CXCR4 and neoplasm: We have investigated the relationship between expression of 5T4, CXCR4 and chemotaxis in several human tumor cell lines including choriocarcinoma, breast and ovarian and all exhibited CXCL12-mediated chemotaxis and showed evidence of a 5T4/CXCR4 complex in the cell membranes (Southgate et al., unpublished).