Epigenetic regulation of miR-21 in colorectal cancer

Abstract

Previous studies have uncovered several transcription factors that determine biological alterations in tumor cells to execute the invasion-metastasis cascade, including the epithelial-mesenchymal transition (EMT). We sought to investigate the role of miR-21 in colorectal cancer regulation. For this purpose, miR-21 expression was quantified in a panel of colorectal cancer cell lines and clinical specimens. High expression was found in cell lines with EMT properties and in the vast majority of human tumor specimens. We demonstrate in a cell-specific manner the occupancy of MIR-21 gene promoter by AP-1 and ETS1 transcription factors and, for the first time, the pattern of histone posttranslational modifications necessary for miR-21 overexpression. We also show that Integrin-β4 (ITGβ4), exclusively expressed in polarized epithelial cells, is a novel miR-21 target gene and plays a role in the regulation of EMT, since it is remarkably de-repressed after transient miR-21 silencing and downregulated after miR-21 overexpression. miR-21-dependent change of ITGβ4 expression significantly affects cell migration properties of colon cancer cells. Finally, in a subgroup of tumor specimens, ROC curve analysis performed on quantitative PCR data sets for miR-21, ITGβ4, and PDCD4 shows that the combination of high miR-21 with low ITGβ4 and PDCD4 expression is able to predict presence of metastasis. In conclusion, miR-21 is a key player in oncogenic EMT, its overexpression is controlled by the cooperation of genetic and epigenetic alterations, and its levels, along with ITGβ4 and PDCD4 expression, could be exploited as a prognostic tool for CRC metastasis.

The role of miRNA-21 and epithelial mesenchymal transition (EMT) process in colorectal cancer

“…However, there has not been ample research conducted on the impact of miRNA-21 and EMT in CRC. Three studies observed high expression levels of miRNA-21 in cancers with up-regulated mesenchymal (snail-1, N-cadherin and vimentin) and down-regulated epithelial (E-cadherin) markers 12 13 20 26 30. Our data, however, indicated high expression levels of miRNA-21 in cancers with high E-cadherin expression and negative snail-1 expression.…”

“…MiRNA-21 high expression levels have also been associated with poor disease survival in colorectal, breast, pancreatic, cervical and lung cancers 19 24. These studies, therefore, suggested that miRNA-21 may be used as a marker of prognosis 12 25–27…”

“…The other study13 showed increased mRNA expression of N-cadherin and vimentin, while E-cadherin expression was decreased. These investigations both suggest that miRNA-21 promotes EMT, thus contributing to the progression of CRC 12 13…”

“…Thus far, only two studies have examined the relationship between miRNA-21 expression levels and EMT in CRC cell lines (Caco-H2, HCT116, Colo-205, Caco-2 and human colorectal carcinoma cell line (RKO) cells) 12 13. One12 of these investigations showed that Caco-2 cells expressed low levels of miRNA-21 compared with other cell lines.…”

“…One12 of these investigations showed that Caco-2 cells expressed low levels of miRNA-21 compared with other cell lines. Furthermore, cell lines with high miRNA-21 expression levels had EMT characteristics, that is, low E-cadherin expression, high vimentin expression and increased cell migration ability.…”