Replication Protein A (RPA), a single-stranded DNA (ssDNA)-binding protein is critically involved in DNA replication, checkpoint regulation and DNA repair. We evaluated RPA1, 2, and 3 sub-units protein expression in 331 ovarian tumours, transcripts in 1287 tumours and bioinformatics in the ovarian TCGA cohort (n = 379). Platinum resistant ovarian cancer cells were depleted for RPA 1 or 2 and tested for cisplatin, olaparib and talazoparib sensitivity. HAMNO (RPA1 protein-protein interaction inhibitor) was tested in sensitive and resistant cells. High nuclear RPA1 and RPA2 protein was significantly associated with high grade serous ovarian cancers (HGSOC), advanced stage, platinum resistance and worse progression free survival (PFS) (all ps <0.05). High RPA1 and RPA2 transcripts also linked with poor PFS. Preclinically, RPA1 or RPA 2 depletion increased sensitivity to cisplatin, olaparib and talazoparib treatment. HAMNO monotherapy was cytotoxic to sensitive and resistant cells. We conclude that RPA directed precision oncology strategy could be a viable strategy in HGSOC.

Background: Osteosarcoma (OSA) is the most common type of bone cancer in canines. Novel therapies are required to prevent the growth, survival, and metastatic progression of this cancer, to increase life expectancy of patients. Immunohistochemical (IHC) studies and RNA sequencing help us gain a deeper understanding into the molecular mechanisms of the disease. Methods: We previously compared canine OSA tissues with patient matched non-tumour tissues, revealing 442 overexpressed genes within the samples. The present research used IHC staining for four of these genes in OSA tissues: G protein-coupled receptor 64 (GPR64), TOX High Mobility Group Box Family Member 3 (TOX3), Matrix Metallopeptidase 12 (MMP-12), and Forkhead Box F1 (FOXF1). H-scoring was performed to quantitatively assess protein expression and qualitatively contextualise staining locations. Additional analyses addressed whether gender or anatomical location of lesions (axial or appendicular tumours) affected protein expression. cBioPortal was employed to analyse expression and genetic alterations in patients. Results:GPR64, TOX3, MMP-12, and FOXF1 showed high mRNA expression and genetic alterations in people with OSA. GPR64, TOX3, MMP-12, and FOXF1 were all expressed in canine OSA with novel findings regarding cellular expression. Additionally, differential sex expression was revealed for GPR64 and TOX3. Potential biomarkers or therapeutic targets were identified. Conclusions: These studies, and subsequent analysis, have provided insights into the molecular mechanisms associated with OSA progression and revealed potential biomarkers for diagnostic and prognostic purposes. A deeper understanding of genetic and protein interactions will support and progress novel pathways towards diagnostic, prognostic, and treatment interventions for OSA in both veterinary and human medicine.

Treatment resistance has become a major challenge in cancer research, particularly for patients with advanced castration resistant prostate cancer (CRPC) where no curative therapies are available. Epigenetic alterations play a significant role in cancer progression. In prostate cancer (PCa), where androgen receptor (AR) is the primary oncogenic driver, epigenetic coregulators, specifically lysine demethylases (KDMs), have previously been identified as factors that alter the transcriptome as cancer cells acquire resistance. KDM7A has been identified as a cancer-promoting factor in many cancers; however, its role in PCa remains largely unexplored. This study investigates the clinical relevance of KDM7A in comparison with the well-studied KDM1A in PCa. Using PCa cell line models, we confirm KDM7A as an AR coregulator. By exploiting commercially available pharmacological inhibitors, we demonstrate that in AR-positive CRPC cell lines, combinatory inhibition of KDM1A and KDM7A leads to a loss of AR and the AR-driven transcriptome, which in turn attenuates cancer-promoting cell phenotypes. These findings highlight the potential of combination-targeted therapies in tackling advanced prostate cancers.

