Experimental and Toxicologic Pathology 62 (2010) 405–412 Absence of chemopreventive influence of propolis on the rat liver altered foci development Roueda Abou Said a , Tony Fernando Grassi b , Clarissa Scolastici b , Rodrigo Ota ´ vio Alves de Lima b , Bruno R. Darros b , Luis Fernando Barbisan c , Joa ˜ o Lauro V. de Camargo b,Ã a Department of Environmental and Agrarian Sciences, Santa Cruz State University, Ilhe´us, Bahia, Brazil b TOXICAM – Nucleus of Evaluation of Environmental Impact on Human Health; Department of Pathology, School of Medicine, Sao Paulo State University, 18618-000 Botucatu, Sao Paulo, Brazil c Department of Morphology, Institute of Biosciences, Sao Paulo State University, Botucatu, Sao Paulo, Brazil Received 27 February 2009; accepted 28 May 2009 Abstract Propolis (bee glue) is a complex mixture of natural substances that exhibits a broad spectrum of biological activities. As the possibility exists that it may exert a chemopreventive role against cancer development, the present study aimed to evaluate the chemopreventive influence of a Brazilian aqueous propolis extract (APE) in a rat two-stage (initiation- promotion) medium-term bioassay for chemical liver carcinogenesis. Male Wistar rats were sequentially initiated with diethylnitrosamine (DEN, 200 mg/kg b.w.) and, 2 weeks later, exposed to a diet containing hexachlorobenzene (HCB, 100 ppm) and to APE 0.1% through drinking water for 6 weeks. Appropriate control groups were also established. The animals were sacrificed at the weeks 8th and 30th when liver samples were processed to evaluate the development of altered hepatocyte foci (AHF) identified under hematoxylin and eosin (H&E) staining and by the immunohisto- chemical expression of the enzyme glutathione S-transferase placental form (GST-P). The results indicate that APE 0.1% did not protect against the development of any of the differentially identified putative preneoplastic foci in DEN- initiated animals, exposed or not to the promoting agent HCB. Also, APE 0.1% by itself did not significantly induce any AHF, what is in line with its already known absence of genotoxic potential. Our results indicate that an aqueous extract of Brazilian propolis did not exert chemoprevention on the hepatocarcinogenesis process chemically induced in the rat. r 2009 Elsevier GmbH. All rights reserved. Keywords: Propolis; Diethylnitrosamine; Hexachlorobenzene; GST-P-positive foci; Hepatocarcinogenesis; Wistar rats 1. Introduction Propolis, a well-known ancient folk medicine, is a resinous substance collected by bees (Apis mellifera) from substances actively secreted by plants as well as substances exuded from plant wounds, like lipophilic materials on leaves and leaf buds, gums and resins (Bankova, 2005). Propolis has been used extensively to ARTICLE IN PRESS www.elsevier.de/etp 0940-2993/$ - see front matter r 2009 Elsevier GmbH. All rights reserved. doi:10.1016/j.etp.2009.05.012 Ã Corresponding author at: Department of Pathology, UNESP Medical School, 18618-000 Botucatu, Sa ˜ o Paulo, Brazil. Tel.:+55 14 38116238. E-mail address: decam@fmb.unesp.br (J.L.V. de Camargo).