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Loss of ATRX confers DNA repair defects and PARP inhibitor sensitivity
Jennifer Garbarino1, Jillian Eckroate2, Ranjini K Sundaram2
1Department of Molecular Biochemistry and Biophysics, Yale University, New Haven, CT 06511, USA.
Abstract:
Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX) is mutated frequently in gliomas and represents a potential target for cancer therapies. ATRX is known to function as a histone chaperone that helps incorporate histone variant, H3.3, into the genome. Studies have implicated ATRX in key DNA damage response (DDR) pathways but a distinct role in DNA repair has yet to be fully elucidated. To further investigate the function of ATRX in the DDR, we created isogenic wild-type (WT) and ATRX knockout (KO) model cell lines using CRISPR-based gene targeting. These studies revealed that loss of ATRX confers sensitivity to poly(ADP)-ribose polymerase (PARP) inhibitors, which was linked to an increase in replication stress, as detected by increased activation of the ataxia telangiectasia and Rad3-related (ATR) signaling axis. ATRX mutations frequently co-occur with mutations in isocitrate dehydrogenase-1 and -2 (IDH1/2), and the latter mutations also induce HR defects and PARP inhibitor sensitivity. We found that the magnitude of PARP inhibitor sensitivity was equal in the context of each mutation alone, although no further sensitization was observed in combination, suggesting an epistatic interaction. Finally, we observed enhanced synergistic tumor cell killing in ATRX KO cells with ATR and PARP inhibition, which is commonly seen in HR-defective cells. Taken together, these data reveal that ATRX may be used as a molecular marker for DDR defects and PARP inhibitor sensitivity, independent of IDH1/2 mutations. These data highlight the important role of common glioma-associated mutations in the regulation of DDR, and novel avenues for molecularly guided therapeutic intervention.
Insights
Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX) mutations in gliomas indicate sensitivity to PARP inhibitors due to DNA damage response defects. ATRX loss enhances tumor cell killing with ATR and PARP inhibition, suggesting new therapeutic strategies.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX) is frequently mutated in gliomas and plays a role in histone variant H3.3 incorporation.
- While ATRX is implicated in DNA damage response (DDR) pathways, its precise function in DNA repair remains unclear.
- ATRX mutations often co-occur with isocitrate dehydrogenase-1 and -2 (IDH1/2) mutations in gliomas.
Purpose of the Study:
- To investigate the role of ATRX in the DNA damage response (DDR) and its impact on glioma cell sensitivity to targeted therapies.
- To elucidate the relationship between ATRX mutations, replication stress, and sensitivity to poly(ADP)-ribose polymerase (PARP) inhibitors.
- To explore the potential of ATRX as a predictive biomarker for DDR defects and therapeutic response in gliomas.
Main Methods:
- Creation of isogenic wild-type (WT) and ATRX knockout (KO) glioma model cell lines using CRISPR-Cas9 gene editing.
- Assessment of DNA damage response activation, including the ataxia telangiectasia and Rad3-related (ATR) signaling axis, under various treatment conditions.
- Evaluation of cell sensitivity to PARP inhibitors and combination therapies, including ATR inhibition.
Main Results:
- Loss of ATRX leads to increased replication stress and sensitivity to PARP inhibitors, mediated by activation of the ATR signaling axis.
- Both ATRX and IDH1/2 mutations independently confer sensitivity to PARP inhibitors, suggesting an epistatic interaction with no additive effect in combination.
- Combined inhibition of ATR and PARP resulted in synergistic tumor cell killing in ATRX-deficient cells.
Conclusions:
- ATRX functions as a key regulator in the DNA damage response, and its loss confers sensitivity to PARP inhibitors.
- ATRX can serve as a molecular marker for DDR defects and predict PARP inhibitor sensitivity, independent of IDH1/2 mutation status.
- Targeting DDR pathways in ATRX-mutated gliomas, particularly in combination with PARP and ATR inhibitors, offers promising therapeutic avenues.
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