Polo-like kinase 1 expression is a prognostic factor in human colon cancer.
OBJECTIVE
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.


CONCLUSIONS
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.
Weichert
Wilko
W
Institute of Pathology, Charite University Hospital, Schumannstrabe 20/21, Berlin 10117, Germany. wilko.weichert@charite.de
Kristiansen
Glen
G
Schmidt
Mathias
M
Gekeler
Volker
V
Noske
Aurelia
A
Niesporek
Silvia
S
Dietel
Manfred
M
Denkert
Carsten
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000145:classification / Q000175:diagnosis* / Q000201:enzymology* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*; D000097869:Polo-Like Kinase 1
D018797:Cell Cycle Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1