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Loss of 53BP1 Causes PARP Inhibitor Resistance in Brca1-mutated Mouse Mammary Tumors

Loss of 53BP1 Causes PARP Inhibitor Resistance in Brca1-mutated Mouse Mammary Tumors

Janneke E Jaspers, Ariena Kersbergen, Ute Boon, Wendy Sol, Liesbeth van Deemter, Serge A Zander, Rinske Drost, Ellen Wientjens, Jiuping Ji, Amal Aly, James H Doroshow, Aaron Cranston, Niall M B Martin, etc.

Cancer Discov. 2013 Jan;3(1):68-81.

PMID: 23103855

Abstract:

Inhibition of PARP is a promising therapeutic strategy for homologous recombination-deficient tumors, such as BRCA1-associated cancers. We previously reported that BRCA1-deficient mouse mammary tumors may acquire resistance to the clinical PARP inhibitor (PARPi) olaparib through activation of the P-glycoprotein drug efflux transporter. Here, we show that tumor-specific genetic inactivation of P-glycoprotein increases the long-term response of BRCA1-deficient mouse mammary tumors to olaparib, but these tumors eventually developed PARPi resistance. In a fraction of cases, this resistance is caused by partial restoration of homologous recombination due to somatic loss of 53BP1. Importantly, PARPi resistance was minimized by long-term treatment with the novel PARP inhibitor AZD2461, which is a poor P-glycoprotein substrate. Together, our data suggest that restoration of homologous recombination is an important mechanism for PARPi resistance in BRCA1-deficient mammary tumors and that the risk of relapse of BRCA1-deficient tumors can be effectively minimized by using optimized PARP inhibitors.
Significance:
In this study, we show that loss of 53BP1 causes resistance to PARP inhibition in mouse mammary tumors that are deficient in BRCA1. We hypothesize that low expression or absence of 53BP1 also reduces the response of patients with BRCA1-deficient tumors to PARP inhibitors.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1174043163	AZD2461		1174043-16-3	Price

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