Recent developments in ovarian cancer genetics

CYR61 overexpression associated with the development and poor prognosis of ovarian carcinoma

Cysteine-rich 61 (CYR61) has been proven to be an oncogene with potential predictive and prognostic implications in a variety of human cancers. However, the expression pattern of CYR61 and its role in ovarian carcinoma remains largely unknown. In this study, the mRNA and protein levels of CYR61 in normal ovaries and ovarian carcinoma tissues were evaluated using reverse transcription-polymerase chain reaction, immunohistochemistry, and Western blotting. Compared to normal ovarian tissues, the mRNA and protein levels of CYR61 were significantly higher in ovarian carcinoma tissues. Moreover, receiver operating characteristic (ROC) curve analysis, Spearman's rank correlation, Kaplan-Meier plots, and the Cox proportional hazards regression model were used to investigate the potential association of the CYR61 protein with the development of ovarian carcinoma in an ovarian carcinoma cohort. Based on ROC curve analysis, high expression of CYR61 was defined as a tumor in which more than 70 % of cells were positively stained. Based on this cutoff value, high expression of CYR61 was detected in 51.5 % of invasive carcinomas, 35.3 % of borderline tumors, 25.9 % of cystadenomas, and 20 % in the normal ovaries. In ovarian carcinomas, CYR61 overexpression was associated with advanced FIGO stage. Univariate survival analysis on the ovarian carcinoma cohorts showed that overexpression of CYR61 was associated with poor survival of ovarian cancer patients. Multivariate analysis suggested that the protein level of CYR61 was an independent and significant prognostic factor for ovarian carcinoma. Our results suggest that the CYR61 protein is an important and independent biomarker for prognostic implications of ovarian carcinoma.

Rab5a overexpression promoting ovarian cancer cell proliferation may be associated with APPL1-related epidermal growth factor signaling pathway

Rab5a is a regulatory guanosine triphosphatase that is associated with the transport and fusion of endocytic vesicles, and participates in regulation of intracellular signaling pathways embraced by cells to adapt to the specific environment. Rab5a is also correlated with lung, stomach, and hepatocellular carcinomas. Here, we detected Rab5a in paraffin-embedded samples of 20 ovarian cysts, 20 benign cystadenomas, and 39 ovarian cancers by immunohistochemistry, and observed that Rab5a expression was significantly higher in ovarian cancer (P = 0.0001). By setting up stable HO-8910 cell lines expressing Rab5a or dominant negative Rab5a (Rab5a:S34N), we found that Rab5a overexpression enhanced the cell growth by promoting G1 into S phase. In contrast, Rab5a:S34N inhibited this process. Additionally, APPL1 (adaptor protein containing PH domain, PTB domain, and Leucine zipper motif), a downstream effector of Rab5a, was also involved in promoting HO-8910 cell cycle progress. But this function was blocked by Rab5a:S34N. Laser scanning confocal microscopy represented the colocalization of APPL1 and Rab5a in the plasmolemma, which changed with the time of epidermal growth factor (EGF) stimulation. We also found APPL1 could transfer from the membranes into the nucleus where it interacted with NuRD/MeCP1 (the nucleosome remodeling and histone deacetylase multiprotein complex). NuRD is reported to be involved in the deacetylation of histone H3 and H4 to regulate nuclear transcription. So Rab5a promoted proliferation of ovarian cancer cells, which may be associated with the APPL1-related epidermal growth factor signaling pathway.

Ovarian carcinomas: CCN genes are aberrantly expressed and CCN1 promotes proliferation of these cells

PURPOSE

The connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed (CCN) family consists of six matricellular proteins that are involved in various cellular functions, such as proliferation, development, and angiogenesis. The purpose of this study was to explore the possibility that CCN genes are involved in ovarian cancers.

EXPERIMENTAL DESIGN

We quantified CCN expression in a series of 59 ovarian cancers using quantitative real-time reverse transcription-PCR. CCN1 protein levels were further determined by immunohistochemistry and Western blot analysis. Overexpression and inhibition of CCN1 expression by small interfering RNA were used to examine its role in ovarian cancer cell proliferation in vitro and in vivo.

RESULTS

We found dysregulation of levels of the various CCN mRNAs in ovarian cancers compared with their expression in normal whole ovaries. Expression of CCN1 protein was detected in normal ovarian epithelial cells and ovarian tumors as well as in ovarian cancer cell lines. Furthermore, estrogen increased CCN1 mRNA and protein levels in ovarian cancer cells. Ectopic expression of CCN1 enhanced the growth of ovarian cancer cells in liquid culture, whereas inhibition of its expression decreased proliferation and increased apoptosis in these cells. The observed changes in cell growth were accompanied with activation of Akt and extracellular signal-regulated kinase (ERK) signaling pathways. Stable expression of CCN1 in SKOV3 cells significantly increased tumorigenicity in nude mice. Finally, overexpression of CCN1 conferred resistant to carboplatin-induced apoptosis in SKOV3 cells.

CONCLUSIONS

This is the first study to show abnormalities in CCN expression in ovarian carcinomas. Furthermore, our results suggest that CCN1 may play a role in ovarian carcinogenesis by stimulating survival and antiapoptotic signaling pathways.