NFAT-induced histone acetylation relay switch promotes c-Myc-dependent growth in pancreatic cancer cells.
OBJECTIVE
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 [(3)H]-thymidine incorporation. Intracellular Ca(2+) 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 Ca(2+) 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.
Köenig
Alexander
A
Department of Gastroenterology and Endocrinology, Philipps-University of Marburg, 35043 Marburg, Germany.
Linhart
Thomas
T
Schlengemann
Katrin
K
Reutlinger
Kristina
K
Wegele
Jessica
J
Adler
Guido
G
Singh
Garima
G
Hofmann
Leonie
L
Kunsch
Steffen
S
Büch
Thomas
T
Schäfer
Eva
E
Gress
Thomas M
TM
Fernandez-Zapico
Martin E
ME
Ellenrieder
Volker
V
D000107:Acetylation; D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D042002:Chromatin Assembly and Disassembly; D047369:Chromatin Immunoprecipitation; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008819:Mice, Nude; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044967:Serum / Q000378:metabolism; D027602:Serum Response Element; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism; D050880:p300-CBP Transcription Factors / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
D019703:Calcineurin; D002118:Calcium; D006657:Histones; D050778:NFATC Transcription Factors; D016271:Proto-Oncogene Proteins c-myc; D050807:ets-Domain Protein Elk-1; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C494112:ELK1 protein, human; C489427:MYC protein, human; C494003:NFATC1 protein, human; C494006:NFATC2 protein, human