[Proto-oncogene expression in human carcinomas of the stomach and in the gastric mucosa of rats exposed to N-methyl-N'-nitro-N-nitrosoguanidine-induced gastric carcinogenesis].

The expression of c-Ha-ras-1, Ki-ras, N-ras, abl, src, fos and myc protooncogenes was analyzed in 13 cases of human gastric carcinomas. The transcriptional activity of both fos and myc protooncogenes was found to be disturbed in 47% and 42% of cases, respectively. An overexpression of fos protooncogenes as well as an appearance in some cases of atypical foc-mRNA transcripts were established. Only an elevation of the number of myc mRNA copies was observed. In one patient with gastric carcinoma a c-Ha-ras-1 overexpression was detected due to its amplification both in tumour tissues and in regional metastasis. The expression of other protooncogenes under investigation was similar to those found in normal gastric mucose. In addition, no differences in expression in protooncogenes mentioned above plus sis protooncogene were established in unchanged, premalignant and malignant stomach tissues in the course of N-methyl-N'-nitro-N-nitrosoguanidin-induced carcinogenesis.