Chemopreventive effects and anti-tumorigenic mechanisms of 2,6-dimethoxy-1,4-benzoquinone, a constituent of Vitis coignetiae Pulliat (crimson glory vine, known as yamabudo in Japan), toward 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice.

Previously, we isolated and identified anti-mutagenic and anti-inflammatory components from Vitis coignetiae (crimson glory vine, known as yamabudo in Japan) as 2,6-dimethoxy-1,4-benzoquinone (DBQ), fertaric acid and caftaric acid. We also reported that the oral intake of a partially purified fraction from yamabudo juice (yamabudo-fr) or DBQ affords significant protection against two-stage skin carcinogenesis in mice. In this study, we found that oral intake of yamabudo-fr or DBQ affords significant protection against a tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse model of lung tumorigenesis. Furthermore, we investigated the anti-tumorigenic mechanisms of yamabudo juice and DBQ. NNK is known to be a DNA-methylating and alkylating agent; thus, we investigated the anti-tumorigenic mechanisms of yamabudo juice and DBQ in relation to DNA methylation. Pretreatment with yamabudo-fr or DBQ dose-dependently decreased formation of O-methylguanine and N-methylguanine in DNA of the A549 human lung epithelial-like cell line treated with a methylating agent, 1-methyl-3-nitro-1-nitrosoguanidine. Yamabudo juice and DBQ inhibited the mutagenicity of NNK in the Ames test using Salmonella typhimurium TA1535 but not S. typhimurium YG7108, an alkylguanine DNA alkyltransferase-deficient strain (same as TA1535 but Δada::Km, Δogt::Cm). Yamabudo juice and DBQ might accelerate the repair of DNA damage caused by NNK and reduce DNA damage to cells. We also investigated the effects of yamabudo juice and DBQ on signaling pathways in A549 cells. With or without epidermal growth factor stimulation, phosphorylation of Erk1/2, Akt and Stat3 in A549 cells was significantly decreased in the presence of yamabudo juice or DBQ, indicating that yamabudo juice and DBQ suppressed PI3K/AKT, MAPK/ERK and JAK/STAT3 signaling pathways. These results suggest that both initiation and growth/progression steps in carcinogenesis, especially anti-oxidant effects, stimulation of repair of alkyl DNA adducts and suppressed growth signaling pathways are potential anti-tumorigenic targets of yamabudo juice and DBQ in NNK-induced lung tumorigenesis.