CXCL12 and neoplasm: Moreover, during the process of CTCs avoiding anoikis to attach to the endothelium, CTC chemokine receptors CXCR4 and CCR7 bind to CXCL12 and CCL21 on endothelial cells to mediate tumor cell arrest and to resist anoikis by regulating the proapoptotic and antiapoptotic Bmf and Bcl-xL proteins [104].