BDNF and Bartsocas-Papas syndrome 1: In urine of IC/BPS patients, anti-proliferative factor (APF), hemoglobin-binding endothelial growth factor (HB-EGF), endothelial growth factor (EGF), nerve growth factor (NGF), and brain-derived nerve growth factor (BDNF) have all been proposed as biomarkers (113, 114).