Vemurafenib-resistant melanoma cells induce an immunosuppressive response in macrophages

MONS J; PEREZ C; FALCON C; CUELLO ORLANDI SF; SANGIACOMO M; ALVAREZ SE

Conferencia; SAIC 2022; 2022

Melanoma is the most aggressive form of skin cancer. Although targeted therapy with BRAF and MEK inhibitors (BRAFi/MEKi) has shown an impressive success, the occurrence of resistance and relapse reduces its efficacy. Many reports have established that the tumor microenvironment and infiltration of different immune cells have a crucial role in cancer progression and resistance. In that sense, expression of the immune checkpoint (IC) Tim-3 and its ligand Galectin 9 (Gal 9) are linked to immune exhaustion. The aim of this work was to elucidate how Vemurafenib (Vem, BRAFi) resistance affects Gal 9 expression in melanoma cells, thus modulating Tim-3 expression in macrophages. The expression of Gal 9 and Tim-3 was evaluated in sensitive and Vem-resistant A375 melanoma cells (A375S and A375R respectively) by RT-qPCR. Resistance was associated with increased expression of Gal 9 and other IC ligands such as PD-L1 and PD-L2. On the other hand, Tim-3 expression was evaluated by treating PMA-differentiated THP-1 cells with conditioned media (CM) derived from A375S and A375R cells. Remarkably, while differentiated macrophages exposed to CM from A375R cells showed an M2-like profile, CM from both cell types induced the down-regulation of Tim-3. To further study the regulation of these proteins, we performed a bioinformatic analysis using the open access web server GEPIA2. In sílico data show a higher expression of both Tim-3 and Gal 9 in melanoma compared to healthy tissue. Altogether, our results indicate that resistance to BRAFi increases Gal 9 expression in melanoma and induces an immunosuppressive response by macrophages. Furthermore, we suggest that secretion of Gal 9 by melanoma cells may modulate the expression of Tim-3 in macrophages.