CA9 and nonpapillary renal cell carcinoma: Using quantification beads, our analysis showed that MMNK-1 cells have an average of 1,278 CAIX molecules, while ccRCC skrc-59 tumor cells have an average of 207,111 molecules on the cell surface, translating into a circa 200-fold CAIX density difference between tumor and normal tissues (Fig. 1E).