Programmed Death Ligand-1 in Melanoma and Extracellular Vesicles Promotes Local and Regional Immune Suppression through M2-like Macrophage Polarization.

Tumor-associated macrophages (TAMs) play dual roles (both pro- and antitumor) in tumor progression. TAMs induce programmed death ligand-1 (PD-L1) expression in cancer cells. However, the regulatory effects of PD-L1 in melanoma cells on TAM phenotypical switching remain underexplored.