BARD1 mystery: tumor suppressors are cancer susceptibility genes

Functional Analysis of BARD1 Missense Variants on Homology-Directed Repair in Ovarian and Breast Cancers

Women with germline BRCA1 mutations face an increased risk of developing breast and ovarian cancers. BARD1 (BRCA1 associated RING domain 1) is an essential heterodimeric partner of BRCA1, and mutations in BARD1 are also associated with these cancers. While BARD1 mutations are recognized for their cancer susceptibility, the exact roles of numerous BARD1 missense mutations remain unclear. In this study, we conducted functional assays to assess the homology-directed DNA repair (HDR) activity of all BARD1 missense substitutions identified in 55 breast and ovarian cancer samples, using the real-world data from the COSMIC and cBioPortal databases. Seven BARD1 variants (V85M, P187A, G491R, R565C, P669L, T719R, and Q730L) were confirmed to impair DNA damage repair. Furthermore, cells harboring these BARD1 variants exhibited increased sensitivity to the chemotherapeutic drugs, cisplatin, and olaparib, compared to cells expressing wild-type BARD1. These findings collectively suggest that these seven missense BARD1 variants are likely pathogenic and may respond well to cisplatin-olaparib combination therapy. This study not only enhances our understanding of BARD1's role in DNA damage repair but also offers valuable insights into predicting therapy responses in patients with specific BARD1 missense mutations.

Identification of ubiquitin markers for survival and prognosis of ovarian cancer

Ovarian cancer (OC) is one of the most common malignancies and a leading cause of death among women worldwide. The ubiquitin pathway plays an important role in OC development. Using the single nucleotide polymorphism data obtained using the prevalence and dominance strategies, four ubiquitin marker genes were identified according to their expression levels: BARD1, BRCA2, FANCA, and BRCA1. Based on these four genes, a consensus clustering of OC expression data was performed. The significant differences in the survival analysis, ESTIMATE, and CIBERSORT results among the clusters indicated the pivotal role of these four genes in OC development. Of the ubiquitin-representative genes in each cluster, two ubiquitin genes, TOP2A and MYLIP, were identified in the survival risk model after univariate survival, Least Absolute Shrinkage and Selection Operator regression, and multivariate survival analyses. The reliability and robustness of both the training and validation data were confirmed by comparing the significant survival difference between high- and low-risk patients. We further explored the association between our risk model and clinical outcomes as well as predicted potentially interacting drugs. The co-expression network showed clear interactions among the four marker genes and two model genes and between high- and low-risk differentially expressed genes. Significantly enriched genes were found in pathways associated with ion channels, channel activity, and neuroactive ligand-receptor interactions. Therefore, suggesting the involvement of ubiquitin genes in the survival and development of OC through neurohumoral regulation. Our results will provide valuable reference or supplementary information for studies investigating OC diagnosis and therapies.

Recent progress and applications of single-cell sequencing technology in breast cancer

Single-cell RNA sequencing (scRNA-seq) technology enables the precise analysis of individual cell transcripts with high sensitivity and throughput. When integrated with multiomics technologies, scRNA-seq significantly enhances the understanding of cellular diversity, particularly within the tumor microenvironment. Similarly, single-cell DNA sequencing has emerged as a powerful tool in cancer research, offering unparalleled insights into the genetic heterogeneity and evolution of tumors. In the context of breast cancer, this technology holds substantial promise for decoding the intricate genomic landscape that drives disease progression, treatment resistance, and metastasis. By unraveling the complexities of tumor biology at a granular level, single-cell DNA sequencing provides a pathway to advancing our comprehension of breast cancer and improving patient outcomes through personalized therapeutic interventions. As single-cell sequencing technology continues to evolve and integrate into clinical practice, its application is poised to revolutionize the diagnosis, prognosis, and treatment strategies for breast cancer. This review explores the potential of single-cell sequencing technology to deepen our understanding of breast cancer, highlighting key approaches, recent advancements, and the role of the tumor microenvironment in disease plasticity. Additionally, the review discusses the impact of single-cell sequencing in paving the way for the development of personalized therapies.

