Genetic sequence variations of BRCA1-interacting genes AURKA, BAP1, BARD1 and DHX9 in French Canadian Families with high risk of breast cancer

Circulating microRNAs as Potential Biomarkers in Pancreatic Cancer-Advances and Challenges

There is an urgent unmet need for robust and reliable biomarkers for early diagnosis, prognosis, and prediction of response to specific treatments of many aggressive and deadly cancers, such as pancreatic cancer, and liquid biopsy-based miRNA profiling has the potential for this. MiRNAs are a subset of non-coding RNAs that regulate the expression of a multitude of genes post-transcriptionally and thus are potential diagnostic, prognostic, and predictive biomarkers and have also emerged as potential therapeutics. Because miRNAs are involved in the post-transcriptional regulation of their target mRNAs via repressing gene expression, defects in miRNA biogenesis pathway and miRNA expression perturb the expression of a multitude of oncogenic or tumor-suppressive genes that are involved in the pathogenesis of various cancers. As such, numerous miRNAs have been identified to be downregulated or upregulated in many cancers, functioning as either oncomes or oncosuppressor miRs. Moreover, dysregulation of miRNA biogenesis pathways can also change miRNA expression and function in cancer. Profiling of dysregulated miRNAs in pancreatic cancer has been shown to correlate with disease diagnosis, indicate optimal treatment options and predict response to a specific therapy. Specific miRNA signatures can track the stages of pancreatic cancer and hold potential as diagnostic, prognostic, and predictive markers, as well as therapeutics such as miRNA mimics and miRNA inhibitors (antagomirs). Furthermore, identified specific miRNAs and genes they regulate in pancreatic cancer along with downstream pathways can be used as potential therapeutic targets. However, a limited understanding and validation of the specific roles of miRNAs, lack of tissue specificity, methodological, technical, or analytical reproducibility, harmonization of miRNA isolation and quantification methods, the use of standard operating procedures, and the availability of automated and standardized assays to improve reproducibility between independent studies limit bench-to-bedside translation of the miRNA biomarkers for clinical applications. Here I review recent findings on miRNAs in pancreatic cancer pathogenesis and their potential as diagnostic, prognostic, and predictive markers.

DHX9-mediated pathway contributes to the malignant phenotype of myelodysplastic syndromes

DHX9 is a member of the DEAH (Asp-Glu-Ala-His) helicase family and regulates DNA replication and RNA processing. DHX9 dysfunction promotes tumorigenesis in several solid cancers. However, the role of DHX9 in MDS is still unknown. Here, we analyzed the expression of DHX9 and its clinical significance in 120 MDS patients and 42 non-MDS controls. Lentivirus-mediated DHX9-knockdown experiments were performed to investigate its biological function. We also performed cell functional assays, gene microarray, and pharmacological intervention to investigate the mechanistic involvement of DHX9. We found that overexpression of DHX9 is frequent in MDS and associated with poor survival and high risk of acute myeloid leukemia (AML) transformation. DHX9 is essential for the maintenance of malignant proliferation of leukemia cells, and DHX9 suppression increases cell apoptosis and causes hypersensitivity to chemotherapeutic agents. Besides, knockdown of DHX9 inactivates the PI3K-AKT and ATR-Chk1 signaling, promotes R-loop accumulation, and R-loop-mediated DNA damage.

KRAS Hijacks the miRNA Regulatory Pathway in Cancer

Extensive studies have focused on the misregulation of individual miRNAs in cancer. More recently, mutations in the miRNA biogenesis and processing machinery have been implicated in several malignancies. Such mutations can lead to global miRNA misregulation, which may promote many of the well-known hallmarks of cancer. Interestingly, recent evidence also suggests that oncogenic Kristen rat sarcoma viral oncogene homolog (KRAS) mutations act in part by modulating the activity of members of the miRNA regulatory pathway. Here, we highlight the vital role mutations in the miRNA core machinery play in promoting malignant transformation. Furthermore, we discuss how mutant KRAS can simultaneously impact multiple steps of miRNA processing and function to promote tumorigenesis. Although the ability of KRAS to hijack the miRNA regulatory pathway adds a layer of complexity to its oncogenic nature, it also provides a potential therapeutic avenue that has yet to be exploited in the clinic. Moreover, concurrent targeting of mutant KRAS and members of the miRNA core machinery represents a potential strategy for treating cancer.

