). Our data suggest that estrogen and progestin regulate HIF-1alpha expression via Akt signaling pathway, affecting nm23-H1 expression in influencing cell metastasis.