Genetic and epigenetic characterization of sarcoma stem cells across subtypes identifies EZH2 as a therapeutic target

Area of Science:

• Oncology
• Cancer Biology
• Epigenetics

Background:

• High-grade soft tissue sarcomas (STS) are aggressive cancers with poor outcomes often linked to chemotherapy resistance.
• Anthracycline chemotherapy is the standard first-line treatment for STS, but resistance significantly impacts patient prognosis.
• Soft tissue sarcoma cancer stem cells (STS-CSCs) are implicated in treatment resistance.

Purpose of the Study:

• To investigate the role of STS-CSCs in doxorubicin resistance.
• To identify a common genetic or epigenetic vulnerability across different STS subtypes that could be therapeutically targeted.
• To evaluate EZH2 as a potential therapeutic target in STS-CSCs.

Main Methods:

• Correlation analysis of STS-CSC abundance with doxorubicin IC50 values.
• Analysis of patient-derived samples from five sarcoma subtypes to identify shared genetic signatures.
• Assessment of Enhancer of Zeste homolog 2 (EZH2) enrichment and activity in STS-CSCs.
• In vitro treatment of doxorubicin-resistant cell lines with tazemetostat, an EZH2 inhibitor.

Main Results:

• A positive correlation was found between STS-CSC abundance and doxorubicin resistance (IC50).
• EZH2, a component of the polycomb repressive complex 2 (PRC2), was enriched in STS-CSCs across multiple sarcoma subtypes.
• Targeting EZH2 with tazemetostat led to a significant reduction in the STS-CSC population.
• A shared epigenetic profile associated with EZH2 was identified in STS-CSCs.

Conclusions:

• STS-CSCs contribute significantly to doxorubicin resistance in high-grade soft tissue sarcomas.
• EZH2 represents a common, targetable vulnerability across diverse STS subtypes.
• Inhibition of EZH2, as demonstrated with tazemetostat, effectively reduces the STS-CSC population, suggesting a promising therapeutic avenue.