To further address the role of autophagy in tumor development in an in vivo model system and to probe the interrelationship of autophagy and p53 deficiency, we inhibited autophagy in a tissue-specific fashion in zebrafish by expressing a dominant-negative form of the autophagy gene atg5 (atg5K130R) from the well-characterized microphthalmia-associated transcription factor a (mitfa) promoter. The gene discussed is MITF; the disease is neoplasm.