Androgen-related expression of G-proteins in ovarian cancer

Abstract

BACKGROUND: Epidemiological and in vitro data implicate androgens in the aetiology of ovarian cancer, but the mechanisms by which this is mediated are unclear. In this study, we wished to examine the effects of androgens on gene expression in ovarian cancer. METHODS: The expression of androgen receptor (AR) in OVCAR3 and OSEC2 cells was confirmed using immunoblotting and response to androgens was measured using flow cytometric assessment of S-phase fraction. The differential gene expression between androgen stimulated and unstimulated OVCAR3 ovarian cancer cells was examined with a cDNA microarray. The upregulation of a subset of these genes was then confirmed with reverse transcriptase PCR in both OVCAR3 and OSEC2, an ovarian epithelial cell line. Finally, the clinical significance of this upregulation was investigated by examining the expression of Rab25 and Rab35, two G-protein-related molecules in an ovarian cancer tissue microarray (TMA). RESULTS: OVCAR3 and OSEC2 cells were shown to express the AR and showed an increase in S-phase fraction in response to androgen treatment. Treatment of OVCAR3 cells with androgen resulted in a significant upregulation of 121 genes. These findings were confirmed for a subset of seven monomeric G-protein-related genes in both OVCAR3 and OSEC2 cells. After staining for Rab25 and Rab35, the majority of TMA sections examined showed expression for Rab25 (92%) and Rab35 (95%). The expression of Rab25 correlated with histological grade, and expression was higher in endometrioid (median histoscore 10.5) than serous (7.5) or mucinous (5.3) tumours. The expression of Rab25 correlated positively with AR expression supporting its role as an androgen responsive gene in ovarian cancer. CONCLUSIONS: These results suggest that androgens can effect expression of the oncogenic GTPases in ovarian cancer. We propose that the androgen responsive Rab35 may have clinical importance as a biomarker of AR function.

Differential expression and phosphorylation of Pak1 and Pak2 in ovarian cancer: effects on prognosis and cell invasion

“…However, we did demonstrate a higher level of p-Pak2 Ser 20 in ovarian cancer cell lines and samples. Its corresponding phosphorylation site, Ser 21 , in Pak1 is responsible for facilitating Pak1 cycling between cytosol and membrane by negatively regulating the binding of Pak1 to Nck, leading to enhanced cell migration. 42 We also demonstrated that knockdown of Pak2 in ovarian cancer cell lines reduced cell migration and invasion.…”

Revisiting the Role of Antiandrogen Strategies in Ovarian Cancer

“…The GTPase Rab35, which is involved in vesicle trafficking, was the most upregulated gene following androgen stimulation. Using immunohistochemistry, Rab35 was expressed in the majority of ovarian tumors (95%) and its expression levels were correlated with those of AR, suggesting that Rab35 might be useful as a biomarker of AR function [49].…”

“…Microarray-based gene expression studies on EOC cell lines before and after androgen treatment were successful in identifying 121 genes that are significantly upregulated [49]. Among these genes, most of which regulate transcrip-tion, proliferation, and G-protein signaling, eight G-protein genes were validated using quantitative reverse transcription-polymerase chain reaction.…”

Steroid Hormones and Ovarian Cancer

“…Furthermore, in ovarian carcinoma cell lines, testosterone and androstenedione were found to increase cell viability, and induce telomerase activity which was blocked by PI3K inhibitors (Nourbakhsh et al, 2010). Sheach et al (2009) found that the ovarian cancer cell lines OVCAR3 and OSEC2 expressed the androgen receptor, and treatment with androgen upregulated 121 genes, including G-protein-related genes Rab25 and Rab35. Level of gene expression correlated with tumor grade as well.…”