Mutation Research 523–524 (2003) 163–172 Mechanism-based in vitro screening of potential cancer chemopreventive agents Clarissa Gerhäuser ∗ , Karin Klimo, Elke Heiss 1 , Isabell Neumann 2 , Amira Gamal-Eldeen 3 , Jutta Knauft, Guang-Yaw Liu 4 , Somkid Sitthimonchai 5 , Norbert Frank Division of Toxicology and Cancer Risk Factors, C010-2 Chemoprevention, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany Received 25 April 2002; received in revised form 22 July 2002; accepted 25 July 2002 Abstract Identification and use of effective cancer chemopreventive agents have become an important issue in public health-related research. For identification of potential cancer chemopreventive constituents we have set up a battery of cell- and enzyme-based in vitro marker systems relevant for prevention of carcinogenesis in vivo. These systems include modulation of drug metabolism (inhibition of Cyp1A activity, induction of NAD(P)H:quinone reductase (QR) activity in Hepa1c1c7 murine hepatoma cell culture), determination of radical scavenging (DPPH scavenging) and antioxidant effects (scavenging of superoxide anion-, hydroxyl- and peroxyl-radicals), anti-inflammatory mechanisms (inhibition of lipopolysaccharide (LPS)-mediated nitric oxide (NO) generation by inducible NO synthase (iNOS) in Raw 264.7 murine macrophages, cyclooxygenase-1 (Cox-1) inhibi- tion), and anti-tumor promoting activities (inhibition of phorbol ester-induced ornithine decarboxylase (ODC) activity in 308 murine keratinocytes). We have tested a series of known chemopreventive substances belonging to several structural classes as reference compounds for the identification of novel chemopreventive agents or mechanisms. These include organosulfur compounds (phenethylisothiocyanate (PEITC), diallylsulfide, diallyldisulfide), terpenes (limonene, perillyl alcohol, oleanolic acid, 18--glycyrrhetinic acid), short-chain fatty acids (sodium butyrate), indoles (indole-3-carbinol), isoflavonoids (quercetin, silymarin, genistein), catechins ((-)-epigallocatechin gallate (EGCG)), simple phenols (ellagic acid, resveratrol, piceatan- nol, curcumin), pharmaceutical agents (piroxicam, acetylsalicylic acid, tamoxifen), and vitamins/derivatives (ascorbic acid, Trolox). We confirmed known chemopreventive mechanisms of these compounds. Additionally, we could demonstrate the usefulness of our approach by identification of hitherto unknown mechanisms of selected agents. As an example, we detected anti-inflammatory properties of PEITC, based on NF-B-mediated inhibition of NO production. Further, PEITC inhibited phorbol ester-induced superoxide anion radical production in granulocytes, and ODC induction in the 308 cell line. These mechanisms might contribute to the chemopreventive potential of PEITC. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Cancer chemoprevention; Bioassay systems; Mechanisms; PEITC; NF-B; iNOS ∗ Corresponding author. Tel.: +49-6221-42-33-06; fax: +49-6221-42-33-59. E-mail address: c.gerhauser@dkfz.de (C. Gerhäuser). 1 Current address: Dartmouth Medical School, Hanover, NH, USA. 2 Current address: Europroteome AG, Henningsdorf, Germany. 3 Current address: National Research Center, Cairo, Egypt. 4 Current address: Chung Shan Medical University, Taichung, Taiwan. 5 Current address: Chulabhorn Research Institute, Bangkok, Thailand. 0027-5107/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0027-5107(02)00332-9