MTAP is an independent prognosis marker and the concordant loss of MTAP and p16 expression predicts short survival in non-small cell lung cancer patients

Abstract

ObjectivesMethylthioadenosine phosphorylase (MTAP), a ubiquitously expressed protein, plays important roles in purine biosynthesis. Locating near to each other on chromosome 9p21-22, codeletion of the MTAP and p16Ink4A genes have been reported in non-small cell lung cancer (NSCLC). The aim of this study is to determine the respective prognostic value of MTAP and p16 by considering their correlation in NSCLC patients. Materials and methodsWe analyzed MTAP and p16 protein expression by immunohistochemical staining on 99 NSCLC tissue microarray samples. The association between MTAP and p16 expression levels and prognosis were analyzed using the Kaplan–Meier method and Cox proportional hazards model for prognosis. ResultsPatients with a low MTAP expression level had poor overall survival (P = 0.010) and disease-free survival (P = 0.002). Low p16 expression indicated a trend toward poor overall survival (P = 0.138) and disease-free survival (P = 0.199). There was a significant positive correlation between MTAP and p16 expression levels (Spearman's ρ = 0.402, P < 0.001). By multivariate analyses, the MTAP expression level retained its independent prognostic power and p16 expression loss of the correlation with prognosis. Concordant loss of MTAP and p16 expression was observed in 24 out of 99 patients (24.2%). Patients with concordant loss of MTAP and p16 expression had the worst prognosis compared to patients with high expression of both markers. ConclusionMTAP expression is an independent prognostic factor and has greater prognostic significance than p16 expression in NSCLC. Concordant loss of MTAP and p16 expression indicates poor outcomes in lung cancer patients.