The ability of PepR-NIR750 to bind CXCR4 was evaluated on cancer cell lines differentially expressing the receptor: FB1, human anaplastic thyroid cancer cells, known to express low level of CXCR4; CHO, Chinese hamster ovarian cells and CHO cells transfected with human CXCR4; PES43, human melanoma cell line and B16 mouse melanoma cell lines transfected with human CXCR4 (B16-CXCR4) (Figure S1)17, 18. The gene discussed is CXCR4; the disease is cancer.