Abstract 484: Tumor suppressor miRNA-101 modulates leukemogenesis by targeting the EZH2/Wnt/β-catenin signaling pathways

Abstract

Abstract The survival rate of acute myeloid leukemia (AML) patients undergoing standard chemotherapy remains poor due to disease relapse. The main cause of relapse is the failure of chemotherapeutic drugs to eradicate self-renewing leukemic stem cells (LSCs) (Cancers 2017;9:74-97). Because of their intrinsic drug resistance, LSCs are extremely difficult to target by single-gene therapies. MicroRNAs (miRNAs), a class of small noncoding RNAs capable of regulating multiple target genes, represent a promising therapeutic target for elimination of LSCs. While miRNA-101 (miR-101) has been identified as a tumor suppressor in several types of cancers including prostate (Science 2008;322:1695-99) and liver cancer (Cancer Res 2009;69:2623-29), its expression and functional role in AML remains unknown. In this study, we uncover that miR-101 plays a crucial role in leukemogenesis through modulation of key epigenetic and signaling pathways activated in LSCs of mixed-lineage leukemia (MLL)-rearranged AML. Our data showed that overexpression of miR-101 in murine pre-LSCs inhibited cell proliferation in vitro and delayed leukemogenesis in vivo, confirming a tumor-suppressor function of miR-101 in MLL-AF9-induced AML, a highly aggressive leukemia. To assess the therapeutic value of miR-101, we next examined the antitumor function of miR-101 in a xenograft model of human MLL-AF9 AML. Briefly, miR-101 was overexpressed in human MLL-AF9 AML cell line, MOLM-13, that was then transplanted into NOD-scid IL2Rgammanull (NSG) mice followed by in vivo bioluminescence imaging to monitor engraftment of human leukemic cells. Our result revealed a significantly lower engraftment in the xenograft mouse model carrying miR-101-overexpressing leukemic cells compared to control mice. This suggests that inhibition of tumor suppressor miR-101 is essential in the initiation of an aggressive form of human AML. To investigate the potential mechanism by which miR-101 impairs leukemogenesis, we examined key oncogenic pathways regulated by miR-101 by performing luciferase assays and Western blotting. Our data showed that miR-101 inhibited leukemogenesis via directly targeting Enhancer of zeste homolog 2 (EZH2), a crucial epigenetic regulator in leukemia maintenance, as well as key components of Wnt/β-catenin signaling, an oncogenic pathway necessary for LSC self-renewal in AML. Furthermore, immunofluorescence analysis revealed a significant reduction in active β-catenin in the nucleus of miR-101-overexpressing leukemic cells, indicating a direct regulation of miR-101 in β-catenin activity. Collectively, these findings reveal a novel role for miR-101 in leukemia progression that may be used to develop a targeted therapy for AML treatment. Citation Format: Estrella Gonzales-Aloy, Dylan G. Grebert-Wade, Jenny Y. Wang. Tumor suppressor miRNA-101 modulates leukemogenesis by targeting the EZH2/Wnt/β-catenin signaling pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 484.