Prostate cancer (PCa) is the most prevalent and leading cause of cancer-related deaths among men in most countries around the world, with sub-Saharan Africa being among the most severely affected regions. Indeed, PCa is more common and lethal in indigenous African men, African Americans, and Afro-Caribbean men as compared to their age-matched white counterparts. While the fundamental aetiology of PCa and the role of androgen signalling are well understood, the basis of this racial disparity in PCa incidence and progression remains poorly understood. In this review we revisit the potential association of human papilloma virus (HPV) and PCa. While several studies support an association between HPV and PCa progression and aggressiveness, the importance of HPV in PCa is not without controversy. Here we evaluate studies that both support and challenge a mechanistic role for HPV in PCa and discuss limitations of these studies. We offer suggestions for future studies to address the contribution of HPV to the racial disparity in PCa incidence and outcomes.

Breast cancer (BC) is a leading cause of cancer-related mortality among women worldwide. BC is regarded as a systemic disease. Consequently, the majority of BC patients undergo systemic therapy to reduce the risk of distant metastasis (DM) and associated mortality. Although systemic therapies improve patients' outcome, they are associated with significant side effects, particularly cardiotoxicity and cardiovascular complications. Such side effects vary significantly in severity and duration. Cardiotoxicity may remain undetected for years post-treatment until the symptoms of heart failure (HF) present in the patient, which can reduce life expectancy, quality of life, and even lead to death. Therefore, it is vital to investigate the cardiotoxic and cardiovascular risks of BC treatment regimens to identify patients who would benefit most from cardiac monitoring. As it stands, cardiotoxicity is reported from individual studies or for selected drug therapies only. This review fulfils a gap in the literature by combining clinical studies of cardiotoxicity together from clinical trial data published on clinicaltrials.gov.uk.

Resistance to platinum-based chemotherapy is a major clinical problem in ovarian cancers. The development of predictive biomarkers and therapeutic approaches is an area of unmet need. p73, a member of the p53 family of transcription factors, has essential functions during DNA repair, proliferation, invasion, and apoptosis. The role of p73 in ovarian cancer pathogenesis and response to therapy is largely unknown. The clinicopathological significance of p73 protein expression was evaluated in 278 human ovarian cancers. TP73 transcripts were investigated in publicly available clinical data sets (n = 522) and bioinformatics analysis was completed in the ovarian TCGA cohort (n = 182). Preclinically, p73 was overexpressed in A2780 platinum-sensitive ovarian cancer cells or depleted in platinum-resistant A2780cis cells and investigated for aggressive phenotypes, as well as platinum sensitivity. High p73 protein expression was linked with high grade (p < 0.001), advanced-stage disease (p = 0.002), and shorter progression-free survival (p < 0.0001). TP73 transcripts were significantly higher in tumours compared to normal tissue (p < 0.0001) and linked with shorter PFS (p = 0.047). Preclinically, p73 overexpression in A2780 cells increased proliferation, invasion, spheroid formation, and DNA repair capacity, and was associated with the upregulation of multiple DNA repair and platinum resistance-associated genes. In contrast, p73 deletion in A2780cis led to reduced proliferation and enhanced sensitivity to cisplatin, along with DNA double-strand break accumulation, G2/M cell cycle arrest, and increased apoptosis. We conclude that p73 is a predictor of platinum resistance. p73 can be exploited for targeted ovarian cancer therapy.

In hormone-dependent cancers, front-line treatment options include surgery and therapies that target hormone dependance. These therapies are effective initially but fail in tumors that recur, develop resistance or present at an advanced stage. Consequently, new therapeutic avenues are urgently needed. Increasing evidence implicates epigenetic modulators in tumor initiation, progression and therapeutic response, making them attractive biomarkers for patient stratification and targets for intervention. Over the past two decades, the discovery and development of small-molecule inhibitors directed against key epigenetic regulators have accelerated. This review provides a comprehensive overview of the major epigenetic targets, the inhibitors developed against them and the clinical trials currently underway in endocrine-related cancers. While epigenetic agents have shown limited benefits as monotherapies, their use in combination regimens is emerging as a strategy to overcome resistance and enhance the efficacy of existing treatments. We summarize the current landscape of combination trials, highlight early signs of clinical activity and discuss the opportunities and challenges inherent in integrating epigenetic drugs into the management of advanced endocrine-related cancers.

