To determine the extent to which CXCR4 contributes to primary breast tumor progression downstream of KLF8, we injected the 231-K8ikd cells, the 231-K8ikd cells with stable overexpression of CXCR4 or its dN20 mutant into the mammary fat pad, induced the knockdown of KLF8 in vivo and examined the growth and invasion of the orthotopic tumor. This evidence concerns the gene KLF8 and neoplasm.