The RUNX1-ETO target gene RASSF2 suppresses t(8;21) AML development and regulates Rac GTPase signaling

Abstract

Large-scale chromosomal translocations are frequent oncogenic drivers in acute myeloid leukemia (AML). These translocations often occur in critical transcriptional/epigenetic regulators and contribute to malignant cell growth through alteration of normal gene expression. Despite this knowledge, the specific gene expression alterations that contribute to the development of leukemia remain incompletely understood. Here, through characterization of transcriptional regulation by the RUNX1-ETO fusion protein, we have identified Ras-association domain family member 2 (RASSF2) as a critical gene that is aberrantly transcriptionally repressed in t(8;21)-associated AML. Re-expression of RASSF2 specifically inhibits t(8;21) AML development in multiple models. Through biochemical and functional studies, we demonstrate RASSF2-mediated functions to be dependent on interaction with Hippo kinases, MST1 and MST2, but independent of canonical Hippo pathway signaling. Using proximity-based biotin labeling we define the RASSF2proximal proteome in leukemia cells and reveal association with Rac GTPase-related proteins, including an interaction with the guanine nucleotide exchange factor, DOCK2. Importantly, RASSF2 knockdown impairs Rac GTPase activation, and RASSF2 expression is broadly correlated with Rac-mediated signal transduction in AML patients. Together, these data reveal a previously unappreciated mechanistic link between RASSF2, Hippo kinases, and Rac activity with potentially broad functional consequences in leukemia.

MicroRNA let-7b downregulates AML1-ETO oncogene expression in t(8;21) AML by targeting its 3′UTR

“…Having observed that let-7b-5p overexpression can reduce AML1-ETO protein expression, we next wondered whether the degree of AML1-ETO downregulation has potential therapeutic relevance. Therefore, we first measured the expression of known transcriptionally repressed AML1-ETO target genes, CEBPA [17] and RASSF2 [59], upon transfection of Kasumi-1 and SKNO-1 cells with the let-7b-5p miRNA mimic. In both cell lines, treatment with the miRNA mimic resulted in a significant increase of both transcripts in comparison to cells treated with a non-targeting control mimic (Fig.…”

KDM4B promotes acute myeloid leukemia associated with AML1‐ETO by regulating chromatin accessibility

“… 17 We then extracted subsets of genes that significantly contributed to the gene enrichment (called “core enrichment genes”, defined by GSEA) for the above two gene sets (Figure S1B ). Indeed, 27 and 16 core enrichment genes were commonly upregulated in SKNO‐1 and Kasumi‐1 for the two gene sets, respectively, which included OGG1 that is involved in base excision repair in AML1‐ETO‐mediated mutagenesis, 35 tumor suppressors RASSF2 36 and TGFBI , 37 and also LAT2 that blocks differentiation in t(8;21)‐positive cells 38 as repressive targets of AML1‐ETO. We further found that KDM4B silencing in SKNO‐1 but not Kasumi‐1 had inhibitory effects on the expression of a broader range of AE‐inducible genes (Figure 2I ), which was compatible with an intensive growth‐suppressive effect following the gene silencing (Figure 2C ).…”

The Landscape of Gene Co-Expression Modules Correlating with Prognostic Genetic Abnormalities in AML

“…The heterogeneity of expression pro les has been studied for AML patients harboring different mutations or chromosomal abnormality [11][12][13][14], but the co-expressed gene modules have not been rarely linked to the genetic markers using WGCNA. Ravasz et al demonstrated hierarchical network modularity for metabolic network, based on which they proposed the utility of Topological Overlap Matrix to measure how strongly the nodes are connected [15].…”