CXCR4 and breast cancer: Previous studies have shown that heparin is capable of antagonising chemokine function both in vitro and in vivo (Castelli et al, 2004) indicating its potential to disrupt the interaction between CXCL12 and CXCR4, thereby preventing the invasion of CXCR4 expressing breast cancer cells (Dowsland et al, 2003).