Poster Presentation 28th Lorne Cancer Conference 2016

Forced expression of miR-101a reverses the epigenetic landscape and genetic events in AML stem cells (#153)

Estrella Gonzales-Aloy 1 , Jenny Y Wang 1 2
  1. Cancer and Stem Cell Biology, Children's Cancer Institute, Randwick, NSW, Australia
  2. School of Women’s and Children’s Health, Faculty of Medicine, UNSW Australia, Randwick, NSW, Australia

The occurrence of relapse in acute myeloid leukaemia (AML) is attributed to the persistence of leukaemic stem cells (LSCs), which possess self-renewal and proliferative ability. Current efforts have been done on developing therapeutic strategies targeting LSCs. Recently, microRNAs (miRNAs), a class of small noncoding RNAs, have been implicated in regulation of cancer stem cells (CSCs). Several studies have shown that depletion of miRNAs leads to cancer and miRNA overexpression represents a promising strategy for cancer treatment. Our data show that miR-101a is supressed in Mixed-Lineage Leukaemia (MLL)-mediated AML stem cells and its forced expression impairs LSC functions via reversing the epigenetic landscape and inhibiting pro-survival pathways, leading to apoptotic cell death.

We performed miRNA microarray analysis of MLL pre-leukemic stem cells (pre-LSCs) compared to control and identified a novel tumour suppressor, miR-101a, that is downregulated in pre-LSCs. qPCR confirmed that miR-101a is suppressed in LSCs compared to normal haematopoietic stem cells. Overexpression of miR-101a in pre-LSCs confers a growth disadvantage in vitro as we have observed 60-70% decrease in colony forming ability of miR-101a. In vivo studies of AML development is ongoing. The marked reduction in cell and colony number of miR-101a overexpressed cells is largely attributed to significant  increase in apoptosis and decrease in expression of pro-survival proteins (i.e. Mcl-1 and Bcl-2).   Strikingly, our result revealed a significant reduction in Ezh2, a crucial epigenetic regulator in maintenance of MLL AML and a known target of miR-101a.  This finding is also accompanied by a global decrease of histone H3K27Me3 mark, implicating that miR-101a may contribute to leukaemogenesis via regulating epigenetic pathways in LSCs.

In summary, our preliminary results suggest that suppression of miR-101a contributes to aberrant epigenetic landscape and activates pro-survival pathways resulting in aggressive AML. Forced expression of miR-101a potentially eliminates leukemia-associated epigenetic marks and thus reverses the epigenetic process that originally altered gene expression in LSCs. This may provide a means to eradicate drug-resistant LSCs.