Hypoxia is a feature of high grade serous ovarian cancer (HGSOC) microenvironment and contributes to platinum and PARP inhibitor resistance. Hypoxia induces activator protein-1 (AP-1) transcription factor (TF) activity leading to sustained proliferation, invasion, metastasis and angiogenesis. The role of AP-1 in DNA damage signaling and repair (DDR) and platinum/PARP resistance is unclear in HGSOC. PARP sensitive and resistant HGSOC cells (PEO1, PEO1R) were monitored for the activity of 48 different TFs using a luciferase-based reporter assay. AP-1 subunits including c-JUN, JUND, JUNB, cFOS and FOSL2 were profiled for protein expression under normoxia and hypoxia (1% O2). PEO1 and PEO1R tumor xenografts were immunohistochemically evaluated for JUNB, FOSL2, MRE11, CA-9 and CD-31 expression. CRISPR knock outs (KO) of JUNB and FOSL2 were generated and investigated for DNA repair gene expression (by DNA repair profiler PCR arrays), whole genome RNA sequencing, proliferation, invasion, cisplatin sensitivity (clonogenic and 3D-spheroids). Functional assays included DNA double strand break (DSB) accumulation, cell cycle progression, apoptosis, immunofluorescence, protein stability assay, co-immunoprecipitation and chromatin immunoprecipitation. The clinicopathological significance of FOSL2, JUNB and MRE11 expression was investigated in 331 clinical epithelial ovarian cancers. In platinum/PARP resistant PEO1R cells, upregulation of AP-1 transcription activity was evident compared to PEO1. Overexpression of JUNB and FOSL2 proteins was observed in normoxia and hypoxia (1% O2). PEO1 and PEO1R tumor xenografts showed high levels of JUNB and FOSL2 in tumor hypoxic areas. Compared to controls, JUNB and FOLS2_KO cells were less proliferative and have increased sensitivity to cisplatin/PARPi (olaparib), which was associated with increased DSBs, G2/M cell cycle arrest and increased apoptosis. DNA repair profiling revealed down regulation of several DNA repair genes in KO cells including MRE11, a key DDR factor. JUNB/FOSL2 proteins physically interacted with MRE11 and promoted its stability. RNA sequencing revealed enrichment of pathways such as platinum response, oxidative phosphorylation, translation and others in KO cells compared to control. In clinical cohorts, high FOSL2, high JUNB and high MRE11 expression was significantly associated with shorter progression-free survival (PFS) and worse overall survival (OS). Our data provides evidence that JUNB and FOSL2 may operate at the hypoxia-DDR interface in HGSOC. JUNB and FOSL2 not only have predictive and prognostic significance but could also be attractive anti-cancer targets including in platinum/PARP resistant HGSOC. Shatha Alqahtani, Rinad Mahmoud, Mashael Algethami, Asmaa Ibrahim, Ahmed Shoqafi, Jennie N. Jeyapalan, Sophie Kellaway, Nigel P. Mongan, Emad A. Rakha, Alan McIntyre, Srinivasan Madhusudan. Unravelling the role of AP-1 transcription factor in DNA damage signaling and response (DDR), platinum and PARP inhibitor resistance in ovarian cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2911.

The cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) ribociclib, abemaciclib, and palbociclib have transformed outcomes in patients with ER+ /HER2 − advanced breast cancer (BC). However, most patients eventually progress, and therapeutic options beyond CDK4/6i are an area of ongoing investigation. Here, we generated and evaluated ribociclib, abemaciclib, and palbociclib-resistant BCs. MCF7 and T47D (ER+ /HER2−) cells were chronically treated with increasing doses of ribociclib (R), abemaciclib (A), or palbociclib (P) over 8 months (0-600 nM). CDK4/6i-resistant cell lines (MCF7rR, MCF7rA, MCF7rP, T47DrR, T47DrA, and T47DrP) were isolated and evaluated for their aggressive phenotypes, cross-resistance, transcriptomic changes, and sensitivity to volasertib (PLK1 inhibitor) and barasertib (AukB inhibitor). Immunohistochemical evaluation of CDK4, CDK6, and p53 (n = 1005) and transcriptomic evaluation of AukB and PLK1 were performed in 5031 clinical breast cancers. MCF7rR, MCF7rA, MCF7rP, T47DrR, T47DrA, and T47DrP cells manifested aggressive phenotypes such as increased spheroid formation, invasion, proliferation, and progression through the G1/S phase of the cell cycle despite CDK4/6i treatment, increased resistance to apoptosis, and cross-resistance to other CDK4/6i. Transcriptomic analysis revealed the enrichment of distinct pathways in resistant cells, particularly the upregulation of cell cycle regulatory genes such as PLK1, AukB, CDKN2B and TGFβ. PLK1 or AukB overexpressing resistant cells were sensitive to volasertib (PLK1 inhibitor) and barasertib (AukB inhibitor) therapy, which was associated with G2/M cell cycle arrest and increased apoptosis. We conclude that cell cycle upregulation leading to G2/M progression is a key route for CDK4/6i resistance. AukB or PLK1 inhibitors that block G2/M phase could be a promising strategy.

