The recent demonstration of aberrant expression of the c-myb proto-oncogene in various cancers suggests that c-myb plays an important role in the development of cancer. On this basis, it has been proposed that ablation of c-myb function might be an effective approach for therapy of c-myb dependent malignancies. We previously used a dominant negative c-myb (DN-myb) construct to induce apoptosis in K562 cells. In this study, DN-myb was expressed in an adenovirus-mediated gene delivery system and introduced into head and neck squamous cell carcinoma cells (HNSCC) in vitro and in vivo to examine its tumor suppressive function and its potential in HNSCC gene therapy. Over expression of DN-myb in HNSCC cells inhibited in vitro cell proliferation, expression of growth factors such as IGF-I, -II, IGF-1R, and VEGF, inhibited Akt/PKB pathway activation, and enhanced induction of apoptosis. Similarly, in vivo administration of DN-myb retarded tumor-growth. Our results support a role for DN-myb in inducing apoptosis and tumor suppression, and, furthermore, suggest that DN-myb gene therapy might provide a powerful tool for treatment of c-myb dependent malignancies such as HNSCC.