ACSS2 Suppresses Ferroptosis to Drive Breast Cancer Brain Metastasis

Brain metastasis in breast cancer patients represents a terminal disease stage, with median survival typically measured in months. Tumors that colonize the brain must adapt to its unique microenvironment, such as high acetate levels. Primary brain tumor cells enhance acetate conversion to acetyl-CoA through phosphorylation of acetyl-CoA synthetase 2 (ACSS2) by cyclin-dependent kinase 5 (CDK5), a process regulated by the nutrient sensor O-GlcNAc transferase (OGT). In this study, we showed that brain-metastatic breast cancer cells exhibited elevated O-GlcNAc, OGT, and phosphorylated ACSS2 (Ser267) compared to their parental counterparts. Both OGT and CDK5 were essential for in vivo tumor growth in the brain, and ACSS2 and a phospho-mimetic S267D mutant drove progression of brain metastatic breast cancer. Mechanistically, ACSS2 supported tumor cell survival by suppressing ferroptosis through E2F1-dependent transcription of the anti-ferroptotic protein SLC7A11. Treatment with brain-penetrant ACSS2 inhibitor AD-5584 induced ferroptosis and significantly suppressed breast cancer brain metastatic growth ex vivo and in vivo. Together, these findings identify ACSS2 as a key metabolic regulator of brain-metastatic breast cancer survival and a promising target for ferroptosis-inducing therapies.