SWI/SNF mutations are found in about 20% of all cancers. We studied two genes in this family — ARID1A and SMARCA4 — and discovered that when either is broken, cancer cells become unusually dependent on their mitochondria (the energy factories inside cells). This means existing drugs that target mitochondrial energy production, like the diabetes drug metformin, might be repurposed to treat these cancers. This is a completely new treatment approach — current drugs for these cancers target different pathways entirely.