In summary, UBIAD1 bind to H-Ras, regulates the H-Ras intracellular trafficking cycle, inhibits Ras/MAPK signaling, suppreses bladder cancer cell proliferation and plays important roles in melanotic mass formation in Drosophila. Our findings confirm the tumor suppressor function of UBIAD1 in cellular circuits in melanotic mass formation in Drosophila. The gene discussed is HRAS; the disease is urinary bladder carcinoma.