RUNX3 Promoter Hypermethylation In Relation To The Prognosis Of Surgically Resected Non-small Cell Lung Cancers

Objective: We investigated the promoter methylation status of RUNX3 in Paraffin-embedded tumor tissue DNA of 80 NSCLC patients who received postoperative adjuvant chemotherapy with cisplatin. The aim of this study was to find out the relationship between promoter methylation status of RUNX3 and clinicopathological parameters, prognosis of NSCLC.Methods: We collected 80 formalin-fixed paraffin-embedded lung cancer tissue samples in non-small cell lung cancers who received postoperative adjuvant chemotherapy with cisplatin. Genomic DNA was extracted through proteinase K digestion - phenol/ chloroform extraction. The methylation status of RUNX3 was determined by nested methylation-specific PCR (nMsp). The survival of the 80 patients was followed up. We investigated the pathological and prognostic characteristics of NSCLCs that had been stratified according to methylation status. Catergorical variables were comparaed using the chi-square test. The relationship between disease-free survival time and RUNX3 methylation status for NSCLCs was studied with multivariate Logistic regression. The Kaplan-Meier method was used to calculate time to overall survival. Differences were assessed using log rank statistics. The prognostic value of RUNX3 methylation status for NSCLCs was studied with multivariate Cox proportional hazards regression models.Results:1. The RUNX3 promoter methylation was observed in 20 of 80 NSCLC samples (25.0%) examined.2. Methylation of RUNX3 was more frequent in adenocarcinomas (16/44 36%) than in squamous cell carcinomas (4/36 11%) (P=0.020). The promoter methylation frequencies of RUNX3 was correlated with recurrence or metastasis (P=0.006) and with death (P=0.019) in three years after a curative resection. The significant correlation between Methylation of RUNX3 and age, gender, smoke history, differentiated types, pleural involvement, TMN stage, N stage was not be found respectively.3. In multivariate Logistic regression, positive RUNX3 methylation status (P =0.011) was found to be independent disease-free survival factor as was N stage (P=0.000).4. Kaplan-Meier curves showed patients with RUNX3 methylation had a significantly poorer overall survival than those without methylation (P= 0.003; log-rank test) , and in multivariate Cox proportional hazards regression analysis, RUNX3 methylation (RR:2.345, 95%CI: 1.130 -4.865 P = 0.022) and N stage (RR : 2.393, 95% CI: 1.518-3.77, P =0.000) were significant independent prognostic factors for overall survival respectively. RUNX3 methylation play a very important role in pathogenesis of NSCLC, tumor progression, postoperative recurrence and metastasis.Conclusion: RUNX3 gene promoter methylation is a common frequency epigenetic modification in non-small cell lung cancer. It may contributes to the pathogenesis of NSCLC. Methylation of RUNX3 was more frequent in adenocarcinomas than in squamous cell carcinomas. Patients with RUNX3 methylation had a significantly poorer overall survival than those without methylation in unvariate analysis. In multivariate analysis, both RUNX3 methylation and N-stage were found to be independent Disease-free survival and prognosis factors respectively. The patients with RUNX3 methylation were easy to occur recurrence or metastasis after a curative resection and had poor prognosis. RUNX3 methylation might be useful as a potential prognosis biomarker of NSCLC.