Colorectal carcinoma (CRC) arises due to the accumulation of morphological and (epi)genetic changes. Despite well-defined histopathological features, there are many lesions with ambiguous histopathological features making diagnosing difficult. For this reason, markers specific for each stage of CRC development could be helpful.
We experimentally validated six genes of the extracellular matrix (ECM), whose expression was identified in the bioinformatics analysis as significantly different between adenoma and CRC. Our study included 105 biopsy tissue samples from 62 patients who had endoscopically or surgically removed adenoma, adenoma with epithelial misplacement, malignant adenoma, or CRC. Experimental validation of expression was performed on mRNA and protein level and (epi)genetic regulation on DNA and RNA level.
We showed that expression of DCN, SPON2, SPARC in SPP1 on mRNA and protein level increased with level of malignancy. Expression of EPHA4 was up-regulated in adenomas with epithelial misplacement, whereas expression of FN1 was similar to healthy mucosa throughout CRC development. Furthermore, we were interested in the (epi)genetic regulation of genes whose expression increased with level of malignancy. Expression of DCN was inversely proportional to miR-200c, while expression of SPARC was correlated to the methylation status of its promotor region. Our analysis did not show any significant associations between selected types of regulation and expression of SPON2. In contrast, expression of SPP1 was associated with the expression of miR-146a, the methylation status of the promotor region, and the copy number variation.
Experimental validation of selected ECM genes and proteins provided further evidence of their important role in the development of CRC. Though the expression patterns of analysed genes and proteins are too complex to be used directly in diagnostic work as markers, they might contribute to a better understanding of ECM changes in CRC development and help in search for new marker(s) and treatment modalities in the future.