Pharmaceutical inhibition of RAS overcomes cytokine mediated resistance to FLT3 inhibition in FLT3-ITD+ AML [ATAC-seq]

AML is characterised by a variety of co-occurring driver mutations in genes associated with cell signallingand growth regulationsuch as the FLT3-ITD. Inhibitors targeting FLT3 (FLT3i) are beingused to treat FLT3-ITD+ patients but most relapse.By profiling the gene regulatory networks of samples from patients before and after FLT3i treatment weobservedan increase in AP-1 mediated and a loss of RUNX1 mediated connections in treatment resistant cells. Treatmentinducesupregulation of signalling pathway genesindicatingthat cytokines mediate resistance to FLT3i, with IL-3 playing a major role. IL3 rescues survival by counteracting FLT3i mediated globalRUNX1 degradation and adown-regulationof bindingof RUNX1 in chromatin.To identify inhibitors which bypass the RUNX1 barrier we inhibitedMAPK signalling with a novel pan-RAS inhibitor which overcomes cytokine mediated resistance.Our data show (I) that cytokinesinstructAML maintenance via the stabilisation of transcriptional regulators and (ii)pan-RAS drugs bypass thisbarrier, suggesting a novel approach to treatment of AML.