CLDN1 and urinary bladder cancer: We found that SMAD4 expression significantly increased with NDRG1 overexpression but decreased with NDRG1 knockdown, primarily causing the alteration of Cytokeratin 7, Claudin-1 and N-cad expression, suggesting that NDRG1 might influence the process of EMT through modulating the expression of SMAD4 and slug in bladder cancer.