Functional genomic screen in mesothelioma reveals that loss of function of BRCA1-associated-protein-1 induces chemoresistance to ribonucleotide reductase inhibition

Agata Okonska, Saskja Bühler, Vasundhara Rao, Manuel Ronner, Maxime Blijlevens, Ida H van der Meulen-Muileman, Renée X de Menezes, Martin Wipplinger, Kathrin Oehl, Egbert F Smit, Walter Weder, Rolf A Stahel, Lorenza Penengo, Victor W van Beusechem, Emanuela Felley-Bosco

Research output: Contribution to journalArticleAcademicpeer-review


Loss of function of BRCA1-associated protein 1 (BAP1) is observed in about 50% of malignant pleural mesothelioma (MPM) cases. The aim of this study was to investigate whether this aspect could be exploited for targeted therapy. A genetically engineered model was established expressing either functional or nonfunctional BAP1, and whole-genome siRNA synthetic lethality screens were performed assessing differentially impaired survival between the two cell lines. The whole-genome siRNA screen unexpectedly revealed 11 hits (FDR < 0.05) that were more cytotoxic to BAP1-proficient cells. Two actionable targets, ribonucleotide reductase (RNR) catalytic subunit M1 (RRM1) and RNR regulatory subunit M2 (RRM2), were validated. In line with the screen results, primary mesothelioma (BAP1 þ/-) overexpressing BAP1 C91A (catalytically dead mutant) was more resistant to RNR inhibition, while BAP1 knockdown in the BAP1-proficient cell lines rescued the cells from their vulnerability to RNR depletion. Gemcitabine and hydroxyurea were more cytotoxic in BAP1-proficient cell line–derived spheroids compared with BAP1 deficient. Upregulation of RRM2 upon gemcitabine and hydroxyurea treatment was more profound in BAP1 mut/del cell lines. Increased lethality mediated by RNR inhibition was observed in NCI-H2452 cells reconstituted with BAP1-WT but not with BAP1 C91A. Upregulation of RRM2 in NCI-H2452-BAP1 WT spheroids was modest compared with control or C91A mutant. Together, we found that BAP1 is involved in the regulation of RNR levels during replication stress. Our observations reveal a potential clinical application where BAP1 status could serve as predictive or stratification biomarker for RNR inhibition-based therapy in MPM.

Original languageEnglish
Pages (from-to)552-563
Number of pages12
JournalMolecular Cancer Therapeutics
Issue number2
Early online date16 Oct 2019
Publication statusPublished - Feb 2020

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