ENIGMA CHEK2gether Project: A Comprehensive Study Identifies Functionally Impaired CHEK2 Germline Missense Variants Associated with Increased Breast Cancer Risk

PURPOSE: Germline pathogenic variants in CHEK2 confer moderately elevated breast cancer risk (odds ratio, OR ∼ 2.5), qualifying carriers for enhanced breast cancer screening. Besides pathogenic variants, dozens of missense CHEK2 variants of uncertain significance (VUS) have been identified, hampering the clinical utility of germline genetic testing (GGT). EXPERIMENTAL DESIGN: We collected 460 CHEK2 missense VUS identified by the ENIGMA consortium in 15 countries. Their functional characterization was performed using CHEK2-complementation assays quantifying KAP1 phosphorylation and CHK2 autophosphorylation in human RPE1-CHEK2-knockout cells. Concordant results in both functional assays were used to categorize CHEK2 VUS from 12 ENIGMA case-control datasets, including 73,048 female patients with breast cancer and 88,658 ethnicity-matched controls. RESULTS: A total of 430/460 VUS were successfully analyzed, of which 340 (79.1%) were concordant in both functional assays and categorized as functionally impaired (N = 102), functionally intermediate (N = 12), or functionally wild-type (WT)-like (N = 226). We then examined their association with breast cancer risk in the case-control analysis. The OR and 95% CI (confidence intervals) for carriers of functionally impaired, intermediate, and WT-like variants were 2.83 (95% CI, 2.35-3.41), 1.57 (95% CI, 1.41-1.75), and 1.19 (95% CI, 1.08-1.31), respectively. The meta-analysis of population-specific datasets showed similar results. CONCLUSIONS: We determined the functional consequences for the majority of CHEK2 missense VUS found in patients with breast cancer (3,660/4,436; 82.5%). Carriers of functionally impaired missense variants accounted for 0.5% of patients with breast cancer and were associated with a moderate risk similar to that of truncating CHEK2 variants. In contrast, 2.2% of all patients with breast cancer carried functionally wild-type/intermediate missense variants with no clinically relevant breast cancer risk in heterozygous carriers

Legionella pneumophila filamentous morphological form and the generation of novel spherical form upon interaction with protozoan hosts

The filamentous form of Legionella pneumophila is acknowledged to be an alternative morphological form of the bacterium in nature, but its characteristics and ecological relevance in the life cycle of L. pneumophila is poorly understood. In this study, we explored the environmental factors that can trigger formation of the filamentous form as well as the interaction of this morphological form with L. pneumophila’s natural protozoan hosts. Our investigation showed that filamentation cannot be neatly pegged to a single dominant factor but is promoted under a concerted influence of environmental conditions leaning towards (i) higher than ambient temperatures, at 37-42°C, (ii) static fluid movement, and (iii) with at least a minimal organic content of 5% buffered yeast extract, or equivalent. In the course of investigating interaction of the filamentous form with protozoan hosts, a spherical form was discovered. Ultrastructural analysis confirmed the cellular nature of this novel entity and revealed morphological variations that are suggestive of a transitional relationship between the filamentous and the spherical forms. In vitro characterization demonstrated that emergence of the spherical form is (i) preceded by the filamentous form, (ii) rapidly triggered by some soluble factors secreted by protozoa, and (iii) independent of de novo protein synthesis. Exposure of a filament-rich bacterial population to secreted factors of protozoa resulted in the decline in abundance of the filamentous form that is paralleled by a transient surge in the spherical form and a gradual prevalence of the bacillary form; indicating that the spherical form may be an intermediate in the filament-to-rod morphological transition in L. pneumophila. Collectively, these findings suggest that under an intricate balance of environmental factors, the predominantly bacillary L. pneumophila is capable of differentiating into the filamentous form, which upon interaction with protozoan hosts may be triggered to differentiate rapidly back into the bacillary form via a spherical intermediate.DOCTOR OF PHILOSOPHY (SBS

