The impact of ERAP1 inhibition on metabolite homeostasis of melanoma cells.

Manipulation of the activity of Endoplasmic Reticulum AminoPeptidase 1 (ERAP1) has emerged as a powerful tool for the modulation of the cellular antigenicity and concomitant adaptive immune responses, with potential applications in cancer immunotherapy and Major Histocompatibility class (MHC)-associated autoimmunity being explored. Small molecule inhibitors often target allosteric sites of ERAP1 to achieve superior selectivity. However, recent findings suggested that ERAP1 functional perturbation may also affect cellular metabolism, raising concerns on the safety of this approach. To address this, we treated a melanoma cancer cell line with near saturating doses of an allosteric ERAP1 inhibitor and compared metabolite homeostasis to untreated and knock-out cells. Analysis of 8625 detected metabolite features revealed non-significant changes in metabolite composition in both inhibitor concentrations tested and only small changes in the ERAP1 knockout (KO) cells, limited to up to 25 metabolite features, most notably choline. Our results suggest that pharmacological inhibition of ERAP1 that targets allosteric sites, does not induce sufficiently large metabolic shifts to alter metabolite homeostasis. This is distinct from genetic deletion of the protein, which induces additional effects, albeit limited. These results encourage the exploration of allosteric ERAP1 inhibitors as pharmacological agents for the modulation of immune responses in the clinic.