Analysis of Microvesicle Microrna Expression Profiles and Their Functional Roles in ALL Subtypes

Abstract 1488

Microvesicles (MVs) released by leukemia cells constitute an important part of the leukemia microenvironment. As a cell-to-cell communication tool, MVs transfer microRNA(miRNA) between cells. MVs miRNAs may be valuable not only as a diagnostic tool but may also provide an insight in the role of miRNAs playing in the underlying of pathophysiologic processes of various leukemia. It is worth evaluating whether MVs possess some unique miRNA content depending on their corresponding leukemia origin that could be applicable in diagnosis.

Hence, we determined the miRNA expression profiles of ALL-derived MVs using Agilent miRNA microarray analysis. The five miRNAs obtained by microarray profiling were validated using real-time PCR. The putative target genes were predicted by bioformation software. Here, we provided MVs miRNA patterns derived from the healthy controls, B-ALL cell line Nalm 6 cells and T-ALL cell line Jurkat cells.

We identified 182 dysregulated miRNAs in MVs derived from Nalm 6 cells as compared with MVs from normal controls (P<0.05); both up regulated(123/182) and down regulated(59/182) expressions were observed. Likewise 166 miRNAs were significantly differentially expressed in MVs derived from Jurkat cells versus MVs from normal peripheral blood (P<0.05), 114 miRNAs of which (114/166) were up expression and 52 miRNAs (52/166) were down expression. We also fould that 44 miRNAs were only detected in B-ALL-derived MVs.

MiR-1290, miR-1246, miR-1268, miR-1226, and miR-424 were top 5 expressed in Nalm 6 derived MVs, suggesting that those miRNAs may play an important role in B-ALL. We observed that 16 miRNAs detected only in T cell derived MVs. MiR-96 is up regulated in MVs from T-ALL cells but not expressed in B-ALL. Specific and functional target sites for miR-96, exist in the 3'-UTR of the miRNA that encodes the putative tumor suppressor transcription factor FOXO1. The expression signatures of miR-96 could discriminate B-ALL from T-ALL. In contrast, the MVs from B-ALL cell line, shared 100 miRNAs with MVs from T-ALL cell line, suggestting that those miRNAs play roles in both B-and T-ALL. Of 100 miRNAs, 99 miRNAs were high expression, indicating that miRNAs were active in ALL. This obsearvation suggusted that miRNA differential expression in MVs were partially significantly related to subtypes of acute lymphoblastic leukemia.

Intriguing is that miR1290 is top higher expression both in MVs derived from Nalm6 cells and from Jurkat cells; miR-1290 is 475-fold higher expressed in Nalm 6 derived MVs versus MVs from normal cells, whereas this miRNA is 245-fold higher expressed in Jurkat cells. Five of these miRNAs were selected to be further assayed and validated by PCR. The qRT-PCR results correlated well with the microarray data. In addition, we found seven miRNAs(miR-148b, miR-484, miR-let-7f, let-7a, miR-223, miR16 and miR-27b) were located near the 11q23 chromosomal region.

With bioinformatic tools (TargetScan), we predicted potential target genes for those miRNAs that exhibited altered expression in MVs from B-ALL and T-ALL. The p85 subunit of phosphatidylinositol 3-kinase (PI3-K) was found to be a potential target of miR-320. Of particular interest, we found that protein tyrosine phosphatase-like member b (PTPLB) may be a potential target of miR-1290. The 474-fold increase in miR-1290 in MVs from Nalm 6 cells, indicating that miR-1290 may participate in the modulation of leukemia by targeting PTPLB, a specific, negative regulator of p210 bcr-abl signal.

In conclusion, we identified miRNAs and found that miRNA expression profiles were ALL subtype-specific. Altered miRNA expression levels may lead to an inappropriate expression of target oncoproteins or target tumor suppressors, thereby facilitating the development of leukemia. These findings expanded the potential diagnostic markers of leukemia and provided useful information to ALL pathogenesis.