The Genetic Analyses of French Canadians of Quebec Facilitate the Characterization of New Cancer Predisposing Genes Implicated in Hereditary Breast and/or Ovarian Cancer Syndrome Families

The French Canadian population of the province of Quebec has been recognized for its contribution to research in medical genetics, especially in defining the role of heritable pathogenic variants in cancer predisposing genes. Multiple carriers of a limited number of pathogenic variants in BRCA1 and BRCA2, the major risk genes for hereditary breast and/or ovarian cancer syndrome families, have been identified in French Canadians, which is in stark contrast to the array of over 2000 different pathogenic variants reported in each of these genes in other populations. As not all such cancer syndrome families are explained by BRCA1 and BRCA2, newly proposed gene candidates identified in other populations have been investigated for their role in conferring risk in French Canadian cancer families. For example, multiple carriers of distinct variants were identified in PALB2 and RAD51D. The unique genetic architecture of French Canadians has been attributed to shared ancestry due to common ancestors of early settlers of this population with origins mainly from France. In this review, we discuss the merits of genetically characterizing cancer predisposing genes in French Canadians of Quebec. We focused on genes that have been implicated in hereditary breast and/or ovarian cancer syndrome families as they have been the most thoroughly characterized cancer syndromes in this population. We describe how genetic analyses of French Canadians have facilitated: (i) the classification of variants in BRCA1 and BRCA2; (ii) the identification and classification of variants in newly proposed breast and/or ovarian cancer predisposing genes; and (iii) the identification of a new breast cancer predisposing gene candidate, RECQL. The genetic architecture of French Canadians provides a unique opportunity to evaluate new candidate cancer predisposing genes regardless of the population in which they were identified.

DEAD-Box RNA Helicases in Cell Cycle Control and Clinical Therapy

Cell cycle is regulated through numerous signaling pathways that determine whether cells will proliferate, remain quiescent, arrest, or undergo apoptosis. Abnormal cell cycle regulation has been linked to many diseases. Thus, there is an urgent need to understand the diverse molecular mechanisms of how the cell cycle is controlled. RNA helicases constitute a large family of proteins with functions in all aspects of RNA metabolism, including unwinding or annealing of RNA molecules to regulate pre-mRNA, rRNA and miRNA processing, clamping protein complexes on RNA, or remodeling ribonucleoprotein complexes, to regulate gene expression. RNA helicases also regulate the activity of specific proteins through direct interaction. Abnormal expression of RNA helicases has been associated with different diseases, including cancer, neurological disorders, aging, and autosomal dominant polycystic kidney disease (ADPKD) via regulation of a diverse range of cellular processes such as cell proliferation, cell cycle arrest, and apoptosis. Recent studies showed that RNA helicases participate in the regulation of the cell cycle progression at each cell cycle phase, including G1-S transition, S phase, G2-M transition, mitosis, and cytokinesis. In this review, we discuss the essential roles and mechanisms of RNA helicases in the regulation of the cell cycle at different phases. For that, RNA helicases provide a rich source of targets for the development of therapeutic or prophylactic drugs. We also discuss the different targeting strategies against RNA helicases, the different types of compounds explored, the proposed inhibitory mechanisms of the compounds on specific RNA helicases, and the therapeutic potential of these compounds in the treatment of various disorders.

The enigmatic helicase DHX9 and its association with the hallmarks of cancer

Much interest has been expended lately in characterizing the association between DExH-Box helicase 9 (DHX9) dysregulation and malignant development, however, the enigmatic nature of DHX9 has caused conflict as to whether it regularly functions as an oncogene or tumor suppressor. The impact of DHX9 on malignancy appears to be cell-type specific, dependent upon the availability of binding partners and activation of inter-connected signaling pathways. Realization of DHX9's pivotal role in the development of several hallmarks of cancer has boosted the enzyme's potential as a cancer biomarker and therapeutic target, opening up novel avenues for exploring DHX9 in precision medicine applications. Our review discusses the ascribed functions of DHX9 in cancer, explores its enigmatic nature and potential as an antineoplastic target.

Literature Review of BARD1 as a Cancer Predisposing Gene with a Focus on Breast and Ovarian Cancers

Soon after the discovery of BRCA1 and BRCA2 over 20 years ago, it became apparent that not all hereditary breast and/or ovarian cancer syndrome families were explained by germline variants in these cancer predisposing genes, suggesting that other such genes have yet to be discovered. BRCA1-associated ring domain (BARD1), a direct interacting partner of BRCA1, was one of the earliest candidates investigated. Sequencing analyses revealed that potentially pathogenic BARD1 variants likely conferred a low-moderate risk to hereditary breast cancer, but this association is inconsistent. Here, we review studies of BARD1 as a cancer predisposing gene and illustrate the challenge of discovering additional cancer risk genes for hereditary breast and/or ovarian cancer. We selected peer reviewed research articles that focused on three themes: (i) sequence analyses of BARD1 to identify potentially pathogenic germline variants in adult hereditary cancer syndromes; (ii) biological assays of BARD1 variants to assess their effect on protein function; and (iii) association studies of BARD1 variants in family-based and case-control study groups to assess cancer risk. In conclusion, BARD1 is likely to be a low-moderate penetrance breast cancer risk gene.