Analysis of clinically relevant variants from ancestrally diverse Asian genomes

Asian populations are under-represented in human genomics research. Here, we characterize clinically significant genetic variation in 9051 genomes representing East Asian, South Asian, and severely under-represented Austronesian-speaking Southeast Asian ancestries. We observe disparate genetic risk burden attributable to ancestry-specific recurrent variants and identify individuals with variants specific to ancestries discordant to their self-reported ethnicity, mostly due to cryptic admixture. About 27% of severe recessive disorder genes with appreciable carrier frequencies in Asians are missed by carrier screening panels, and we estimate 0.5% Asian couples at-risk of having an affected child. Prevalence of medically-actionable variant carriers is 3.4% and a further 1.6% harbour variants with potential for pathogenic classification upon additional clinical/experimental evidence. We profile 23 pharmacogenes with high-confidence gene-drug associations and find 22.4% of Asians at-risk of Centers for Disease Control and Prevention Tier 1 genetic conditions concurrently harbour pharmacogenetic variants with actionable phenotypes, highlighting the benefits of pre-emptive pharmacogenomics. Our findings illuminate the diversity in genetic disease epidemiology and opportunities for precision medicine for a large, diverse Asian population.Peer reviewe

Case report: olaparib use in metastatic lung adenocarcinoma with BRCA2 pathogenic variant

Poly (ADP-ribose) polymerase (PARP) inhibitors have been approved in malignancies associated with germline BRCA1 or BRCA2 pathogenic variants, such as breast, ovarian, prostate, and pancreatic cancer. In malignancies not associated with germline BRCA1 or BRCA2 pathogenic variants, the therapeutic relevance of PARP inhibitors is less clear. Non-small-cell lung cancer (NSCLC) is known to demonstrate somatic alterations in BRCA1 or BRCA2 gene. The current report is on a gentleman with metastatic lung adenocarcinoma with a somatic BRCA2 pathogenic variant, who was effectively treated with olaparib. Furthermore, we discuss the existing data for use of PARP inhibitors in NSCLC. This study highlights the utility of next-generation sequencing in identifying gene mutations and demonstrates how such information can be used to select targeted therapies in patients with actionable molecular alterations.Published versio

COVID-19 vaccination uptake and safety profile among germline BRCA1 and BRCA2 pathogenic variant carriers in Singapore

Background: Although Singapore is one of the highest vaccinated countries in the world, vaccine hesitancy remains in a subpopulation, including individuals with cancer predisposition syndromes. At the Cancer Genetics Service National Cancer Centre Singapore, we see patients with germline genetic alterations, most being BRCA1/2 pathogenic/likely pathogenic variant (PV/LPV) carriers. While reported safe for cancer patients, there are limited studies addressing the safety profile and outcomes of COVID-19 vaccination among individuals with germline PV/LPV in cancer predisposition genes such as BRCA1/2. This study aims to evaluate the outcomes of COVID-19 vaccination among germline PV/LPV carriers in BRCA1/2. Methods: We conducted a phone call survey of COVID-19 vaccination uptake and toxicity in a prospective cohort of 189 participants with germline BRCA1/2 PV/LPV between 1st Sept 2021 and 30th Sept 2021. We collected demographics data including gender, race, age, history of cancer, types of cancer, and number of cancers. Statistical difference in baseline demographics between responders with history of cancer and those without were assessed using Chi-square, Fisher’s exact and independent t-test analysis. Logistic regression was used to evaluate effect of demographics on the occurrence of post-vaccination side effects. Results: Among 189 BRCA1/2 PV/LPV carriers responded, 97 carried PV/LPV in BRCA1 and 92 in BRCA2. Majority were vaccinated (89.5%) and had completed the two-dose vaccine schedule, with 7 (4.1%) received only one dose. The most common post-vaccination side effects was myalgia (56.5%) followed by fever (40.2%), headache (16.3%) and fatigue (11.2%). There were no major severe side events. Evaluation by logistic regression showed that the occurrence of side effects was not affected by PV/LPV gene (BRCA1 or BRCA2), gender, race, age or history of cancer. Conclusion: The post-vaccination side effects profile among individuals with germline PV/LPV in BRCA1/2 is consistent with the Singaporean general population, hence recommendations for COVID-19 vaccination for these individuals should not differ from non-carriers and should be encouraged by their healthcare providers.Published versio

