Nef-M1 (Nef-Motif-1) is an antagonist peptide targeting CXCR4 and an apoptosis (apoptosis) inducer derived from the myristoylated protein encoded by the HIV nef gene. Nef-M1 inhibits tumor angiogenesis and epithelial-mesenchymal transition (EMT) by activating the apoptotic pathway through increased levels of caspase-3 in cancer cells. Additionally, it suppresses VEGF-A, p-GSK-3β, and vimentin while enhancing E-cadherin, thereby hindering angiogenesis and EMT processes. Nef-M1 is applicable in colorectal cancer and breast cancer research.