BCAT1, a cytosolic aminotransferase for branched-chain amino acids (BCAAs), is aberrantly activated and functionally required for disease progression in chronic myeloid leukaemia. Cellular metabolic changes are commonly observed in various cancers. How they directly influence cancer development is under investigation. Ayuna Hattori et al. show that the metabolic enzyme BCAT1 is upregulated in chronic myeloid leukemia, mediated by Musashi2. BCAT1 is shown to function by aminating branch-chain keto acids to BCAAs. Inhibition of BCAT1 leads to differentiation and impaired propagation of chronic myeloid leukaemia in mice. In humans, elevated BCAT1 expression is also associated with poorer outcome of the illness and therefore might be used alongside other biomarkers to help predict disease outcome in patients. Reprogrammed cellular metabolism is a common characteristic observed in various cancers1,2. However, whether metabolic changes directly regulate cancer development and progression remains poorly understood. Here we show that BCAT1, a cytosolic aminotransferase for branched-chain amino acids (BCAAs), is aberrantly activated and functionally required for chronic myeloid leukaemia (CML) in humans and in mouse models of CML. BCAT1 is upregulated during progression of CML and promotes BCAA production in leukaemia cells by aminating the branched-chain keto acids. Blocking BCAT1 gene expression or enzymatic activity induces cellular differentiation and impairs the propagation of blast crisis CML both in vitro and in vivo. Stable-isotope tracer experiments combined with nuclear magnetic resonance-based metabolic analysis demonstrate the intracellular production of BCAAs by BCAT1. Direct supplementation with BCAAs ameliorates the defects caused by BCAT1 knockdown, indicating that BCAT1 exerts its oncogenic function through BCAA production in blast crisis CML cells. Importantly, BCAT1 expression not only is activated in human blast crisis CML and de novo acute myeloid leukaemia, but also predicts disease outcome in patients. As an upstream regulator of BCAT1 expression, we identified Musashi2 (MSI2), an oncogenic RNA binding protein that is required for blast crisis CML. MSI2 is physically associated with the BCAT1 transcript and positively regulates its protein expression in leukaemia. Taken together, this work reveals that altered BCAA metabolism activated through the MSI2–BCAT1 axis drives cancer progression in myeloid leukaemia.

Cancer progression by reprogrammed BCAA metabolism in myeloid leukaemia