Overexpression of the recently identified oncogene REDD1 correlates with tumor progression and is an independent unfavorable prognostic factor for ovarian carcinoma

Background: Regulated in development and DNA damage response (REDD1), a gene responding to hypoxia or multiple DNA damage events, was recently implicated in cancer development and progression. Previously, in vivo and in vitro experiments indicated that REDD1 functions as an oncogene in ovarian cancer cells. However, the role of REDD1 in cancer cell migration and invasion and in clinical significance of prognostic values is not examined in detail. Methods: We detected the REDD1 protein expression by immunohistochemistry in 18 normal ovarian surface epithelium or fallopian tube epithelium specimens, 24 ovarian borderline tumors, and 229 ovarian cancers. Fisher's exact test, logistic regression analysis, the Kaplan-Meier method, and the log-rank test were used to evaluate the association of REDD1 with clinical factors, overall survival and disease-free survival. The prognostic predictive value of REDD1 for ovarian cancer patients was evaluated using multivariate Cox proportional hazard regression models. REDD1 expression in HEY, HEY A8, SKOV3, SKOV3 ip1, OVCA429, OVCA433 and A2780 human ovarian epithelial cancer cell lines was detected by western blotting. The role of REDD1 in cell invasion and migration was assessed by transwell migration and invasion assays using SKOV3, A2780, HEY, HEYA8, and SKOV3-REDD1 with parental A2780-REDD1 HEY-REDD1i and HEY A8-REDD1i. Results: High expression of REDD1 was observed in 35.4% of primary ovarian carcinoma samples. Overexpression of cytoplasmic REDD1 in ovarian cancer was significantly associated with serous carcinoma (P<0.001), late-stage disease (P<0.001), ascites (P<0.001), and partial or non-response to chemotherapy (P<0.001). High cytoplasmic expression of REDD1 was correlated with poorer overall survival (P<0.001) and disease-free survival (P<0.001). The multivariate Cox proportional hazards regression analysis indicated that patients with high cytoplasmic REDD1 expression had a high risk of death (P<0.001) and high risk of an event (i.e., recurrence, progression, or death) (P<0.001). REDD1 was first reported as an independent prognostic factor in ovarian cancer patients. In addition, REDD1 overexpression enhanced ovarian cancer cell migration and invasion. Conclusion: REDD1 is an independent unfavorable prognostic factor in ovarian carcinoma and may promote ovarian cancer metastasis.