NRG4 and urinary bladder cancer: Expression of the receptors HER3 and HER4, and ligands HRG1α, HRG1β, HRG2α, HRG2β, HRG3 and HRG4 was detected in 99, 63, 90, 61, 63, 43, 75 and 91% of the bladder cancer cases, respectively.