Expression of cyclin-dependent kinase-associated protein phosphatase in colorectal carcinomas

Abstract

Background : Cyclin-dependent kinase-associated phosphatase (KAP) is a human dual-specificity protein phosphatase that dephosphorylates Cdk2 on threonine160 in a cyclin-dependent manner and that is known as an up-regulated molecule in some malignant tumors. We investigated the expression and clinicopathologic significance of KAP protein in relation to tumorigenesis of colorectal carcinoma. Methods : The expression patterns of KAP protein in tumor tissue were examined by reverse transcription-PCR and immunohistochemical staining. Results : An enhanced transcriptional level of KAP mRNA was observed in 11 out of 12 colorectal carcinoma specimens. Immunohistochemical examination showed that KAP protein was more highly expressed in the tumors than that in the adjacent non-neoplastic mucosal tissues for 52 of 102 colorectal cancer tissues. The statistical analysis showed that an increased level of KAP protein in the colorectal cancer tissues was inversely correlated with the histologic grade, tumor size and Duke’s stage. Conclusion : The present study suggests that alteration of KAP might play a role, at least in part, in the tumorigenicity of colorectal carcinoma through the mechanism of cell cycle regulation.