Objective To investigate the relationship between expression of tumor suppressor gene p16 in non-small cell lung cancer (NSCLC) tissues and clinicopathological parameters, to further study on DNA methyltransferase inhibitors 5-nitrogen impurity-2′-deoxycytidine (5-Aza-CdR) in human lung cancer cell line A549 in regulating the expression of p16. Methods The expression of p16 protein in 76 cases of NSCLC tissues and normal tissue adjacent to carcinoma were detect by immunohistochemical SP method and the differences of p16 protein expression were analyzed. p16 gene promoter region of DNA methylation status were detect by MSP method in 5-Aza-CdR processing A549 cells, the expression of p16 in A549 lung cancer cell and effect of 5-Aza-CdR were detect by Western blot method. Results 32 cases (42.11%) of p16 protein expression was positive, significantly lower than that of the normal tissue adjacent to carcinoma (positive expression in 59 cases, 77.63%) in 76 cases of NSCLC tissues; There were statistically significant differences (P
