Related Experiment Video

Updated: Apr 21, 2026

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Published on: August 12, 2015

Interactions Between Ataxia Telangiectasia Mutated Kinase Inhibition, Poly(ADP-ribose) Polymerase-1 Inhibition and

Józefa Węsierska-Gądek¹, Sarah Heinzl¹

¹Cell Cycle Regulation Group, Department of Medicine I, Division: Institute of Cancer Research, Comprehensive Cancer Center, Medical University of Vienna, Austria.

Journal of Cancer Prevention

|October 23, 2014

Abstract

Background:

Cells harboring BRCA1/BRCA2 mutations are hypersensitive to inhibition of poly(ADP-ribose) polymerase-1 (PARP-1). We recently showed that interference with PARP-1 activity by NU1025 is strongly cytotoxic for BRCA1-positive BT-20 cells but not BRCA1-deficient SKBr-3 cells. These unexpected observations prompted speculation that other PARP-1 inhibitor(s) may be more cytotoxic towards SKBr-3 cells. In addition, interference with the DNA damage signaling pathway via (for instance) Ataxia telangiectasia mutated (ATM) kinase inhibition may induce synthetic lethality in DNA repair-deficient breast cancer cells and pharmacological interference with ATM activity may sensitize breast cancer cells to PARP-1 inactivation.

Methods:

We determined drug cytotoxicity in human MCF-7 and SKBr-3 breast cancer cells using the CellTiterGLO Luminescent cell viability assay and a Tecan multi-label, multitask plate counter to measure generated luminescence. Changes in cell cycle progression were monitored by flow cytometric measurement of DNA content in cells stained with propidium iodide.

Results:

Unlike NU1025, AZD2461, a new PARP-1 inhibitor, markedly reduced the numbers of living MCF-7 and SKBr-3 cells. ATM kinase inhibition (CP466722) was also cytotoxic for both MCF-7 and SKBr-3 cells. Furthermore, AZD2461 enhanced the cytotoxicity of CP466722 in both cell lines by inducing apoptosis, and concurrent inhibition of ATM and PARP-1 reduced cell proliferation more strongly than either single treatment.

Conclusions:

Our data show that inhibition of PARP-1 by AZD2461 is synthetically lethal for NU1025-resistant MCF-7 and SKBr-3 breast cancer cells. They also indicate that DNA damage signaling is essential for survival of both SKBr-3 and MCF-7 cells, especially after inactivation of PARP-1.

Insights

New PARP-1 inhibitor AZD2461 shows synthetic lethality in resistant breast cancer cells. Combining AZD2461 with ATM kinase inhibition (CP466722) is highly effective in reducing cell proliferation and inducing apoptosis.

Area of Science:

Oncology
Molecular Biology
Cancer Therapeutics

Background:

BRCA1/2 mutations confer sensitivity to PARP-1 inhibitors.
Previous PARP-1 inhibitor NU1025 showed unexpected cytotoxicity patterns in BRCA1-deficient cells.
ATM kinase inhibition may induce synthetic lethality in DNA repair-deficient breast cancer cells.

Purpose of the Study:

To investigate the efficacy of a new PARP-1 inhibitor, AZD2461, against breast cancer cells.
To evaluate the combined effect of AZD2461 and ATM kinase inhibition on breast cancer cell lines.
To explore synthetic lethality strategies in PARP-1 inhibitor-resistant breast cancer.

Main Methods:

Drug cytotoxicity assessed using CellTiterGLO assay in MCF-7 and SKBr-3 cells.
Cell cycle progression monitored by flow cytometry.
Luminescence measured using a Tecan multi-label plate counter.

Main Results:

AZD2461 significantly reduced viability in both MCF-7 and SKBr-3 cells.
ATM kinase inhibitor CP466722 was also cytotoxic to both cell lines.
Concurrent inhibition of ATM and PARP-1 enhanced apoptosis and reduced proliferation more than single treatments.

Conclusions:

AZD2461 demonstrates synthetic lethality in NU1025-resistant MCF-7 and SKBr-3 breast cancer cells.
DNA damage signaling is crucial for the survival of these cells, particularly after PARP-1 inhibition.
Combined ATM and PARP-1 inhibition presents a promising therapeutic strategy for resistant breast cancers.

Read full analysis

Keywords:

Apoptosis Caspase-3 Cell cycle DNA damage DNA repair Poly(ADP-ribose) polymerases

More Related Videos

Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1

Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1

Published on: February 17, 2011

Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo

Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo

Published on: February 6, 2015

Related Concept Videos

DNA Damage can Stall the Cell Cycle

DNA Damage can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...

DNA Damage Can Stall the Cell Cycle

DNA Damage Can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...

Interactions Between Signaling Pathways

Interactions Between Signaling Pathways

Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...

Inhibition of Cdk Activity

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...

The Intrinsic Apoptotic Pathway

The Intrinsic Apoptotic Pathway

Internal cellular stress, such as cellular injury or hypoxia, triggers intrinsic apoptosis. The B-cell lymphoma 2 (Bcl-2) family of proteins are the primary regulators of the intrinsic apoptotic pathway. For example, during DNA damage, checkpoint proteins, such as Ataxia Telangiectasia Mutated (ATM protein) and Checkpoints Factor-2 (Chk2) proteins, are activated. These proteins phosphorylate p53 which further activates pro-apoptotic proteins, such as Bax, Bak, PUMA, and Noxa, and inhibits...

PI3K/mTOR/AKT Signaling Pathway

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast, mTORC2 consists of a...

Articles linked to this work by shared authors, journal, and citation graph.

Targeting p53 as a promising therapeutic option for cancer by re-activating the wt or mutant p53's tumor suppression.

Future medicinal chemistry·2018

Why (multi)targeting of cyclin-dependent kinases is a promising therapeutic option for hormone-positive breast cancer and beyond.

Future medicinal chemistry·2015

Differential Potential of Pharmacological PARP Inhibitors for Inhibiting Cell Proliferation and Inducing Apoptosis in Human Breast Cancer Cells.

Journal of cellular biochemistry·2015

PARP inhibition potentiates the cytotoxic activity of C-1305, a selective inhibitor of topoisomerase II, in human BRCA1-positive breast cancer cells.

Biochemical pharmacology·2012

The impact of CDK inhibition in human malignancies associated with pronounced defects in apoptosis: advantages of multi-targeting small molecules.

Future medicinal chemistry·2012

Synergistic effects of erlotinib and everolimus on bronchial carcinoids and large-cell neuroendocrine carcinomas with activated EGFR/AKT/mTOR pathway.

Neuroendocrinology·2012

See all related articles