Overexpression of vasoactive intestinal peptide receptors and cyclooxygenase-2 in human prostate cancer. Analysis of potential prognostic relevance.

Abstract

Vasoactive intestinal peptide (VIP) is a potent inductor of cyclooxygenase-2 (COX-2) expression in human prostate cancer cell lines. There are conflicting data regarding the role of COX-2 in the progression of this disease. Here we examined the expression of VIP receptors (VPAC1 and VPAC2) and COX-2 in prostate cancer specimens. Correlations among protein levels and various clinicopathological factors and prognosis of patients were statistically analyzed. For these purposes, formaldehyde-fixed, paraffin-embedded prostate tissue specimens from 63 patients with prostate cancer and 9 control samples were used. The expression of VPAC1 and VPAC2 receptors and COX-2 was analyzed at mRNA levels by quantitative reverse transcriptase-PCR. The corresponding expression at protein level was studied by immunohistochemistry, scored as negative, weak, moderate, or strong, and correlated with different clinicopathological factors by means of multivariate analysis. 88% of prostate cancer tissues overexpressed VPAC1-receptor at mRNA level, 72% VPAC2-receptor and 77% COX-2. Simultaneous overexpression of the three genes was seen in 52% of patients. Similar overexpression patterns were observed at protein level. The correlation between VPAC1 and VPAC2 receptor protein levels was statistically significant. However, no significant correlations existed among protein levels of VPAC receptors and COX-2 with patient age, prostate-specific antigen (PSA) levels, tumor stage, Gleason score and survival time. The overexpression of VPAC1 and VPAC2 receptors and COX-2 in cancer tissue gives them a potential role as targets for diagnosis of prostate cancer but results do not support a clear value as biomarkers for the clinical prognosis of this disease.