title: Stochastic simulation of hepatic preneoplastic foci development for four chlorobenzene congeners in a medium-term bioassay.
abstract: A combination of experimental and simulation approaches was used to analyze clonal growth of glutathione-S-transferase pi (GST-P) enzyme-altered foci during liver carcinogenesis in an initiation-promotion regimen for 1,4-dichlorobenzene (DCB), 1,2,4,5-tetrachlorobenzene (TECB), pentachlorobenzene (PECB), and hexachlorobenzene (HCB). Male Fisher 344 rats, eight weeks of age, were initiated with a single dose (200 mg/kg, ip) of diethylnitrosamine (DEN). Two weeks later, daily dosing of 0.1 mol/kg chlorobenzene was maintained for six weeks. Partial hepatectomy was performed three weeks after initiation. Liver weight, normal hepatocyte division rates, and the number and volume of GST-P positive foci were obtained at 23, 26, 28, 47, and 56 days after initiation. A clonal growth stochastic model separating the initiated cell population into two distinct subtypes (referred to as A and B cells) was successfully used to describe the foci development data for the four chlorobenzenes. The B cells are initiated cells that display a selective growth advantage under conditions that inhibit the growth of initiated A cells or normal hepatocytes. The simulation exercise for the four chlorobenzenes indicates a positive correlation between the estimated net growth rate of B cells during the 2-week regeneration period following partial hepatectomy and final foci volume at the end of the bioassay. This observation is consistent with the sensitivity analysis of model parameters. While TECB, PECB, and HCB all significantly increased foci volume, only HCB increased normal hepatocyte proliferation. Together, these results indicate that examining effects of chemicals on regenerative responses following partial hepatectomy may be a means for understanding the carcinogenicity potential of chlorobenzene compounds.
authors.affiliation: Preclinical Development, Human Genome Sciences, Inc., Rockville, Maryland 20850, USA.
authors.forename: Ying C
authors.initials: YC
authors.lastname: Ou
authors.forename: Rory B
authors.initials: RB
authors.lastname: Conolly
authors.forename: Russell S
authors.initials: RS
authors.lastname: Thomas
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Gustafson
authors.forename: Michael E
authors.initials: ME
authors.lastname: Long
authors.forename: Ivan D
authors.initials: ID
authors.lastname: Dobrev
authors.forename: Laura S
authors.initials: LS
authors.lastname: Chubb
authors.forename: Yihua
authors.initials: Y
authors.lastname: Xu
authors.forename: Smadar A
authors.initials: SA
authors.lastname: Lapidot
authors.forename: Melvin E
authors.initials: ME
authors.lastname: Andersen
authors.forename: Raymond S H
authors.initials: RS
authors.lastname: Yang
mesh_terms: D000284:Administration, Oral; D000818:Animals; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000008:administration & dosage / Q000633:toxicity*; D002722:Chlorobenzenes / Q000008:administration & dosage / Q000633:toxicity*; D002999:Clone Cells; D003198:Computer Simulation; D004052:Diethylnitrosamine / Q000633:toxicity; D004359:Drug Therapy, Combination; D020518:Focal Nodular Hyperplasia / Q000139:chemically induced* / Q000201:enzymology / Q000473:pathology; D005982:Glutathione Transferase / Q000378:metabolism; D006498:Hepatectomy; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000201:enzymology / Q000473:pathology; D008297:Male; D011230:Precancerous Conditions / Q000139:chemically induced* / Q000473:pathology; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D002273:Carcinogens; D002722:Chlorobenzenes; D004052:Diethylnitrosamine; D005982:Glutathione Transferase