Mirna Expression Profile of Microvesicles Derived From K562 Cells

Abstract 4411

MicroRNAs (miRNAs) are small non-coding RNA sequences of about 22nt and play an important role in disease progression including carcinogenesis. Recent evidences reveal that genetic exchange of miRNAs between cells can be accomplished through microvesicles(MVs).

MVs are small exosomes of endocytic origin released not only by activated platelets but also by hematologic malignancies such as leukemia. Sheded from the plasma membrane MVs move into the extracellular environment to facilitate communication between cells. MVs containing miRNAs would enable intercellular cross-talk in vivo. This prompted us to investigate specific variations of miRNA expression patterns in MVs derived from leukemia.

We examined the miRNA expression profile of MVs both from chronic myeloid leukemia cell line K562 and normal human volunteers’ peripheral blood. Agilent miRNA microarray was employed for detection and then real-time PCR for verification. Bioinformatic software tools were used to predict the target genes of identified microRNAs and define their function.

Our study figures out miRNAs of MVs from leukemia and normal cells and characterizes specific miRNAs expression. We found that MVs from K562 cells express 348 miRNAs of 888 miRNAs. While 77 miRNAs displayed down regulation, 134 were upregulated. Interestingly, most of the miRNAs dysregulated in MVs display up regulated expression, suggesting their prevalent roles as tumor promotors.

Among the aberrantly expressed miRNAs, miR-1290 was identified whose expression levels was more than 900 times than that of normal cell derived MVs. While the expression of miR-125a-3p was up-regulated by more than 300 times. And miR-654-5p, miR-654-5p, miR-1268 and miR-1246 were up-regulated more than 200 times. Five of the disregulated miRNAs (miR-1290, miR-125a-3p, let-7a, let-7f, miR-26a) were further assayed and validated by Q-RT-PCR results which correlated well with the microarray data.

Of note, upexpression of miR-663, miR-1237, miR-149, miR-634, miR-1181, miR-92b, miR-130b as well as downregulation of let-7a, let-7f, miR-26a, miR-26a, miR-26b, miR-266, miR-126, miR-93, miR-451, miR-103, miR-107, miR-27a were similar to what was previously reported about leukemia, thus supporting the general roles of these miRNAs as tumor suppressors or oncomiRNAs in leukemia.

Meanwhile we noticed a reduced expression of miR-1237, miR-365, miR-223b, miR-27b, miR-151-5p, miR-23a, miR-21, miR-30e, miR-361-5p, miR-484, miR-185, miR-374a, miR-197 in our study, as recently stated in solid tumor, thus suggesting that significantly lower abundance of these miRNAs is shared in leukemia.

In addition to identify the already known leukemia-associated miRNAs, we had checked out dozens of novel miRNAs without any articles published until now, namely miR-502-3p, miR-718, miR-877, miR-1470, miR-720, miR-1267, miR-127, miR-767-3p, miR-1974-v14.0, miR-361-5p, miR-374b and so on.

Using bioinformatic tools (TargetScan), we predicted potential targets for those miRNAs that exhibited altered expression in MVs from leukemia cells. Of particular interest, we found that hsa-miR-125a-3p which was refered above may regulate 34 potential genes of which five are located around the chromosome open reading frame. We hypothesised that miR-125a-3p may participate in the modulation of leukemia through these genes by affecting chromosome.

Taken together, our study identifies miRNAs of MVs from leukemia and normal cells and characterizes specific miRNAs expression. These findings highlight a number of miRNAs from leukemia-derived MVs that may contribute to the development of hematopoietic malignancies. Further investigation will reveal the function of these differentially expressed miRNAs and may provide potential targets for novel therapeutic strategies.