Lei Li1, Zhaoshen Li2, Xiangyu Kong3, Dacheng Xie4, Zhiliang Jia5, Weihua Jiang6, Jiujie Cui6, Yiqi Du1, Daoyan Wei5, Suyun Huang7, Keping Xie8. 1. Department of Gastroenterology, Shanghai Changhai Hospital, Second Military Medical University, Shanghai, People's Republic of China. 2. Department of Gastroenterology, Shanghai Changhai Hospital, Second Military Medical University, Shanghai, People's Republic of China. Electronic address: zhaoshenli.smmu.edu@hotmail.com. 3. Department of Gastroenterology, Shanghai Changhai Hospital, Second Military Medical University, Shanghai, People's Republic of China; Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: xiangyukong185@hotmail.com. 4. Shanghai Key Laboratory of Pancreatic Diseases Research and Department of Oncology, Shanghai Jiaotong University Affiliated First People's Hospital, Shanghai, People's Republic of China. 5. Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, Texas. 6. Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, Texas; Shanghai Key Laboratory of Pancreatic Diseases Research and Department of Oncology, Shanghai Jiaotong University Affiliated First People's Hospital, Shanghai, People's Republic of China. 7. Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas. 8. Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: kepxie@mdanderson.org.
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.
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.