Prenylated chalcone xanthohumol associates with histones in breast cancer cells: a novel target identified by a monoclonal antibody

Scope : The intracellular fate of xanthohumol (XN) from hops is an underexplored field in the research for the molecular mechanisms causing its wide range of effects in chemoprevention and gene expression involved in hepatic metabolism. Methods and results : We aimed to elucidate possible targets for binding of XN in a human mammary carcinoma cell line (MCF-7/6), using a mAB. We investigated the overall solubility and stability of XN in growth medium and the cellular uptake and distribution of XN in MCF-7/6 cells using an optimized immunocytochemistry technique. After incubation of MCF-7/6 cells, with 10 mu M XN for 0.5 h up to 6 h, we observed primarily a granular nuclear staining, which intensified with increasing exposure times. Immunoprecipitation of cell lysates (treated with 10 mu M XN for 2 h) revealed binding of XN to a fraction of proteins with a molecular weight below 20 kDa. Further analysis of the protein mixture via LC-MS/MS (Q-TOF) resulted in the identification of specific members of the histone family, i.e. histone H2A, H2B, and H4. The identity of histone H2A was confirmed using immunodetection with a specific anti-histone H2A antibody. Conclusion : In summary, we did successfully apply a mAB against XN in immunocytochemistry and precipitation with highly unexpected results

Cosupplementation of isoflavones, prenylflavonoids, and lignans alters human exposure to phytoestrogen-derived 17beta-estradiol equivalents

The microbial metabolism of dietary phytoestrogens varies considerably among individuals and influences the final exposure to bioactive compounds. In view of the increasing number of food supplements combining several classes of phytoestrogens, the microbial potential to activate various proestrogens within an individual was evaluated in 3 randomized dietary crossovers. Treatment allocation was based on participants' eligibility (>45% in vitro bioactivation of >= 2 separate proestrogens by fecal cultures; n = 40/100). After a run-in of >= 4 d, participants were given soy-, hop-, and/or flax-based food supplements dosed either separately (SOY: 2.83 mg daidzein aglycone equivalents/supplement, HOP: 1.20 mg isoxanthohumol (IX)/supplement, or FLAX: 2.08 mg secoisolariciresinol (SECO) aglycone equivalents/supplement; reference intervention) or simultaneously (MIX; test intervention) 3 times/d for 5 cl, followed by a washout period l >= 7 d) and the second intervention. Before and after each (co)supplementation, spot urine and serum were collected. In total, 22 equol, 19 8-prenylnaringenin (8-PN), and 21 enterolactone (ENL) producers completed the SOY+MIX, HOP+MIX, and FLAX+MIX trials, respectively, The microbial bioactivation of daidzein, IX, and SECO, generally decreased upon coincubation in vitro (equol: 4.4%, P = 0.164; 8-PN: 20.5%, P < 0.001; ENL: 44.3%, P < 0.001) and cosupplementation in vivo (equol: 28.3%, P = 0.009; 8-PN: 35.4%, P = 0,107; ENL: 35.9%, P = 0.003). Although the bioavailabilities of total isoflavones, prenylflavonoids, and lignans were not significantly affected upon coadministration, participants were exposed to lower phytoestrogen-derived 17 beta-estradiol equivalents. In conclusion, the bioavailability of phytoestrogens, especially when given in mixtures, is subject to high interindividual variation. These findings support the importance of personalized screening when assessing the efficacy of such products and mixtures. J. Nutr. 139: 2293-2300,2009