Alterations of the transforming growth factor-beta signaling pathway in hepatocellular carcinomas induced endogenously and exogenously in rats.
To elucidate involvement of the transforming growth factor-beta (TGF-beta) signaling pathway in endogenous and exogenous liver carcinogenesis, we investigated mutations of TGF-beta receptor type II (TGF-betaRII), Smad2 and Smad4 genes, and expression of TGF-betaRII in hepatocellular carcinomas (HCCs) induced by a choline-deficient L-amino acid-defined (CDAA) diet and by N-nitrosodiethylamine (DEN). Male Fischer 344 rats received a CDAA diet continuously and HCCs were sampled after 75 weeks. Administration of DEN was followed by partial hepatectomy (PH), with colchicine to induce cell cycle disturbance and a selection pressure regimen, HCCs being obtained after 42 weeks. Total RNAs were extracted from individual HCCs and mutations in TGF-betaRII, Smad2 and Smad4 were investigated by reverse transcription (RT)-polymerase chain reaction (PCR)-restriction-single-strand conformation polymorphism (SSCP) analysis followed by sequencing analysis. Mutations of Smad2 were detected in 2 out of 12 HCCs (16.7%) induced by the CDAA diet, a GGT-to-GGC transition (Gly to Gly) at codon 30 and a TCT-to-GCT (Ser to Ala) transversion at codon 118, without any TGF-betaRII or Smad4 alterations. No mutations of TGF-betaRII, Smad2 and Smad4 were encountered in eleven HCCs induced by the exogenous carcinogen. Semi-quantitative RT-PCR revealed reduced expression of TGF-betaRII in 2 HCCs (16.7%) without Smad2 mutations out of 12 HCCs induced by the CDAA diet and none of 11 induced by DEN. These results suggest that the TGF-beta signaling pathway may be disturbed in endogenous liver carcinogenesis in rats.
Sasaki
Y
Y
Department of Oncological Pathology, Cancer Center, Nara Medical University, Kashihara, Nara 634-8521, Japan.
Tsujiuchi
T
T
Murata
N
N
Tsutsumi
M
M
Konishi
Y
Y
D000477:Alkylating Agents; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000209:etiology / Q000235:genetics*; D002794:Choline; D004268:DNA-Binding Proteins / Q000235:genetics; D004052:Diethylnitrosamine; D008113:Liver Neoplasms / Q000209:etiology / Q000235:genetics*; D008297:Male; D018807:Polymorphism, Single-Stranded Conformational; D051381:Rats; D011916:Rats, Inbred F344; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics*; D051899:Smad2 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000235:genetics*
D000477:Alkylating Agents; D004268:DNA-Binding Proteins; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051901:Smad4 Protein; C490811:Smad4 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D004052:Diethylnitrosamine; D002794:Choline