Publisher Correction: Truncated FGFR2 is a clinically actionable oncogene in multiple cancers.

This paper was originally published under a standard Springer Nature license

BRCA1 RING Function Is Essential for Tumor Suppression but Dispensable for Therapy Resistance

SummaryHereditary breast cancers are frequently caused by germline BRCA1 mutations. The BRCA1C61G mutation in the BRCA1 RING domain is a common pathogenic missense variant, which reduces BRCA1/BARD1 heterodimerization and abrogates its ubiquitin ligase activity. To investigate the role of BRCA1 RING function in tumor suppression and therapy response, we introduced the Brca1C61G mutation in a conditional mouse model for BRCA1-associated breast cancer. In contrast to BRCA1-deficient mammary carcinomas, tumors carrying the Brca1C61G mutation responded poorly to platinum drugs and PARP inhibition and rapidly developed resistance while retaining the Brca1C61G mutation. These findings point to hypomorphic activity of the BRCA1-C61G protein that, although unable to prevent tumor development, affects response to therapy

Loss of 53BP1 causes PARP inhibitor resistance in Brca1-mutated mouse mammary tumors

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. 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 inhibitor

Mechanisms of therapy resistance in patient-derived xenograft models of brca1-deficient breast cancer

Background: Although BRCA1-deficient tumors are extremely sensitive to DNA-damaging drugs and poly(ADP-ribose) polymerase (PARP) inhibitors, recurrences do occur and, consequently, resistance to therapy remains a serious clinical problem. To study the underlying mechanisms, we induced therapy resistance in patient-derived xenograft (PDX) models of BRCA1- mutated and BRCA1-methylated triple-negative breast cancer. Methods: A cohort of 75 mice carrying BRCA1-deficient breast PDX tumors was treated with cisplatin, melphalan, nimustine, or olaparib, and treatment sensitivity was determined. In tumors that acquired therapy resistance, BRCA1 expression was investigated using quantitative real-time polymerase chain reaction and immunoblotting. Next-generation sequencing, methylation-specific multiplex ligation-dependent probe amplification (MLPA) and Target Locus Amplification (TLA)-based sequencing were used to determine mechanisms of BRCA1 re-expression in therapy-resistant tumors. Results: BRCA1 protein was not detected in therapy-sensitive tumors but was found in 31 out of 42 resistant cases. Apart from previously described mechanisms involving BRCA1-intragenic deletions and loss of BRCA1 promoter hypermethylation, a novel resistance mechanism was identified in four out of seven BRCA1-methylated PDX tumors that re-expressed BRCA1 but retained BRCA1 promoter hypermethylation. In these tumors, we found de novo gene fusions that placed BRCA1 under the transcriptional control of a heterologous promoter, resulting in re-expression of BRCA1 and acquisition of therapy resistance. Conclusions: In addition to previously described clinically relevant resistance mechanisms in BRCA1-deficient tumors, we describe a novel resistance mechanism in BRCA1-methylated PDX tumors involving de novo rearrangements at the BRCA1 locus, demonstrating that BRCA1-methylated breast cancers may acquire therapy resistance via both epigenetic and genetic mechanisms

Mechanisms of therapy resistance in patient-derived xenograft models of brca1-deficient breast cancer

Background: Although BRCA1-deficient tumors are extremely sensitive to DNA-damaging drugs and poly(ADP-ribose) polymerase (PARP) inhibitors, recurrences do occur and, consequently, resistance to therapy remains a serious clinical problem. To study the underlying mechanisms, we induced therapy resistance in patient-derived xenograft (PDX) models of BRCA1- mutated and BRCA1-methylated triple-negative breast cancer. Methods: A cohort of 75 mice carrying BRCA1-deficient breast PDX tumors was treated with cisplatin, melphalan, nimustine, or olaparib, and treatment sensitivity was determined. In tumors that acquired therapy resistance, BRCA1 expression was investigated using quantitative real-time polymerase chain reaction and immunoblotting. Next-generation sequencing, methylation-specific multiplex ligation-dependent probe amplification (MLPA) and Target Locus Amplification (TLA)-based sequencing were used to determine mechanisms of BRCA1 re-expression in therapy-resistant tumors. Results: BRCA1 protein was not detected in therapy-sensitive tumors but was found in 31 out of 42 resistant cases. Apart from previously described mechanisms involving BRCA1-intragenic deletions and loss of BRCA1 promoter hypermethylation, a novel resistance mechanism was identified in four out of seven BRCA1-methylated PDX tumors that re-expressed BRCA1 but retained BRCA1 promoter hypermethylation. In these tumors, we found de novo gene fusions that placed BRCA1 under the transcriptional control of a heterologous promoter, resulting in re-expression of BRCA1 and acquisition of therapy resistance. Conclusions: In addition to previously described clinically relevant resistance mechanisms in BRCA1-deficient tumors, we describe a novel resistance mechanism in BRCA1-methylated PDX tumors involving de novo rearrangements at the BRCA1 locus, demonstrating that BRCA1-methylated breast cancers may acquire therapy resistance via both epigenetic and genetic mechanisms

