Targeting MUC1-C suppresses polycomb repressive complex 1 in multiple myeloma.

Area of Science:

• Epigenetics
• Molecular Oncology
• Cancer Biology

Background:

• Polycomb Repressive Complex 1 (PRC1) proteins, including BMI1, RING1, and RING2, are crucial for multiple myeloma (MM) cell survival.
• The MUC1-C oncoprotein is overexpressed in MM cells, promoting survival and activating MYC.

Purpose of the Study:

• To investigate the role of MUC1-C in regulating PRC1 components (BMI1, RING1, RING2) in MM cells.
• To elucidate the molecular mechanisms by which MUC1-C controls PRC1 expression.
• To assess the therapeutic potential of targeting MUC1-C in MM.

Main Methods:

• Stable and inducible silencing of MUC1-C.
• CRISPR/Cas9 gene editing to target MUC1-C.
• Pharmacologic inhibition of MUC1-C using GO-203.
• Analysis of gene transcription, promoter occupancy (MYC, NF-κB p65), and histone modification (H2A ubiquitylation).

Main Results:

• Targeting MUC1-C (via silencing, editing, or GO-203) downregulated BMI1, RING1, and RING2 expression.
• MUC1-C activates BMI1 transcription through a MYC-dependent mechanism, increasing MYC binding to the BMI1 promoter.
• MUC1-C, via the MUC1-C→MYC pathway, induces RING2 expression.
• MUC1-C drives RING1 expression via an NF-κB p65-dependent pathway.
• MUC1-C targeting reduced PRC1 E3 ligase activity (histone H2A ubiquitylation) and reactivated PRC1-repressed tumor suppressor genes (PTEN, CDNK2A, BIM).

Conclusions:

• MUC1-C plays a critical role in the epigenetic regulation of MM cells by controlling PRC1 component expression.
• The MUC1-C→MYC and MUC1-C→NF-κB pathways are key regulators of PRC1 in MM.
• Targeting MUC1-C represents a promising therapeutic strategy for MM by disrupting PRC1-mediated epigenetic silencing and reactivating tumor suppressors.