Complete cDNA sequence of the Ki-ras proto-oncogene in the liver of wild English sole (Pleuronectes vetulus) and mutation analysis of hepatic neoplasms and other toxicopathic liver lesions

Abstract

A complete copy of Ki-ras b cDNA from English sole (Pleuronectes vetulus), a benthic marine flatfish, was cloned and sequenced. The percent identity between the predicted amino acid sequence of English sole and human Ki-ras b was 97%, whereas the percent identity between the English sole gene and rainbow trout or Rivulus Ki-ras b was 98%. Areas of amino-acid sequence conservation included codons 12, 13, and 61, the positions in which mutations are observed in ras cellular oncogenes in other species. The 5' untranslated region (UTR), consisting of 217 nt, was not highly GC rich but contained four ATG start codons upstream of the major open reading frame. The 3' UTR, containing 26 nt, was AU rich. Analysis of Ki-ras mutations was performed on a variety of necrotic, preneoplastic, and neoplastic lesions in livers from 13 English sole collected from contaminated waterways in Puget Sound, WA. Despite reports of Ki-ras mutations in hepatic tumors from other fish, no mutations in codons 12, 13, or 61 were found in hepatic lesions from English sole by direct DNA sequencing of polymerase chain reaction-amplified genomic DNA. Although mutations could exist at levels below the detection limits of this analysis, the results suggest that Ki-ras has a role in liver carcinogenesis that varies according to the fish species or carcinogen. Furthermore, future studies of the etiology of chemically induced cancer in feral English sole should consider mutations in other cancer-related genes, such a5p53, Ha-ras, and N-ras.

Molecular markers of cancer in cartilaginous fish: immunocytochemical study of PCNA, p‐53, myc and ras expression in neoplastic and hyperplastic tissues from free ranging blue sharks, Prionace glauca (L.)

“…The high degree of homology between the tumour suppressor gene p‐53 and oncogenes of the myc and ras families among bony fish and mammals has been shown in several studies (Caron de Fromentel, Pakdel, Chapus, Baney, May & Soussi 1992; Panno & McKeown 1995; Vincent, Jaunet, Galgani, Besselink & Koeman 1995; Krause, Rhodes & Van Beneden 1997; Peck‐Miller, Myers, Collier & Stein 1998; Bhaskaran, May, Rand‐Weaver & Tyler 1999; Franklin, Lee, Köhler & Chipman 2000; Vincent‐Hubert 2000; Liu, Kullman, Bencic, Torten & Hinton 2003). Alterations in the expressions of the above genes in fish tumourigenesis have been widely documented in natural and experimental settings (Vincent, de Boer, Pfohl‐Leszkowicz, Cherrel & Galgani 1998; Baumann & Okihiro 2000; Rotchell, Lee, Chipman & Ostrander 2001; Liu et al.…”