CXCR4 and prostate cancer: Interestingly, most of these HER2-overexpressing cell lines express CXCR4, which is reportedly associated with haematogenous metastasis in breast, colon and prostate cancer patients (Muller et al, 2001; Brand et al, 2005), and is known to be regulated by HER2 through the PI3K/Akt pathway (Li et al, 2004).