PO-395 Mechanistic investigation of epigenetic modifications induced by metabolic changes in AML

Abstract

IntroductionAcute Myeloid Leukaemia is the most common and aggressive adult leukaemia with a high frequency of relapse and mortality. This is likely due to the failure to eliminate the malignant stem like population (LSCs) composed by low cycling cells that give rise to highly proliferating blast type progenitors. Although the currently available chemotherapeutic agents efficiently eradicate blasts, LSCs can be retained and cause relapse. Therefore, new therapeutic strategies aimed to specifically eradicate them is urgently needed.These insights led to an increasing interest in understanding the molecular mechanisms governing LSCs biology. Along this line, recent reports (Raffel et al. Nature 2017) highlight the crucial role of Branched Chain Amino Acid (BCAA) catabolism in LSCs. Indeed, BCAA Transaminase 1 (BCAT1) is highly expressed in LSCs and led to reduction of alpha-ketoglutarate (aKG) levels, with consequent impairment of aKG-dependent dioxygenases activity, such as TET1/2, and increase in DNA methylation, resembling AML with TET or an IDH mutation. Moreover, BCAT1 overexpression is associated with poor overall survival in patients which have no TET or IDH mutation.However, aKG is also a cofactor of histone-demethylases and it remains unclear whether BCAT1 also affects these enzymes, which regulate chromatin structure and activity.Material and methodsGenome wide approaches (i.e. ChIPseq for specific histone marks, ATACseq, RNAseq, DNA methylation) are used to mechanistically dissect the connexion between BCAT1 mediated metabolic changes and alterations in the chromatin landscape of AML cell lines (HL-60, SKM1-MOLM-13) and LSCs,Results and discussionsIn order to understand if BCAT1 is controlling the chromatin structure, the transcription factor binding and the histone methylation status, we performed H3K27ac-H3K27me3-H3K4me1-H3K4me3 ChIPseq experiments and ATACseq on control and BCAT overexpressing cells. Despite the global DNA methylation changes observed in BCAT1 overexpressing cells,Raffel et al., Nature 2017 ChIPseq and ATACseq analyses did not show a global change in chromatin structure and modifications. Nonetheless, differences in specific loci were identified after BCAT1 overexpression suggesting a more complicated scenario and opening the road for further analyses.ConclusionThis work will provide rationale for the use of metabolic enzyme inhibitors (alone or in combination with epigenetic inhibitors) as a therapeutic approach in AML and other solid BCAT1 overexpressing tumour entities.