TRAP1 expression elicits pro-tumoral functions in macrophages associated to malignant peripheral nerve sheath tumor cells.

Background: Metabolic adaptations can sustain the pro-neoplastic functions exerted by macrophages in the tumor microenvironment. Malignant peripheral nerve sheath tumors (MPNSTs), aggressive and incurable sarcomas that develop either sporadically or in the context of the genetic syndrome Neurofibromatosis type 1, are highly infiltrated by macrophages, whose contribution to MPNST growth remains poorly characterized. Here, we analyze the role played by the molecular chaperone TRAP1, a regulator of mitochondrial metabolic pathways, in shaping the pro-tumoral activity of macrophages associated to MPNST cells.

Methods: We have studied the phenotypic changes elicited by a MPNST cell-conditioned medium in macrophages with or without TRAP1, and their subsequent ability to support MPNST cell growth and migration and endothelial cell angiogenesis.

Results: The presence of TRAP1 is required in both naive and M2-like macrophages for eliciting phenotypic changes that lead to the acquisition of pro-neoplastic features. TRAP1-expressing macrophages become able to sustain MPNST cell growth and migration and to exert pro-angiogenic properties on endothelial cells through accumulation of the metabolite succinate and the ensuing activation of a HIF-1α-dependent transcriptional program.

Conclusions: Our data provide evidence of a molecular crosstalk between MPNST cellular components, in which soluble factors released by cancer cells drive phenotypic changes in macrophages that in turn enhance pro-tumoral biological routines in both MPNST and endothelial cells. TRAP1-dependent metabolic rewiring in macrophages is mandatory for sustaining this interplay, as a TRAP1-succinate-HIF-1α signaling axis orchestrates their acquisition of tumor-promoting features.