Rel transcription factors contribute to elevated urokinase expression in human ovarian carcinoma cells

Elevated levels of the urokinase-type plasminogen activator (uPA) in tumor cells are conductive to tumor cell spread and metastasis. In a previous study we observed that suppression of RelA dramatically reduced endogenous uPA synthesis in the human ovarian cancer cell line OV-MZ-6. Because the uPA promoter contains three potential Rel-like protein binding motifs (RRBE, 5'- NF-κB, and 3'-NF-κB) we conducted the first thorough systematic uPA promoter analysis to examine the direct impact of Rel proteins on uPA gene transcription. Disruption of RRBE resulted in a ~40% decrease in uPA promoter activity, mutation of the 5'-NF-κB motif led to an additional 20% decrease. The 3'-NF-κB motif was not active. Overexpression of RelA significantly enhanced uPA promoter activity, whereas IκB-α overexpression reduced uPA promoter activity by 40%. These data were supported by the finding that endogenous uPA was also increased sixfold by overexpression of RelA and decreased by 30% upon overexpression of IκB-α. Transfection of OV- MZ-6 cells with antisense deoxynucleotides directed to RelA expression reduced uPA promoter activity by at least 40%. Our data clearly suggest that by binding to uPA promoter elements, Rel transcription factors contribute directly to elevated uPA gene expression in human ovarian cancer cells, thereby promoting the multiple functions of uPA during tumor growth and metastasis.