RORγ bridges cancer-driven lipid dysmetabolism and myeloid immunosuppression

Despite well-documented metabolic and hematopoietic alterations during tumor development, the mechanisms underlying this crucial immunometabolic intersection remain elusive. Of particular interest is the connection between lipid metabolism and the retinoic-acid-related orphan receptor (RORC1/RORγ), whose transcriptional activity modulates cancer-related emergency myelopoiesis and is boosted by cholesterol metabolites, while hypercholesterolemia itself is associated with dysregulated myelopoiesis. Here, we show that cancer and hypercholesterolemic diet independently or cooperatively activate RORγ-dependent expansion of myeloid-derived suppressor cells (MDSCs) and M2-polarized tumor-associated macrophages (TAMs), supporting cancer spread. Moreover, we report that tumor-induced expression of IL-1b and IL-6 promotes hepatic expression of proprotein convertase subtilisin/kexin type 9 (PCSK9) in preclinical models and patients. Importantly, lowering cholesterol levels, by genetic or pharmacological inhibition of PCSK9, prevents MDSC expansion, M2 TAM accumulation and tumor progression in a RORγ-dependent manner, unleashing specific anti-tumor immunity. Overall, we identify RORγ as a key sensor of lipid disorders, bridging hypercholesterolemia and pro-tumor myelopoiesis.