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Published on: January 7, 2019
Polθ activity modulates sensitivity to standard therapies in DNMT3A-deficient leukemia
Bac Viet Le1, Umeshkumar Vekariya1, Monika M Toma1
1Fels Cancer Institute for Personalized Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA.
Abstract:
Myeloid malignancies carrying somatic DNMT3A mutations (DNMT3Amut) are refractory to standard therapy. DNMT3Amut leukemia cells accumulate toxic DNA double-strand breaks (DSBs) and stalled replication forks, rendering them dependent on DNA damage response (DDR). We report here that DNA polymerase theta (Polθ), a key element in DSB repair by end-joining (Polθ-mediated end-joining [TMEJ]) and in fork restarting, promotes survival and proliferation of DNMT3Amut leukemia cells. Polθ is overexpressed in DNMT3Amut leukemia cells due to abrogation of PARP1 PARylation-dependent UBE2O E3 ligase-mediated ubiquitination and proteasomal degradation of Polθ. In addition, PARP1-mediated recruitment of the SMARCAD1-MSH2/MSH3 repressive complex to DSBs is diminished in DNMT3Amut leukemia cells, which facilitates association of Polθ with DNA damage. Polθ inhibitors enhance the anti-leukemic effects of standard drugs such as FLT3 kinase inhibitor quizartinib, cytarabine ± doxorubicin, and etoposide in vitro and in mice with DNMT3Amut leukemia. Altogether, Polθ is an attractive target in DNMT3Amut hematological malignancies.
Insights
DNA polymerase theta (Polθ) drives survival in difficult-to-treat DNMT3A-mutated myeloid leukemias. Inhibiting Polθ enhances standard therapies, offering a new therapeutic strategy for these aggressive blood cancers.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- Myeloid malignancies with DNMT3A mutations (DNMT3Amut) show resistance to conventional treatments.
- DNMT3Amut leukemia cells exhibit increased DNA double-strand breaks (DSBs) and replication stress, creating a dependency on DNA damage response (DDR) pathways.
Purpose of the Study:
- To investigate the role of DNA polymerase theta (Polθ) in the survival and proliferation of DNMT3Amut leukemia cells.
- To explore the therapeutic potential of targeting Polθ in DNMT3Amut hematological malignancies.
Main Methods:
- Analysis of Polθ expression and its regulation in DNMT3Amut leukemia cells.
- Investigation of Polθ's involvement in DNA repair pathways, specifically Polθ-mediated end-joining (TMEJ).
- Evaluation of Polθ inhibitors in combination with standard chemotherapies and targeted agents in vitro and in vivo mouse models.
Main Results:
- Polθ promotes survival and proliferation in DNMT3Amut leukemia by participating in DSB repair and replication fork restart.
- Polθ is overexpressed in DNMT3Amut leukemia due to impaired degradation, linked to abrogation of PARP1-mediated ubiquitination.
- Polθ inhibition synergizes with standard treatments (quizartinib, cytarabine, doxorubicin, etoposide) to enhance anti-leukemic effects.
Conclusions:
- Polθ is a critical factor for the survival of DNMT3Amut leukemia cells.
- Targeting Polθ represents a promising therapeutic strategy for DNMT3Amut hematological malignancies, potentially overcoming treatment resistance.
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