Elevated nuclear CDK6 is associated with an unfavorable prognosis in lung adenocarcinoma patients

It has been recently reported that cyclin-dependent kinase 6 (CDK6) is abnormally expressed in several human malignant tumors; however, CDK6 nuclear expression has not been fully studied in lung adenocarcinoma. We determined the correlation between the level of CDK6 expression and clinicopathologic data in lung adenocarcinoma patients, including survival.

The level of expression of CDK6 protein was detected by immunohistochemical analysis in 143 paraffin-embedded lung adenocarcinoma tissues and 35 normal paraffin-embedded lung tissues. The data showed that overexpression of nuclear CDK6 protein was present in lung adenocarcinoma. Further, we analyzed the correlation between the levels of nuclear CDK6 expression and clinical features, including survival prognosis. Higher expression of nuclear CDK6 protein was significantly associated with N stage (P=0.012), clinical stage (P=0.008), and degree of differentiation (P=0.015), but there was no association with T stage (P=0.472) or distant metastasis (P=0.163). Increased CDK6 expression was associated with poorer overall survival rates than low expression of CDK6 (P=0.004). Multivariate analysis indicated that high expression of nuclear CDK6 was an independent prognostic indicator of patient survival.

Our findings demonstrate that nuclear CDK6 protein is overexpressed and plays a detrimental role in disease progression and poor outcome with lung adenocarcinoma patients.