Expression analysis and RNA localization of PAI-RBP1 (SERBP1) in epithelial ovarian cancer: association with tumor progression.

The plasminogen activator system (PA) plays an important role in invasion and metastasis of solid tumors. The PA Inhibitor type 1 (PAI-1) is the main physiologic regulator of plasminogen activation. A recently characterized protein, PAI-RBP1 (PAI-1 mRNA Binding Protein 1), appears to regulate the stability of PAI-1 mRNA. Expression of PAI-RBP1 (the new, approved gene symbol is SERBP1) has not been previously analyzed in human tumors. We present herein for the first time expression analysis of PAI-RBP1 in epithelial ovarian cancer. PAI-RBP1 was identified as gene overexpressed in ovarian cancer by an in silico approach using EST database mining. A thorough expression analysis of PAI-RBP1 and PAI-1 was performed in normal ovary (n=4), benign (n=6) and malignant (n=42) ovarian lesions using non-radioactive RNA in situ hybridization and immunohistochemistry, respectively. PAI-RBP1 mRNA and PAI-1 were significantly overexpressed in tumor epithelial cells as compared to benign and normal ovarian tissue. A significant correlation between PAI-RBP1 expression and advanced disease stage (FIGO) was found (p=0.042). In ovarian cancer, PAI-RBP1 is significantly overexpressed in tumor epithelial cells, suggesting a biological role in tumor invasion and metastasis. Its expression is higher in advanced disease, thus the prognostic significance of PAI-RBP1 in ovarian cancer remains to be evaluated in further studies.