Background: Differences in the embryonic development of the colonic mucosa determine the physiological embryonic-anatomical asymmetry of its structure and can manifest themselves via different molecular phenotypes (expression profiles) of the colon segments. These molecular characteristics are hypothesized to determine differences in the carcinogenesis mechanisms and influence the prognosis of right- or left-sided colorectal cancer (CRC). Studies of the tumors molecular phenotypes depending on their localization may be of interest for assessment of the prognosis and choice of treatment for CRC.
Aim: To perform comparative analysis of molecular phenotypes of the normal colonic mucosa and adenocarcinoma CRC tissues depending on the natural embryonic anatomic asymmetry of the colon.
Materials and methods: We performed a retrospective study of molecular phenotypes (mRNA expression of 61 genes) from different embryonic-anatomical parts of healthy colon and CRC. The normal group included 254 samples of mucosa from three different parts of the colon from 74 healthy donors who had no cancer and no organic abnormalities of the colon, including 90 samples from the right colon, 116 from the left colon, and 48 from the rectum. The CRC group consisted of 154 samples of localized stage T1–4N0–2M0 adenocarcinoma from 154 patients who had not received neoadjuvant radio- and chemotherapy, including 40 samples from the right colon, 54 from the left colon, and 60 from the rectum. The relative mRNA abundance of 61 genes was assessed by reverse-transcriptase polymerase chain reaction. In both groups, the resulting expression phenotypes were compared between the anatomical parts of the colon. Statistical management of the data included the discriminant analysis with stepwise inclusion of variables.
Results: Based on the assessment of the mRNA level of the studied genes, a discriminant model was built that allows for classification of the normal group samples according to their anatomic origin in the colon with an accuracy of 95.8%. The most significant (p 0.05) for classification are the following 19 genes: CCND1, SCUBE2, TERT, BAG1, NDRG, IL1b, IL2Ra, IL7, ESR1, TGFb, IGF1, MMP9, MMP11, PAPPA, CD45, CD69, TLR2, TLR4, LIFR. The discriminant model built for the CRC group included 27 genes and made it possible to differentiate samples from three parts of colon with an accuracy of 75.2%. A statistically significant (p 0.05) contribution to the samples differentiation by the discriminant model was made by the COX-2, BIRC5, LIFR, TPA, IL1b, MMP11, MMP7, and P16INK4A genes. When combining samples from the two groups into one model in accordance with their embryonic-anatomical origin, there was a clear separation of tumor tissue samples and healthy colonic mucosa in the discriminant function space.
Conclusion: The analysis of CRC gene expression profiles using the discriminant model showed that genetic changes in the colonic mucosa in CRC flatten the molecular phenotypic boundaries of the embryonic-anatomical parts. These changes are specific to CRC, forming a particular “pathological” molecular phenotype.