Infiltrating Ductal Breast Carcinoma in a Male Patient With Associated BARD1 Mutation

Male breast cancer is an uncommon diagnosis with limited research on management and prognosis due to its rarity. We discuss a case of a 55-year-old male with a non-contributory past medical history who presented with an enlarging palpable mass of his right breast tissue at the 10:00 position. The ultrasound of the right breast showed a 2.8 cm heterogenous mass with irregular borders highly suspicious for malignancy. The follow-up sonogram-guided core biopsy was performed, and the pathology of the mass confirmed high-grade infiltrating ductal carcinoma. A modified radical mastectomy of the right breast with extensive axillary lymph node excision was performed. Genetic testing of the excised tumor revealed a MUTYH gene mutation and a BARD1 (BRCA1-associated RING domain 1) gene mutation of unknown significance. Histopathological analysis confirmed a Grade 2, ER/PR-positive, KI 67-positive, and HER2-negative tumor.

Germline BARD1 variants predispose to mesothelioma by impairing DNA repair and calcium signaling

We report that ~1.8% of all mesothelioma patients and 4.9% of those younger than 55, carry rare germline variants of the BRCA1 associated RING domain 1 (BARD1) gene that were predicted to be damaging by computational analyses. We conducted functional assays, essential for accurate interpretation of missense variants, in primary fibroblasts that we established in tissue culture from a patient carrying the heterozygous BARD1V523A mutation. We found that these cells had genomic instability, reduced DNA repair, and impaired apoptosis. Investigating the underlying signaling pathways, we found that BARD1 forms a trimeric protein complex with p53 and SERCA2 that regulates calcium signaling and apoptosis. We validated these findings in BARD1-silenced primary human mesothelial cells exposed to asbestos. Our study elucidated mechanisms of BARD1 activity and revealed that heterozygous germline BARD1 mutations favor the development of mesothelioma and increase the susceptibility to asbestos carcinogenesis. These mesotheliomas are significantly less aggressive compared to mesotheliomas in asbestos workers.

Genomic profiles and their relationships with clinical characteristics and immune features in cervical cancer

OBJECTIVE

This study aimed to investigate the genomic alteration profiles of cervical cancer patients, examine the correlation between mutation patterns and clinical and immune attributes, and discover novel targets for treatment of individuals with cervical cancer.

METHODS

We performed targeted next-generation sequencing of tumor tissues and blood samples obtained from 45 cervical cancer patients to analyze somatic alterations, mutation patterns, and HLA alleles comprehensively. Additionally, we used flow cytometry to assess expression levels of immune checkpoint genes.

RESULTS

Notably, genes such as AR (78%), KMT2D (76%), and NOTCH1 (62%) exhibited higher mutation frequencies. Moreover, the tumor mutation burden (TMB) was significantly greater in HPV-positive cervical cancer patients than in HPV-negative patients (P=0.029). BMI (P=0.047) and mutations in BARD1 (P=0.034), CEP290 (P=4E-04), and SLX4 (P=0.0128) were identified as predictors of shorter overall survival in cervical cancer patients. Furthermore, the present study revealed significant upregulation of PD-1 (P=0.027) and Tim-3 (P=0.048) in the high mutant-allele tumor heterogeneity (MATH) cohort. In the elderly cervical cancer patient population, HLA-A03:01 emerged as a high-risk allele (OR=3.2, P<0.0001); HLA-C07:02 (OR=0.073, P=0.02) and HLA-B*07:02 (OR=0.257, P=0.037) were associated with a reduced risk among patients with low TMB.

CONCLUSIONS

This study offers insights into the mutation characteristics of cervical cancer patients and identifies potential therapeutic.

A new framework for exploratory network mediator analysis in omics data

Omics methods are widely used in basic biology and translational medicine research. More and more omics data are collected to explain the impact of certain risk factors on clinical outcomes. To explain the mechanism of the risk factors, a core question is how to find the genes/proteins/metabolites that mediate their effects on the clinical outcome. Mediation analysis is a modeling framework to study the relationship between risk factors and pathological outcomes, via mediator variables. However, high-dimensional omics data are far more challenging than traditional data: (1) From tens of thousands of genes, can we overcome the curse of dimensionality to reliably select a set of mediators? (2) How do we ensure that the selected mediators are functionally consistent? (3) Many biological mechanisms contain nonlinear effects. How do we include nonlinear effects in the high-dimensional mediation analysis? (4) How do we consider multiple risk factors at the same time? To meet these challenges, we propose a new exploratory mediation analysis framework, medNet, which focuses on finding mediators through predictive modeling. We propose new definitions for predictive exposure, predictive mediator, and predictive network mediator, using a statistical hypothesis testing framework to identify predictive exposures and mediators. Additionally, two heuristic search algorithms are proposed to identify network mediators, essentially subnetworks in the genome-scale biological network that mediate the effects of single or multiple exposures. We applied medNet on a breast cancer data set and a metabolomics data set combined with food intake questionnaire data. It identified functionally consistent network mediators for the exposures' impact on the outcome, facilitating data interpretation.

