Wang L et al. first revealed that the knockdown of PCSK9 expression could reduce the process of tumor cell epithelial-mesenchymal transition and depress the activation of PI3K/AKT signaling, as well as induce M1 macrophage polarization, thus suppressing tumor cell proliferation, migration, invasion, and epithelial-mesenchymal transition in vitro and tumor cell metastasis in vivo [53]. This evidence concerns the gene PCSK9 and neoplasm.