Functional analysis of germline RAD51C missense variants highlight the role of RAD51C in replication fork protection

Monoallelic or biallelic RAD51C germline mutations results in chromosome instability disorders such as fanconi anemia (FA) and cancers. The bona fide function of RAD51C is to assist RAD51 nucleoprotein filament onto single strand DNA to complete Homologous Recombination (HR) repair. In addition to HR repair, the role of RAD51C in DNA replication is emerging when replication forks are transiently or irreversibly stalled. We identified novel RAD51C variants of uncertain significance (VUS) from breast, ovarian, pancreatic, and gastric cancer patients and functionally characterized the effect of these variants in replication fork protection and double-strand breaks (DSB's) repair. In RAD51C deficient chinese hamster CL-V4B cells, expression of RAD51C F164S, A87E, L134S and E49K variants heightened sensitivity to mitomycin C (MMC), etoposide and PARP inhibition. Differently, expression of a subset RAD51C variants R24L, R24W, and R212H displayed mild sensitivity to MMC, etoposide and PARP inhibition. Further functional characterization of a subset of variants revealed that Rad51C F164S, A87E, L134S and E49K variants displayed reduced RAD51 foci formation and increased overall nuclear single strand DNA levels in the presence of replication stress. Additionally, DNA fiber assay revealed that RAD51C F164S, A87E, L134S and E49K variants displayed defective replication fork protection upon prolonged fork stalling. Investigations using patient-derived lymphoblastoid cell line carrying heterozygous RAD51C L134S variant showed an impairment in RAD51 chromatin association and replication fork protection, suggestive of deleteriousness of this VUS variant. Overall, our findings provide more insights into molecular roles of RAD51C in replication fork integrity maintenance and in DSB repair. Disclosure Summary The authors report no relevant conflicts of interest in this work.Ministry of Education (MOE)National Medical Research Council (NMRC)Singapore Ministry of Education (MOE) under its Academic Research Fund ( AcRF) Tier 1 [2019-T1-001-018]; National Cancer Centre Research Fund Terry Fox Grant [NCCRF-YR2018-NOV-1]; National Medical Research Council (NMRC) Clinician Scientist Award [MOH-000654]

Functional analysis of clinical BARD1 germline variants

Germline pathogenic variants in BRCA1/2 account for one-third of familial breast cancers. The majority of BRCA1 function requires heterodimerization with BARD1. In contrast to BRCA1, BARD1 is a low-penetrance gene with an unclear clinical relevance, partly because of limited functional evidence. Using patient-derived lymphoblastoid cells, we functionally characterized two pathogenic variants (c.1833dupT, c.2099delG) and three variants of uncertain significance (VUSs) (c.73G>C, c.1217G>A, c.1918C>A). Three of these patients had breast cancers, whereas the remaining had colorectal cancers (n = 3). Both patients with pathogenic variants (c.1833dupT, c.2099delG) developed breast cancers with aggressive disease phenotypes such as triple-negative breast cancer and high cancer grades. As BARD1 encompasses multiple functional domains, including those of apoptosis and homologous recombination repair, we hypothesized that the function being impaired would correspond with the domain where the variant was located. Variants c.1918C>A, c.1833dupT, c.1217G>A, and c.2099delG, located within and proximal to apoptotic domains of ankyrin and BRCT, were associated with impaired apoptosis. Conversely, apoptosis function was preserved in c.73G>C, which was distant from the ankyrin domain. All variants displayed normal BRCA1 heterodimerization and RAD51 colocalization, consistent with their location being distal to BRCA1-and RAD51-binding domains. In view of deficient apoptosis, VUSs (c.1217G>A and c.1918C>A) may be pathogenic or likely pathogenic variants. In summary, functional analysis of BARD1 VUSs requires a combination of assays and, more importantly, the use of appropriate functional assays with consideration to the variant's location.National Medical Research Council (NMRC)Published versionWe thank our sources of support: National Medical Research Council (CSA) (NMRC/CSAINV/0017/2017) and Singhealth Foundation Research Grant (SHF/PRISM002/2015) to J.N. and SingHealth (SMSTDA-Project FY2018) to M.R.T

