Studies on inhibitors of skin tumor promotion, VI. Inhibitory effects of quinones on Epstein-Barr virus activation.

To search for possible antitumor promoters, we carried out a primary screening of fifty-one quinones (anthraquinones, naphthoquinones, azaanthraquinones, and azafluorenones) and related compounds, using their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Some of these quinones, notably 5-hydroxy-1,2-methylenedioxy-anthraquinone [9], shikonin [29], 2-acetylfuranonaphthoquinone [32], 5,8-dihydroxycleistopholine [37], and 5,8-dihydroxy-2-methyl-1-azaanthraquinone [45], were observed to significantly inhibit the EBV-EA activation at low doses. The position and number of hydroxyl groups on phenyl rings of these quinones affected the inhibitory activity on EBV-EA activation. The investigation indicates that 9, 29, 32, 37, and 45 might be valuable anti-tumor promoters.