Gastroenterology

Gastroenterology

Volume 136, Issue 5, May 2009, Pages 1689-1700
Gastroenterology

Basic—Alimentary Tract
The miR-106b-25 Polycistron, Activated by Genomic Amplification, Functions as an Oncogene by Suppressing p21 and Bim

https://doi.org/10.1053/j.gastro.2009.02.002Get rights and content

Background & Aims

Barrett's esophagus (BE) is a highly premalignant disease that predisposes to the development of esophageal adenocarcinoma (EAC); however, the involvement of microRNAs (miRs) in BE-EAC carcinogenic progression is not known.

Methods

Esophageal cultured cells (HEEpiC, QhTRT, ChTRT, GihTRT, and OE-33) and esophageal tissues (22 normal epithelia, 24 BE, and 22 EAC) were studied. MiR microarrays and quantitative reverse-transcription polymerase chain reaction (RT-PCR) were employed to explore and verify differentially expressed miRs. Quantitative genomic PCR was performed to study copy number variation at the miR-106b-25 polycistron and MCM7 gene locus on chromosome 7q22.1. In vitro cell proliferation, cell cycle, and apoptosis assays and in vivo tumorigenesis experiments were performed to elucidate biologic effects of the miR-106b-25 polycistron. Western blotting and luciferase assays were performed to confirm direct messenger RNA (mRNA) targeting by the miR-106b-25 polycistron.

Results

The miR-106b-25 polycistron exerted potential proliferative, antiapoptotic, cell cycle-promoting effects in vitro and tumorigenic activity in vivo. MiRs-93 and -106b targeted and inhibited p21, whereas miR-25 targeted and inhibited Bim. This polycistron was up-regulated progressively at successive stages of neoplasia, in association with genomic amplification and overexpression of MCM7. In addition, miRs-93 and -106b decreased p21 mRNA, whereas miR-25 did not alter Bim mRNA, suggesting the following discrete miR effector mechanisms: (1) for p21, mRNA degradation; (2) for Bim, translational inhibition.

Conclusions

The miR-106b-25 polycistron is activated by genomic amplification and is potentially involved in esophageal neoplastic progression and proliferation via suppression of 2 target genes: p21 and Bim.

Section snippets

Materials and Methods

See also Supplementary Materials and Methods for full description.

MiR Microarrays Define Novel EAC-Specific Candidate Tumor-Suppressive miRs and Oncogenic miRs

As a first approach to studying the involvement of miRs in BE-associated neoplasms, we performed miR microarray investigations of nonimmortalized primary normal esophageal (NE) epithelial cells (HEEpiC), BE-derived cell lines (QhTRT, ChTRT, and GihTRT), and an EAC-derived cell line (OE-33). Representative results of these experiments are displayed in Table 1. Several miRs were aberrantly regulated in BE or EAC cells vs NE cells. In particular, we found that miRs-25, -93, and -106b, all of which

Discussion

Although the first miR, lin-4, was discovered in 199318 and the second miR, let-7, in 200019 in Caenorhabditis elegans, only recently has the study of this class of small regulatory RNAs in humans become more widespread.20 Experimental evidence that has accumulated in recent years has led oncologists to speculate that unrevealed molecular actors—particularly noncoding RNAs previously classified as “junk”—play important roles in carcinogenesis. In fact, approximately 70% of the genome has been

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported partially by NIH awards CA85069 and CA01808.

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