Abstract
Understanding how cellular pathways interact is crucial for treating complex diseases like cancer. Individual gene-gene interaction studies have provided valuable insights, but may miss pathways working together. Here we develop a multi-gene approach to pathway mapping which reveals that acute myeloid leukaemia (AML) depends on an unexpected link between complex II and purine metabolism. Through stable-isotope metabolomic tracing, we show that complex II directly supports de novo purine biosynthesis and that exogenous purines rescue AML cells from complex II inhibition. The mechanism involves a metabolic circuit where glutamine provides nitrogen to build the purine ring, producing glutamate that complex II metabolizes to sustain purine synthesis. This connection translates into a metabolic vulnerability whereby increasing intracellular glutamate levels suppresses purine production and sensitizes AML cells to complex II inhibition. In a syngeneic AML mouse model, targeting complex II leads to rapid disease regression and extends survival. In individuals with AML, higher complex II gene expression correlates with resistance to BCL-2 inhibition and worse survival. These findings establish complex II as a central regulator of de novo purine biosynthesis and a promising therapeutic target in AML.