Introduction: Melanoma is an aggressive cancer characterized by a rapid metastatic process. Thus, understanding the mechanisms underlying its progression is urgently needed to improve patient outcomes. In this regard, there is consistent evidence of a tumor-sustaining crosstalk between melanoma and subcutaneous adipose tissue; however, the role of EVs in this communication still needs to be clarified.

Methods: After isolation by SEC, EVs were characterized by NTA, TEM and Western blot analysis. The impact of these particles on melanoma cell growth was evaluated by cell proliferation and colony formation assays, and the effects on metastatic potential were assessed by transwell assay. Melanoma cell stem-like traits, including spherogenic ability, ABCG2 enrichment and vemurafenib response, were investigated by sphere formation assay, flow cytometry and cell viability assay. The metabolic consequences of EV treatment were analyzed by Western blot and cytofluorimetric assays.

Results: We demonstrated that the EVs derived from adipocytes did not alter melanoma cell proliferation, but significantly promoted tumor cell migration and invasion by determining an enrichment in mesenchymal markers, such as N-cadherin and vimentin. In particular, these changes were accompanied by the transition towards a stem-like phenotype, characterized by enhanced spherogenic ability and ABCG2 upregulation. Interestingly, this led to a reduced response to vemurafenib, with diminished apoptotic rates and decreased caspase 3 and PARP cleavage. Mechanistically, an increase in PGC-1α expression was found, resulting in higher mitochondrial mass and activity; of note, the treatment of melanoma cells with XCT790 and SR-18292, two specific inhibitors of mitochondrial biogenesis, successfully counteracted the above EV-related effects, suggesting that this process could be targeted to suppress the EV-mediated interactions between subcutaneous adipocytes and melanoma.

Conclusions: Taken together, these results highlight the crucial role played by EVs in the melanoma microenvironment, highlighting the ability of adipocyte-derived vesicles to sustain melanoma cell aggressiveness via PGC-1α activation.