The study was selleck screening library reviewed and approved by the Institutional Review Board at the Beijing Cancer Hospital. Written informed consent was obtained from all participants. The smoking status of patients was decided during their first visit. A smoker was defined as the one who smoked more than 100 cigarettes in his/her life time. Patients were treated with either TKI therapy or platinum-based
chemotherapy as the first line of treatment until their disease progressed, justified by imaging evidence or aggravated symptoms. The learn more response Evaluation Criteria in Solid Tumors (RECIST)  including progressive disease (PD), stable disease (SD), partial remission (PR) and complete remission (CR) was used to evaluate the drug response after patients received treatment every 6 weeks to 2 months. The objective response rate (ORR) was defined as the sum of PR and CR, while the disease control rate (DCR)
was defined as the sum of SD, PR, and CR. Progression-free survival(PFS) was assessed from the beginning of therapy to disease progress or death from any cause. Overall survival(OS) selleckchem was assessed from the beginning of first-line therapy until death from any cause.
DNA extraction and methylation-specific PCR Genomic DNA of tumor tissues from patients biopsied before TKI treatment were extracted using QIAmp FFPE DNA kit (Qiagen). The methylation status of the CpG sites within the gene loci of SFRP1, SFRP2, SFRP5, WIF1, DKK3, APC, and CDH1 was decided by MSP assays as described previously [25–27]. Briefly, genomic DNA was treated with sodium bisulfite, followed by PCR amplifications using the primer pairs that can specific detect either the methylated or the unmethylated CpG sites. Genes were defined as methylated if the PCR products could be detected using the methylated DNA-specific Astemizole primer pairs, while they were defined as unmethylated if the PCR products could only be detected using the unmethylated DNA-specific primer pairs. DNA from the human adenocarcinomic alveolar basal epithelial cell lines, A549 and A549/DDP, was used as the positive control for methylated DNA, while DNA from lymphocytes of healthy nonsmoking volunteers was used as the negative control. The methylation status results were confirmed by at least one repeat of the methylation-specific PCR assays.