AQP4 and nonpapillary renal cell carcinoma: The expression levels of MIP, AQP1, AQP2, AQP3, AQP4, AQP5, AQP6, and AQP9 were negatively correlated with tumor purity (P < .05), suggesting that these AQPs were highly expressed in the ccRCC microenvironment (Fig. 9).