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Gastroenterology. 2014 Jan;146(1):278-90. doi: 10.1053/j.gastro.2013.10.009. Epub 2013 Oct 9.

Nuclear death receptor TRAIL-R2 inhibits maturation of let-7 and promotes proliferation of pancreatic and other tumor cells.

Author information

1
Division of Molecular Oncology, Institute for Experimental Cancer Research, University of Kiel, Kiel, Germany.
2
Institute of Immunology, University of Kiel, Kiel, Germany.
3
Institute of Clinical Molecular Biology, University of Kiel, Kiel, Germany.
4
Zoological Institute, University of Kiel, Kiel, Germany.
5
Division of Molecular Oncology, Institute for Experimental Cancer Research, University of Kiel, Kiel, Germany; Clinic for General Surgery, Visceral, Thoracic, Transplantation and Pediatric Surgery, University of Kiel, Kiel, Germany.
6
Clinic for General Surgery, Visceral, Thoracic, Transplantation and Pediatric Surgery, University of Kiel, Kiel, Germany.
7
Clinic for Diagnostic Radiology, University of Kiel, Kiel, Germany.
8
Center for Anatomy, Institute of Cell Biology and Neurobiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
9
Institute of Pathology, University of Kiel, Kiel, Germany.
10
Department of General, Visceral and Transplantation Surgery, Centre of Surgery, University of Ulm, Ulm, Germany.
11
Centre for Cell Death, Cancer and Inflammation, University College London Cancer Institute, London, United Kingdom.
12
Division of Molecular Internal Medicine, Department of Internal Medicine II, University Hospital Würzburg, Würzburg, Germany.
13
Division of Molecular Oncology, Institute for Experimental Cancer Research, University of Kiel, Kiel, Germany. Electronic address: atrauzold@email.uni-kiel.de.

Abstract

BACKGROUND & AIMS:

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL-R1) (TNFRSF10A) and TRAIL-R2 (TNFRSF10B) on the plasma membrane bind ligands that activate apoptotic and other signaling pathways. Cancer cells also might have TRAIL-R2 in the cytoplasm or nucleus, although little is known about its activities in these locations. We investigated the functions of nuclear TRAIL-R2 in cancer cell lines.

METHODS:

Proteins that interact with TRAIL-R2 initially were identified in pancreatic cancer cells by immunoprecipitation, mass spectrometry, and immunofluorescence analyses. Findings were validated in colon, renal, lung, and breast cancer cells. Functions of TRAIL-R2 were determined from small interfering RNA knockdown, real-time polymerase chain reaction, Drosha-activity, microRNA array, proliferation, differentiation, and immunoblot experiments. We assessed the effects of TRAIL-R2 overexpression or knockdown in human pancreatic ductal adenocarcinoma (PDAC) cells and their ability to form tumors in mice. We also analyzed levels of TRAIL-R2 in sections of PDACs and non-neoplastic peritumoral ducts from patients.

RESULTS:

TRAIL-R2 was found to interact with the core microprocessor components Drosha and DGCR8 and the associated regulatory proteins p68, hnRNPA1, NF45, and NF90 in nuclei of PDAC and other tumor cells. Knockdown of TRAIL-R2 increased Drosha-mediated processing of the let-7 microRNA precursor primary let-7 (resulting in increased levels of mature let-7), reduced levels of the let-7 targets (LIN28B and HMGA2), and inhibited cell proliferation. PDAC tissues from patients had higher levels of nuclear TRAIL-R2 than non-neoplastic pancreatic tissue, which correlated with increased nuclear levels of HMGA2 and poor outcomes. Knockdown of TRAIL-R2 in PDAC cells slowed their growth as orthotopic tumors in mice. Reduced nuclear levels of TRAIL-R2 in cultured pancreatic epithelial cells promoted their differentiation.

CONCLUSIONS:

Nuclear TRAIL-R2 inhibits maturation of the microRNA let-7 in pancreatic cancer cell lines and increases their proliferation. Pancreatic tumor samples have increased levels of nuclear TRAIL-R2, which correlate with poor outcome of patients. These findings indicate that in the nucleus, death receptors can function as tumor promoters and might be therapeutic targets.

KEYWORDS:

Apoptosis Regulation; DGCR8; EGFP; HMGA2; LNA; LSM; MALDI-TOF; PCR; PDAC; Pancreatic Cancer; TRAIL; diGeorge syndrome critical region gene 8; enhanced green fluorescent protein; heterogenous ribonucleoprotein A1; high mobility group AT-hook protein 2; hnRNPA1; laser scanning microscopy; locked nucleic acid; miRNA; microRNA; microRNA Processing; nTRAIL-R2; nuclear TRAIL-R2; pancreatic ductal adenocarcinoma; polymerase chain reaction; pri-; primary; siRNA; small interfering RNA; tumor necrosis factor-related apoptosis inducing ligand

PMID:
24120475
DOI:
10.1053/j.gastro.2013.10.009
[Indexed for MEDLINE]

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