title: A critical assessment of the methodologies to investigate the role of inhibition of apoptosis in rodent hepatocarcinogenesis.
abstract: Non-genotoxic carcinogens act by promoting the clonal expansion of preneoplastic cells by directly or indirectly stimulating cell division or inhibiting cell loss in the target organ. The specific mode-of-action (MoA) by which some non-genotoxic carcinogens ultimately cause cancer is not completely understood. To date, there are several proposed MoAs for non-genotoxic carcinogens, and some of these propose inhibition of apoptosis as one of the key events. In general, inhibition of apoptosis is considered a necessary step for cell survival and in theory can occur in combination or in association with other key promotional events, such as cell proliferation, oxidative stress and inhibition of intercellular communication to promote carcinogenesis. However, the evidence supporting the role of inhibition of apoptosis as a necessary step in promoting specific chemically induced tumors is often debated. To address this evidence, we reviewed studies that utilized prototypical nuclear receptor-mediated hepatocarcinogens. Based on this review, it is proposed that the ability to determine the importance of inhibition of apoptosis as a key event in the MoA for tumor promotion is hampered by the limitations of the methods utilized for its detection. This review provides an assessment of the strengths and limitations of the current methodology used for detection of apoptosis and provides suggestions for improving its detection, thereby strengthening the weight of evidence supporting inhibition of apoptosis as a key event in a MoA for tumor promotion.
authors.affiliation: Toxicology and Environmental Research & Consulting, The Dow Chemical Company , Midland, MI , USA.
authors.forename: Radhakrishna
authors.initials: R
authors.lastname: Sura
authors.forename: Raja S
authors.initials: RS
authors.lastname: Settivari
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: LeBaron
authors.forename: J Craig
authors.initials: JC
authors.lastname: Rowlands
authors.forename: Edward W
authors.initials: EW
authors.lastname: Carney
authors.forename: B Bhaskar
authors.initials: BB
authors.lastname: Gollapudi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D035843:Biomedical Research / Q000379:methods / Q000639:trends; D017173:Caenorhabditis elegans / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D063646:Carcinogenesis / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D002273:Carcinogens / Q000737:chemistry / Q000633:toxicity*; D002450:Cell Communication / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004195:Disease Models, Animal; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D015394:Molecular Structure; D018384:Oxidative Stress / Q000187:drug effects; D021281:Quantitative Structure-Activity Relationship
chemical_list: D002273:Carcinogens
keywords: Apoptosis; hepatocarcinogens; key event; non-genotoxic carcinogens; rodent