Colorectal Cancer
Copyright ©The Author(s) 2005. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Sep 28, 2005; 11(36): 5644-5650
Published online Sep 28, 2005. doi: 10.3748/wjg.v11.i36.5644
Polo-like kinase 1 expression is a prognostic factor in human colon cancer
Wilko Weichert, Glen Kristiansen, Mathias Schmidt, Volker Gekeler, Aurelia Noske, Silvia Niesporek, Manfred Dietel, Carsten Denkert
Wilko Weichert, Glen Kristiansen, Aurelia Noske, Silvia Niesporek, Manfred Dietel, Carsten Denkert, Institute of Pathology, Charité University Hospital, Berlin 10117, Germany
Mathias Schmidt, Volker Gekeler, Altana Pharma AG, Konstanz 78467, Germany
Author contributions: All authors contributed equally to the work.
Correspondence to: Dr. Wilko Weichert, Institute of Pathology, Charité University Hospital, Schumannstraße 20/21, Berlin 10117, Germany. wilko.weichert@charite.de
Telephone: +49-30450536006 Fax: +49-30450536922
Received: December 7, 2004
Revised: January 1, 2005
Accepted: January 5, 2005
Published online: September 28, 2005
Abstract

AIM: To clarify the expression patterns and prognostic implications of the mitotic regulator Polo-like kinase 1 (PLK1) in colon cancer.

METHODS: Expression of PLK1 was investigated by immunohistochemistry (158 cases) and immunoblotting in tissue of colon adenomas and adenocarcinomas. PLK1 expression patterns were correlated with clinicopathological parameters and patient prognosis. In addition, expression of PLK1 was evaluated by immunoblot and PCR in colon carcinoma cell lines, and coexpression of PLK1 with the proliferation marker Ki-67 was investigated.

RESULTS: Weak PLK1 expression was observed in normal colon mucosa and adenomas. In contrast, 66.7% of carcinomas showed strong expression of PLK1. Overexpression of PLK1 correlated positively with Dukes stage (P < 0.001), tumor stage (P = 0.001) and nodal status (P < 0.05). Additionally, PLK1 expression was a prognostic marker in univariate survival analysis (P < 0.01) and had independent prognostic significance (RR = 3.3, P = 0.02) in patients with locoregional disease. Expression of PLK1 mRNA and protein was detected in all cell lines investigated. Coexpression of PLK1 and Ki-67 was observed in the majority of colon cancer cells, but a considerable proportion of cells showed PLK1 positivity without Ki-67 expression.

CONCLUSION: PLK1 is a new prognostic marker for colon carcinoma patients and may be involved in tumorigenesis and progression of colon cancer. Strategies focusing on PLK1 inhibition in vivo might therefore represent a promising new therapeutic approach for this tumor entity.

Keywords: Polo-like kinase; Colon carcinoma; Survival; Immunohistochemistry; Mitosis