ARG1 and neoplasm: Taken together, these data indicate that MPNST cells have the ability to activate both Mφ and M2 macrophages through the release of secreted factors, and that the mitochondrial chaperone TRAP1 enhances the induction of metabolic enzymes (i.e. ARG-1 and ARG-2), of the transcription factor HIF-1α and of its target genes MMP-9 and VEGF-A, which are known to be involved in tumor invasion and angiogenesis.