CLDN4 and breast cancer: As regards claudin-4, no significant difference was found between BC cell lines (5637: 0.88 ± 0.38, UM-UC-3: 0.93 ± 0.27, and T24: 0.99 ± 0.31) and that of noncancer urothelial cell line sv-huc-1 (1.0 ± 0.29, P > 0.05, Figure 1(a)).