We conclude that CEB4 induces cytotoxicity through apoptotic cell death in HSC-4 oral cancer cells, and that the induction of apoptosis is brought about by the activation of p53, which triggers the intrinsic pathway through Bcl-2 and Bax, and finally through caspase-9 and -3 activation. The gene discussed is CASP9; the disease is lip and oral cavity carcinoma.