Downregulation of c-Myc is involved in TLR3-mediated tumor death of neuroblastoma xenografts
Journal
Laboratory Investigation
Journal Volume
96
Journal Issue
7
Pages
719-730
Date Issued
2016
Author(s)
Abstract
Neuroblastoma (NB) is the deadliest pediatric solid tumor due to its pleomorphic molecular characteristics. In the innate immune system, toll-like receptor 3 (TLR3) recognizes viral double-stranded RNAs to initiate immune signaling. Positive TLR3 expression indicates a favorable prognosis in NB patients, and is associated with MYCN-non-amplified. However, TLR3-mediated innate immune responses remain elusive in NB. In this study, we attempted to dissect the molecular mechanism underlying TLR3-agonist polyinosinic-polycytidylic acid [poly(I:C)] treatment in NB in vivo. We established NB xenograft models in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice with MYCN-amplified SK-N-DZ (DZ) cells or MYCN-non-amplified SK-N-AS (AS) cells. Poly(I:C) treatment led to significant tumor regression in AS xenografts, but not in DZ xenografts. Through immunohistochemical analysis, significant suppression of tumor proliferation, downregulation of c-Myc expression, and upregulation of TLR3 expression were found in the treatment group. Poly(I:C) inducing activation of TLR3/IRF3-mediated innate immunity associated with downregulation of c-Myc can be found in MYCN-non-amplified SK-N-AS cells, but not in MYCN-amplified BE(2)-M17 cells. Knockdown of TLR3 disturbed poly(I:C)-induced suppression of c-Myc and upregulation of p-IRF3 in AS cells. Furthermore, poly(I:C) treatment upregulated active NF-κB, mitochondrial antioxidant manganese superoxide dismutase and 8-hydroxydeoxyguanosine, which works with reactive oxygen species (ROS) generation and DNA damage. Upregulation of active caspase 3 and cleaved poly [ADP-ribose] polymerase 1 were found in poly(I:C)-treated AS xenografts, which indicates the induction of apoptosis. Thus, our results suggest that c-Myc overexpression may increase sensitivity to poly(I:C)-induced tumor growth arrest and ROS-mediated apoptosis in NB. This study demonstrates that c-Myc protein expression has an important role in TLR3-induced innate immune responses, providing future treatment recommendations. ? 2016 USCAP, Inc All rights reserved.
SDGs
Other Subjects
8 hydroxydeoxyguanosine; caspase 3; DNA; manganese superoxide dismutase; Myc protein; nicotinamide adenine dinucleotide adenosine diphosphate ribosyltransferase 1; polyinosinic polycytidylic acid; reactive oxygen metabolite; toll like receptor 3; CASP3 protein, human; caspase 3; immunoglobulin enhancer binding protein; Myc protein; MYC protein, human; polyinosinic polycytidylic acid; reactive oxygen metabolite; TLR3 protein, human; toll like receptor 3; animal experiment; animal model; animal tissue; apoptosis; Article; controlled study; DNA damage; down regulation; gene overexpression; human; human cell; immunohistochemistry; in vivo study; innate immunity; male; mouse; mouse model; neuroblastoma; neuroblastoma cell line; nonhuman; priority journal; protein expression; tumor growth; tumor regression; tumor xenograft; upregulation; agonists; animal; apoptosis; cell proliferation; down regulation; drug effects; genetics; immunotherapy; innate immunity; metabolism; neuroblastoma; nonobese diabetic mouse; oncogene myc; RNA interference; SCID mouse; tumor cell line; xenograft; Animals; Apoptosis; Caspase 3; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Genes, myc; Heterografts; Humans; Immunity, Innate; Immunotherapy; Male; Mice; Mice, Inbred NOD; Mice, SCID; Neuroblastoma; NF-kappa B; Poly I-C; Proto-Oncogene Proteins c-myc; Reactive Oxygen Species; RNA Interference; Toll-Like Receptor 3; Up-Regulation
Publisher
Nature Publishing Group
Type
journal article