Hot-spot mutations in the p53 gene of liver nodules induced in rats fed DL-ethionine with a methyl-deficient diet

Abstract

Summary Male F-344 rats were fed for 15 weeks a methyl-deficient L-amino acid defined diet containing 0.05% DL-ethionine. Nodules protruding from the surface of the liver were dissected free of surrounding tissue, and polyadenylated RNA isolated from the nodules was reverse transcribed. The region of the p53 gene comprising codons 120-290 was amplified by the polymerase chain reaction, and cDNAs were sequenced. Mutations were detected in nodules obtained from 7 of 12 rats. In all seven cases, the same two point mutations were present. The first was at the first base of codon 246 and consisted of a C-*T transition (C:G--T:A, Arg-*Cys), while the second was at the second base of codon 247 and consisted of a G-*T transversion (G:C->T:A, Arg->Leu). It is concluded that the hepatocarcinogen ethionine induces specific hot-spot p53 gene mutations; this is in contrast to the mutations at various sites previously observed to occur in rats fed a hepatocarcinogenic methyl-deficient diet alone. The results also provide the first evidence that ethionine is mutagenic in the rat.

Identification of co-expressed gene sets for major molecular initiating events in rodent liver carcinogenesis using wild type and knock out rats

“…All of the compounds identified using the PPARα consensus set are well-known activators, including bezafibrate, clofibrate, dehydroepiandrosterone, fenofibrate, and WY-14,643 (Corton, Peters, and Klaunig 2018; Mastrocola et al 2003). The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

“…• The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

Identification of co-expressed gene sets for major molecular initiating events in rodent liver carcinogenesis using wild type and knock out rats

“…All of the compounds identified using the PPARα consensus set are well-known activators, including bezafibrate, clofibrate, dehydroepiandrosterone, fenofibrate, and WY-14,643 (Corton, Peters, and Klaunig 2018; Mastrocola et al 2003). The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

“…• The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

Endogenous liver carcinogenesis in the rat *

“… 52,53 In the livers of rats fed the CD diet, frequent p53 mutations were found in both preneoplastic nodules and HCC in association with c‐myc amplification. 54–56 While it is not clear why there is a discrepancy in terms of the p53 mutations between the CDAA and CD cases, it has been suggested that the p53 mutations may not be an obligatory step for hepatocarcinogenesis due to dietary choline deficiency. 55 Therefore, it is possible that the non‐obligatory p53 mutations may be skipped in the CDAA case in which hepatocarcinogenesis is progressed more rapidly than in the CD case.…”

Identification of co-expressed gene sets for major molecular initiating events in rodent liver carcinogenesis using wild type and knock out rats

“…All of the compounds identified using the PPARα consensus set are well-known activators, including bezafibrate, clofibrate, dehydroepiandrosterone, fenofibrate, and WY-14,643 (Corton, Peters, and Klaunig 2018; Mastrocola et al 2003). The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

“…• The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

Endogenous liver carcinogenesis in the rat *

“… 52,53 In the livers of rats fed the CD diet, frequent p53 mutations were found in both preneoplastic nodules and HCC in association with c‐myc amplification. 54–56 While it is not clear why there is a discrepancy in terms of the p53 mutations between the CDAA and CD cases, it has been suggested that the p53 mutations may not be an obligatory step for hepatocarcinogenesis due to dietary choline deficiency. 55 Therefore, it is possible that the non‐obligatory p53 mutations may be skipped in the CDAA case in which hepatocarcinogenesis is progressed more rapidly than in the CD case.…”

Identification of co-expressed gene sets for major molecular initiating events in rodent liver carcinogenesis using wild type and knock out rats

“…All of the compounds identified using the PPARα consensus set are well-known activators, including bezafibrate, clofibrate, dehydroepiandrosterone, fenofibrate, and WY-14,643 (Corton, Peters, and Klaunig 2018; Mastrocola et al 2003). The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

“…• The p53 consensus gene set identified only three compounds with known ability to activate p53, including thioctic acid (Simbula et al 2007), acetamidofluorene (Ohlson, Koroxenidou, and Hällström 1998), and ethionine (Tsujiuchi et al 1997). Notably, of these three compounds, only acetamidofluorene is a direct genotoxicant, highlighting the diversity of p53 inputs.…”

Endogenous liver carcinogenesis in the rat *

“… 52,53 In the livers of rats fed the CD diet, frequent p53 mutations were found in both preneoplastic nodules and HCC in association with c‐myc amplification. 54–56 While it is not clear why there is a discrepancy in terms of the p53 mutations between the CDAA and CD cases, it has been suggested that the p53 mutations may not be an obligatory step for hepatocarcinogenesis due to dietary choline deficiency. 55 Therefore, it is possible that the non‐obligatory p53 mutations may be skipped in the CDAA case in which hepatocarcinogenesis is progressed more rapidly than in the CD case.…”