The Function of BARD1 in Centrosome Regulation in Cooperation with BRCA1/OLA1/RACK1

Breast cancer gene 1 (BRCA1)-associated RING domain protein 1 (BARD1) forms a heterodimer with BRCA1, a tumor suppressor associated with hereditary breast and ovarian cancer. BRCA1/BARD1 functions in multiple cellular processes including DNA repair and centrosome regulation. Centrosomes are the major microtubule-organizing centers in animal cells and are critical for the formation of a bipolar mitotic spindle. BRCA1 and BARD1 localize to the centrosome during the cell cycle, and the BRCA1/BARD1 dimer ubiquitinates centrosomal proteins to regulate centrosome function. We identified Obg-like ATPase 1 (OLA1) and receptor for activated C kinase (RACK1) as BRCA1/BARD1-interating proteins that bind to BARD1 and BRCA1 and localize the centrosomes during the cell cycle. Cancer-derived variants of BRCA1, BARD1, OLA1, and RACK1 failed to interact, and aberrant expression of these proteins caused centrosome amplification due to centriole overduplication only in mammary tissue-derived cells. In S-G2 phase, the number of centrioles was higher in mammary tissue-derived cells than in cells from other tissues, suggesting their involvement in tissue-specific carcinogenesis by BRCA1 and BARD1 germline mutations. We described the function of BARD1 in centrosome regulation in cooperation with BRCA1/OLA1/RACK1, as well as the effect of their dysfunction on carcinogenesis.

Summary of BARD1 Mutations and Precise Estimation of Breast and Ovarian Cancer Risks Associated with the Mutations

Over the last two decades, numerous BARD1 mutations/pathogenic variants (PVs) have been found in patients with breast cancer (BC) and ovarian cancer (OC). However, their role in BC and OC susceptibility remains controversial, and strong evidence-based guidelines for carriers are not yet available. Herein, we present a comprehensive catalog of BARD1 PVs identified in large cumulative cohorts of ~48,700 BC and ~20,800 OC cases (retrieved from 123 studies examining the whole coding sequence of BARD1). Using these resources, we compared the frequency of BARD1 PVs in the cases and ~134,100 controls from the gnomAD database and estimated the effect of the BARD1 PVs on BC and OC risks. The analysis revealed that BARD1 is a BC moderate-risk gene (odds ratio (OR) = 2.90, 95% CIs:2.25–3.75, p < 0.0001) but not an OC risk gene (OR = 1.36, 95% CIs:0.87–2.11, p = 0.1733). In addition, the BARD1 mutational spectrum outlined in this study allowed us to determine recurrent PVs and evaluate the variant-specific risk for the most frequent PVs. In conclusion, these precise estimates improve the understanding of the role of BARD1 PVs in BC and OC predisposition and support the need for BARD1 diagnostic testing in BC patients.

AURKA rs2273535 T>A Polymorphism Associated With Cancer Risk: A Systematic Review With Meta-Analysis

Aurora kinase A (AURKA) is a cell cycle regulatory serine/threonine kinase that promotes cell cycle progression. It plays an important role in regulating the transition from G2 to M phase during mitosis. The association between the AURKA rs2273535 T>A polymorphism and cancer risk has been investigated, but the results remain inconsistent. To get a more accurate conclusion, we conducted a comprehensive meta-analysis of 36 case-control studies, involving 22,884 cancer cases and 30,497 healthy controls. Crude odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine the association of interest. Pooled analysis indicated that the AURKA rs2273535 T>A polymorphism increased the overall risk of cancer (homozygous: OR = 1.17, 95% CI = 1.04-1.33; recessive: OR = 1.15, 95% CI = 1.05-1.25; allele: OR = 1.07, 95% CI = 1.02-1.13). Stratification analysis by cancer type further showed that this polymorphism was associated with an increased breast cancer risk. This meta-analysis indicated that the AURKA rs2273535 T>A polymorphism was associated with an overall increased cancer risk, especially breast cancer. Further validation experiments are needed to strengthen our conclusion.

Advances in Deubiquitinating Enzyme Inhibition and Applications in Cancer Therapeutics

Since the discovery of the ubiquitin proteasome system (UPS), the roles of ubiquitinating and deubiquitinating enzymes (DUBs) have been widely elucidated. The ubiquitination of proteins regulates many aspects of cellular functions such as protein degradation and localization, and also modifies protein-protein interactions. DUBs cleave the attached ubiquitin moieties from substrates and thereby reverse the process of ubiquitination. The dysregulation of these two paramount pathways has been implicated in numerous diseases, including cancer. Attempts are being made to identify inhibitors of ubiquitin E3 ligases and DUBs that potentially have clinical implications in cancer, making them an important target in the pharmaceutical industry. Therefore, studies in medicine are currently focused on the pharmacological disruption of DUB activity as a rationale to specifically target cancer-causing protein aberrations. Here, we briefly discuss the pathophysiological and physiological roles of DUBs in key cancer-related pathways. We also discuss the clinical applications of promising DUB inhibitors that may contribute to the development of DUBs as key therapeutic targets in the future.

