MicroRNAs Expression signatures of microvesicles Derived-From Three Different Leukemia Cell Lines

Abstract 4649

MicroRNAs(miRNAs) are short non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. Recent studies revealed that genetic exchange of miRNAs between cells can be accomplished through microvesicles(MVs),which are small exosomes/vesicles of endocytic origin shed from the surface membranes of activated platelets and normal or malignant cells. Generally, MVs are enriched in various bioactive molecules of their parental cells, such as proteins, DNA, mRNA and miRNAs. So, exploration of changes of the miRNAs profiles of MVs derived from leukemia cells will contribute to a better understanding of the pathogenesis of leukemias and then provide valuable suggestions about how to diagnose, prevent and control leukemia.

In the present study,we used Agilent miRNA microarray to analyze the miRNAs of MVs derived from three different leukemia cell lines (K562, Nalm-6 and Jurkat) and their cell counterparts, and normal plasma derived MVs as normal control. The significantly differentially expressed

miRNAs between test group and normal control group were determined by t-test(P<0.05 and Fold Change>2).The putative target genes of the differentially expressed miRNAs were predieted by Targetscan.

We observed that 125 miRNAs (93 up-regulated and 32 down-regulated) were determined to be differentially expressed in MVs derived from three leukemia cell lines compared with their normal control counterparts. Four miRNAs including miR-1290, miR-1268,miR-1246 and miR-1305 were found to be hundreds fold alteration. In addition, let-7f, miR-26a, miR-26b and miR-223 were significantly under expressed.

We next found that MVs derived from lymphocytic leukemia cell lines(Nalm-6 and Jurkat) shared 100 miRNAs of 888 miRNAs, 99 upregulated and only one miRNA downregulated. Meanwhile, 44 miRNAs were just altered in Nalm-6-MVs, 9 miRNAs are just altered in Jurkat-MVs. Moreover, we found 22 miRNAs were only altered in K562-MVs, only one miRNAs(miR-191) altered in lymphocytic-MVs. We also found that MVs miRNA profiles were significantly different, compared the MVs derived from three leukemia cell lines with their cell counterparts. K562 cells and K562 MVs shared 112 miRNAs. 122 miRNAs were only altered in cells and 77 miRNAs were only altered in their MVs. Similarly, Nalm-6 cells and nalm-6 MVs shared 154 miRNAs, and 9 miRNAs were only altered in cells and 102 miRNAs were only altered in their MVs. Jurkat cells and Jurkat MVs shared 111 miRNAs, and 15 miRNAs were only altered in cells and 95 miRNAs were only altered in their MVs.

The results of real-time qRT-PCR consisitanted with that observed in the microarray assays.

We identified target genes of these differently expressed miRNAs by TargetScan, and retrievaled recent literature on the properties and biogenesis of these aberrant miRNAs and their potential role in cancer progression. Differentially expressed miRNAs include known oncomirs (e.g miR-96) as well as miRNAs that were not previously universally associated with cancer. Specific examples include let-7f,miR-191 and miR-21, which were consistently down regulated and miR-223 which is consistently up regulated in cancer, in the context of our cohort. Furthermore, miR-1246 mediates the functions of p53 family members, and BCL-2,KRAS may be target of miR-1305.

In summary,we firstly used the miRNA microarray to seek for miRNAs with differential expression in MVs derived from K562, Nalm-6 and Jurkat cells. Predicting the putative target genes of the miRNAs with bioinformatic softwares may play a foundation for further studies exploring the biomolecular mechanism of oncogensis and development of leukemia and searching for related biomolecular markers of diagnosis and treatment in leukemia.