The expression of CXCR4 on human RCC cells correlates with their ability to metastasize to specific organs in SCID mice bearing orthotopic (A) or heterotopic (B) tumors. SCID mice were subjected to orthotopic or heterotopic xenoengraftment of either SN12C-VC or SN12C-VHL-KD cells. Six animals were included in each group. Data are expressed as the percentage of GFP+ cells found in each organ examined by FACS analysis. Data represent mean ± SEM.