Relationship between Aurora-A V57I Polymorphism and the Risk of Cancer: A Meta-Analysis and Trial Sequential Analysis

Background: It is still conflicting for the correlation between cancer susceptibility and Aurora-A V57I (rs1047972) gene variant from the published researches. This meta-analysis was performed to access the correlation between cancer susceptibility and Aurora-A rs1047972 gene polymorphism by using meta-analysis methods.

Methods: Eligible studies published before Nov 1, 2019 were systematically searched in PMC, PubMed, EMBASE, Web of Science, Cochrane Library Database, China National Knowledge Infrastructure, Wanfang databases, in order to collect qualified case-control or cohort studies. The odds ratio (OR) and its 95% confidence interval (95%CI) were used to evaluate the correlation between Aurora-A rs1047972 gene polymorphism and cancer risk. Sensitivity analysis was used to examine the stability of the results; Egger's test and Begg's funnel chart were used to assess possible publication bias. Trial sequential analysis (TSA) was used to access whether the sample size of our meta-analysis was sufficient.

Results: The sample set extracted from 24 case-control studies involving 35,926 subjects (14,639 cases and 21,287 controls) for the association of Aurora-A rs1047972 gene polymorphism with cancer susceptibility. In our meta-analysis, Aurora-A rs1047972 polymorphism was associated with an increased risk of cancer susceptibility in overall populations (GA+GG vs. AA: P=0.039, OR=1.106; 95% CI 1.005-1.218; AA vs. GG: P=0.003, OR= 0.814; 95% CI, 0.710-0.934), and the GA/GG variant might be a risk factor for cancer susceptibility. In the stratified analysis by ethnicity, we found a significant association between Aurora-A rs1047972 variant and the susceptibility of the cancer in Caucasian population. In a subgroup analysis by cancer type, we observed a significantly increased susceptibility of lung cancer. In addition, an increased risk was found between Aurora-A rs1047972 polymorphism and cancer susceptibility in MALDI-TOF group and among population-based study (PB) patients. Our results were in a sufficiently large number of participants according to TSA and did not require more studies to confirm such association.

Conclusion: Our meta-analysis revealed that the susceptibility of cancer was associated with Aurora-A rs1047972 polymorphism, especially in Caucasians. And the GA/GG variant might be a risk factor for cancer susceptibility.

Mesothelioma developing in carriers of inherited genetic mutations

Malignant mesothelioma is associated with the exposure to asbestos fibers. Recent discovery of the BAP1 cancer syndrome, a Mendelian disorder with high-penetrance autosomal dominant inheritance fostered the genotyping for nucleotide-level or larger structural alteration of germline DNA. Inherited heterozygous mutations of the BAP1 gene increase the susceptibility to carcinogenic fibers, leading to a concept of gene x environment interaction (GxE) as a pathogenetic mechanism of mesothelioma. Several studies on cohorts of unselected patients with mesothelioma or on familial/early-onset cohorts of mesothelioma cases converged on BAP1 as the more frequent germline mutated gene, followed by other genes involved in DNA repair and homologous recombination. Evidence has been emerging that patients with mesothelioma carrying germline mutations of BAP1 and of other genes, such as those involved in DNA repair and tumor suppressor genes, have better prognosis and higher chemosensitivity when compared with patients with germline wildtype Bap1. We report here a germline genomic analysis targeted 22 genes in a cohort of 101 Japanese patients irrespective of asbestos exposure, age at diagnosis, or personal or family history of cancer. By comparing the results with the Human Genetic Variation Database (HGVD) and the Genome Aggregation Database (gnomAD) we selected rare germline variants with a Combined Annotation Dependent Depletion (CADD) >20. We show here that 31 of 101 subjects were carrying 25 rare variants in 14 genes, neither reported in the HGVD nor in the gnomAD database for 14/25 variants. Besides pathogenic variants of BAP1, rare missense variants were found in genes encoding lysine-specific histone methyltransferase SETD2 and SETDB1 and genes encoding subunits of the mSWI/SNF chromatin remodeling complex. The complete scenario of the genetic background consisting of pathogenic germline variants required for the predisposition and GxE for pathogenesis of mesothelioma appears complex, and further large-scale studies are warranted.

BARD1 is A Low/Moderate Breast Cancer Risk Gene: Evidence Based on An Association Study of the Central European p.Q564X Recurrent Mutation

In addition to several well-established breast cancer (BC) susceptibility genes, the contribution of other candidate genes to BC risk remains mostly undefined. BARD1 is a potentially predisposing BC gene, however, the rarity of its mutations and an insufficient family/study size have hampered corroboration and estimation of the associated cancer risks. To clarify the role of BARD1 mutations in BC predisposition, a comprehensive case-control association study of a recurring nonsense mutation c.1690C>T (p.Q564X) was performed, comprising ~14,000 unselected BC patients and ~5900 controls from Polish and Belarusian populations. For comparisons, two BARD1 variants of unknown significance were also genotyped. We detected the highest number of BARD1 variants in BC cases in any individual BARD1-specific study, including 38 p.Q564X mutations. The p.Q564X was associated with a moderately increased risk of BC (OR = 2.30, p = 0.04). The estimated risk was even higher for triple-negative BC and bilateral BC. As expected, the two tested variants of unknown significance did not show significant associations with BC risk. Our study provides substantial evidence for the association of a deleterious BARD1 mutation with BC as a low/moderate risk allele. The p.Q564X was shown to be a Central European recurrent mutation with potential relevance for future genetic testing.

