Cyclin-dependent kinase 6 (CDK6) is a candidate diagnostic biomarker for early non-small cell lung cancer

BACKGROUND: Cyclin-dependent kinase 6 (CDK6) is an important regulatory protein of the cell cycle and plays an important role in tumor progression. The aim of this study was to investigate the expression of CDK6 in T1 stage non-small cell lung cancer (NSCLC) and to explore the association of CDK6 with the clinicopathological features of the disease. METHODS: CDK6 expression was analyzed by real-time PCR (RT-PCR) and immunohistochemistry (IHC) in tumor tissue samples and the distal normal tissue samples from 56 T1 stage NSCLC patients. The correlation between CDK6 expression and clinicopathological features was analyzed using the independent samples t-test and nonparametric tests. RESULTS: We found CDK6 had a tendency to increase in tumor tissues compared to normal tissues at the transcriptional level (P=0.073). Moreover, the expression of CDK6 protein in NSCLC tissues was also significantly higher than in normal lung tissues (P=0.003). With an increase of smoking quantity, the expression of CDK6 mRNA was increased (P=0.009). Remarkably, CDK6 expression was increased in squamous cell carcinoma (SCC) tissues but decreased in adenocarcinoma (AD) tissues at both the transcription and protein levels (P<0.001). After stratification based on pathological type, CDK6 gene expression was not associated with any clinicopathological features in SCC, while it was negatively associated with tumor diameter in AD (P=0.049). CONCLUSIONS: Taken together, these results indicated that abnormal expression of the CDK6 gene in NSCLC might be associated with pathological type, which may serve as a diagnostic biomarker for NSCLC.