Possible involvement of c-myc but not ras genes in hepatocellular carcinomas developing after spontaneous hepatitis in LEC rats
✍ Scribed by Yoshinori Fujimoto; Yukihito Ishizaka; Tomoko Tahira; Hideko Sone; Hidetoshi Takahashi; Katsuhiko Enomoto; Michio Mori; Takashi Sugimura; Minako Nagao
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 541 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0899-1987
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✦ Synopsis
LEC (Long-Evans with a cinnamon-like coat color) rats develop hepatocellular carcinomas (HCCs) spontaneously. We examined mutations of codons 12, 13, and 61 of the Ha-ras, Ki-ras, and N-ras genes in four HCCs by the polymerase chain reaction (PCR)-single-stranded DNA direct sequencing method. No ras gene mutations were observed, suggesting that ras activation is not involved in spontaneous hepatocarcinogenesis in LEC rats. The expression of mRNAs for c-myc, Ha-ras, c-raf, and the protein phosphatase 2A alpha gene (PP-2A alpha) was also examined in the four HCCs by northern blot analysis. Three of the four HCCs had c-myc expression levels approximately 30-fold higher than that in the liver of control Long-Evans rats with an agouti coat color (LEA), a sibling line of LEC rats, while the remaining HCC had an expression level sevenfold higher than that of control. In contrast, the expression levels of the Ha-ras, c-raf, and PP-2A alpha genes were the same as those in the livers of control rats. Studies of c-myc expression and mitotic index in five other HCCs, two hyperplastic nodules, and two nontumorous portions of livers of HCC-bearing LEC rats that had chronic-phase hepatitis suggested that the high level of c-myc gene expression was not due only to increased cell proliferation but might possibly be more integrally involved in hepatocarcinogenesis.