Polycomb target genes are silenced in multiple myeloma

Area of Science:

• Epigenetics
• Cancer Genomics
• Hematologic Malignancies

Background:

• Multiple myeloma (MM) is a fatal, genetically diverse plasma cell malignancy.
• Identifying common mechanisms for MM initiation and progression remains a challenge.
• Previous studies linked Polycomb group (PcG) proteins to gene silencing via H3K27 trimethylation.

Purpose of the Study:

• To identify a common gene expression signature in multiple myeloma patient cells.
• To investigate the role of Polycomb-mediated gene silencing in MM pathogenesis.
• To evaluate the therapeutic potential of epigenetic modulators in MM.

Main Methods:

• Integrative genomics to identify underexpressed gene signatures in MM cells.
• Chromatin immunoprecipitation (ChIP) assays to detect H3K27me3 enrichment.
• Treatment of MM cell lines and an in vivo mouse model with epigenetic drugs (DZNep, LBH589).

Main Results:

• An underexpressed gene signature, enriched for H3K27-trimethylated genes, was identified in MM cells, particularly in advanced stages (ISS stage III).
• Epigenetic inhibitors (DZNep, LBH589) reactivated silenced genes, depleted EZH2, and induced apoptosis in MM cell lines.
• LBH589 treatment in a 5T33MM mouse model reduced tumor burden and improved survival.

Conclusions:

• A common gene silencing signature mediated by the Polycomb repressor complex is implicated in multiple myeloma.
• Targeting H3K27 trimethylation with epigenetic drugs demonstrates therapeutic potential for MM.
• Further studies are warranted to explore the role of this gene signature in MM initiation and progression.