Spectrum of somatic mutations in APC, k-Ras and TP53 genes at the Russian patients with colorectal cancer and premalignant diseases of the large intestine

Aim of investigation. Complex analysis of a spectrum of somatic mutations in TP53, APC, k-Ras and BRAF genes in Russian patients with malignant neoplasms, polyps and inflammatory diseases, evaluation of diagnostic information value of such analysis.

Stuff and methods. Analysis of somatic mutations of APC, k-Ras, TP53 and BRAF genes in biopsy samples or surgical specimens in patients with adenocarcinoma (n=24), adenomatous polyps (n=37), hyperplastic polyps (n=17) and inflammatory bowel diseases (n=69), as well as for patients with irritable bowel syndrome, that formed a control group (n=25) was carried out. DNA sequencing was performed with the ABI Prism BigDye Terminator Cycle Sequencing Ready Reaction Kit on the ABI Prism 3100 Genetic Analyzer («Applied Biosystems», USA; «Hitachi», Japan) according to the manufacture manual as well as with use of original mass-spectrometry minisequencing method.

Results. 50 pathogenic somatic mutations were determined: 31 – in APC gene, 5 – in k-Ras gene and 14 – in TP53 gene. Mutations in BRAF gene were not revea­led. 12 novel somatic mutations of APC gene and one extended deletion in gene TP53 were revealed. General detectability of mutations in adenocarcinoma patients was 66%, in adenomatous and hyperplastic polyps – 49 and 59% respectively. Mutations were not found in patients with inflammatory bowel diseases and control group patients. Potential diagnostic sensitivity of these mutations for diagnostics of colorectal neoplasms was 58% (95%-confidence interval was 47–69%) at 100%- specificity of the method.

Conclusion. Statistically significant difference in TP53 gene mutation frequencies in patients with adenocarcinomas and patients with benign colorectal neoplasms (p=0,02) was demonstrated. Information value of the studied genetical markers for early diagnostics of colorectal cancer and evaluation of clinical and morphological features of disease is discussed.

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