The pathophysiology of coronavirus disease 2019 (COVID-19) is mainly dependent on the underlying mechanisms that mediate the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the host cells of the various human tissues/organs. Recent studies have indicated a higher order of complexity of the mechanisms of infectivity, given that there is a wide-repertoire of possible cell entry mediators that appear to co-localise in a cell- and tissue-specific manner. The present study provides an over-view of the 'canonical' SARS-CoV-2 mediators, namely angiotensin converting enzyme 2, transmembrane protease serine 2 and 4, and neuropilin-1, expanding on the involvement of novel candidates, including glucose-regulated protein 78, basigin, kidney injury molecule-1, metabotropic glutamate receptor subtype 2, ADAM metallopeptidase domain 17 (also termed tumour necrosis factor-α convertase) and Toll-like receptor 4. Furthermore, emerging data indicate that changes in microRNA (miRNA/miR) expression levels in patients with COVID-19 are suggestive of further complexity in the regulation of these viral mediators. An in silico analysis revealed 160 candidate miRNAs with potential strong binding capacity in the aforementioned genes. Future studies should concentrate on elucidating the association between the cellular tropism of the SARS-CoV-2 cell entry mediators and the mechanisms through which they might affect the clinical outcome. Finally, the clinical utility as a biomarker or therapeutic target of miRNAs in the context of COVID-19 warrants further investigation.

Background: H2AX can be of prognostic value in breast cancer, since in advanced stage patients with high levels, there was an association with worse overall survival (OS). However, the clinical relevance of H2AX in ovarian cancer (OC) remains to be elucidated. Methods: OC H2AX expression studied using the TCGA/GTEX datasets. Subsequently, patients were classified as either high or low in terms of H2AX expression to compare OS and perform gene set enrichment. qRT-PCR validated in-silico H2AX findings followed by immunohistochemistry on a tissue microarray. The association between single nucleotide polymorphisms in the area of H2AX; prevalence and five-year OC survival was tested in samples from the UK Biobank. Results: H2AX was significantly overexpressed in OCs compared to normal tissues, with higher expression associated with better OS (p = 0.010). Gene Set Enrichment Analysis demonstrated gene sets involved in G2/M checkpoint, DNA repair mTORC1 signalling were enriched in the H2AX highly expressing OCs. Polymorphisms in the area around the gene were associated with both OC prevalence (rs72997349-C, p = 0.005) and worse OS (rs10790282-G, p = 0.011). Finally, we demonstrated that H2AX gene expression correlated with γ-H2AX staining in vitro. Conclusions: Our findings suggest that H2AX can be a novel prognostic biomarker for OC.

Background: Approximately 50% of ovarian cancer patients harbour homologous recombination repair deficiencies. These deficiencies have been successfully targeted using poly (ADP-ribose) polymerase inhibitors (PARPi) particularly for patients harbouring BRCA1/2 mutations. The aim of this study is to assess the effects of the PARPi rucaparib in vitro using cell lines with BRCA2 mutations in comparison to those with BRCA2 wild type. Methods: Cell proliferation assays, RT-qPCR, immunofluorescence, annexin V/PI assays were used to assess the effects of rucaparib in vitro. Results: The BRCA2 mutant ovarian cancer cell line PEO1 exhibited higher PARP1 activity when treated with H2O2 compared to wild type cell lines. The migratory and proliferative capacity of PEO1 cells was compromised following treatment with rucaparib 10 µM compared to BRCA2 wild-type cell lines via a mechanism involving the mTOR pathway. Rucaparib treatment significantly increased DNA damage primarily in PEO1 cells and SKOV3 cells compared with wild type. Conclusions: Appropriate identification of robust predictive biomarkers for homologous recombination deficiency using ‘liquid’ biopsies would facilitate the identification of patients suitable for PARPi therapy. Preliminary efforts to undertake such testing are described here. This study also demonstrates the mechanisms of action of rucaparib (PARPi) which may involve elements of the mTOR pathway.

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ObjectiveFifty percent of patients with high-grade serous ovarian cancer harbor defects in the homologous recombination repair pathway. RAD51 foci form where DNA is damaged, indicating its involvement in repairing double-stranded breaks. High levels of RAD51 in ovarian cancer tissue have been associated with a poorer prognosis.ObjectiveTo demonstrate RAD51 foci in circulating cancer-associated cells of patients with ovarian cancer and their association with clinical outcomes.MethodsOne hundred and twenty-four patients with high-grade serous ovarian cancer had blood samples taken at strategic points during treatment and follow-up. Cells were stained using WT1 and RAD51 antibodies with immunofluorescence and reviewed under Leica camera microscopy; RAD51 foci were counted. Correlations were made between numbers of RAD51 foci and treatment response,BRCAstatus, and progression-free survival.ResultsRAD51 foci were identified in all patients (n=42) with wild-typeBRCA. BRCAmutant/homologous recombination deficiency-positive patients (n=8) had significantly lower numbers of RAD51 foci (p=0.009). Responders to treatment (n=32) had a reduction in circulating cells (p=0.02) and RAD51 foci (p=0.0007). Numbers of RAD51 foci were significantly higher in the platinum-resistant population throughout treatment: at the start of treatment, in 56 platinum-sensitive patients there was a mean of 3.6 RAD51 foci versus 6.2 in 15 platinum-resistant patients (p=0.02). Patients with a high number of RAD51 foci had worse median progression-free survival: in 39 patients with a mean of <3 RAD51 foci at treatment start, median progression-free survival had not been reached, compared with 32 patients with >3 RAD51 foci whose progression-free survival was 13 months (p=0.04).ConclusionsLevels of RAD51 foci in circulating cancer-associated cells of patients with high-grade serous ovarian cancer are associated with clinical outcomes and may be a more pragmatic method of determining a homologous repair-deficient population.