POINT MUTATIONS AT CODON 61 OF THE c-H-RAS GENE DETECTED IN PARAFFIN SECTIONS OF SPONTANEOUS HEPATOCELLULAR TUMORS IN AGED B6C3F1 MICE

Abstract

The frequency and mutational profile of c-H-ras gene activation were determined in spontaneous hepatocellular tumors in aged B6C3F1 mice.
After DNA isolation from formalin-fixed paraffin-embedded tissue sections and amplification by a polymerase chain reaction (PCR), a non-isotopic method using chemiluminescence for dot blot hybridi-zation was applied to detect c-H-ras mutations.
DNA sequence analysis of the c-H-ras gene from 59 hepatocellular tumors (39 carcinomas and 20 adenomas) revealed that 49 (83%) contained a point mutation at codon 61. Of 34 hepatocellular carcinomas with mutations, 15 tumors (44%) had a CAA to AAA transversion at the first base of the codon, and 11 (32%) and 8 (24%) had a CAA to CTA transversion and CAA to CGA transition, respectively, at the second base. Of 15 hepatocellular adenomas with mutations, 5 (33%) had CAA to AAA, 6 (40%) CAA to CTA, and 4 (27%) CAA to CGA mutations. There was no association between the morphological features of the spontaneous mouse liver tumors and the presence or pattern of codon 61 mutations.
These results show that spontaneous mouse liver tumors contain at least three different codon 61 mutations of the c-H-ras gene and that the non-isotopic method employed is useful in conventional laboratories to examine oncogene mutations.