NFAT-Induced Histone Acetylation Relay Switch Promotes c-Myc-Dependent Growth in Pancreatic Cancer Cells
Background & Aims
Induction of immediate early transcription factors (ITF) represents the first transcriptional program controlling mitogen-stimulated cell cycle progression in cancer. Here, we examined the transcriptional mechanisms regulating the ITF protein c-Myc and its role in pancreatic cancer growth in vitro and in vivo.
Methods
Expression of ITF proteins was examined by reverse-transcription polymerase chain reaction and immunoblotting, and its implications in cell cycle progression and growth was determined by flow cytometry and [3H]-thymidine incorporation. Intracellular Ca2+ concentrations, calcineurin activity, and cellular nuclear factor of activated T cells (NFAT) distribution were analyzed. Transcription factor complex formations and promoter regulation were examined by immunoprecipitations, reporter gene assays, and chromatin immunoprecipitation. Using a combination of RNA interference knockdown technology and xenograft models, we analyzed the significance for pancreatic cancer tumor growth.
Results
Serum promotes pancreatic cancer growth through induction of the proproliferative NFAT/c-Myc axis. Mechanistically, serum increases intracellular Ca2+ concentrations and activates the calcineurin/NFAT pathway to induce c-Myc transcription. NFAT binds to a serum responsive element within the proximal promoter, initiates p300-dependent histone acetylation, and creates a local chromatin structure permissive for the inducible recruitment of Ets-like gene (ELK)-1, a protein required for maximal activation of the c-Myc promoter. The functional significance of this novel pathway was emphasized by impaired c-Myc expression, G1 arrest, and reduced tumor growth upon NFAT depletion in vitro and in vivo.
Conclusions
Our study uncovers a novel mechanism regulating cell growth and identifies the NFAT/ELK complex as modulators of early stages of mitogen-stimulated proliferation in pancreatic cancer cells.
Key words: Pancreatic Cancer, c-Myc, NFAT, Transcription
Abbreviations used in this paper: ChIP, chromatin immunoprecipitation, CsA, cyclosporine A, FCS, fetal calf serum, HAT, histone acetyltransferase, ITF, immediate early transcription factors, NFAT, nuclear factor of activated T cells, PCR, polymerase chain reaction
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Conflicts of interest The authors disclose no conflicts.
Funding Supported by the Deutsche Forschungsgemeinschaft (DFG, SFB-TR17; to V.E., A.G., and J.M.) and the Max Eder program of the German Cancer Research Foundation (Deutsche Krebshilfe, 70-3022-El I; to V.E.) and by the Miles and Shirley Fiterman Center for Digestive Diseases, Division of Gastroenterology and Hepatology, Division of Oncology Research, Mayo Clinic Cancer Center, Mayo Clinic Pancreatic SPORE P50 CA102701 and CA136526 (to M.E.F.-Z.).
PII: S0016-5085(09)01942-8
doi:10.1053/j.gastro.2009.10.045
© 2010 AGA Institute. Published by Elsevier Inc. All rights reserved.
