APBB1IP and nonpapillary renal cell carcinoma: The expression of circ-APBB1IP was up-regulated in ccRCC cells, in order to further investigate the role of circ-APBB1IP in ccRCC, we used a specific siRNA targeting circ-APBB1IP to knockdown the expression of circ-APBB1IP in 786-O and Caki-1 cells.