Relationship between Expression of Onco-Related miRNAs and the Endoscopic Appearance of Colorectal Tumors

Abstract

Accumulating data indicates that certain microRNAs (miRNAs or miRs) are differently expressed in samples of tumors and paired non-tumorous samples taken from the same patients with colorectal tumors. We examined the expression of onco-related miRNAs in 131 sporadic exophytic adenomas or early cancers and in 52 sporadic flat elevated adenomas or early cancers to clarify the relationship between the expression of the miRNAs and the endoscopic morphological appearance of the colorectal tumors. The expression levels of miR-143, -145, and -34a were significantly reduced in most of the exophytic tumors compared with those in the flat elevated ones. In type 2 cancers, the miRNA expression profile was very similar to that of the exophytic tumors. The expression levels of miR-7 and -21 were significantly up-regulated in some flat elevated adenomas compared with those in exophytic adenomas. In contrast, in most of the miR-143 and -145 down-regulated cases of the adenoma-carcinoma sequence and in some of the de novo types of carcinoma, the up-regulation of oncogenic miR-7 and/or -21 contributed to the triggering mechanism leading to the carcinogenetic process. These findings indicated that the expression of onco-related miRNA was associated with the morphological appearance of colorectal tumors.

MicroRNA-7 Is Associated with Malignant Potential and Poor Prognosis in Human Colorectal Cancer

“…Another group showed that miR-7 was gradually increasingly overexpressed with each subsequent step of carcinogenesis, from low-grade dysplasia to advanced CRC. Moreover, the transfection of human colon cancer DLD-1 cells with anti-miR-7 suppressed proliferation, suggesting that miR-7 might function as an oncogenic role in CRC (14). Consistent with these findings, our current study also demonstrated that miR-7 expression levels were higher in CRC tissues compared with normal mucosae, especially in advanced cancer.…”

“…Previous studies characterised miR-7 as a tumour-suppressor gene in several types of cancer, including melanoma (11) and breast cancer (12). In those studies, miR-7 was shown to reduce the expression of several oncogenes, such as epidermal growth factor receptor (14), p21-activated kinase 1 (15), and others (16).…”

Clinical Potential of microRNA-7 in Cancer

“…In colorectal cancer (CRC), miR-7 was found to be upregulated in advanced cancers and in selected cell lines (SW480, DLD-1, and COLO201) compared to normal mucosa. In addition, transfection with anti-miR-7 was shown to suppress cell growth in DLD-1 and COLO201 [ 67 ]. miR-7 was also reported to be increased in the stool of CRC patients, giving rise to the notion of a screening method for CRC [ 68 ].…”

MicroRNA-320 family is downregulated in colorectal adenoma and affects tumor proliferation by targeting CDK6

“…The percentage of gene mutation in the protruded tumor is hypothesized to be different from that of the LST [13] . When we focused on miRNA, expression changes of some miRNAs in exophytic and flat elevated tumors were reported [14] ; however, there is no analysis comparing miRNA expressions of the LST with those of the protruded tumor.…”