MELK serves as a potent independent biomarker to predict survival of diffuse large B‐cell lymphoma patients treated with rituximab‐CHOP regimen

Abstract

Introduction: Maternal embryonic leucine zipper kinase (MELK) is a novel oncogene, which plays pivotal roles in maintenance of cancer stem cells and cancer cell survival. However, the clinical significance of MELK in the progression of diffuse large B-cell lymphoma (DLBCL) remains poorly understood. Currently, 30% to 40% DLBCL patients remain incurable with standard therapy (cyclophosphamide, doxorubicin, vincristine, prednisone combined with rituximab, and R-CHOP), resulting in multiple studies on identifying effective prognostic biomarker. Herein, we aimed to assess prognostic significance of MELK in DLBCL patients with R-CHOP regimen. Methods: MELK expression pattern in DLBCL and normal lymph node tissues was characterized in microarray from Gene Expression Ominous (GEO) GSE56315. Prognostic value of MELK expression was evaluated in 471 de novo DLBCL patients treated with R-CHOP, collected as part of the International DLBCL R-CHOP Consortium Program Study, on tissue microarray from GSE31312 using Affymetrix GeneChip Human Genome HG-U133 Plus 2.0 chips. Optimal cutoff value of MELK expression was determined by calculating Youden's index from receiver operating characteristic (ROC) curve. Kaplan-Meier survival curve analyses with log-rank test, univariate and multivariate Cox regression model analyses of overall survival (OS), and progression-free survival (PFS) were performed. Gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) analysis in whole-genome profiling were conduct to predict potential functions of MELK in DLBCL. Results: Markedly increased expression of MELK in DLBCL tissues (9.299 ± 0.081, n = 89) compared with B cells from normal tonsil tissues (7.218 ± 0.243, n = 33) were observed (Figure A). Furthermore, in the cohort of 471 DLBCL patients with R-CHOP treatment, stratified high MELK expression is closely associated with advanced Ann Arbor stage (P = .026), high IPI score (P = .036), activated B-cell–like (ABC) DLBCL subtype (P = .013), and patients' non-CR rates (P = .001). Kaplan-Meier survival curve analyses indicated MELK overexpression was of significant correlation with inferior OS (P = .001) and PFS (P = .018) (Figure B, C). Multivariate Cox regression analysis adjusting for validated significant parameters in univariate analysis confirmed independent prognostic value of MELK in OS of DLBCL patients (HR: 1.600; 95% CI, 1.096-2.335, P = .015). Functional enrichment assays indicate that MELK is tightly associated with biological processes including cell division, apoptosis process and cell cycle. Besides, MELK might contribute to cancer progression of DLBCL via regulating PI3K/Akt, Ras, and p53 signaling pathways. Keywords: diffuse large B-cell lymphoma (DLBCL); gene expression profile (GEP); R-CHOP