In BALB/c mice with orthotopic 4T1 tumors, CA/ZYII-siP-c-L accumulation in tumors was 3.5-fold higher than that of free drugs, significantly enriching helper T cells and cytotoxic T lymphocytes while reducing regulatory T cells and suppressive dendritic cells in the tumor immune microenvironment; this immunomodulatory effect, combined with PD-L1 silencing at protein levels, contributed to ~62% inhibition of tumor growth with no organ damage (confirmed by hematoxylin and eosin staining of major organs and normal biochemical indices). This evidence concerns the gene CD274 and neoplasm.