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Glutathione S-transferase P1-1 (GSTP1-1) is a phase II drug metabolism enzyme implicated in carcinogenesis and development of resistance to anti-cancer drugs. It was previously shown that both activating protein 1 (AP-1) and nuclear factor κB (NF-κB) are involved in its regulation. In the present study we examined the inhibitory effect of several chemopreventive agents on the tumor necrosis factor (TNF) α- or 12-O-tetradecanoylphorbol 13 acetate (TPA)-induced promoter activity of GSTP1-1, as demonstrated by transient transfection experiments in K562 and U937 leukemia cells. Our results provide evidence for a differential effect of chemopreventive agents such as β-lapachone, emodin, sanguinarine and capsaicin, which significantly inhibit reporter gene expression as well as TNFα- and TPA-induced binding of AP-1 and NF-κB, whereas trans-anethole and silymarin do not produce any inhibitory effect. Our …