BRCA1 Interactors - Rad50 and BRIP1: As Prognostic and Predictive Molecules for the Severity of Triple-Negative Breast Cancer

BRIP1 is one of the major interacting partner of BRCA1 which plays an important role in repair by homologous recombination (HR). This gene is mutated in around 4% cases of breast cancer, however, its mechanism of action is unclear. In this study, we presented the fundamental role of BRCA1 interactors BRIP1 and RAD50 in the development of differential severity in Triple-Negative Breast Cancer(TNBC) among various affected individuals. We showed that in some TNBC lines like MDA-MB-231 the functioning of both BRCA1/TP53 is compromised. Furthermore, the sensing of DNA damage is affected, depicted through the low expression of damage sensing molecule Rad50 and reduced formation of H2AX foci. Due to less damage sensing capability and low availability of BRCA1 at the damage sites, the repair by HR becomes inefficient leading to more damage. Accumulation of damage sends a signal for over activation of NHEJ repair pathways. Over expressed NHEJ molecules with compromised HR and checkpoint conditions lead to higher proliferation and error-prone repair, which increases the mutation rate and corresponding tumor severity. The severity phenotypes were more in cells having compromised BRCA1-BRIP1 functioning. The in silico analysis of the TCGA-UCSC xena datasets with genes expression in deceased population shows a significant correlation of BRCA1 expression with OS in TNBCs (0.0272). The association of BRCA1 with OS becomes stronger with the addition of BRIP1expression (0.000876**). Since the overall survival(OS) is directly proportional to the extent of severity, the data analysis hints at the role of BRIP1 in controlling the severity of TNBC.

Prognostic Relevance of BRCA1 Expression in Survival of Patients With Cervical Cancer

ObjectiveBRCA1 expression can be lost by a variety of mechanisms including germline or somatic mutation and promotor hypermethylation. Given the potential importance of BRCA1 loss as a predictive and prognostic biomarker in several cancers, the objective of this study was to investigate BRCA1 expression using immunohistochemistry (IHC) in cervical cancer and its possible prognostic relevance.MethodsSeventy patients with cervical cancer were enrolled in this study. Samples from each tumor were stained for BRCA1 and reviewed independently by gynecologic pathologists blinded to the BRCA status. Kaplan–Meier methods were used to estimate overall survival according to BRCA1 expression. Differentially expressed genes (DEGs) by BRCA1 expression were selected using GSE44001 dataset, which included 300 samples treated with radical hysterectomy. In addition, cox regression analysis with backward elimination was performed to select independent prognostic markers. Gene set enrichment analysis (GSEA) was done using these DEGs.ResultsBRCA1 IHC was positive in 62.9% (44/70) of cases. Patients with BRCA1 expression showed better overall survival (100% vs. 76.2%, HR 0.20, 95% CI 0.04 – 0.99, p = 0.028) than those without BRCA1 expression. Analysis of gene expression profiles according to BRCA1 expression identified 321 differentially expressed mRNAs. Gene set enrichment analysis results showed two dysregulated pathways (VEGF_A_UP.V1_DN and E2F1_UP.V1_UP). Of these DEGs, alterations of 20 gene signatures were found to be independently associated with survival outcomes of patients.ConclusionsBRCA1 expression in cervical cancer tissue is associated with survival. In addition, the identification of specific gene alterations associated with BRCA1 expression could help to provide individualized prediction in these patients.

Specific BRCA and immune configurations determine optimal response to platinum-based chemotherapy in triple negative breast and ovarian carcinomas

