CD4 and neoplasm: On the one hand, inhibition of MEK can accumulate the infiltration of CD4+ and CD8+ T cell into the tumor, increase stem cell‐like memory T cells [489], increase expression of melanoma antigen and MHC I expression, which was associated with enhanced sensitivity to antigen‐specific T cells [490], promote the maturation of DCs [491], and decrease immunosuppressive cytokines (such as IL‐6 and IL‐10), which lead to reduced accumulation of MDSCs, TAMs, Tregs, and Bregs [492, 493].