Deep sequencing of a QTL-rich region spanning 128-136Mbp of pig chromosome 15

The present study shows the characterization of the chromosome 15 (SSC15) region that is highly rich in quantitative traits loci (QTLs) associated with pork quality, growth performance, fat and meat carcass contents. The analytic method that was utilized included targeted enrichment DNA sequencing and RNA hybridisation probes. The research included two pig breeds (Puławska and Polish Landrace) that are significantly different in terms of carcass and meat quality features. Filtered sequences were aligned to the Sscrofa10.2 assembly genome with the STAR aligner and GATK HaplotypeCaller was used for identified gene variants in SSC15 region. In Puławska pigs, which were characterized by high meat quality, mutations were predominantly observed in non-coding regions such as introns and intergenic regions. The highest over 50% frequencies of alternate alleles were identified in the introns of TNS1, VIL1 and USP37 genes. In the upstream gene regions of the Polish Landrace pigs, were observed more mutations than in the upstream gene regions of Puławska. The present study showed interesting gene variant panel that could be analyzed in the further association studies in order to understand the impact on important productive pig traits.

The biology of DHX9 and its potential as a therapeutic target

DHX9 is member of the DExD/H-box family of helicases with a “DEIH” sequence at its eponymous DExH-box motif. Initially purified from human and bovine cells and identified as a homologue of the Drosophila Maleless (MLE) protein, it is an NTP-dependent helicase consisting of a conserved helicase core domain, two double-stranded RNA-binding domains at the N-terminus, and a nuclear transport domain and a single-stranded DNA-binding RGG-box at the C-terminus. With an ability to unwind DNA and RNA duplexes, as well as more complex nucleic acid structures, DHX9 appears to play a central role in many cellular processes. Its functions include regulation of DNA replication, transcription, translation, microRNA biogenesis, RNA processing and transport, and maintenance of genomic stability. Because of its central role in gene regulation and RNA metabolism, there are growing implications for DHX9 in human diseases and their treatment. This review will provide an overview of the structure, biochemistry, and biology of DHX9, its role in cancer and other human diseases, and the possibility of targeting DHX9 in chemotherapy.

The RNA helicase A in malignant transformation

The RNA helicase A (RHA) is involved in several steps of RNA metabolism, such as RNA processing, cellular transit of viral molecules, ribosome assembly, regulation of transcription and translation of specific mRNAs. RHA is a multifunctional protein whose roles depend on the specific interaction with different molecular partners, which have been extensively characterized in physiological situations. More recently, the functional implication of RHA in human cancer has emerged. Interestingly, RHA was shown to cooperate with both tumor suppressors and oncoproteins in different tumours, indicating that its specific role in cancer is strongly influenced by the cellular context. For instance, silencing of RHA and/or disruption of its interaction with the oncoprotein EWS-FLI1 rendered Ewing sarcoma cells more sensitive to genotoxic stresses and affected tumor growth and maintenance, suggesting possible therapeutic implications.

Herein, we review the recent advances in the cellular functions of RHA and discuss its implication in oncogenesis, providing a perspective for future studies and potential translational opportunities in human cancer.

Dualistic Role of BARD1 in Cancer

BRCA1 Associated RING Domain 1 (BARD1) encodes a protein which interacts with the N-terminal region of BRCA1 in vivo and in vitro. The full length (FL) BARD1 mRNA includes 11 exons and encodes a protein comprising of six domains (N-terminal RING-finger domain, three Ankyrin repeats and two C-terminal BRCT domains) with different functions. Emerging data suggest that BARD1 can have both tumor-suppressor gene and oncogene functions in tumor initiation and progression. Indeed, whereas FL BARD1 protein acts as tumor-suppressor with and without BRCA1 interactions, aberrant splice variants of BARD1 have been detected in various cancers and have been shown to play an oncogenic role. Further evidence for a dualistic role came with the identification of BARD1 as a neuroblastoma predisposition gene in our genome wide association study which has demonstrated that single nucleotide polymorphisms in BARD1 can correlate with risk or can protect against cancer based on their association with the expression of FL and splice variants of BARD1. This review is an overview of how BARD1 functions in tumorigenesis with opposite effects in various types of cancer.

