The immune landscape of melanoma microenvironmental crosstalk.

Melanoma is a highly aggressive skin malignancy characterized by early metastasis, marked therapeutic resistance, and poor clinical outcomes in advanced disease. Increasing evidence indicates that immune dysregulation within the tumor microenvironment (TME) is a central determinant of melanoma progression, metastatic dissemination, and treatment failure. The melanoma immune microenvironment is shaped by complex interactions among tumor-associated macrophages, tumor-infiltrating lymphocytes, regulatory T cells, myeloid-derived suppressor cells, stromal cells, endothelial cells, and extracellular matrix components, together with hypoxia and acidosis, all of which cooperatively drive immune evasion, chronic inflammation, angiogenesis, and resistance to therapy. Mechanistically, cancer-associated fibroblasts promote immune tolerance by secreting CXCL12 and CCL17, thereby recruiting regulatory T cells and reinforcing a suppressive stromal niche; melanoma-derived factors and metabolic perturbations reprogram tumor-associated macrophages toward a pro-tumoral phenotype through lipid metabolic remodeling, endoplasmic reticulum stress, and immunosuppressive mediator production; and hypoxic stress amplifies CD39/CD73-dependent adenosine generation, which suppresses dendritic cell maturation and cytotoxic T-cell activity while facilitating immune escape. These immunosuppressive networks not only impair effective antitumor immune surveillance but also limit the long-term efficacy of immune checkpoint blockade and other systemic treatments. This review summarizes the immunopathological mechanisms underlying melanoma progression within the immune microenvironment and highlights emerging therapeutic strategies targeting immune and stromal crosstalk, providing a valuable theoretical basis for understanding melanoma immune escape and an important reference for the development of more effective and durable immunotherapeutic interventions.