Involvement of Aryl hydrocarbon receptor in myelination and in human nerve sheath tumorigenesis

Area of Science:

• Molecular Biology
• Neuroscience
• Oncology

Background:

• Aryl hydrocarbon receptor (AHR) is a transcription factor regulating xenobiotic metabolism.
• Malignant peripheral nerve sheath tumors (MPNSTs) arise from plexiform neurofibromas (PNFs) and are therapy-resistant.
• MPNSTs are primarily composed of Schwann cells, often associated with NF1 gene inactivation.

Purpose of the Study:

• To investigate the role of AHR in the development and progression of PNFs and MPNSTs.
• To explore the endogenous function of AHR in Schwann cell physiology and peripheral myelination.
• To evaluate AHR as a potential therapeutic target for nerve sheath tumors.

Main Methods:

• Quantification of AHR and related gene mRNA expression in human PNF and MPNST biopsies.
• Assessment of AHR localization in MPNSTs via nuclear staining.
• Inhibition of AHR using siRNA and antagonists (CH-223191, trimethoxyflavone) in MPNST cells and in vivo models (Ahr knockout mice).
• Analysis of myelin structure, gene expression, and beta-catenin signaling in Ahr-deficient mice.

Main Results:

• AHR and its ligand biosynthetic enzymes are overexpressed in human PNFs and MPNSTs, with strong nuclear localization in MPNSTs.
• AHR inhibition induces apoptosis in human MPNST cells.
• AHR ablation in mice leads to locomotion defects, thinner myelin sheaths, and dysregulated myelin gene expression.
• AHR inhibition increases beta-catenin levels and its binding to myelin gene promoters, independent of direct promoter binding by AHR.

Conclusions:

• AHR plays an endogenous role in peripheral myelination and is dysregulated in peripheral nerve sheath tumors.
• Targeting AHR presents a potential therapeutic strategy for MPNSTs.
• AHR influences myelination through beta-catenin signaling pathways.