Background: The majority of BRCA1-mutant breast cancers are characterized by a triple-negative phenotype and a basal-like molecular subtype, associated with aggressive clinical behavior. Current... Show moreBackground: The majority of BRCA1-mutant breast cancers are characterized by a triple-negative phenotype and a basal-like molecular subtype, associated with aggressive clinical behavior. Current treatment options are limited, highlighting the need for the development of novel targeted therapies for this tumor subtype. Methods: Our group previously showed that EZH2 is functionally relevant in BRCA1-deficient breast tumors and blocking EZH2 enzymatic activity could be a potent treatment strategy. To validate the role of EZH2 as a therapeutic target and to identify new synergistic drug combinations, we performed a high-throughput drug combination screen in various cell lines derived from BRCA1-deficient and -proficient mouse mammary tumors. Results: We identified the combined inhibition of EZH2 and the proximal DNA damage response kinase ATM as a novel synthetic lethality-based therapy for the treatment of BRCA1-deficient breast tumors. We show that the combined treatment with the EZH2 inhibitor GSK126 and the ATM inhibitor AZD1390 led to reduced colony formation, increased genotoxic stress, and apoptosis-mediated cell death in BRCA1-deficient mammary tumor cells in vitro. These findings were corroborated by in vivo experiments showing that simultaneous inhibition of EZH2 and ATM significantly increased anti-tumor activity in mice bearing BRCA1-deficient mammary tumors. Conclusion: Taken together, we identified a synthetic lethal interaction between EZH2 and ATM and propose this synergistic interaction as a novel molecular combination for the treatment of BRCA1-mutant breast cancer. Show less
Pulver, E.M.; Mukherjee, C.; Kamp, G. van de; Roobol, S.J.; Rother, M.B.; Gulden, H. van der; ... ; Jonkers, J. 2021
The BRCA1 tumor suppressor gene encodes a multidomain protein for which several functions have been described. These include a key role in homologous recombination repair (HRR) of DNA double-strand... Show moreThe BRCA1 tumor suppressor gene encodes a multidomain protein for which several functions have been described. These include a key role in homologous recombination repair (HRR) of DNA double-strand breaks, which is shared with two other highrisk hereditary breast cancer suppressors, BRCA2 and PALB2. Although both BRCA1 and BRCA2 interact with PALB2, BRCA1 domain are considered variants of uncertain clinical significance (VUS). Using genetically engineered mice, we show here that a BRCA1 coiled-coil domain VUS, Brca1 p.L1363P, disrupts the interaction with PALB2 and leads to embryonic lethality. Brca1 p.L1363P led to a similar acceleration in the development of Trp53deficient mammary tumors as Brca1 loss, but the tumors showed distinct histopathologic features, with more stable DNA copy number profiles in Brca1 p.L1363P tumors. Nevertheless, Brca1 p.L1363P mammary tumors were HRR incompetent and responsive to cisplatin and PARP inhibition. Overall, these results provide the first direct evidence that a BRCA1 missense variant outside of the RING and BRCT domains increases the risk of Show less
Haas, R.L.; Floot, B.G.J.; Scholten, A.N.; Graaf, W.T.A. van der; Houdt, W. van; Schrage, Y.; ... ; Vens, C. 2021
Currently, all soft tissue sarcomas (STS) are irradiated by the same regimen, disregarding possible subtype-specific radiosensitivities. To gain further insight, cellular radiosensitivity was... Show moreCurrently, all soft tissue sarcomas (STS) are irradiated by the same regimen, disregarding possible subtype-specific radiosensitivities. To gain further insight, cellular radiosensitivity was investigated in a panel of sarcoma cell lines. Fourteen sarcoma cell lines, derived from synovial sarcoma, leiomyosarcoma, fibrosarcoma and liposarcoma origin, were submitted to clonogenic survival assays. Cells were irradiated with single doses from 1-8 Gy and surviving fraction (SF) was calculated from the resulting response data. Alpha/beta (alpha/beta) ratios were inferred from radiation-response curves using the linear-quadratic (LQ)-model. Cellular radiosensitivities varied largely in this panel, indicating a considerable degree of heterogeneity. Surviving fraction after 2 Gy (SF2) ranged from 0.27 to 0.76 with evidence of a particular radiosensitive phenotype in only few cell lines. D-37% on the mean data was 3.4 Gy and the median SF2 was 0.52. The median alpha/beta was 4.9 Gy and in six cell lines the alpha/beta was below 4 Gy. A fairly homogeneous radiation response was observed in myxoid liposarcoma cell lines with SF2 between 0.64 and 0.67. Further comparing sarcomas of different origin, synovial sarcomas, as a group, showed the lowest SF2 values (mean 0.35) and was significantly more radiosensitive than myxoid liposarcomas and leiomyosarcomas (P = 0.0084 and 0.024, respectively). This study demonstrates a broad spectrum of radiosensitivities across STS cell lines and reveals subtype-specific radiation responses. The particular cellular radiasensitivity of synovial sarcoma cells supports consideration of the different sarcoma entities in clinical studies that aim to optimize sarcoma radiotherapy. (C) 2021 by Radiation Research Society Show less
