Mutations at codon 61 of the Ha-ras proto-oncogene in precancerous liver lesions of the B6C3F1 mouse

✍ Scribed by Albrecht Buchmann; Johanna Mahr; Richard Bauer-Hofmann; Michael Schwarz

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 464 KB
• Volume: 2
• Category: Article
• ISSN: 0899-1987
• DOI: 10.1002/mc.2940020303

✦ Synopsis

ederal Republic of Germany Liver tumors of the B6C3F1 mouse frequently contain mutations at specific sites of codon 61 of the Ha-ras proto-oncogene. To address whether these mutations occur early or late during carcinogenesis, w e analyzed mutations in the Ha-ras gene in small precancerous liver lesions of the B6C3F1 mouse. For this purpose, 10-bm frozen liver sections were prepared and stained for glucose-6-phosphatase activity. Using punching cannuli. we then took small tissue samples of approximately 5-30 p, g from enzyme-deficient liver lesions and from normal parts o f the liver. These tissue samples were analyzed for mutations in the Ha-rasgene by in vitro amplification of DNA via the polymerase chain reaction combined with selective oligonucleotide hybridization. By this approach we were able t o analyze mutations in the Ha-ras gene within lesions with diameters of less than 0.5 mm. Our resultsdemonstrate that approximately 15% of the glucose-6-phosphatase-negative lesions that occurred 24-28 wk after a single injection of diethylnitrosamine contain either C+A transversions at the first base or A 4 transitions and A-+T transversions at the second base of codon 61 of the Ha-rasgene. The same types of mutations, although with a somewhat higher frequency (33%), were found in liver turn06 taken 68 wk after diethylnitrosamine treatment. These findings demonstrate that Ha-ras mutations can be detected even in very small precancerous liver lesions, suggesting that these mutations may be an early, perhaps even the first, critical event during murine hepatocarcinogenesis.