Activation of estrogen receptor α by estradiol and cisplatin induces platinum-resistance in ovarian cancer cells.

Activation of Estrogen receptor (ER) α (α) promotes cell growth and influences the response of cancer cell to chemotherapeutic agents. However, the mechanism by which ERα activation antagonizes cells to chemotherapy-induced cytotoxicity remains unclear. Here, we investigated the effect of cisplatin on ERα activation. In addition, we examined whether down-regulation of ERα modulate cisplatin-mediated cytotoxicity using 2 human ovarian cancer cells (Caov-3 and Ovcar-3) transduced with ERα short hairpin RNA (shRNA). The proliferation assay showed that 17ß-estradiol (E2) induced cell proliferation via activation of Akt and extracellular signal-regulated kinase (ERK) cascades, while shRNA mediated downregulation of ERα inhibited the cell proliferation. Immunoblot analysis revealed that cisplatin induced the phosphorylation of ERα at serine 118 via ERK cascade. Luciferase assay showed that cisplatin increases transcriptional activity of estrogen-responsive element (ERE). The E2-stimulated ERα activation attenuated cisplatin-induced cytotoxicity. Meanwhile, down-regulation of ERα inhibited E2-induced protective effect on cisplatin toxicity as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Moreover, Pretreatment with E2 followed by cisplatin decreased the expression of cleaved PARP, and increased the expression of anti-apoptotic protein Bcl-2. Collectively, our findings suggest that activation of ERα by E2 and cisplatin can induce platinum-resistance by increasing the expression of anti-apoptotic protein in ovarian cancer cells. Therefore, our findings provide valuable information that ERα might be a promising therapeutic target for platinum-resistant ovarian cancer.

The Wilms' Tumor Gene WT1 - 17AA/- KTS Splice Variant Increases Tumorigenic Activity Through Up-Regulation of Vascular Endothelial Growth Factor in an In Vivo Ovarian Cancer Model.

The Wilms' tumor 1 gene WT1 encodes a zinc transcription factor involved in a variety of cancer-related processes. In this study, we sought to investigate the effects of WT1 splice variants on tumorigenic activity and survival in an in vivo ovarian cancer model. To this end, we established stable ovarian cancer cell lines transduced with lentiviral constructs containing each of the four WT1 splice variants (- 17AA/- KTS, + 17AA/- KTS, - 17AA/+ KTS, and + 17AA/+ KTS). In mice inoculated intraperitoneally with SKOV3ip1 cells expressing WT1 - 17AA/- KTS, disseminated tumor weights and production of ascites were significantly increased compared with those in mice inoculated with cells expressing the control vector. The overall survival in mice inoulated with WT1 - 17AA/- KTS-expressing cells was significantly shorter than that in mice inoculated with control cells (P = .0115). Immunoblot analysis revealed that WT1 - 17AA/- KTS significantly increased the expression of vascular endothelial growth factor (VEGF) compared with the control. Greater numbers of CD31-immunopositive vessels were observed in tumors from mice injected with cells expressing WT1 - 17AA/- KTS than in tumors from control mice. Finally, WT1 - 17AA/- KTS significantly increased tumor microvessel density compared with that in the control (P < .05). Treatment with anti-VEGF antibody (bevacizumab) inhibited tumor growth, dissemination, and ascites production in mice injected with cells expressing WT1 - 17AA/- KTS. The overexpression of WT1 - 17AA/- KTS induced a more aggressive phenotype in ovarian cancer cells through VEGF up-regulation in an in vivo ovarian cancer model. Our findings indicated that WT1 - 17AA/- KTS enhanced tumorigenic activity and could decreased patient survival through up-regulation of VEGF expression in ovarian cancers.

High levels of Wilms' tumor 1 (WT1) expression were associated with aggressive clinical features in ovarian cancer.

AIM: The aim of the present study was to evaluate the correlation between WT1 expression levels and clinical features, to investigate the prognostic value of WT1 expression and to use lentiviral constructs to examine whether overexpression of WT1 affects cell proliferation and invasion in ovarian cancer patients. MATERIALS AND METHODS: Real-time quantitative PCR (qPCR) methods were employed to analyze WT1 expression levels in clinical samples from 63 patients with ovarian cancer. The correlation between the copy number of WT1 mRNA and clinical variables was analyzed. RESULTS: The median copy number of WT1 mRNA was 53.94 (range=2.135-32,257) in all subjects and WT1 expression levels were found significantly increased in patients with a higher stage cancer (p<0.05), lymphnode (p<0.001) and omentum metastasis (p<0.001), as well as ascites production (p<0.05), compared to patients lacking these clinical variables. No significant difference in WT1 expression levels were observed between patients with and without recurrence. The median disease-free survival time in patients with low WT1 expression levels was significantly longer (p=0.038) than that in patients with high WT1 expression. However, overall survival curves showed no statistically significant (p=0.457) differences between patients with high- and low-WT1 expression levels. An in vitro study revealed that WT1 over-expression enhanced cell proliferation and invasion in ovarian cancer cells transduced with lentiviral constructs. CONCLUSION: Using qPCR, we found that high levels of WT1 expression correlated with aggressive clinical features in ovarian cancer. High WT1 expression may impact on median disease-free survival in ovarian cancer.

Non-sex cord-stromal ovarian tumors frequently produce and secrete estrogen in postmenopausal women: impact on bone metabolism and abnormal endometrial histology.

OBJECTIVE: We investigated whether the estrogen released from non-sex cord-stromal ovarian tumors has biological effects on bone and endometrial tissue in postmenopausal women. MATERIALS AND METHODS: A total of 132 patients with malignant (n = 112) or benign (n = 20) gynecological disease with normal postmenopausal ovaries were recruited as a control group (group C). The 75 patients with ovarian tumors were divided into 2 groups: group L (serum estradiol [E2] level of < 20 pg/ml; n = 42) and group H (serum E2 level of > 20 pg/ml; n = 33). The subjects' serum E2 levels, bone mineral density, urinary levels of the N-telopeptide of type I collagen, and serum levels of bone-specific alkaline phosphatase were measured before and after surgery. Histological examinations of the endometrium were carried out in the 75 patients with non-sex cord-stromal ovarian tumors. RESULTS: High serum E2 levels were detected in 33 (44%) of 75 patients with ovarian tumors. The serum E2 levels of group H were significantly decreased after surgery. In the other subjects, there were no significant differences between the serum E2 levels observed before and after surgery. The mean preoperative N-telopeptide of type I collagen and bone-specific alkaline phosphatase levels of group H were significantly lower than those of group C. The bone mineral density values of groups L and H were significantly decreased after surgery. Five (6.7%) of 75 patients with non-sex cord-stromal ovarian tumors displayed abnormal endometrial histology, including 4 patients with grade 1 endometrioid cancer. CONCLUSIONS: The E2 released from ovarian tumors might have biological effects on bone metabolism and the incidence of abnormal endometrial histology.