Resumen
Stimulation of the host immune responses, through the use of biotech drugs that remove a brake on the immune system (immune checkpoint inhibitors), is a current widely used strategy to treat a variety of advanced-stage tumors with impressive outcomes also in patients refractory to standard chemotherapy. However, as in the case of metastatic melanoma, many patients fail to achieve a long-lasting clinical benefit. The aim of this article is to provide an overview of the current scientific evidence concerning the role played by cells of the tumor micro-environment, and in particular tumor-associated M2 macrophages, on the innate or acquired resistance of melanoma to immune checkpoint inhibitors. A special focus will be given to potential therapeutic interventions capable of counteracting tumor ability to evade the control of the immune system in order to enhance the efficacy of immune checkpoint inhibitors.