We also investigated whether increased 64CuCl2 uptake could be correlated with expression of the main cellular copper importer, hCtr1, since several studies had previously suggested that increased 64CuCl2 uptake in different tumors, such as melanoma [17], breast [21] and prostate [18,26] cancers, was dependent on CTR1 overexpression. This evidence concerns the gene SLC31A1 and cancer.