CD8A and cancer: Several studies in preclinical models and in patients with cancer have demonstrated that targeting the MAPK pathway (ie, with RAF and MEK inhibitors) induces CD8+ T cell infiltration into tumors and improved immunotherapy efficacy.26 44–47 Mechanistically, MAPK pathway inhibition has a dual effect: on the one hand, it downregulates the expression of immunosuppressive factors such as IL-8 and IL-1 and increases the infiltration of activated CD8+ T cells, but on the other hand, it counteracts immune activation through upregulation of PD-L1 by tumor cells.