Functional characterisation guides classification of novel BAP1 germline variants

We have identified six patients harbouring distinct germline BAP1 mutations. In this study, we functionally characterise known BAP1 pathogenic and likely benign germline variants out of these six patients to aid in the evaluation and classification of unknown BAP1 germline variants. We found that pathogenic germline variants tend to encode truncated proteins, show diminished expression of epithelial-mesenchymal transition (EMT) markers, are localised in the cytosol and have reduced deubiquitinase capabilities. We show that these functional assays are useful for BAP1 variant curation and may be added in the American College of Medical Genetics and Genomics (ACMG) criteria for BAP1 variant classification. This will allow clinicians to distinguish between BAP1 pathogenic and likely benign variants reliably and may aid to quickly benchmark newly identified BAP1 germline variants. Classification of novel BAP1 germline variants allows clinicians to inform predisposed patients and relevant family members regarding potential cancer risks, with appropriate clinical interventions implemented if required.Ministry of Health (MOH)National Medical Research Council (NMRC)National Research Foundation (NRF)Published versionWe would like to thank the patients and research participants for their contribution to the study. This work was supported by the Khoo Postdoctoral Fellowship Award (Duke-NUS-KPFA/2019/0034 to J.H.H), the National Medical Research Council Open Fund—Young Individual Research Grant (MOH-000232 to J.H.H), the National Medical Research Council Open Fund—Individual Research Grant (MOH-000144 to B.T.T), the National Medical Research Council Singapore Translational Research Investigator Award (MOH-000248 to B.T.T.), the NRF-NSFC Joint Research Grant (Data Science) (NRF2016NRF-NSFC001–057 to B.T.T), the LKC Startup Grant (LKC MOE to J.N.), the National Research Foundation Singapore under its Clinical Scientist Award (NMRC/CSA-INV/0017/2017) and administered by the Singapore Ministry of Health’s National Medical Research Council (to J.N.). This work is also partially funded by NCC Research Fund, NCC Cancer Fund, Terry Fox and Lee Foundation supporting funds to J.N

Impact of variant reclassification in cancer predisposition genes on clinical care

PURPOSE: Genetic testing has clinical utility in the management of patients with hereditary cancer syndromes. However, the increased likelihood of encountering a variant of uncertain significance in individuals of non- European descent such as Asians may be challenging to both clinicians and patients. This study aims to evaluate the impact of variant reclassification in an Asian country with variants of uncertain significance reported in cancer predisposition genes. METHODS: A retrospective analysis of patients seen at the Cancer Genetics Service at the National Cancer Centre Singapore between February 2014 and March 2020 was conducted. The frequency, direction, and time to variant reclassification were evaluated by comparing the reclassified report against the original report. RESULTS: A total of 1,412 variants of uncertain significance were reported in 49.9% (845 of 1,695) of patients. Over 6 years, 6.7% (94 of 1,412) of variants were reclassified. Most variants of uncertain significance (94.1%, 80 of 85) were downgraded to benign or likely benign variant, with a smaller proportion of variants of uncertain significance (5.9%, 5 of 85) upgraded to pathogenic or likely pathogenic variant. Actionable variants of uncertain significance upgrades and pathogenic or likely pathogenic variant downgrades, which resulted in management changes, happened in 31.0% (39 of 126) of patients. The median and mean time taken for reclassification were 1 and 1.62 year(s), respectively. CONCLUSION: We propose a clinical guideline to standardize management of patients reported to have variants of uncertain significance. Management should be based on the patient's personal history, family history, and variant interpretation. For clinically relevant or suspicious variants of uncertain significance, follow-up is recommended every 2 years, as actionable reclassifications may happen during this period.Ministry of Health (MOH)National Medical Research Council (NMRC)National Research Foundation (NRF)Supported by the National Research Foundation Singapore under its Clinical Scientist Award (NMRC/CSA-INV/0017/2017) and administered by the Singapore Ministry of Health’s National Medical Research Council. This project was partially funded by NCC Research Fund, NCC Cancer Fund, and Terry Fox supporting funds. J.N. was funded by the National Medical Research Council Singapore and also received research funding from AstraZeneca