MicroRNA Expression Profiling of Normal and Malignant Human Colonic Stem Cells Identifies miRNA92a as a Regulator of the LRIG1 Stem Cell Gene

Abstract

MicroRNAs (miRNAs) have a critical role in regulating stem cells (SCs) during development, and because aberrant expression of miRNAs occurs in various cancers, our goal was to determine if dysregulation of miRNAs is involved in the SC origin of colorectal cancer (CRC). We previously reported that aldehyde dehydrogenase (ALDH) is a marker for normal and malignant human colonic SCs and tracks SC overpopulation during colon tumorigenesis. MicroRNA expression was studied in ALDH-positive SCs from normal and malignant human colon tissues by Nanostring miRNA profiling. Our findings show that: (1) A unique miRNA signature distinguishes ALDH-positive CRC cells from ALDH-positive normal colonic epithelial cells, (2) Expression of four miRNAs (miRNA200c, miRNA92a, miRNA20a, miRNA93) are significantly altered in CRC SCs compared to normal colonic SCs, (3) miRNA92a expression is also upregulated in ALDH-positive HT29 CRC SCs as compared to ALDH-negative SCs, (4) miRNA92a targets the 3′UTR of LRIG1 SC gene, and (5) miRNA92a modulates proliferation of HT29 CRC cells. Thus, our findings indicate that overexpression of miRNA92a contributes to the SC origin of CRC. Strategies designed to modulate miRNA expression, such as miRNA92a, may provide ways to target malignant SCs and to develop more effective therapies against CRC.

The Role of miRNAs, miRNA Clusters, and isomiRs in Development of Cancer Stem Cell Populations in Colorectal Cancer

“…Indeed, an investigation of the literature shows that many miRNAs have been reported to target SC genes or genes involved in regulating SC properties ( Table S1 ). Moreover, using miRNA expression profiling of isolated normal and malignant human colonic SCs [ 138 , 139 ], we showed that miR-23b and miR-92a are regulators of the LGR5 and LRIG1 SC genes, respectively. Findings from these two published studies and from our review of TCGA study results are described further below.…”

“…We also took an independent approach to identify miRNAs in purified human colonic SCs [ 139 ], which was based on a more extensive screen involving miRNA expression profiling of ALDH+ SCs isolated from fresh normal colonic epithelium and CRC tissue. This was done to identify additional miRNAs involved in the SC origin of CRC.…”

“…A review of miRNAs that target SC genes in normal versus cancerous colonic tissues was done herein using the two sets of miRNAs ( n = 164 total miRNAs) from our previous published studies on differentially expressed miRNAs in colon CSCs [ 138 , 139 ]. A literature review was then done to see whether these miRNAs are reported to target SC genes in normal colon vs. CRC.…”

“…A literature review was then done to see whether these miRNAs are reported to target SC genes in normal colon vs. CRC. The miRNAs from these two studies on colonic SCs [ 138 , 139 ] were cross referenced with miRNAs reported in the TCGA database for: (a) miRNA expression in normal vs CRC tissue, (b) prediction of target SC genes, (c) whether the expression of a miRNA inversely correlates with the mRNA levels of the target gene, and (d) correlation of the expression of miRNAs with CRC patient survival and other clinical parameters. The results ( Table 1 ) showed that 53 miRNAs are predicted to target the SC genes analyzed in the study and 39 of them showed differences ( p < 0.01; Table S2 ) in expression between normal and CRC tissues (see examples in Figure 2 ).…”

Molecular and Translational Research on Colorectal Cancer

“…Within this context, the expression of four miRNAs has been found to be altered in CRC stem cells with respect to normal stem cells. In particular, the overexpression of miRNA92a appears to contribute to cancer stem cell origin [8].…”