AB119. Induction of suppressor of cytokine signaling-3 in FLT3-ITD positive MV4-11 acute myeloid leukemia cells in response to 5-Azacytidine and Trichostatin A

Background and objective: Suppressor of cytokine signaling-3 (SOCS-3) has been shown to be an important candidate in molecular therapeutic strategies in management of acute myeloid leukemia (AML), particularly in patients carrying FLT3-ITD mutation. SOCS-3 suppresses cytokine signalling by inhibiting the activity of Janus Kinase-2 (JAK-2), and by competing with signal transducer and activator of transcription (STAT) molecules that leads to underexpression. The study aims to determine the epigenetically silence genes in AML cells carrying a FLT3-ITD mutation and epigenetically expressed genes afer treatment with demethylating agent and histone deacetylase inhibitor.

Methods: MV4-11, a FLT3-ITD positive AML cell line was treated with epigenetic modulating agents; 5-azacytidine (5-Aza, a DNA demethylating agent) and Trichostatin A (TSA, a histone deacetylase inhibitor) at IC₅₀ concentrations. One-Color Microarray-based expression analysis (Agilent SurePrint Technology) was utilized and the data was collected and analyzed by Genespring 12.6 software. The gene expression datasets were subjected to pathway analysis by online DAVID tool (http://david.abcc.ncifcrf.gov/) using KEGG pathway database. The microarray results were validated by quantitative real-time PCR to determine the relative quantification (RQ) values.

Results: Microarray analysis detected 1,291 expressed genes related to drug interactions. Pathway analysis by KEGG database revealed that the 1,291 genes were: 21 genes from MAPK pathway, 19 genes from pathways in cancers, 17 genes from cytokine-cytokine receptor interaction, 12 from focal adhesion, 12 from regulation of action cytoskeleton, 10 genes from JAK/STAT pathway, 10 genes from Calcium signalling and several other pathways with less than 10 genes involved. Among the 10 genes in JAK/STAT pathway, SOCS-3 was highly expressed in 5-Aza and TSA with 66.24 and 147.43 folds (Genespring analysis, Benjamini Hochberg, P<0.05), respectively compared to untreated cells. Whereas, STAT6 was down regulated by −8.57 and −2.28 folds, respectively. Validation of microarray result showed RQ of SOCS-3 gene was upregulated by 3.7 and 18.2 folds, whereas STAT6 by 0.7 and 0.1 folds in 5-Aza and TSA respectively. SOCS-3 over expression reduces STAT6 activities and thus induces cell death in AML cells.

Conclusions: SOCS-3 was epigenetically silenced in AML cells and re-expressed after 5-Aza and TSA treatments. Whereas, STAT6 plays a role in a negative feedback loop. The finding suggests that, SOCS-3 expression is associated with pathogenesis of AML and can be served as prognosis marker in molecular targeted therapy of AML.

Keywords: Suppressor of cytokine signaling-3 (SOCS-3); MV4-11; acute myeloid leukemia (AML); 5-Aza; Trichostatin A (TSA)