In this study, we first detected PCSK9 expression in colon cancer versus normal tissues for association with clinicopathological characteristics from patients and then assessed the downregulation of PCSK9 expression (vs. PCSK9 overexpression) in the regulation of tumor cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro and tumor cell metastasis in vivo. The gene discussed is PCSK9; the disease is colonic neoplasm.