Correlation of BARD1 gene polymorphisms with risk of neuroblastoma: a meta-analysis

BRCA1-associated RING domain protein 1 (BARD1) gene polymorphisms may be associated with neuroblastoma (NB) susceptibility. However, the results remain controversial. Relevant studies were identified by searching PubMed, Web of Science, Embase, China National Knowledge Infrastructure databases up to March 5, 2023. The strength of the association between BARD1 polymorphisms and susceptibility of NB was assessed by calculating odds ratios (ORs) and 95% confidence intervals (95% CIs) through the fixed- or random-effects model. Eight articles involving 12 studies were finally included. We found that rs6435862 T > G, rs3768716 A > G, rs17487792 C > T and rs7587476 C > T variant increase the risk of NB in allelic, dominant, recessive, homozygous and heterozygous genetic models, while rs7585356 G > A variant appeared protective against NB. When stratified by ethnicity, subgroup analysis indicated that the above association remained significant in Caucasian populations in all genetic models, except for rs7585356G > A polymorphism in Asians. In Asian populations, we found the similar results in the allelic and dominant model of rs6435862 T > G, rs3768716 A > G, rs17487792 C > T and rs7587476 C > T as in Caucasians, while there lacked a significant association in the other three model. In addition, rs7585356 G > A was not associated with an increased risk of NB in the Asian population. After Bonferroni correction, significant associations for rs7585356 G > A disappeared in both Asian and Caucasian populations, with no significant association found for rs7587476 in the allelic and dominant models among Asians. BARD1 polymorphisms might be significantly associated with NB susceptibility. It is crucial that these finding should be further confirmed through extensive and well-planned studies.

Invasive papillary carcinoma of the breast

Invasive papillary carcinoma is a rare form of breast cancer that is more likely to occur in postmenopausal women. Previous studies have been limited to case reports and small retrospective studies, leading to low awareness of this type of tumor and difficult clinical management. According to the available literature, invasive papillary carcinoma exhibits unique pathological features and biological behaviors. Invasive papillary carcinoma is mostly luminal type, with a low rate of lymph node metastasis, which underlies its favorable prognosis. The effectiveness of adjuvant therapy in reducing tumor burden and improving prognosis in patients with invasive papillary carcinoma remains uncertain. Due to the rarity of the lesion, conducting prospective clinical trials is impractical. The use of biological models, such as organoids, can help alleviate the impact of the scarcity of this condition on research. In addition, invasive papillary carcinoma is affected by specific genomic events, and more extensive studies of gene expression profiling may provide molecular-level insights to make optimal therapeutic decisions.

Germline structural variation globally impacts the cancer transcriptome including disease-relevant genes

Germline variation and somatic alterations contribute to the molecular profile of cancers. We combine RNA with whole genome sequencing across 1,218 cancer patients to determine the extent germline structural variants (SVs) impact expression of nearby genes. For hundreds of genes, recurrent and common germline SV breakpoints within 100 kb associate with increased or decreased expression in tumors spanning various tissues of origin. A significant fraction of germline SV expression associations involves duplication of intergenic enhancers or 3' UTR disruption. Genes altered by both somatic and germline SVs include ATRX and CEBPA. Genes essential in cancer cell lines include BARD1 and IRS2. Genes with both expression and germline SV breakpoint patterns associated with patient survival include GCLM. Our results capture a class of phenotypic variation at work in the disease setting, including genes with cancer roles. Specific germline SVs represent potential cancer risk variants for genetic testing, including those involving genes with targeting implications.

