Kub5-Hera RPRD1B Deficiency Promotes "BRCAness" and Vulnerability to PARP Inhibition in BRCA-proficient Breast Cancers

Edward A. Motea, Farjana J. Fattah, Ling Xiao, Luc Girard, Amy Rommel, Julio C. Morales, Praveen Patidar, Yunyun Zhou, Andrew Porter, Yang Xie, John D Minna, David A Boothman

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Purpose: Identification of novel strategies to expand the use of PARP inhibitors beyond BRCA deficiency is of great interest in personalized medicine. Here, we investigated the unannotated role of Kub5-Hera RPRD1B (K-H) in homologous recombination (HR) repair and its potential clinical significance in targeted cancer therapy. Experimental Design: Functional characterization of K-H alterations on HR repair of double-strand breaks (DSB) were assessed by targeted gene silencing, plasmid reporter assays, immunofluorescence, and Western blots. Cell survival with PARP inhibitors was evaluated through colony-forming assays and statistically analyzed for correlation with K-H expression in various BRCA1/2 nonmutated breast cancers. Gene expression microarray/qPCR analyses, chromatin immunoprecipitation, and rescue experiments were used to investigate molecular mechanisms of action. Results: K-H expression loss correlates with rucaparib LD 50 values in a panel of BRCA1/2 nonmutated breast cancers. Mechanistically, K-H depletion promotes BRCAness, where extensive upregulation of PARP1 activity was required for the survival of breast cancer cells. PARP inhibition in these cells led to synthetic lethality that was rescued by wild-type K-H reexpression, but not by a mutant K-H (p.R106A) that weakly binds RNAPII. K-H mediates HR by facilitating recruitment of RNAPII to the promoter region of a critical DNA damage response and repair effector, cyclin-dependent kinase 1 (CDK1). Conclusions: Cancer cells with low K-H expression may have exploitable BRCAness properties that greatly expand the use of PARP inhibitors beyond BRCA mutations. Our results suggest that aberrant K-H alterations may have vital translational implications in cellular responses/survival to DNA damage, carcinogenesis, and personalized medicine.

Original languageEnglish (US)
Pages (from-to)6459-6470
Number of pages12
JournalClinical Cancer Research
Issue number24
StatePublished - Dec 15 2018

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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