Abstract 1931: MiR182 mediated control over myeloid differentiation provides novel mechanism of Imatinib resistance in chronic myeloid leukemia

Abstract

Abstract MiR182 is an evolutionarily conserved miR, present in a cluster with miR183, and miR96 on human chromosome 7q32.2. This cluster is over-expressed in hESCs, and iPSCs. Developmentally, miR182 is over-expressed during erythropoiesis from CD34 cells. Erythroid differentiation of CML cells induced by Imatinib treatment provides an alternate mechanism of Imatinib escape, and also emphasizes the need to explore miR182 function in this context. In cancerous cells, miR182 regulates metastasis in melanoma cells by regulation of MITF and FOXO3, and DNA repair in breast cancer by targeting BRCA1. These reports provide some understanding of miR182 function by transient in-vitro assays. To refine functional importance, targeted deletion of MIR182 has been done on mice retinal cells where it is shown an over-expressed candidate by quantitative methods; nevertheless MIR182 deletion does not show any phenotypic change indicating challenges to study their functions along with better model systems. We focus to study K562 cells, CML blast crisis cell line with wild type Bcr-Abl tyrosine kinase, partially differentiated cells able to differentiate in different lineages upon induction. We exploit use of CRISPR/Cas9 mediated knock-out approach to find out miR182 function in K562 cells. We show that we have successfully deleted MIR182 loci in K562 cells by CRISPR. We hypothesize if miR182 regulates proliferation or differentiation in bi-potent K562 cells. Using phenotypic characterization, we studied MIR182 deleted cells. We show that myeloid differentiation is augmented by MIR182 deletion. Homozygous MIR182 deleted cells display decreased proliferation. We find striking inverse correlation with notch signalling genes in the context of Imatinib resistance. Notch signalling has been documented in cancer cells where its role has been shown in context dependent which require more explanation of its regulation. Hes1, one of main transcriptional regulator of notch signalling pathway, is targeted by miR182 shown by both bio-informatics, and in-vitro assays. Hes1 manipulation confirms it as down-stream target of miR182 in CML cells. We next explored Imatinib resistance phenotype in the context of miR182 given its expression in CD34 cells. We demonstrate miR182 is over-expressed in CML cells towards Imatinib treatment in ex-vivo, and in-vitro. We find miR182 essential for proliferation of K562 cells, Imatinib resistance. Taken together, our studies highlight miR182 targets notch signalling genes in CML cells implication of which we have shown in the context of Bcr-Abl independent Imatinib resistance mediated by differentiation deregulation. Citation Format: Deepak Arya, P. Sasikala, Shang Li, Dasaradhi Palakodeti, Cecil Ross, Sudhir Krishna. MiR182 mediated control over myeloid differentiation provides novel mechanism of Imatinib resistance in chronic myeloid leukemia. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1931.