Expression of Polo-Like Kinase 1 (PLK1) Protein Predicts the Survival of Patients with Gastric Carcinoma

OBJECTIVE: To assess the prognostic value of polo-like kinase 1 (PLK1), an important regulator of cell cycle progression, in patients with gastric carcinoma. METHODS: PLK1 expression was determined in 160 gastric carcinoma patients by immunohistochemistry and compared with p53 expression and the proliferating cell nuclear antigen-labeling index (PCNA-LI) to evaluate the effect of PLK1 on tumor progression. Furthermore, PLK mRNA expression was determined in 26 advanced gastric cancer patients by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: PLK mRNA expression was detected in 25 (96.2%) patients by RT-PCR. Immunohistochemical staining revealed PLK1 expression in 84 (52.5%) patients. There were no significant relationships between PLK1 expression and various clinicopathological factors. PLK1 expression was significantly correlated with the PCNA-LI, but not p53 expression. The prognosis of patients with PLK1-positive tumors was significantly worse than that of patients with PLK1-negative tumors (p < 0.05). Moreover, multivariate analysis revealed that PLK1 expression was an independent prognostic factor. Patients with PLK1-positive and high PCNA-LI tumors showed a significantly poorer prognosis than patients with PLK1-negative and/or low PCNA-LI tumors. Furthermore, the prognosis of patients with PLK1- and p53-positive tumors was significantly worse than that of patients with PLK1- and p53-negative or PLK1-negative and p53-positive tumors. CONCLUSION: PLK1 expression may be a critical indicator of a poor prognosis in patients with gastric carcinoma.