ABSTRACT
BACKGROUND: Acute pancreatitis is the most common complication of diagnostic and therapeutic endoscopic retrograde cholangiopancreatography (ERCP). In spite of continuing research, no pharmacologic agent capable of effectively reducing the incidence of ERCP-induced pancreatitis has found its way into clinical practise. A number of experimental studies suggest that intrapancreatic calcium concentrations play an important role in the initiation of intracellular protease activation, an initiating step in the course of acute pancreatitis. Magnesium can act as a calcium-antagonist and counteracts effects in calcium signalling. It can thereby attenuate the intracellular activation of proteolytic digestive enzymes in the pancreas and reduces the severity of experimental pancreatitis when administered either intravenously or as a food supplement. METHODS: We designed a randomized, double-blind, placebo-controlled phase III study to test whether the administration of intravenous magnesium sulphate before and after ERCP reduces the incidence and the severity of post-ERCP pancreatitis. A total of 502 adult patients with a medical indication for ERCP are to be randomized to receive either 4930 mg magnesium sulphate (= 20 mmol magnesium) or placebo 60 min before and 6 hours after ERCP. The incidence of clinical post-ERCP pancreatitis, hyperlipasemia, pain levels, use of analgetics and length of hospital stay will be evaluated. CONCLUSIONS: If magnesium sulphate is found to be effective in preventing post-ERCP pancreatitis, this inexpensive agent with limited adverse effects could be used as a routine pharmacological prophylaxis. TRIAL REGISTRATION: Current Controlled Trials ISRCTN46556454.
Subject(s)
Cholangiopancreatography, Endoscopic Retrograde/adverse effects , Magnesium Sulfate/therapeutic use , Pancreatitis/etiology , Pancreatitis/prevention & control , Acute Disease , Administration, Intravenous , Adult , Calcium Signaling/drug effects , Double-Blind Method , Humans , Incidence , Magnesium Sulfate/administration & dosage , Magnesium Sulfate/pharmacology , Pancreatitis/epidemiology , Severity of Illness IndexABSTRACT
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 [(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.
Subject(s)
Adenocarcinoma/metabolism , Cell Proliferation , Chromatin Assembly and Disassembly , Histones/metabolism , NFATC Transcription Factors/metabolism , Pancreatic Neoplasms/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Acetylation , Adenocarcinoma/genetics , Adenocarcinoma/pathology , Animals , Binding Sites , Blotting, Western , Calcineurin/metabolism , Calcium/metabolism , Cell Cycle , Cell Line, Tumor , Chromatin Immunoprecipitation , Flow Cytometry , Humans , Immunohistochemistry , Male , Mice , Mice, Nude , NFATC Transcription Factors/genetics , Neoplasm Transplantation , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/pathology , Promoter Regions, Genetic , Proto-Oncogene Proteins c-myc/genetics , RNA Interference , Reverse Transcriptase Polymerase Chain Reaction , Serum/metabolism , Serum Response Element , Signal Transduction , Time Factors , Transcription, Genetic , Transfection , ets-Domain Protein Elk-1/metabolism , p300-CBP Transcription Factors/metabolismABSTRACT
The nuclear factor of activated T cell (NFAT) proteins are a family of Ca2+/calcineurin-responsive transcription factors primarily recognized for their central roles in T lymphocyte activation and cardiac valve development. We demonstrate that NFATc1 is commonly overexpressed in pancreatic carcinomas and enhances the malignant potential of tumor cells through transcriptional activation of the c-myc oncogene. Activated NFATc1 directly binds to a specific element within the proximal c-myc promoter and upregulates c-myc transcription, ultimately resulting in increased cell proliferation and enhanced anchorage-independent growth. Conversely, c-myc transcription and anchorage-dependent and -independent cell growth is significantly attenuated by inhibition of Ca2+/calcineurin signaling or siRNA-mediated knock down of NFATc1 expression. Together, these results demonstrate that ectopic activation of NFATc1 and the Ca2+/calcineurin signaling pathway is an important mechanism of oncogenic c-myc activation in pancreatic cancer.