BARD1 deletion in a patient with suspected hereditary colorectal cancer

Deleterious germline variants in the BRCA1-associated ring domain (BARD1) gene moderately elevate breast cancer risk; however, their potential association with other neoplasms remains unclear. Here, we present the case of a 43-year-old female patient diagnosed with sigmoid colon adenocarcinoma whose maternal family members met the Amsterdam Criteria II for Lynch syndrome. Comprehensive multigene panel testing revealed a heterozygous BARD1 exon 3 deletion.

MCM2 is involved in subtyping and tamoxifen resistance of ERα-positive breast cancer by acting as the downstream factor of ERα

Tamoxifen (TAM) resistance is finally developed in over 40% of patients with estrogen receptor α-positive breast cancer (ERα+ -BC), documenting that discovering new molecular subtype is needed to confer perception to the heterogeneity of ERα+ -BC. We obtained representative gene sets subtyping ERα+ -BC using gene set variation analysis (GSVA), non-negative matrix factorization (NMF), and COX regression methods on the basis of METABRIC, TCGA, and GEO databases. Furthermore, the risk score of ERα+ -BC subtyping was established using least absolute shrinkage and selection operator (LASSO) regression on the basis of genes in the representative gene sets, thereby generating the two subtypes of ERα+ -BC. We further found that minichromosome maintenance complex component 2 (MCM2) functioned as the hub gene subtyping ERα+ -BC using GO, KEGG, and MCODE. MCM2 expression was capable for specifically predicting 1-year overall survival (OS) of ERα+ -BC and correlated with T stage, AJCC stage, and tamoxifen (TAM) sensitivity of ERα+ -BC. The downregulation of MCM2 expression inhibited proliferation, migration, and invasion of TAM-resistant cells and promoted G0/G1 arrest. Altogether, tamoxifen resistance entails that MCM2 is a hub gene subtyping ERα+ -BC, providing a novel dimension for discovering a potential target of TAM-resistant BC.

Combining single-cell sequencing and spatial transcriptome sequencing to identify exosome-related features of glioblastoma and constructing a prognostic model to identify BARD1 as a potential therapeutic target for GBM patients

Background

Glioblastoma (GBM) is a malignant primary brain tumor. This study focused on exploring the exosome-related features of glioblastoma to better understand its cellular composition and molecular characteristics.

Methods

Single-cell RNA sequencing (scRNA-seq) and spatial transcriptome RNA sequencing (stRNA-seq) were used to analyze the heterogeneity of glioblastomas. After data integration, cell clustering, and annotation, five algorithms were used to calculate scores for exosome-related genes(ERGs). Cell trajectory analysis and intercellular communication analysis were performed to explore exosome-related communication patterns. Spatial transcriptome sequencing data were analyzed to validate the findings. To further utilize exosome-related features to aid in clinical decision-making, a prognostic model was constructed using GBM's bulk RNA-seq.

Results

Different cell subpopulations were observed in GBM, with Monocytes/macrophages and malignant cells in tumor samples showing higher exosome-related scores. After identifying differentially expressed ERGs in malignant cells, pseudotime analysis revealed the cellular status of malignant cells during development. Intercellular communication analysis highlighted signaling pathways and ligand-receptor interactions. Spatial transcriptome sequencing confirmed the high expression of exosome-related gene features in the tumor core region. A prognostic model based on six ERGs was shown to be predictive of overall survival and immunotherapy outcome in GBM patients. Finally, based on the results of scRNA-seq and prognostic modeling as well as a series of cell function experiments, BARD1 was identified as a novel target for the treatment of GBM.

Conclusion

This study provides a comprehensive understanding of the exosome-related features of GBM in both scRNA-seq and stRNA-seq, with malignant cells with higher exosome-related scores exhibiting stronger communication with Monocytes/macrophages. In terms of spatial data, highly scored malignant cells were also concentrated in the tumor core region. In bulk RNA-seq, patients with a high exosome-related index exhibited an immunosuppressive microenvironment, which was accompanied by a worse prognosis as well as immunotherapy outcomes. Prognostic models constructed using ERGs are expected to be independent prognostic indicators for GBM patients, with potential implications for personalized treatment strategies for GBM. Knockdown of BARD1 in GBM cell lines reduces the invasive and value-added capacity of tumor cells, and thus BARD1-positively expressing malignant cells are a risk factor for GBM patients.

