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

Figure 2 Expression of PLK1 in frozen colon tissue and colon carcinoma cell lines. A: Expression of PLK1 protein (68 ku) in colon carcinoma and normal colon mucosa; B/C : Strong expression of PLK1 protein (B, immunoblot, 68 ku) and mRNA (C: RT-PCR, 1 807 bp) in colon carcinoma cell lines; D/E: Coexpression of PLK1 (red staining of the cytoplasm) and Ki-67 (brown staining of the nucleus) in RKO colon carcinoma cell line. A considerable number of cells were PLK1 positive, but remained Ki-67 negative (arrowheads). Note cells in M-phase (small arrows) strongly expressing both proteins. Original magnifications D: ×200, E: ×500.