International audienceNeuroblastoma is the most common solid tumour of childhood, yet the prognosis for high risk disease remains poor. We demonstrate that arginine metabolism via Arginase 2 (ARG2) drives neuroblastoma cell proliferation. Targeting arginine metabolism by blocking Cationic Amino Acid Transporter 1 (CAT-1) dependent arginine uptake in vitro or therapeutic depletion of arginine by pegylated-recombinant arginase BCT-100 significantly delays tumour development and prolongs murine survival. Tumour cells polarise infiltrating monocytes to a M1- macrophage phenotype, which release IL-1 and TNF-a in an RAC-alpha serine/threonine-protein kinase (AKT)-dependent manner. Il-1 and TNF- signal-back to upregulate ARG2 expression via p38 and Extracellular regulated kinases 1/2 (ERK1/2) signalling in neuroblastoma and neural crest-derived cells. Proteomic analysis reveal Stage IV human tumour microenvironments are enriched in IL-1 and TNF-a, which is associated with a worse prognosis. Thus we describe an immune-metabolic regulatory loop between tumour cells and infiltrating myeloid cells regulating ARG2, which could clinically exploited. Statement of significance: Neuroblastoma polarised macrophages released IL-1and TNF which signal back to regulate Arginase2 in tumour cells and drive their proliferatio