Loss of homologous recombination repair (HRR) via germline and somatic BRCA1 or BRCA2 gene mutations and via BRCA1 promoter methylation has been associated with better response to platinum agents and PARP inhibitors, in both triple negative breast cancer (TNBC) and ovarian carcinoma (OvCa). A major conundrum arising from recent clinical studies is why cancers with BRCA1 promoter methylation (BRCA1meth) respond more poorly as compared to those bearing mutations in BRCA1 and BRCA2 (BRCAmut), given the biologically equivalent HRR deficiency in both states. We dissected this problem through detailed genomic analyses of primary TNBC and OvCa cohorts, as well as experimentation with patient-derived xenograft (PDX) models and genetically engineered cell lines. Using the precise genomic scar of the tandem duplicator phenotype as a precise genomic indicator of BRCA1 deficiency, we found that, in all cohorts, BRCA1mut and BRCA1meth cancers share an equivalent degree of BRCA1-linked genomic rearrangements. Nonetheless, we consistently found that patients with BRCAmut cancers, but not those with BRCA1meth cancers, had significantly better response outcomes when compared to those with BRCA proficient cancers. When fully promoter methylated BRCA1 PDX TNBCs were exposed to a single short course of platinum chemotherapy an unmethylated BRCA1 promoter allele emerged in resultant tumors associated with an increase in BRCA1 expression. A separate analysis of PDXs derived from treatment naive TNBCs featured complete methylation of the BRCA1 promoter, whereas those derived from post-chemotherapy TNBCs invariably had only partial methylation. PDXs with partial methylation were significantly associated with lower response rates to in vivo platinum-based therapy compared to those with complete promoter methylation. Using single cell clonal expansions from a partially BRCA1meth PDX, we confirmed that the reduced level of methylation was due to the demethylation of one of the BRCA1 promoter alleles and not to the outgrowth of a nonmethylated clone. Clinically, analysis of primary OvCas confirmed that high levels of BRCA1 methylation were significantly associated with reduced BRCA1 gene expression whereas cancers with lower levels of BRCA1 methylation had expression levels approaching those found in BRCA1 proficient cancers. These data suggest that unlike BRCAmut cancers, where HRR deficiency is achieved via mutations that are genetically 'fixed', BRCA1meth cancers are highly adaptive to genotoxin exposure and more likely to recover BRCA1 expression, which may explain their poorer therapeutic response. We further found that an increased immune transcriptional signal, especially an elevated M1 macrophage signature, is associated with enhanced response to platinum-based chemotherapy only in patients with BRCA proficient cancers, in both TNBC and OvCa cohorts underscoring the importance of characterizing molecular heterogeneity to enhance predictive precision in assigning response probabilities in TNBC and OvCa.

Identification of Molecular Markers Associated With Ovarian Cancer Prognosis Using Bioinformatics Analysis

Background Ovarian cancer is associated with a high mortality rate worldwide. However, the pathogenesis, clinicopathological features, and genetic mechanisms of ovarian cancer are still unclear, and it is essential to identify prognostic markers for its clinical diagnosis and treatment. Here, we utilized bioinformatic analysis to identify potential genes involved in mediating BRCA1 expression to elucidate the potential mechanisms underlying ovarian cancer. Methods Gene expression profiling (GSE14407) was performed to identify differentially expressed genes (DEGs) and analyze the weighted gene co-expression network. We selected the key module that was significantly associated with BRCA1 expression and performed gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses for genes in the hub module. We then screened the hub genes utilizing the Search Tool for the Retrieval of Interacting Genes Database (STRING) and Molecular Complex Detection (MCODE) plug-in in Cytoscape. We validated gene expression levels through The Cancer Genome Atlas and GTEx databases for hub genes and screened genes that were related to overall survival in patients with ovarian cancer using the Kaplan-Meier plotter database. Results In total, 3124 DEGs were detected, including 433 upregulated genes and 2691 downregulated genes. We selected the brown module, which was the most significantly associated with BRCA1 expression. GO analysis showed that the hub module genes were significantly enriched in biological processes, including the mitotic cell cycle process, chromosome segregation, and cell division. KEGG analysis showed that the hub module genes were particularly enriched in the cell cycle, p53 signaling pathway, and small cell lung cancer. We selected 30 hub genes from the protein-protein interaction network, which had 88 nodes and 721 edges. Further analyses identified PBK as a prognosis-associated hub gene. Notably, PBK expression was significantly increased in ovarian cancer tissues, as demonstrated by immunohistochemistry analysis using samples from the Human Protein Atlas database.Conclusion PBK was found to be associated with overall survival in patients with ovarian cancer. Our results provide insights into our understanding of the molecular mechanisms and molecular diagnosis of ovarian cancer.

BRCA1 Gene Expression is Down Regulated in Both Familial and Sporadic Breast Cancer Cases in Baghdad- Iraq

Breast cancer is the commonest cancer and the leading cause of malignancies-related mortality in women worldwide. Understanding the underlying biology of the disease could improve patients’ stratification and may offer novel therapeutic targets and strategies. This study was set to investigate the association between BRCA1 gene expression and some of the clinical features of breast cancer patients in Baghdad-Iraq. Eighty peripheral blood samples were collected from sixty patients diagnosed with breast cancer and twenty healthy age-matched controls for BRCA1 qPCR gene expression analysis. The results showed a significant reduction in BRCA1 gene expression in all of the breast cancer patients with the vast majority of them (75%) having BRCA1expression below 25%. The down regulation of BRCA1 expression also showed consistency in breast cancer patients of both sporadic (n=45) and family history (n=15) cases,with expression averages of 18% and 20.19%, respectively. Moreover, the redcuation in BRCA1 expression was negatively associated with the disease’s grades,asbreast cancer patients with the advanced stage III (n=19) showed the lowest expression average of BRCA1 (13.8%) as compared to those in stages II (n=29) and I (n=12) of the disease (17.7% and 19.8%, respectively). Overall, the study highlights the key role of BRCA1gene expression in the development of breast cancer and suggests its potential utility in the diagnosis strategies and preventing the progression of the disease, especially the sporadic type.