CXCR4 and cancer: Based on the clear site‐dependent antimetastatic potency achieved by T22‐GFP‐H6‐FdU in the prevention of metastasis experiments (Fig 6A, Appendix Fig S8A, and Table 1), on its dependence on CXCR4 membrane expression for cell internalization (Fig 2E) and capacity to selectively kill CXCR4+ cancer cells (Fig 3A and B), we investigated if CXCR4 expression after therapy correlated with the observed antimetastatic effect at the different sites.