Homologous recombination mRNAs (RAD21, RAD50 and BARD1) have a potentially poor prognostic role in ERBB2-low bladder cancer patients

Human epidermal growth factor receptor 2 (HER2/ERBB2) factor is known to be implicated in many malignancies and the potential of it as a prognostic biomarker was reported years ago. Molecular subtypes of HER2/ERBB2 negative and positive with distinct clinical outcomes have been identified in recent years; however, it is still under investigation for bladder cancer. This study evaluates the biological and prognostic significance of RAD21, RAD50 and BARD1 (homologous recombination biomarkers) mRNA levels with ERBB2 low and high expression to explore their impact on bladder cancer patient survival and cancer aggressiveness. The expression of ERBB2, RAD21, RAD50 and BARD1 mRNA levels was assessed in The Cancer Genome Atlas (TCGA) bladder cancer dataset along with four validation cohorts. Outcome analysis was evaluated using disease-free survival (DFS) and overall survival (OS). Univariate and multivariate analysis were used to evaluate the relationship between RAD21, RAD50, BARD1 and ERBB2 expression and clinicopathological variables. A significant increase in mRNA expression levels of RAD21, RAD50 and BARD1 was noticed in ERBB2-low patients compared to ERBB2-high patients. This overexpression of the homologous recombination repair transcripts was associated with poor outcome in ERBB2-low tumors, not in ERBB2-high tumors. Furthermore, the combined expression of high RAD21/RAD50, high RAD21/BARD1 or high RAD50/BARD1 were significantly associated with worse DFS and a better outcome for those with low co-expression in the ERBB2-low cohort. High expression of either RAD21/RAD50 or RAD21/BARD1 in ERBB2-low cohort associated with higher chance of metastasis. In addition, gene expression of BARD1 alone or in combination with RAD50 acted as an independent prognostic factor for worst survival. The data presented in this study reveal a connection between RAD21, RAD50, BARD1 and ERBB2 and patient survival. Importantly, it provided novel findings and potential prognostic markers, particularly in ERBB2-low bladder cancer.

Zooming into the structure-function of RING finger proteins for anti-cancer therapeutic applications

Cancer is one of the most common and widely diagnosed diseases worldwide. With an increase in prevalence and incidence, many studies in cancer biology have been looking at the role pro-cancer proteins play. One of these proteins is the Really Interesting New Gene (RING), which has been studied extensively due to its structure and functions such as apoptosis, neddylation, and its role in ubiquitination. The RING domain is a cysteine-rich domain known to bind Cysteine and Histidine residues. It also binds two zinc ions that help stabilize the protein in various patterns, often with a 'cross-brace' topology. Different RING finger proteins have been studied and found to have suitable targets for developing anti-cancer therapeutics. These identified candidate proteins include Parkin, COP1, MDM2, BARD1, BRCA-1, PIRH2, c-CBL, SIAH1, RBX1 and RNF8. Inhibiting these candidate proteins provides opportunities for shutting down pathways associated with tumour development and metastasis.

Multiprotein Assemblies, Phosphorylation and Dephosphorylation in Neuronal Cytoskeleton

Filament systems are comprised of fibrous and globular cytoskeletal proteins and are key elements regulating cell shape, rigidity, and dynamics. The cellular localization and assembly of neurofilaments depend on phosphorylation by kinases. The involvement of the BRCA1 (Breast cancer associated protein 1)/BARD1 (BRCA1-associated RING domain 1) pathways in Alzheimer disease (AD) is suggested by colocalization studies. In particular, BRCA1 accumulation within neurofibrillary tangles and colocalization with tau aggregates in the cytoplasm of AD patients implicates the involvement of mutant forms of BRCA1/BARD1 proteins in disease pathogenesis. The purpose of this study is to show that the location of mutations in the translated BARD1, specifically within ankyrin repeats, has strong correlation with the Cdk5 motifs for phosphorylation. Mapping of the mutation sites on the protein's three-dimensional structure and estimation of the backbone dihedral angles show transitions between the canonical helical and extended conformations of the tetrapeptide sequence of ankyrin repeats. Clustering of mutations in BARD1 ankyrin repeats near the N-termini of the helices with T/SXXH motifs provides a basis for conformational transitions that might be necessary to ensure the compatibility of the substrate with active site geometry and accessibility of the substrate to the kinase. Ankyrin repeats are interaction sites for phosphorylation-dependent dynamic assembly of proteins including those involved in transcription regulation and signaling, and present potential targets for the design of new drugs.

