We then proceeded to exploit the apoptotic kinship between Nef M1 and CXCR4 to suppress the growth and metastasis of primary colorectal tumors in mice [31–32] and recently found that M1 exhibits profound anti-proliferative activity against various CXCR4-expressing breast carcinomas [33–34]. The gene discussed is CXCR4; the disease is breast carcinoma.