The molecular mechanisms that instigate a healthy cell to become malignant are fueled by (epi)genetic alterations in so-called driver genes. While the Holy Grail of precision medicine is to... Show moreThe molecular mechanisms that instigate a healthy cell to become malignant are fueled by (epi)genetic alterations in so-called driver genes. While the Holy Grail of precision medicine is to identify these genetic dependencies and to target them with specific compounds in a personalized fashion, this has proven a daunting task, as tumors are exquisitely characterized by genetic instability and a mutator phenotype. Genetically engineered mouse models (GEMMs) are uniquely suited for functional in vivo validation of genotype-phenotype relationships, as they enable in vivo assessment of de novo tumorigenesis in a mammalian organism with intact immune and stromal compartments upon perturbation of (combinations of) oncogenes and/or tumor suppressor genes. Somatic modeling of cancer using CRISPR technology in vivo proved to be a true game-changing tool, allowing for rapid functional validation of candidate cancer genes enrolling from forward genetic screens and catalogs of alterations in human tumors. In this work, I showed how CRISPR approaches were deployed to precisely engineer tumorigenic events in the mouse mammary gland for dissecting oncogenic cascades, unraveling new therapeutic vulnerabilities and mechanisms of therapy resistance in different breast cancer subtypes. Show less
Gogola, E.; Duarte, A.A.; Ruiter, J.R. de; Wiegant, W.W.; Schmid, J.A.; Bruijn, R. de; ... ; Rottenberg, S. 2019
The defect in homologous recombination (HR) found in BRCA1-associated cancers can be therapeutically exploited by treatment with DNA-damaging agents and PARP inhibitors. We and others previously... Show moreThe defect in homologous recombination (HR) found in BRCA1-associated cancers can be therapeutically exploited by treatment with DNA-damaging agents and PARP inhibitors. We and others previously reported that BRCA1-deficient tumors are initially hypersensitive to the inhibition of topoisomerase I/II and PARP, but acquire drug resistance through restoration of HR activity by the loss of end-resection antagonists of the 53BP1/RIF1/REV7/Shieldin/CST pathway. Here, we identify radiotherapy as an acquired vulnerability of 53BP1; BRCA1-deficient cells in vitro and in vivo. In contrast to the radioresistance caused by HR restoration through BRCA1 reconstitution, HR restoration by 53BP1 pathway inactivation further increases radiosensitivity. This highlights the relevance of this pathway for the repair of radiotherapy-induced damage. Moreover, our data show that BRCA1-mutated tumors that acquire drug resistance due to BRCA1-independent HR restoration can be targeted by radiotherapy.Significance: These findings uncover radiosensitivity as a novel, therapeutically viable vulnerability of BRCA1-deficient mouse mammary cells that have acquired drug resistance due to the loss of the 53BP1 pathway. Show less
Noordermeer, S.M.; Adam, S.; Setiaputra, D.; Barazas, M.; Pettitt, S.J.; Ling, A.K.; ... ; Durocher, D. 2018