Pathogenic variants in MDFIC cause recessive central conducting lymphatic anomaly with lymphedema

Central conducting lymphatic anomaly (CCLA), characterized by the dysfunction of core collecting lymphatic vessels including the thoracic duct and cisterna chyli, and presenting as chylothorax, pleural effusions, chylous ascites, and lymphedema, is a severe disorder often resulting in fetal or perinatal demise. Although pathogenic variants in RAS/mitogen activated protein kinase (MAPK) signaling pathway components have been documented in some patients with CCLA, the genetic etiology of the disorder remains uncharacterized in most cases. Here, we identified biallelic pathogenic variants in MDFIC, encoding the MyoD family inhibitor domain containing protein, in seven individuals with CCLA from six independent families. Clinical manifestations of affected fetuses and children included nonimmune hydrops fetalis (NIHF), pleural and pericardial effusions, and lymphedema. Generation of a mouse model of human MDFIC truncation variants revealed that homozygous mutant mice died perinatally exhibiting chylothorax. The lymphatic vasculature of homozygous Mdfic mutant mice was profoundly mispatterned and exhibited major defects in lymphatic vessel valve development. Mechanistically, we determined that MDFIC controls collective cell migration, an important early event during the formation of lymphatic vessel valves, by regulating integrin β1 activation and the interaction between lymphatic endothelial cells and their surrounding extracellular matrix. Our work identifies MDFIC variants underlying human lymphatic disease and reveals a crucial, previously unrecognized role for MDFIC in the lymphatic vasculature. Ultimately, understanding the genetic and mechanistic basis of CCLA will facilitate the development and implementation of new therapeutic approaches to effectively treat this complex disease

BRCA1(185delAG) tumors may acquire therapy resistance through expression of RING-less BRCA1

markdownabstractHeterozygous germline mutations in breast cancer 1 (BRCA1) strongly predispose women to breast cancer. BRCA1 plays an important role in DNA double-strand break (DSB) repair via homologous recombination (HR), which is important for tumor suppression. Although BRCA1-deficient cells are highly sensitive to treatment with DSB-inducing agents through their HR deficiency (HRD), BRCA1-associated tumors display heterogeneous responses to platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors in clinical trials. It is unclear whether all pathogenic BRCA1 mutations have similar effects on the response to therapy. Here, we have investigated mammary tumorigenesis and therapy sensitivity in mice carrying the Brca1 _185stop_ and Brca1 _5382stop_ alleles, which respectively mimic the 2 most common BRCA1 founder mutations, BRCA1 _185delAG_ and BRCA1 _5382insC_. Both the Brca1185stop and Brca1 _5382stop_ mutations predisposed animals to mammary tumors, but Brca1 _185stop_ tumors responded markedly worse to HRD-targeted therapy than did Brca1 _5382stop_ tumors. Mice expressing Brca1 _185stop_ mutations also developed therapy resistance more rapidly than did mice expressing Brca1 _5382stop_. We determined that both murine Brca1 _185stop_ tumors and human BRCA1 _185delAG_ breast cancer cells expressed a really interesting new gene domain-less (RING-less) BRCA1 protein that mediated resistance to HRD-targeted therapies. Together, these results suggest that expression of RING-less BRCA1 may serve as a marker to predict poor response to DSB-inducing therapy in human cancer patients

O-50 Exposome project for health and occupational research (EPHOR) mega cohort

Introduction The EPHOR project is constructing a mega cohort for pooled analysis of data from multiple European cohort studies of occupation and health. The objective is to provide new evidence of the impact of occupational exposures on the risk of major non-communicable diseases, through systematic and agnostic analyses across the life-course. Materials and Methods Cohorts are registered in an online inventory. Cohort data and occupational information are being harmonised and documented in an online variable catalogue, and will be linked with a newly developed European Job-Exposure Matrix (EuroJEM) characterising multiple: chemical and particle, ergonomic, physical, and psychosocial exposures and precariousness. Cohort information on working time will also be harmonised. Knowledge gaps on occupational exposures in relation to major non-communicable diseases were identified. Both meta-analysis and decentralized analysis approaches will be used, as appropriate. Ethics approval is provided by all relevant committees. Results Currently 29 European cohorts covering a broad range of countries as well as multi-country studies are participating, containing more than 20 million participants. Cohort designs range from smaller scale studies including hundreds to thousands of workers with detailed exposure and/or outcome characterisation, to large-scale general population cohorts including multiple millions of participants with occupational information captured using registry-based methods. Cohorts were largely established and followed-up during the 2000s through the current time, though some were established earlier. Occupational information primarily entails the working lifetime or follow-up period. Outcome information includes disease incidence, disability, and mortality. In some studies, information about genetics, epigenetics, other biomarkers and clinical/functional evaluations is available. Analysis will address knowledge gaps of cancer, respiratory, cardiovascular/metabolic, and neurodegenerative diseases, mental and musculoskeletal disorders, and work participation. Conclusions We expect the mega cohort will be a useful long-term resource to study relationships of occupations, work-related exposures and health in Europe to inform policy and prevention