CA9 and renal cell carcinoma: We also confirmed a high percentage of CA9+ and/or CD147+ expression, with an average of 84%, on the cell membrane of CTCs (DAPI+/CD45-) captured by CA9-/CD147-based enrichment approach in 94% (31 out of 33) samples we examined, which was accompanied by positive staining of CA9 and CD147 in the corresponding RCC samples as revealed by IHC (Figure 4A and Table 3).