EZH2-Deficient T-cell Acute Lymphoblastic Leukemia Is Sensitized to CHK1 Inhibition through Enhanced Replication...

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Loss-of-function mutations in EZH2, a key component of PRC2, are linked to poor prognosis and chemotherapy resistance in T-cell acute lymphoblastic leukemia (T-ALL).
• Currently, no targeted therapies exist for T-ALL with EZH2 mutations, highlighting an unmet clinical need.

Purpose of the Study:

• To identify synthetic lethal drug targets in EZH2-deficient T-ALL.
• To investigate the therapeutic potential of targeting identified vulnerabilities in preclinical models.

Main Methods:

• Utilized CRISPR/Cas9 to create isogenic T-ALL cell lines with and without EZH2 mutations.
• Performed cell-based synthetic lethal drug screening.
• Validated findings using genetic and small-molecule inhibition of CHK1 in vitro and in vivo.
• Analyzed gene expression and regulatory mechanisms, including MYCN enhancer activity.

Main Results:

• EZH2-deficient T-ALL cells showed increased sensitivity to CHK1 inhibitors.
• CHK1 inhibition delayed tumor progression in EZH2-deficient T-ALL models in vivo.
• EZH2 loss led to MYCN upregulation, increased replication stress, and dependency on CHK1.
• This phenotype was mediated by the derepression of a PRC2-regulated MYCN enhancer.

Conclusions:

• Loss of EZH2 function in T-ALL confers synthetic lethality with CHK1 inhibition.
• Targeting CHK1 represents a novel and clinically relevant therapeutic strategy for EZH2-mutated T-ALL.
• This pathway involves MYCN-driven replication stress and offers a new approach for aggressive T-ALL subtypes.