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Published on: April 28, 2021
Replication-induced DNA damage after PARP inhibition causes G2 delay, and cell line-dependent apoptosis, necrosis and
Idun Dale Rein1, Kirsti Solberg Landsverk1, Francesca Micci2,3
1a Group for Molecular Radiation Biology ; Department of Radiation Biology ; The Norwegian Radium Hospital ; Oslo , Norway.
Abstract:
PARP inhibitors have been approved for treatment of tumors with mutations in or loss of BRCA1/2. The molecular mechanisms and particularly the cellular phenotypes resulting in synthetic lethality are not well understood and varying clinical responses have been observed. We have investigated the dose- and time-dependency of cell growth, cell death and cell cycle traverse of 4 malignant lymphocyte cell lines treated with the PARP inhibitor Olaparib. PARP inhibition induced a severe growth inhibition in this cell line panel and increased the levels of phosphorylated H2AX-associated DNA damage in S phase. Repair of the remaining replication related damage caused a G2 phase delay before entry into mitosis. The G2 delay, and the growth inhibition, was more pronounced in the absence of functional ATM. Further, Olaparib treated Reh and Granta-519 cells died by apoptosis, while U698 and JVM-2 cells proceeded through mitosis with aberrant chromosomes, skipped cytokinesis, and eventually died by necrosis. The TP53-deficient U698 cells went through several rounds of DNA replication and mitosis without cytokinesis, ending up as multinucleated cells with DNA contents of up to 16c before dying. In summary, we report here for the first time cell cycle-resolved DNA damage induction, and cell line-dependent differences in the mode of cell death caused by PARP inhibition.
Insights
PARP inhibitors like Olaparib severely inhibit cancer cell growth and cause DNA damage. Cell death pathways vary depending on cell type and ATM/TP53 status, impacting treatment response.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- PARP inhibitors are approved for BRCA1/2-mutated tumors.
- Mechanisms of synthetic lethality and variable clinical responses require further investigation.
Purpose of the Study:
- To investigate the dose- and time-dependency of cell growth, death, and cell cycle progression in malignant lymphocyte cell lines treated with the PARP inhibitor Olaparib.
- To elucidate cell cycle-resolved DNA damage induction and cell line-dependent cell death modes following PARP inhibition.
Main Methods:
- Treatment of 4 malignant lymphocyte cell lines with Olaparib.
- Assessment of cell growth, cell death, cell cycle traverse, DNA damage (phosphorylated H2AX), and ATM/TP53 functional status.
Main Results:
- Olaparib induced severe growth inhibition and S-phase DNA damage.
- A G2 phase delay occurred due to replication damage repair, exacerbated by ATM deficiency.
- Cell death occurred via apoptosis (Reh, Granta-519) or mitotic catastrophe with necrosis (U698, JVM-2).
- TP53-deficient U698 cells underwent endoreduplication, forming multinucleated cells before necrotic death.
Conclusions:
- PARP inhibition causes significant DNA damage and cell cycle arrest.
- Cell death pathways following PARP inhibition are cell line-dependent and influenced by ATM and TP53 status.
- Understanding these phenotypes is crucial for optimizing PARP inhibitor therapy.
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