BARD1 Gene Polymorphisms Confer Nephroblastoma Susceptibility

BRCA1-associated RING domain protein 1 (BARD1) is a tumor suppressor, which forms a heterodimer with BRCA1. Three BARD1 gene polymorphisms (rs7585356 G>A, rs6435862 T>G and rs3768716 A>G) were initially identified as high-risk neuroblastoma susceptibility loci by a previous GWAS. Because of the general tumor-suppressing function of BARD1, we hypothesized that these BARD1 gene polymorphisms might modify the susceptibility to nephroblastoma. We genotyped these polymorphisms in 145 cases and 531 controls using Taqman methods. Out of three polymorphisms, only the rs7585356 G>A polymorphism was significantly associated with increased susceptibility to nephroblastoma [AA vs. GG: adjusted odds ratio (OR)=1.78, 95% confidence interval (CI)=1.01-3.12]. Combined analysis of three polymorphisms indicated that subjects with 3 risk genotypes exhibited significantly elevated nephroblastoma risk, when compared with subjects with 0-2 risk genotypes (adjusted OR=1.72, 95% CI=1.02-2.89). Stratified analysis revealed that in term of clinical stage, rs7585356 AA carriers were associated with increased risk of developing clinical stage I+II nephroblastoma. The presence of three risk genotypes was significantly associated with nephroblastoma risk in females and clinical stage I+II nephroblastoma. Our results suggested that BARD1 rs7585356 G>A may be associated with nephroblastoma risk.

In Vivo Selection Against Human Colorectal Cancer Xenografts Identifies an Aptamer That Targets RNA Helicase Protein DHX9

The ability to selectively target disease-related tissues with molecules is critical to the design of effective therapeutic and diagnostic reagents. Recognizing the differences between the in vivo environment and in vitro conditions, we employed an in vivo selection strategy to identify RNA aptamers (targeting motifs) that could localize to tumor in situ. One of the selected molecules is an aptamer that binds to the protein DHX9, an RNA helicase that is known to be upregulated in colorectal cancer. Upon systemic administration, the aptamer preferentially localized to the nucleus of cancer cells in vivo and thus has the potential to be used for targeted delivery.

Decreased expression of BRCA1-associated protein 1 predicts unfavorable survival in gastric adenocarcinoma

BRCA1-associated protein 1 (BAP1) has been reported as a novel tumor suppressor, while in gastric adenocarcinoma, the function of this protein was still await to be uncovered. Based on a large group of patients with gastric adenocarcinoma, our study aimed to have a further understanding about the correlation of BAP1 expression and patients' clinical outcomes. We performed quantitative PCR and Western blot to examine BAP1 expression in 38 cases of gastric adenocarcinoma samples and adjacent non-cancerous tissues. Immunochemistry was used to evaluate BAP1 expression in a large cohort of 474 paraffin-embedded specimens. The clinical and prognostic significance of BAP1 expression was statistically analyzed. Postoperative survival between groups was using Kaplan-Meier analysis. BAP1 was overexpressed in paracancerous normal mucosa compared with gastric cancer. Decreased BAP1 expression was associated with higher histologic grade (P = 0.044), tumor infiltration (P < 0.001), metastasis status (P = 0.023), and TNM stage (P < 0.001). Patients with low expression of BAP1 had shorter overall survival compared with those with high expression (P < 0.001). Patients' survival in stage N0 could be stratified by the expression of BAP1. Multivariate analysis showed that in gastric adenocarcinoma, BAP1 expressing level was an independent prognostic factor (RR = 0.575, P < 0.001). Decreased expression of BAP1 suggests pessimistic prognosis for gastric adenocarcinoma patients. Further studies are warranted.

BAP1 promotes breast cancer cell proliferation and metastasis by deubiquitinating KLF5

The transcription factor KLF5 is highly expressed in basal-like breast cancer and promotes breast cancer cell proliferation, survival, migration and tumour growth. Here we show that, in breast cancer cells, KLF5 is stabilized by the deubiquitinase (DUB) BAP1. With a genome-wide siRNA library screen of DUBs, we identify BAP1 as a bona fide KLF5 DUB. BAP1 interacts directly with KLF5 and stabilizes KLF5 via deubiquitination. KLF5 is in the BAP1/HCF-1 complex, and this newly identified complex promotes cell cycle progression partially by inhibiting p27 gene expression. Furthermore, BAP1 knockdown inhibits tumorigenicity and lung metastasis, which can be rescued partially by ectopic expression of KLF5. Collectively, our findings not only identify BAP1 as the DUB for KLF5, but also reveal a critical mechanism that regulates KLF5 expression in breast cancer. Our findings indicate that BAP1 could be a potential therapeutic target for breast and other cancers.

The zinc finger-containing transcription factor KLF5 drives cell proliferation and migration. Here, the authors show that the debuquitinase BAP1 directly stabilizes KLF5, thus promoting basal-like breast cancer cell-cycle progression and metastasis.

