Comparative segmental evaluation of molecular features of colonic mucosa in villous adenomas

Aim. This study aims to determine the frequency of solitary villous adenomas by colon segment and to compare the molecular genetic features of villous adenomas with the mucosa of the indexed segment and between different colon segments, as well as to consider the characteristics of unchanged mucosa of similar colon segments.

Methods. A continuous cross-sectional retrospective study of 3,086 colonoscopy results was performed. In the study, 347 cellular specimens were analysed, including 109 villous adenomas, 101 index segment mucosa samples and 137 normal mucosa samples. Detection of miRNAs and mRNAs was conducted using real-time PCR. Somatic mutations were identified with allele-specific PCR and a hydrolysable probe.

Results. The overall frequency of villous adenomas in the structure of all detected epithelial neoplasms was 3%. The frequency of villous adenomas was predominant in the sigmoid colon, while in other segments of the colon their frequency did not differ significantly. The frequency of severe dysplasia was associated with the adenoma diameter. Gene mutations similar to changes in villous adenomas were detected in the mucosa of index segments in the rectum, sigmoid colon and descending colon. Evaluation of the relative expression of 9 miRNAs and 9 protein-coding genes associated with the development of CRC in the mucosa of index segments and similar mucosal segments without adenomas did not reveal significant differences. The medians of relative expression levels of the most relevant markers – NOX1, LGR5, S4A12, TIMP, Ki-67, and TERT genes, as well as miRNA-135b, -20a, -21, -31, and -34a – were compared between different colon sections.

Conclusion. The results suggest that inspecting and biopsying unchanged mucosa, even within the index segment, does not provide insight into the risk of developing villous adenoma.

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