The lipogenic regulator SREBF2 induces Transferrin in circulating melanoma cells and suppresses ferroptosis.

Circulating tumor cells (CTCs) are shed by cancer into the bloodstream, where a viable subset overcomes oxidative stress to initiate metastasis. We show that single CTCs from melanoma patients coordinately upregulate lipogenesis and iron homeostasis pathways. These are correlated with both intrinsic and acquired resistance to BRAF inhibitors across clonal cultures of BRAF-mutant CTCs. The lipogenesis regulator SREBF2 directly induces transcription of the iron carrier Transferrin (TF), reducing intracellular iron pools, reactive oxygen species (ROS) and lipid peroxidation, thereby conferring resistance to inducers of ferroptosis. Knockdown of endogenous TF impairs tumor formation by melanoma CTCs, and their tumorigenic defects are partially rescued by the lipophilic anti-oxidants Ferrostatin-1 and Vitamin E. In a prospective melanoma cohort, presence of CTCs with high lipogenic and iron metabolic RNA signatures is correlated with adverse clinical outcome, irrespective of treatment regimen. Thus, SREBF2-driven iron homeostatic pathways contribute to cancer progression, drug resistance and metastasis.