CXCR4 and nonpapillary renal cell carcinoma: Then, the human ccRCC cell lines (SW839 and OSRC-2) and the human normal kidney epithelial cell-line HK2 were obtained, and analysis of the data in Figure 1(j,k) supported that CXCR4 tended to be high-expressed in the ccRCC cells, compared to the normal HK2 cells.