Comparative segmental assessment of the colon mucosa in non-villous adenomas
Authors:   Novokuznetsk State Institute for Advanced Medical Studies — branch of the Russian Medical Academy of Continuous Professional Education, Novokuznetsk, Korotkevich A.G. ,   A.A. Lutsik Novokuznetsk City Clinical Hospital No. 29, Novokuznetsk, Zhilina N.M. ,   Novokuznetsk State Institute for Advanced Medical Studies — branch of the Russian Medical Academy of Continuous Professional Education, Novokuznetsk, Demenkov P.S. ,   Novosibirsk State University, Novosibirsk,   Institute of Cytology and Genetics of the Siberian Branch of the RAS, Novosibirsk, Veryaskina Yu.A. ,   Institute of Cytology and Genetics of the Siberian Branch of the RAS, Novosibirsk,   Institute of Molecular and Cellular Biology of the Siberian Branch of the RAS, Novosibirsk, Titov S.E. ,   Novosibirsk State University, Novosibirsk,   Institute of Molecular and Cellular Biology of the Siberian Branch of the RAS, Novosibirsk,   Vector-Best, Koltsovo, Novosibirsk region
Published: January 2025

Aim: to determine the prevalence of single non-villous adenomas in various segments of the colon and compare the segment-specific expression
profiling of 9 genes and 9 microRNAs (miRNAs) between different tissue types, including single non-villous adenomas, the corresponding
index segment mucosa, and the normal mucosa of similar segments from patients without adenomas.
Materials and Methods: a retrospective analysis of 3086 colonoscopy results performed between 2019 and 2020 was conducted to assess
the distribution of colonic adenomas. Additionally, a prospective study (2022–2023) was conducted involving 111 patients with non-villous
adenomas. Biopsies were obtained from each segment of the colon, utilizing samples for the preparation of smears and histology. Relative
expression levels of 9 miRNAs associated with colorectal cancer (CRC) were quantified in the collected smears. The selected miRNAs included
miRNA-135b-5p, -141-3p, -143-3p, -200a-3p, -20a-5p, -21-5p, -31-5p, -34a-5p, and -92a-3p, with small nuclear RNA U6 (snRNA U6) and two reference miRNAs (miRNA-16-5p and -191-5p) used for normalization. Furthermore, expression levels of mRNA transcripts for 9 key
protein-coding genes (MUC2, CDX2, NOX1, LGR5, SMAD4, MS4A12, TIMP1, Ki-67, and TERT) were assessed with normalization against the
housekeeping genes PGK1 and PUM1. A total of 372 cell samples were analyzed, including 92 samples from adenomas, 111 from the mucosa
of the index segments, and 169 from normal mucosa derived from patients without adenomas.
Results: the majority of the detected single adenomas were non-villous adenomas, but their distribution across colon segments varied
significantly (χ2=17.6, p<0.001). There were also notable differences in the frequency and types of somatic mutations in the BRAF and KRAS
genes, along with the microsatellite instability (MSI) / microsatellite stability (MSS) status in different colon segments (χ2=6.0, p=0.014).
Pairwise comparisons of miRNA/mRNA expression profiles showed no significant differences between the mucosa of the index segments
and normal mucosa from patients without adenomas. However, the expression patterns of protein-coding genes, including LGR5, TIMP1,
MS4A12, and Ki-67, varied across colon segments. These expression patterns were consistently altered in both mucosa with adenomas and
normal mucosa, with the exception of the caecum and rectum.
Conclusion: this study identified significant differences in the prevalence and mutation frequency of single non-villous adenomas across colon
segments. However, comparison of somatic mutations, MSI status, and miRNA/mRNA expression profiles between index segment mucosa and
analogous normal mucosa suggests comparable molecular characteristics, with exceptions noted in the cecum and rectum. These findings
challenge the widely-accepted model of adenomas as strict precursors to CRC.
Keywords: non-villous adenomas, colorectal cancer, miRNA/mRNA expression, microsatellite instability, protein-coding genes.
For citation: Korotkevich A.G., Zhilina N.M., Demenkov P.S., Veryaskina Yu.A., Titov S.E. Comparative segmental assessment of the colon
mucosa in non-villous adenomas. RMJ. 2024;10:9–17. DOI: 10.32364/2225-2282-2024-10-2