MiR-15a and miR-16-1 cluster functions in human leukemia

Abstract

MicroRNAs (miRNAs) are short noncoding RNAs regulating gene expression that play roles in human diseases, including cancer. Each miRNA is predicted to regulate hundreds of transcripts, but only few have experimental validation. In chronic lymphocytic leukemia (CLL), the most common adult human leukemia, miR-15a and miR-16-1 are lost or down-regulated in the majority of cases. After our previous work indicating a tumor suppressor function of miR-15a/16-1 by targeting the BCL2 oncogene, here, we produced a high-throughput profiling of genes modulated by miR-15a/16-1 in a leukemic cell line model (MEG-01) and in primary CLL samples. By combining experimental and bioinformatics data, we identified a miR-15a/16-1-gene signature in leukemic cells. Among the components of the miR-15a/16-1 signature, we observed a statistically significant enrichment in AU-rich elements (AREs). By examining the Gene Ontology (GO) database, a significant enrichment in cancer genes (such as MCL1, BCL2, ETS1, or JUN) that directly or indirectly affect apoptosis and cell cycle was found.

Fig. 1.

MiR15a/16-1 cluster inhibits the growth of MEG-01 tumor engraftments in nude mice. (A) Growth curve of engrafted tumors in nude mice injected with MEG-01 cells pretransfected with pRS-E or pRS15/16 or mock transfected. (B) Comparison of tumor engraftment sizes of mock-, pRS-E-, and pRS15/16-transfected MEG-01 cells 28 days after injection in nude mice. (C) Tumor weights ± SD in nude mice.

Fig. 2.

Validation of some of the targets of miR-15a/16-1 identified by microarray or proteomics in MEG-01. (A) qRT-PCR validation of PDCD4, RAB21, IGSF4, SCAP2 (down-regulated in the microarray), BCL2, and WT1 (down-regulated in proteomics). IFG1, ACE, and ERBB2 are negative controls. The results were normalized to pRS-E-transfected cells. Samples were normalized with β-tubulin. (B) Luciferase assay of IGSF4 in MEG-01 cells, showing that the miR-15a/16-1 cluster directly targets this gene.