Down-regulation of microRNA-494 via loss of SMAD4 increases FOXM1 and β-catenin signaling in pancreatic ductal adenocarcinoma cells.

Abstract

BACKGROUND & AIMS:

Dysregulation of β-catenin and the transcriptional activator FOXM1 mediate oncogenesis, but it is not clear how these proteins become dysregulated in tumors that do not typically carry mutations in adenomatous polyposis coli (APC) or β-catenin, such as pancreatic ductal adenocarcinomas (PDACs). We searched for microRNAs that regulate levels of FOXM1 in PDAC cells and samples from patients.

METHODS:

We identified microRNAs that affect levels of FOXM1 in PDACs using bioinformatic, genetic, and pharmacologic approaches. We altered expression of the microRNA-494 (miR-494) in PDAC cell lines (AsPC-1 and PANC-1) and examined the effects on FOXM1 and β-catenin signaling and cell proliferation and colony formation. The cells were injected into immunocompromised mice and growth of xenograft tumors and liver metastases were measured. We performed immunohistochemical analyses of 10 paired PDAC and nontumor pancreatic tissue samples collected from untreated patients during surgery.

RESULTS:

We identified miR-494 as a negative regulator of FOXM1 levels in PDAC cells, and found that levels of this microRNA were reduced in PDAC specimens, compared with nontumor tissues. Loss of response of PDAC cells to transforming growth factor β, owing to SMAD4 deficiency, reduced expression of miR-494. Transgenic expression of miR-494 in PDAC cells produced the same effects as reducing expression of FOXM1 or blocking nuclear translocation of β-catenin, reducing cell proliferation, migration, and invasion, and increasing their sensitivity to gemcitabine. Reduced expression of miR-494 correlated with PDAC metastasis and reduced survival times of patients.

CONCLUSIONS:

Loss of SMAD4 in PDAC cells leads to reduced levels of miR-494, increased levels of FOXM1, and nuclear localization of β-catenin. miR-494 might be developed as a prognostic marker for patients with PDAC or a therapeutic target.

• Authors: Lei Li, Zhaoshen Li, Xiangyu Kong, Dacheng Xie, Zhiliang Jia, Weihua Jiang, Jiujie Cui, Yiqi Du, Daoyan Wei, Suyun Huang, Keping Xie
• Journal: Gastroenterology (Gastroenterology) Vol. 147 Issue 2 Pg. 485-97.e18 (Aug 2014) ISSN: 1528-0012 [Electronic] United States
• PMID: 24859161 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.

Chemical References

• Antibiotics, Antineoplastic
• CTNNB1 protein, human
• FOXM1 protein, human
• Forkhead Box Protein M1
• Forkhead Transcription Factors
• MIRN494 microRNA, human
• MicroRNAs
• SMAD4 protein, human
• Smad4 Protein
• beta Catenin
• Deoxycytidine
• Gemcitabine

Topics

• Active Transport, Cell Nucleus
• Animals
• Antibiotics, Antineoplastic (pharmacology)
• Carcinoma, Pancreatic Ductal (genetics, metabolism, mortality, secondary)
• Cell Line, Tumor
• Cell Movement
• Cell Proliferation
• Cell Survival (drug effects)
• Deoxycytidine (analogs & derivatives, pharmacology)
• Dose-Response Relationship, Drug
• Down-Regulation
• Female
• Forkhead Box Protein M1
• Forkhead Transcription Factors (genetics, metabolism)
• Gene Expression Regulation, Neoplastic
• Humans
• Kaplan-Meier Estimate
• Liver Neoplasms (genetics, metabolism, secondary)
• Male
• Mice
• Mice, Inbred BALB C
• Mice, Nude
• MicroRNAs (genetics, metabolism)
• Middle Aged
• Neoplasm Invasiveness
• Pancreatic Neoplasms (genetics, metabolism, mortality, pathology)
• RNA Interference
• Signal Transduction (drug effects)
• Smad4 Protein (genetics, metabolism)
• Time Factors
• Transfection
• Up-Regulation
• beta Catenin (genetics, metabolism)
• Gemcitabine