Comprehensive review of BAP1 tumor predisposition syndrome with report of two new cases

The BRCA1-associated protein-1 (BAP1) tumor predisposition syndrome (BAP1-TPDS) is a recently identified hereditary cancer syndrome. Germline mutations in this tumor suppressor gene predispose families to the development of various malignancies. The molecular functions of the gene as well as the clinical phenotype of the syndrome are still being clarified. We sought to conduct a comprehensive review of published research into BAP1-TPDS to more thoroughly delineate the clinical implications of germline BAP1 mutations. We also report two additional families with germline BAP1 mutations. Current evidence demonstrates that germline BAP1 mutations predispose families to uveal melanoma, renal cell carcinoma, malignant mesothelioma, cutaneous melanoma, and possibly to a range of other cancers as well. Some of these cancers tend to be more aggressive, have a propensity to metastasize, and onset earlier in life in patients with BAP1 mutations as compared to non-predisposed patients with equivalent cancers. Although further research is necessary, this information can aid in the management, diagnosis, and therapy of these patients and their families, and highlights the importance of genetic counseling.

Analysis of large mutations in BARD1 in patients with breast and/or ovarian cancer: the Polish population as an example

Only approximately 50% of all familial breast cancers can be explained by known genetic factors, including mutations in BRCA1 and BRCA2. One of the most extensively studied candidates for breast and/or ovarian cancer susceptibility is BARD1. Although it was suggested that large mutations may contribute substantially to the deleterious variants of BARD1, no systematic study of the large mutations in BARD1 has been performed. To further elucidate the role of large mutations in BARD1, we designed a multiplex ligation-dependent probe amplification (MLPA) assay and performed an analysis of 504 women with a familial breast and/or ovarian cancer and 313 patients with ovarian cancer. The investigation did not reveal any large mutations in the BARD1 gene. Although the analysis was not focused on identification of small mutations, we detected seven deleterious or potentially deleterious point mutations, which contribute substantially to the total number of BARD1 mutations detected so far. In conclusion, although we cannot exclude the presence of large mutations in BARD1, our study indicates that such mutations do not contribute substantially to the risk of breast and/or ovarian cancer. However, it has to be noted that our results may be specific to the Polish population.

Tumours associated with BAP1 mutations

BAP1 (BRCA1-Associated Protein 1) was initially identified as a protein that binds to BRCA1. BAP1 is a tumour suppressor that is believed to mediate its effects through chromatin modulation, transcriptional regulation, and possibly via the ubiquitin-proteasome system and the DNA damage response pathway. Germline mutations of BAP1 confer increased susceptibility for the development of several tumours, including uveal melanoma, epithelioid atypical Spitz tumours, cutaneous melanoma, and mesothelioma. However, the complete tumour spectrum associated with germline BAP1 mutations is not yet known. Somatic BAP1 mutations are seen in cutaneous melanocytic tumours (epithelioid atypical Spitz tumours and melanoma), uveal melanoma, mesothelioma, clear cell renal cell carcinoma, and other tumours. Here, we review the current state of knowledge about the functional roles of BAP1, and summarise data on tumours associated with BAP1 mutations. Awareness of these tumours will help pathologists and clinicians to identify patients with a high likelihood of harbouring germline or somatic BAP1 mutations. We recommend that pathologists consider testing for BAP1 mutations in epithelioid atypical Spitz tumours and uveal melanomas, or when other BAP1-associated tumours occur in individual patients. Tumour tissues may be screened for BAP1 mutations/loss/inactivation by immunohistochemistry (IHC) (demonstrated by loss of nuclear staining in tumour cells). Confirmatory sequencing may be considered in tumours that exhibit BAP1 loss by IHC and in those with equivocal IHC results. If a BAP1 mutation is confirmed in a tumour, the patient's treating physician should be informed of the possibility of a BAP1 germline mutation, so they can consider whether genetic counselling and further testing of the patient and investigation of their family is appropriate. Recognition and evaluation of larger numbers of BAP1-associated tumours will also be necessary to facilitate identification of additional distinct clinico-pathological characteristics or other genotype-phenotype correlations that may have prognostic and management implications.

Germline BAP1 mutation predisposes to uveal melanoma, lung adenocarcinoma, meningioma, and other cancers

OBJECTIVE

To investigate the potential contribution of germline sequence alterations in the BAP1 gene in uveal melanoma (UM) patients with possible predisposition to hereditary cancer.

DESIGN

A total of 53 unrelated UM patients with high risk for hereditary cancer and five additional family members of one proband were studied. Mutational screening was carried out by direct sequencing.

RESULTS

Of the 53 UM patients studied, a single patient was identified with a germline BAP1 truncating mutation, c. 799 C→T (p.Q267X), which segregated in several family members and was associated with UM and other cancers. Biallelic inactivation of BAP1 and decreased BAP1 expression were identified in the UM, lung adenocarcinoma and meningioma tumours from three family members with this germline BAP1 mutation. Germline BAP1 variants of uncertain significance, likely non-pathogenic, were also identified in two additional UM patients.

CONCLUSION

This study reports a novel hereditary cancer syndrome caused by a germline BAP1 mutation that predisposes patients to UM, lung carcinoma, meningioma, and possibly other cancers. The results indicate that BAP1 is the candidate gene in only a small subset of hereditary UM, suggesting the contribution of other candidate genes.

