DNA Hypomethylation Is Not Cell Intrinsically Toxic to Polycomb Repressive Complex 2 Deficient Malignant Peripheral...

Area of Science:

• Oncology
• Epigenetics
• Genetics

Background:

• Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas and a leading cause of death in neurofibromatosis type 1 (NF1).
• MPNST development involves loss of Polycomb Repressive Complex 2 (PRC2), leading to global H3K27me3 depletion and gene dysregulation.
• Compensatory hypermethylation was previously suggested to counteract PRC2 loss in MPNSTs.

Purpose of the Study:

• To investigate the interplay between PRC2 status, DNA methylation, and transcriptome in MPNSTs.
• To evaluate the differential effects of DNA methyltransferase inhibitors (DNMTi) decitabine and azacitidine on MPNSTs.
• To determine if DNA hypomethylation alone is sufficient for MPNST cell killing.

Main Methods:

• Genome-wide DNA methylation and transcriptome analysis in MPNST cell lines.
• Utilized CRISPR-engineered isogenic human Schwann cells with PRC2-deficient and -proficient status.
• Assessed effects of decitabine and azacitidine treatment on cellular and molecular profiles.

Main Results:

• PRC2 status did not significantly impact global DNA methylation or methylation across genomic features.
• Decitabine and azacitidine exhibited distinct effects: azacitidine induced RNA processing gene upregulation and cytotoxicity, while decitabine upregulated immune response genes and suppressed tumor growth via microenvironment modulation.
• DNA hypomethylation alone was insufficient to induce cell death in MPNSTs, irrespective of PRC2 status.

Conclusions:

• PRC2 loss in MPNSTs does not alter global DNA methylation patterns.
• DNMT inhibitors decitabine and azacitidine have differential therapeutic mechanisms and targets in MPNSTs.
• Combination therapies involving DNMT inhibitors alongside other targeted treatments are recommended for MPNST patients.