The miR-106b-25 polycistron, activated by genomic amplification, functions as an oncogene by suppressing p21 and Bim.
OBJECTIVE
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 upregulated 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.
Division of Gastroenterology, Department of Medicine, The Johns Hopkins University School of Medicine and Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland 21287, USA.
Takatsugu
T
Kan
Fumiaki
F
Sato
Tetsuo
T
Ito
Nobutoshi
N
Matsumura
Stefan
S
David
Yulan
Y
Cheng
Rachana
R
Agarwal
Bogdan C
BC
Paun
Zhe
Z
Jin
Alexandru V
AV
Olaru
Florin M
FM
Selaru
James P
JP
Hamilton
Jian
J
Yang
John M
JM
Abraham
Yuriko
Y
Mori
Stephen J
SJ
Meltzer
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D001471:Barrett Esophagus / Q000235:genetics* / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000378:metabolism; D005784:Gene Amplification; D015972:Gene Expression Regulation, Neoplastic; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D009857:Oncogenes / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation; D014162:Transfection
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D008565:Membrane Proteins; D035683:MicroRNAs; D011518:Proto-Oncogene Proteins