ZIP4 regulates pancreatic cancer cell growth by activating IL-6/STAT3 pathway through zinc finger transcription factor CREB.
OBJECTIVE
Recent studies indicate a strong correlation of zinc transporter ZIP4 and pancreatic cancer progression; however, the underlying mechanisms are unclear. We have recently found that ZIP4 is overexpressed in pancreatic cancer. In this study, we investigated the signaling pathway through which ZIP4 regulates pancreatic cancer growth.


METHODS
The expression of cyclin D1, interleukin 6 (IL-6), and signal transducer and activator of transcription 3 (STAT3) in pancreatic cancer xenografts and cells were examined by real-time PCR, Bio-Plex cytokine assay, and Western blot, respectively. The activity of cAMP response element-binding protein (CREB) is examined by a promoter activity assay.


RESULTS
Cyclin D1 was significantly increased in the ZIP4 overexpressing MIA PaCa-2 cells (MIA-ZIP4)-injected orthotopic xenografts and was downregulated in the ZIP4-silenced ASPC-1 (ASPC-shZIP4) group. The phosphorylation of STAT3, an upstream activator of cyclin D1, was increased in MIA-ZIP4 cells and decreased in ASPC-shZIP4 cells. IL-6, a known upstream activator for STAT3, was also found to be significantly increased in the MIA-ZIP4 cells and xenografts and decreased in the ASPC-shZIP4 group. Overexpression of ZIP4 led to a 75% increase of IL-6 promoter activity and caused increased phosphorylation of CREB.


CONCLUSIONS
Our study suggest that ZIP4 overexpression causes increased IL-6 transcription through CREB, which in turn activates STAT3 and leads to increased cyclin D1 expression, resulting in increased cell proliferation and tumor progression in pancreatic cancer. These results elucidated a novel pathway in ZIP4-mediated pancreatic cancer growth and suggest new therapeutic targets, including ZIP4, IL-6, and STAT3, in pancreatic cancer treatment.
Michael E DeBakey Department of Surgery, Baylor College of Medicine, Molecular Surgeon Research Center, University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
Yuqing
Y
Zhang
Uddalak
U
Bharadwaj
Craig D
CD
Logsdon
Changyi
C
Chen
Qizhi
Q
Yao
Min
M
Li
D000818:Animals; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D010766:Phosphorylation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D015854:Up-Regulation
D027682:Cation Transport Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D015850:Interleukin-6; C486791:SLC39A4 protein, human; D050796:STAT3 Transcription Factor; D019938:Cyclin D1