The difference in uptake between the PC3-CXCR4 and PC3-WT tumors was statistically significant (p < 0.001), resulting in a PC3-CXCR4-to-PC3-WT tumor uptake ratio of 2.0 ± 0.2 at 1 h p.i. and 2.8 ± 0.1 at 2 h p.i. By 2 h p.i. the PC3-CXCR4-to-blood ratio was 31.1 ± 0.1, and the ratio to all normal tissue except kidneys (5.3 ± 0.1) was greater than 10. This evidence concerns the gene CXCR4 and neoplasm.