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MAF mediates crosstalk between Ras-MAPK and mTOR signaling in NF1.

Brundage ME, Tandon P, Eaves DW, Williams JP, Miller SJ, Hennigan RH, Jegga A, Cripe TP, Ratner N - Oncogene (2014)

Bottom Line: Mutations in the neurofibromatosis type 1 (NF1) tumor suppressor gene are common in cancer and can cause resistance to therapy.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Experimental Hematology and Cancer Biology, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.

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.

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Related in: MedlinePlus

MAF regulates glial differentiation markers and the neural crest marker SOX9(A) RT-PCR analysis of S462TY MPNST cells transduced with mCherry tagged MAF or mCherry control for 48 hours. mRNA levels are expressed relative to β-actin. (B) Immohistochemistry shows expression of differentiation markers (S100β, MBP, and BLBP) in MAF transduced MPNST cells. (C) RT-PCR and western blot analysis showing relative expression of SOX9 in MAF transduced MPNST cells before (white bar) and after (black bar) induction with doxycycline for 48 hours. (D) ChIP analysis of MAF occupancy of the SOX9 promoter.
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Figure 3: MAF regulates glial differentiation markers and the neural crest marker SOX9(A) RT-PCR analysis of S462TY MPNST cells transduced with mCherry tagged MAF or mCherry control for 48 hours. mRNA levels are expressed relative to β-actin. (B) Immohistochemistry shows expression of differentiation markers (S100β, MBP, and BLBP) in MAF transduced MPNST cells. (C) RT-PCR and western blot analysis showing relative expression of SOX9 in MAF transduced MPNST cells before (white bar) and after (black bar) induction with doxycycline for 48 hours. (D) ChIP analysis of MAF occupancy of the SOX9 promoter.

Mentions: MAF can bind the MPNST biomarker SOX9 (29), and MAF is known to promote tissue specification and terminal differentiation in many cell types (26, 27, 29, 38). We explored whether low MAF expression was relevant to the failure of MPNST cells differentiation. RT-PCR revealed upregulation of glial lineage markers S100β, MBP, and BLBP in MPNST cells after transduction with MAF (Figure 3A). Immunohistochemical staining verified increased expression of these proteins in MAF transduced MPNST cells (Figure 3B). Because the neural crest marker gene SOX9 has MAF binding sites in its promoter (data not shown), we tested whether restoring MAF expression downregulates SOX9. RT-PCR and western bot analysis revealed decreased SOX9 mRNA and SOX9 protein when MAF was overexpressed (Figure 3C). Chromatin immunoprecipitation analysis showed MAF occupancy of the SOX9 promoter (Figure 3D), suggesting that MAF transcriptionally represses SOX9 in MPNST.


MAF mediates crosstalk between Ras-MAPK and mTOR signaling in NF1.

Brundage ME, Tandon P, Eaves DW, Williams JP, Miller SJ, Hennigan RH, Jegga A, Cripe TP, Ratner N - Oncogene (2014)

MAF regulates glial differentiation markers and the neural crest marker SOX9(A) RT-PCR analysis of S462TY MPNST cells transduced with mCherry tagged MAF or mCherry control for 48 hours. mRNA levels are expressed relative to β-actin. (B) Immohistochemistry shows expression of differentiation markers (S100β, MBP, and BLBP) in MAF transduced MPNST cells. (C) RT-PCR and western blot analysis showing relative expression of SOX9 in MAF transduced MPNST cells before (white bar) and after (black bar) induction with doxycycline for 48 hours. (D) ChIP analysis of MAF occupancy of the SOX9 promoter.
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Related In: Results  -  Collection

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Figure 3: MAF regulates glial differentiation markers and the neural crest marker SOX9(A) RT-PCR analysis of S462TY MPNST cells transduced with mCherry tagged MAF or mCherry control for 48 hours. mRNA levels are expressed relative to β-actin. (B) Immohistochemistry shows expression of differentiation markers (S100β, MBP, and BLBP) in MAF transduced MPNST cells. (C) RT-PCR and western blot analysis showing relative expression of SOX9 in MAF transduced MPNST cells before (white bar) and after (black bar) induction with doxycycline for 48 hours. (D) ChIP analysis of MAF occupancy of the SOX9 promoter.
Mentions: MAF can bind the MPNST biomarker SOX9 (29), and MAF is known to promote tissue specification and terminal differentiation in many cell types (26, 27, 29, 38). We explored whether low MAF expression was relevant to the failure of MPNST cells differentiation. RT-PCR revealed upregulation of glial lineage markers S100β, MBP, and BLBP in MPNST cells after transduction with MAF (Figure 3A). Immunohistochemical staining verified increased expression of these proteins in MAF transduced MPNST cells (Figure 3B). Because the neural crest marker gene SOX9 has MAF binding sites in its promoter (data not shown), we tested whether restoring MAF expression downregulates SOX9. RT-PCR and western bot analysis revealed decreased SOX9 mRNA and SOX9 protein when MAF was overexpressed (Figure 3C). Chromatin immunoprecipitation analysis showed MAF occupancy of the SOX9 promoter (Figure 3D), suggesting that MAF transcriptionally represses SOX9 in MPNST.

Bottom Line: Mutations in the neurofibromatosis type 1 (NF1) tumor suppressor gene are common in cancer and can cause resistance to therapy.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Experimental Hematology and Cancer Biology, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.

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.

Show MeSH
Related in: MedlinePlus