USP9x, due to its ability to regulate SMAD family member 4 (SMAD4) and apoptosis signal-regulating kinase 1 (ASK1), is also involved in regulating cancer-associated transforming growth factor- β (TGF-β) [75] and mitogen-activated protein kinase (MAPK) signaling pathways [76]. The gene discussed is SMAD4; the disease is cancer.