SLC49A4 and renal carcinoma: We found that the dye-specific fluorescence was significantly lower in the MUC1-expressing renal cancer cells (ACHN EV = 48 994 ± 8 636 vs. ACHN MUC1FL = 27 178 ± 6259, p < 0.05; RCC4 = 11 455 ± 2046 vs. RCC4 MUC1KO = 22 642 ± 3498, p < 0.05), suggesting a higher activity of ABC transporters in MUC1-expressing cells, leading to more effective drug effluxes (Figure 6A,B).