Lack of association between BARD1 Cys557Ser variant and breast cancer risk: a meta-analysis of 11,870 cases and 7,687 controls

PURPOSE

The BRCA1-associated RING domain (BARD1) gene has been identified as a high-penetrance gene for breast cancer, whose germline and somatic mutations were reported in both non-BRCA1/2 hereditary site-specific and sporadic breast cancer cases. Some association studies suggested that the BRAD1 Cys557Ser variant might be associated with increased risk of breast cancer, but the results remain conflicting rather than conclusive. In order to derive a more precise estimation of the relationship, this meta-analysis was performed.

METHODS

Eligible studies were identified by searching several databases for relevant reports published before March 2011. In total, 14 studies (11,870 cases and 7,687 controls) were included in the present meta-analysis. The pooled odds ratio (OR) with 95% confidence interval (CI) for breast cancer risk associated with Cys557Ser carrier was estimated.

RESULTS

The carrier frequency of the Cys557Ser mutation was 3.85% (457/11,870) in patients with breast cancer and 3.29% (253/7,687) in healthy controls. When all studies were pooled into the meta-analysis, there was no evidence for significant association between Cys557Ser mutation and breast cancer risk (OR 1.14, 95% CI 0.94-1.34). In the subgroup analyses by design of experiment and family history with BRCA1/2 status (unselected cases, family history with non-BRCA1/2 cases, and family history with BRCA1/2-positive cases), no significant associations were found in any subgroup of population.

CONCLUSIONS

This meta-analysis strongly suggests that BARD1 Cys557Ser mutation is not associated with increased breast cancer risk.

BARD1 homozygous deletion, a possible alternative to BRCA1 mutation in basal breast cancer

Hereditary breast cancers (BCs) are incompletely explained by BRCA genes abnormalities, as ∼70% of them are not associated with known genetic alterations. Array-based comparative genomic hybridization (aCGH) of tumors provides an opportunity for identifying new BC susceptibility genes. By analyzing our database of high-resolution aCGH profiles of 330 BCs, we identified a case with homozygous deletion of the entire BARD1 gene. The BARD1-deleted case displayed a familial history of BC and other clinico-pathological features of BRCAness, and a 17% probability of BRCA1/2 mutation. Analysis of constitutional DNA showed a BARD1 germline heterozygous deletion without BRCA1/2 mutation. Gene expression analysis using DNA microarrays classified the tumor as basal-like, with very low BARD1 and ID4 expression, but high expression of BRCA1, RAD51, PARP1, CHEK1, and FANCA. The tumor displayed a BRCA1-mutated expression profile. This is the first report of a non-BRCA1/2-mutated BC with somatic homozygous and germ-line heterozygous deletion of the entire BARD1 gene. This observation suggests that BARD1 might be a BC susceptibility gene that follows the Knudson rule. Identification of BARD1 deletion could have clinical applications including screening for hereditary forms. © 2010 Wiley-Liss, Inc.

Features of double-stranded RNA-binding domains of RNA helicase A are necessary for selective recognition and translation of complex mRNAs

The DExH protein RNA helicase A (RHA) plays numerous roles in cell physiology, and post-transcriptional activation of gene expression is a major role among them. RHA selectively activates translation of complex cellular and retroviral mRNAs. Although RHA requires interaction with structural features of the 5'-UTR of these target mRNAs, the molecular basis of their translation activation by RHA is poorly understood. RHA contains a conserved ATPase-dependent helicase core that is flanked by two α-β-β-β-α double-stranded RNA-binding domains at the N terminus and repeated arginine-glycine residues at the C terminus. The individual recombinant N-terminal, central helicase, and C-terminal domains were evaluated for their ability to specifically interact with cognate RNAs by in vitro biochemical measurements and mRNA translation assays in cells. The results demonstrate that N-terminal residues confer selective interaction with retroviral and junD target RNAs. Conserved lysine residues in the distal α-helix of the double-stranded RNA-binding domains are necessary to engage structural features of retroviral and junD 5'-UTRs. Exogenous expression of the N terminus coprecipitates junD mRNA and inhibits the translation activity of endogenous RHA. The results indicate that the molecular basis for the activation of translation by RHA is recognition of target mRNA by the N-terminal domain that tethers the ATP-dependent helicase for rearrangement of the complex 5'-UTR.

BARD1, a possible biomarker for breast and ovarian cancer

Breast cancer is the leading cause of cancer death in women. Ovarian cancer, although less frequent, is detected very late, and survival is correlated to early detection. Therefore, better methods for early detection would help to increase the number of survivors. The incidence of young women diagnosed with breast cancer is increasing. These women and women who are at risk because of a family history of breast cancer would benefit from more accurate and less invasive screening methods than those in place today. A blood test based on BARD1, a protein that interacts with the breast cancer gene product BRCA1, is a promising candidate for fulfilling these conditions. The science behind BARD1 and its role in breast and ovarian cancer is explained in this article.