Ven, M. van de; Koffijberg, H.; Retel, V.; Monkhorst, K.; Smit, E.; Harten, W. van; IJzerman, M. 2021
The continued introduction of biomarkers and innovative testing methods makes already complex diagnosis in patients with stage IV nonesmall-cell lung cancer (NSCLC) even more complex. This study... Show moreThe continued introduction of biomarkers and innovative testing methods makes already complex diagnosis in patients with stage IV nonesmall-cell lung cancer (NSCLC) even more complex. This study primarily analyzed variations in biomarker testing in clinical practice in patients referred to a comprehensive cancer center in the Netherlands. The secondary aim was to compare the cost of biomarker testing with the cost of whole-genome sequencing. The cohort included 102 stage IV NSCLC patients who received biomarker testing in 2017 or 2018 at the comprehensive cancer center. The complete biomarker testing history of the cohort was identified using linked data from the comprehensive cancer center and the nationwide network and registry of histopathology and cytopathology in the Netherlands. Unique biomarker-test combinations, costs, turnaround times, and test utilization were examined. The results indicate substantial variation in test utilization and sequences. The mean cost per patient of biomarker testing was 2259.92 +/- 1217.10 USD, or 1881.23 +/- 1013.15 EUR. Targeted gene panels were most frequently conducted, followed by IHC analysis for programmed cell death protein ligand 1. Typically, the most common biomarkers were assessed within the first tests, and emerging biomarkers were tested further down the test sequence. At the cost of current biomarker testing, replacing current testing with whole-genome sequencing would have led to costsavings in only two patients (2%). Show less
Little is known about the characteristics and treatments of patients with severe asthma across Europe, but both are likely to vary. This is the first study in the European Respiratory Society... Show moreLittle is known about the characteristics and treatments of patients with severe asthma across Europe, but both are likely to vary. This is the first study in the European Respiratory Society Severe Heterogeneous Asthma Research collaboration, Patient-centred (SHARP) Clinical Research Collaboration and it is designed to explore these variations. Therefore, we aimed to compare characteristics of patients in European severe asthma registries and treatments before starting biologicals.This was a cross-sectional retrospective analysis of aggregated data from 11 national severe asthma registries that joined SHARP with established patient databases.Analysis of data from 3236 patients showed many differences in characteristics and lifestyle factors. Current smokers ranged from 0% (Poland and Sweden) to 9.5% (Belgium), mean body mass index ranged from 26.2 (Italy) to 30.6 kg.m(-2) (the UK) and the largest difference in mean pre-bronchodilator forced expiratory volume in 1 s % predicted was 20.9% (the Netherlands versus Hungary). Before starting biologicals patients were treated differently between countries: mean inhaled corticosteroid dose ranged from 700 to 1335 mu g.day(-1) between those from Slovenia versus Poland when starting anti-interleukin (IL)5 antibody and from 772 to 1344 mu g.day(-1) in those starting anti-IgE (Slovenia versus Spain). Maintenance oral corticosteroid use ranged from 21.0% (Belgium) to 63.0% (Sweden) and from 9.1% (Denmark) to 56.1% (the UK) in patients starting anti-IL-5 and anti-IgE, respectively.The severe asthmatic population in Europe is heterogeneous and differs in both clinical characteristics and treatment, often appearing not to comply with the current European Respiratory Society/American Thoracic Society guidelines definition of severe asthma. Treatment regimens before starting biologicals were different from inclusion criteria in clinical trials and varied between countries. Show less
