CTLA4 and neoplasm: Second, it enhances antitumor immune response by regulating the tumor immune microenvironment: ZVI‐NP transforms tumor‐promoting M2 macrophages into antitumor M1 macrophages, reduces the proportion of regulatory T cells (Tregs), and down‐regulates the expression of PD‐1 and CTLA4 in CD8+ T cells, which enhances their cytotoxic activity, while attenuating the expression of PD‐L1 in cancer cells.