Overexpression of Antiapoptotic MCL-1 Predicts Worse Overall Survival of Patients With Non-small Cell Lung Cancer

Background/Aim: Myeloid cell leukemia-1 (MCL1) is a member of the B-cell lymphoma-2 (Bcl-2) family of proteins, which regulate the intrinsic (mitochondrial) apoptotic cascade. MCL-1 inhibits apoptosis, which may be associated with resistance to cancer therapy. Therefore, in this study, the clinical role of MCL-1 in non-small cell lung cancer (NSCLC) was explored. Patients and Methods: This retrospective study included 80 patients with stage 1-3A NSCLC, who underwent surgery without preoperative treatment between 2010 and 2011. MCL-1 expression and Ki-67 index were determined via immunohistochemical staining. Apoptotic index (AI) was determined via terminal deoxynucleotidyl transferase dUTP nick end labeling. Results: The receiver operating characteristic curve analysis (area under curve=0.6785) revealed that MCL-1 expression in 30.0% of the NSCLC tumor cells was a significant cut-off for predicting prognosis. Tumors were considered MCL-1positive if staining was observed in > 30% of the cells. Thirty-six tumors (45.0%) were MCL-1-positive. However, there were no significant differences between MCL- 1 expression and clinical variables. AI was lower in MCL-1positive (2.2 +/- 3.6%) than in MCL-1-negative (5.2 +/- 7.9%) tumors, although the difference was not significant (p=0.1080). The Ki-67 index was significantly higher in MCL-1-positive than in MCL-1-negative tumors (18.0% vs. 3.0%; p<0.001). Five-year survival rate was significantly worse in patients with MCL-1-positive tumors (68.3%) than in those with MCL-1-negative tumors (93.1%, p=0.0057). Univariate [hazard ratio (HR)=5.041, p=0.0013], and multivariate analyses revealed that MCL-1 expression was a significant prognostic factor (HR=3.983, p=0.0411). Conclusion: MCL-1 expression in NSCLC cells correlated inversely with AI and positively with Ki-67 index. MCL-1 may serve as a potential prognostic biomarker and a novel therapeutic target in NSCLC.