Germline heterozygous exons 8-11 pathogenic BARD1 gene deletion reported for the first time in a family with suspicion of a hereditary colorectal cancer syndrome: more than an incidental finding?

BACKGROUND

Colorectal cancer (CRC) is a highly prevalent disease in developed countries. Inherited Mendelian causes account for approximately 5% of CRC cases, with Lynch syndrome and familial adenomatous polyposis being the most prevalent forms. Scientific efforts are focused on the discovery of new candidate genes associated with CRC and new associations of phenotypes with well-established cancer-related genes. BRCA1-associated ring domain (BARD1) gene deleterious germline variants are associated with a moderate increase in the relative risk of breast cancer, but their association with other neoplasms, such as CRC, remains unclear.

CASE PRESENTATION

We present the case of a 49-year-old male diagnosed with rectal adenocarcinoma whose maternal family fulfilled Amsterdam clinical criteria for Lynch syndrome. Genetic test confirmed the presence in heterozygosis of a germline pathogenic deletion of exons 8-11 in BARD1 gene. The predictive genetic study of the family revealed the presence of this pathogenic variant in his deceased cancer affected relatives, confirming co-segregation of the deletion with the disease.

CONCLUSIONS

To the best of our knowledge, this is the first published work in which this BARD1 deletion is detected in a family with familial colorectal cancer type X (FCCTX) syndrome, in which the clinical criteria for Lynch syndrome without alteration of the DNA mismatch repair (MMR) system are fulfilled. Whether this incidental germline finding is the cause of familial colorectal aggregation remains to be elucidated in scientific forums. Patients should be carefully assessed in specific cancer genetic counseling units to account for hypothetical casual findings in other genes, in principle unrelated to the initial clinical suspicion, but with potential impact on their health.

Pulmonary Artery Intimal Sarcoma in a Patient with Lynch Syndrome: Response to an Immune Checkpoint Inhibitor

Intimal sarcoma is an extremely rare mesenchymal tumor arising in the great vessels. To date, intimal sarcoma has not been reported in patients with Lynch syndrome (LS), even though this syndrome lacks DNA mismatch repair ability genetically and is prone to various malignancies. This patient was diagnosed with LS by the Revised Amsterdam Criteria II, and she suffered from intimal sarcoma in the left pulmonary artery. She had a germline missense variant of PMS2 (c.1399G>A, pV467I) which is classified as a variant of unknown significance. In her intimal sarcoma, PMS2 expression was decreased. Additionally, it exhibited microsatellite instability and a high tumor mutational burden (69 mutations/Mb) which are features of mismatch repair deficiency, although PMS2 (c.1399G>A, pV467I) missense is a variant of unknown significance. The metastatic lesions of intimal sarcoma in this patient responded heterogeneously to pembrolizumab, an immune checkpoint inhibitor. Cytotoxic agents and radiation were also effective for some metastatic lesions, but some lesions, including her liver metastases, were resistant. The hypermutable nature of the LS genotype might acquire resistance to an immune checkpoint inhibitor and other cytotoxic agents such as occurred with her liver metastases.

Genetic landscape of colorectal cancer patients manifesting tumor shrinkage during SARS-Cov-2 infection

We previously described three patients affected by metastatic colorectal cancer (mCRC) who experienced spontaneous tumour shrinkage during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Thereafter, the patients were closely monitored and no systemic treatments were applied. Here, we report follow-up clinical information about these patients as well as genetic characterization of their primary tumours through the TruSigt™Oncology 500 Next Generation Sequencing test targeting 523 cancer-relevant genes. An Illumina NovaSeq 6000 platform was used to perform sequencing. Time-to-progression was 23 and 2 months, respectively, in Patients 2 and 3 while it was not reached in Patient 1. Patients 1 and 2 had the greatest anti-SARS-CoV-2 IgG titres. Assessment of genetic landscapes evidenced common mutation in BARD1 gene (p.Val507Met) in Patients 1 and 2. Although our report is descriptive in its nature, we suggest that complex and unexplored interactions between genetic background and components of the immune response to SARS-CoV-2 infection could be responsible of unexpected rare mCRC shrinkage.