FOXM1c promotes pancreatic cancer epithelial-to-mesenchymal transition and metastasis via upregulation of expression of the urokinase plasminogen activator system.
OBJECTIVE
The transcription factor Forkhead box M1 (FOXM1) plays important roles in the formation of several human tumors, including pancreatic cancer. However, the molecular mechanisms by which FOXM1 promotes pancreatic tumor epithelial-to-mesenchymal transition (EMT) and metastasis are unknown.


METHODS
The effect of altered expression of FOXM1 and urokinase-type plasminogen activator receptor (uPAR) on EMT and metastasis was examined using animal models of pancreatic cancer. Also, the underlying mechanisms of altered pancreatic cancer invasion and metastasis were analyzed using in vitro molecular biology assays. Finally, the clinical relevance of dysregulated FOXM1/uPAR signaling was investigated using pancreatic tumor and normal pancreatic tissue specimens.


RESULTS
Pancreatic tumor specimens and cell lines predominantly overexpressed the FOXM1 isoform FOXM1c. FOXM1c overexpression promoted EMT in and migration, invasion, and metastasis of pancreatic cancer cells, whereas downregulation of FOXM1 expression inhibited these processes. The level of FOXM1 expression correlated directly with that of uPAR expression in pancreatic cancer cell lines and tumor specimens. Moreover, FOXM1c overexpression upregulated uPAR expression in pancreatic cancer cells, whereas inhibition of FOXM1 expression suppressed uPAR expression. Furthermore, transfection of FOXM1c into pancreatic cancer cells directly activated the uPAR promoter, whereas inhibition of FOXM1 expression by FOXM1 siRNA suppressed its activation in these cells. Finally, we identified an FOXM1-binding site in the uPAR promoter and demonstrated that FOXM1 protein bound directly to it. Deletion mutation of this site significantly attenuated uPAR promoter activity.


CONCLUSIONS
Our findings demonstrated that FOXM1c contributes to pancreatic cancer development and progression by enhancing uPAR gene transcription, and thus, tumor EMT and metastasis.
Authors' Affiliations: Shanghai Key Laboratory of Pancreatic Diseases Research; Departments of General Surgery and Oncology, Shanghai Jiaotong University Affiliated First People's Hospital; Department of Oncology and Tumor Institute, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, People's Republic of China; and Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Chen
C
Huang
Dacheng
D
Xie
Jiujie
J
Cui
Qi
Q
Li
Yong
Y
Gao
Keping
K
Xie
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D047369:Chromatin Immunoprecipitation; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology*; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D009361:Neoplasm Invasiveness / Q000473:pathology; D009362:Neoplasm Metastasis; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D046888:Tissue Array Analysis; D014162:Transfection; D015854:Up-Regulation
C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; D034741:RNA, Small Interfering; D055293:Receptors, Urokinase Plasminogen Activator