BACKGROUNDSerine threonine kinase 15 (STK15) is a kind of mitotic kinase. The overexpression of STK15 is significantly associated with carcinogenesis in many tumors, however, its expression and significance in human lung cancer are still unclear. The aim of this study is to investigate the expression of STK15 in squamous cell carcinoma and adenocarcinoma of the lung and to analyze the correlation between STK15 expression and clinicopathological factors.

METHODSThe pattern of STK15 protein expression was detected in 44 squamous cell carcinomas, 36 adenocarcinomas and 20 paracancerous lung tissue samples by immunohistochemistry method using anti-STK15 antibody. The relative quantity of STK15 protein expression was detected by Western blot, and STK15 mRNA expression was detected by RT-PCR in 40 fresh lung cancer samples and corresponding paracancerous lung tissues.

RESULTSPositive expression rate of STK15 protein was 68.75% (55/80) in lung cancer tissues and 0% in paracancerous controls (P < 0.001). STK15 expression was significantly related to differentiation grade of lung cancer (P=0.011), but not to histological classification, TNM stages or lymphatic metastasis (P > 0.05). The relative expression levels of STK15 protein (P < 0.001 ) and STK15 mRNA (P < 0.001) in lung cancer tissues were both significantly higher than those of corresponding paracancerous lung tissues.

CONCLUSIONSThe expression of STK15 protein and STK15 mRNA is significantly higher in lung cancer tissues than that in paracancerous lung tissues. The expression of STK15 correlates with differentiation of lung cancer.