ABSTRACT
Mutations in the neurofibromatosis type 1 (NF1) tumor suppressor gene are common in cancer and can cause resistance to therapy. Using transcriptome analysis we identified MAF as an NF1- regulated transcription factor and verified MAF regulation through RAS/MAPK/AP-1 signaling in malignant peripheral nerve sheath tumor (MPNST) cell lines. MAF was also downregulated in human MPNST. Acute re-expression of MAF promoted expression of glial differentiation markers in MPNST cells in vitro, decreased self-renewal of embryonic precursors and transiently affected tumor cell phenotypes in vitro by increasing MPNST cell death and reducing metabolic activity and anchorage-independent growth. Paradoxically, chronic MAF overexpression enhanced MPNST cell tumor growth in vivo, correlating with elevated pS6 in vitro and in vivo. RAD001 blocked MAF-mediated tumor growth, and MAF regulated the mTOR pathway through DEPTOR. MAPK inhibition with NF1 loss of function is predicted to show limited efficacy due to reactivation of mTOR signaling via MAF.
Subject(s)
MAP Kinase Signaling System , Nerve Sheath Neoplasms/genetics , Neurofibromatosis 1/genetics , Neurofibromin 1/metabolism , Proto-Oncogene Proteins c-maf/physiology , TOR Serine-Threonine Kinases/metabolism , ras Proteins/metabolism , Animals , Cell Differentiation , Down-Regulation , Female , Gene Expression Regulation, Neoplastic , Genes, Neurofibromatosis 1 , Humans , Mice , Mice, Nude , Neoplasm Transplantation , Nerve Sheath Neoplasms/metabolism , Neurofibromatosis 1/metabolism , Neuroglia/metabolism , Oligonucleotide Array Sequence Analysis , Phenotype , Schwann Cells/cytology , Signal Transduction , TranscriptomeABSTRACT
Malignant peripheral nerve sheath tumors (MPNSTs) develop sporadically or in the context of neurofibromatosis type 1. Epidermal growth factor receptor (EGFR) overexpression has been implicated in MPNST formation, but its precise role and relevant signaling pathways remain unknown. We found that EGFR overexpression promotes mouse neurofibroma transformation to aggressive MPNST (GEM-PNST). Immunohistochemistry demonstrated phosphorylated STAT3 (Tyr705) in both human MPNST and mouse GEM-PNST. A specific JAK2/STAT3 inhibitor FLLL32 delayed MPNST formation in an MPNST xenograft nude mouse model. STAT3 knockdown by shRNA prevented MPNST formation in vivo. Finally, reducing EGFR activity strongly reduced pSTAT3 in vivo. Thus, an EGFR-STAT3 pathway is necessary for MPNST transformation and establishment of MPNST xenografts growth but not for tumor maintenance. Efficacy of the FLLL32 pharmacological inhibitor in delaying MPNST growth suggests that combination therapies targeting JAK/STAT3 might be useful therapeutics.
Subject(s)
ErbB Receptors/physiology , Nerve Sheath Neoplasms/etiology , STAT3 Transcription Factor/physiology , Signal Transduction/physiology , Animals , Cells, Cultured , Curcumin/analogs & derivatives , Curcumin/pharmacology , Genes, Neurofibromatosis 1 , Humans , Janus Kinase 2/physiology , Mice , Mice, Inbred C57BL , STAT3 Transcription Factor/antagonists & inhibitors , Sarcoma/etiologyABSTRACT
Excessive alcohol intake, characteristic of an alcohol use disorder (AUD), results in neurodegeneration as well as cognitive deficits that may recover in abstinence. Neurodegeneration in psychiatric disorders such as AUDs is due to various effects on tissue integrity. Several groups report that alcohol-induced neurodegeneration and recovery include a role for adult neurogenesis. Therefore, the initial purpose of this study was to investigate the effect of alcohol on the temporal profile of neural progenitor cells using the radial glia marker, vimentin, in a model of an AUD. However, striking vimentin expression throughout corticolimbic regions led, instead, to the discovery of a significant gliosis response in this model. Adult male rats were subjected to a 4-day binge model of an AUD and brains harvested for immunohistochemistry at 0, 2, 4, 7, 14, and 28 days following the last dose of ethanol. A prominent increase in vimentin immunoreactivity was apparent at 4 and 7 days post binge that returned to control levels by 14 days in the corticolimbic regions examined. Vimentin-positive cells co-labeled with glial fibrillary acidic protein (GFAP), which suggested that cells were reactive astrocytes. A second experiment supported that increased vimentin was not primarily due to alcohol withdrawal seizures and is more likely due to alcohol-induced cell death. As this gliosis was remarkably distinct in regions where cell death had not previously been reported in this model, adjacent tissue sections were processed for FluoroJade B staining for cell death. FluoroJade B-positive cells were evident immediately following the last ethanol dose as expected, but were significantly elevated in the hippocampal dentate gyrus and CA3 regions and corticolimbic regions from 2 to 7 days post binge. Intriguingly, vimentin labeling of astrogliosis is more widespread than FluoroJade B labeling of cell death, which suggests that 4-day binge ethanol consumption is more damaging than originally realized.
