Alterations of the M6p/Igf2 receptor gene in hepatocellular carcinomas induced by N-nitrosodiethylamine and a choline-deficient L-amino acid-defined diet in rats.

Abstract

To elucidate whether the M6p/Igf2 receptor (M6p/Igf2r) gene might be involved in exogenous and endogenous liver carcinogenesis, we investigated its alteration in hepatocellular carcinomas (HCCs) induced by N-nitrosodiethylamine (DEN) and by a choline-deficient L-amino acid-defined (CDAA) diet in rats. Male F344 rats, 6 wk old, received a single intraperitoneal (i.p.) injection of DEN at a dose of 10 mg/kg body weight, followed by combined treatment with partial hepatectomy and colchicine to induce cell cycle disturbance, and a selection procedure regimen, HCCs being obtained after 42 wk. With continuous CDAA diet feeding, tumors were sampled after 75 wk. Total RNA was extracted from individual HCCs for assessment of mutations within exons 27, 28, 31, 33, and 34, and aberrant transcript of the M6p/Igf2r gene by reverse transcription (RT)-polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) and RT-PCR analyses, respectively. Mutations were detected in three of 15 HCCs (20%) induced by the CDAA diet, a TTT to TTG (Phe to Leu) transversion at codon 1516 and two AAG to AGG (Lys to Arg) transitions at codon 1620, but in none of those caused by DEN. Aberrant transcripts were found in seven of 15 HCCs after DEN treatment (46.7%) and in two of 15 HCCs induced by the CDAA diet (13.3%). These results suggest that alterations of the M6p/Igf2r gene may be involved in both exogenous and endogenous liver carcinogenesis with the different patterns and frequencies.