The data show that cytotoxic effects of ellipticine in tumor tissues are dictated by (I) levels of CYP expression (and/or peroxidase expression); (II) levels of cytochrome b5 expression; and (III) its own potency to induce CYP1A1, CYP3A and cytochrome b5 in tumor tissues and cells. This evidence concerns the gene CYP3A4 and neoplasm.