Association between distinct gene and miRNA expression profiles and utilization of stereotyped subset #4 in the cells of CLL patients [MicroRNA Profiling]

Highly homologous B-cell receptors, stereotyped BCR, are expressed in a recurrent fraction of patients with chronic lymphocytic leukemia (CLL). In this study, we investigated the biological and molecular features of leukemic cells from 16 patients utilizing stereotyped subset #4 BCR (IGHV4-34) in a prospective cohort of 462 Binet stage A CLL patients. All subset #4 patients were characterized by the IGHV mutated gene configuration and by the absence of unfavorable cytogenetic lesions, and NOTCH1 and SF3B1 mutations. Gene expression profiling demonstrated a significant downregulation of WDFY4, MF2A and upregulation of PDGFA, FGFR1 and TFEC genes in leukemic cells from subset #4 compared to those from the remaining IGHV-mutated patients. Similarly, in the cells from subset #4 cases there was a specific miRNA expression pattern involving the upregulation of miR-497 and miR-29c. Furthermore transfection of miR-497 mimic in primary leukemic CLL cells induced a downregulation of BCL2, known to be a validated target of this miRNA. Our data identify a distinct gene and miRNA expression profile of the cells from subset #4 patients, providing further evidence for the putative role of BCR in shaping the features of the leukemic cells. This series of microarray experiments contains the gene expression profiles of purified B-cell chronic lymphocytic leukemia (B-CLL) cells obtained from 217 patients (Binet stage A). Peripheral blood mononuclear cells from CLL patients were isolated by Ficoll-Hypaque (Seromed, Biochrom KG, Berlin, Germany) density-gradient centrifugation. For gene and miRNA expression profiling experiments CLL cells were enriched by negative selection with the EasySep-Human B cell enrichment kit without CD43 depletion (Stem Cell Technologies) using the fully automated protocol of immunomagnetic cell separation with RoboSepTM (Stem Cell Technologies).