Gogola, E.; Duarte, A.A.; Ruiter, J.R. de; Wiegant, W.W.; Schmid, J.A.; Bruijn, R. de; ... ; Rottenberg, S. 2019
Ovarian cancer (OC) is a heterogeneous disease usually diagnosed at a late stage. Experimental in vitro models that faithfully capture the hallmarks and tumor heterogeneity of OC are limited and... Show moreOvarian cancer (OC) is a heterogeneous disease usually diagnosed at a late stage. Experimental in vitro models that faithfully capture the hallmarks and tumor heterogeneity of OC are limited and hard to establish. We present a protocol that enables efficient derivation and long-term expansion of OC organoids. Utilizing this protocol, we have established 56 organoid lines from 32 patients, representing all main subtypes of OC. OC organoids recapitulate histological and genomic features of the pertinent lesion from which they were derived, illustrating intra-and interpatient heterogeneity, and can be genetically modified. We show that OC organoids can be used for drug-screening assays and capture different tumor subtype responses to the gold standard platinum-based chemotherapy, including acquisition of chemoresistance in recurrent disease. Finally, OC organoids can be xenografted, enabling in vivo drug-sensitivity assays. Taken together, this demonstrates their potential application for research and personalized medicine. Show less
Barazas, M.; Gasparini, A.; Huang, Y.; Kucukosmanoglu, A.; Annunziato, S.; Bouwman, P.; ... ; 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
Gogola, E.; Duarte, A.A.; Ruiter, J.R. de; Wiegant, W.W.; Schmid, J.A.; Bruijn, R. de; ... ; Rottenberg, S. 2018
In a relatively short period of time, massive open online courses (MOOCs) have become aconsiderable topic of research and debate, and the number of available MOOCs is rapidlygrowing. Along with... Show moreIn a relatively short period of time, massive open online courses (MOOCs) have become aconsiderable topic of research and debate, and the number of available MOOCs is rapidlygrowing. Along with issues of formal recognition and accreditation, this growth in thenumber of MOOCs being developed increases the relevance of assessment quality. Withinthe context of a typical xMOOC, the current study focuses on peer assessment of essayassignments. In the literature, two contradicting theoretical arguments can be found: thatlearners should be matched with same-ability peers (homogeneously) versus that studentsshould be matched with different-ability peers (heterogeneously). Considering thesearguments, the relationship between peer reviewers’ ability and authors’ essayperformance is explored. Results indicate that peer reviewers’ ability is positively related toauthors’ essay performance. Moreover, this relationship is only established for intermediateand high ability authors; essay performance of lower ability authors appeared not to berelated to the ability of their reviewing peers. Results are discussed in relation to thematching of learners and instructional design of peer assessment in MOOCs. Show less
Mitchell, J.R.; Verweij, M.; Brand, K.; Ven, M. van de; Goemaere, N.; Engel, S. van den; ... ; Bruin, R.W.F. de 2010
P>Dietary restriction (DR) extends lifespan and increases resistance to multiple forms of stress, including ischemia reperfusion injury to the brain and heart in rodents. While maximal effects... Show moreP>Dietary restriction (DR) extends lifespan and increases resistance to multiple forms of stress, including ischemia reperfusion injury to the brain and heart in rodents. While maximal effects on lifespan require long-term restriction, the kinetics of onset of benefits against acute stress is not known. Here, we show that 2-4 weeks of 30% DR improved survival and kidney function following renal ischemia reperfusion injury in mice. Brief periods of water-only fasting were similarly effective at protecting against ischemic damage. Significant protection occurred within 1 day, persisted for several days beyond the fasting period and extended to another organ, the liver. Protection by both short-term DR and fasting correlated with improved insulin sensitivity, increased expression of markers of antioxidant defense and reduced expression of markers of inflammation and insulin/insulin-like growth factor-1 signaling. Unbiased transcriptional profiling of kidneys from mice subject to short-term DR or fasting revealed a significant enrichment of signature genes of long-term DR. These data demonstrate that brief periods of reduced food intake, including short-term daily restriction and fasting, can increase resistance to ischemia reperfusion injury in rodents and suggest a rapid onset of benefits of DR in mammals. Show less