The RNA modification N6-methyladenosine (m6A) plays a key role in RNA processing. It is catalysed by the RNA methyltransferase complex (MTC) which includes METTL3, METTL14 and CBLL1. Recently, a METTL3 inhibitor demonstrated promising preclinical results in several cancer types, yet the therapeutic potential of targeting m6A in breast cancer (BCa) remains poorly understood. Utilising a large BCa cohort, we identified that increased METTL14 and CBLL1 expression was associated with a more favourable prognosis, whereas increased METTL3 expression was associated with poorer patient outcomes in Triple Negative BCa (TNBC). Using siRNA depletion, we identified distinct METTL3, METTL14 and CBLL1 regulated gene networks in BCa cell lines. METTL3 inhibition reduced proliferation and invasion of BCa cell lines and induced an immune activation transcriptional signature. These results provide insight into the clinical functions of METTL3, METTL14 and CBLL1 in BCa and support the therapeutic potential of targeting METTL3 in BCa, particularly in TNBC.

Osteosarcoma (OSA) is the most prevalent bone malignancy in people and dogs. Current survival rates show the need for advances in novel therapies to help overcome the growth, survival and metastatic progression of the cancer. Canine models are often used to advance prognostic and treatment opportunities for OSA due to the similarities in the disease between species. This study focusses on the genetic and molecular similarities of OSA between human and canine specimens. Differentially expressed genes (DEGs) were compared and identified in canine and human OSA tumours, revealing 86 common genes, 36 having high and 50 having low expression. Further immunohistochemical analysis of the corresponding proteins of three identified DEGs (ASPN, STK3, BAMBI) allowed for the visualisation of protein expression in canine OSA tissues (n = 19). Overall nuclear and cytoplasmic H-scores were generated, and nuclear and cytoplasmic scores in males and females and in different anatomical locations (axial versus appendicular) were also investigated, presenting unique opportunities to understand the expression in this cancer type. This study contributes to a deeper knowledge of genetic pathways changes and identifies avenues for the diagnosis, prognosis and treatment of OSA in people and dogs, whilst encompassing the One Health concept in medicine.

Background: p73, a member of the p53 family of transcription factors, plays important roles in DNA repair, cell proliferation, angiogenesis, invasion, metastasis, immune evasion, and cytotoxic therapy response. The clinicopathological significance of p73 in breast cancer, particularly in the context of TP53 mutation, remains largely unknown. Methods: Clinicopathological significance of p73 and p53 protein expression was evaluated in 1369 invasive BC and 317 ductal carcinomas in situ (DCIS), including in p53 wild-type or p53 mutant tumours. p73 transcripts and splice variants were investigated in breast cancer genomes (TCGA). Results: High cytoplasmic p73 was significantly associated with high tumour grades, high pleomorphism scores, high mitotic scores, high risk Nottingham prognostic index, negative expression of oestrogen receptors (ERs), triple negative phenotypes (all p values ≤ 0.01), and poor breast cancer specific survival (BCSS) (p = 0.013). In TP53 mutant breast cancers, high p73 was significantly associated with aggressive histopathological features (all p ≤ 0.001) and poor BCSS (p = 0.001) but not in p53 wild-type tumours. Conclusions: Cytoplasmic p73 may be a marker of aggressive phenotype and worse prognosis, particularly in p53 mutant breast cancer. p73, in conjunction with altered p53 expression, may be involved in breast cancer pathogenesis.

Backgrund: The cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) ribociclib, abemaciclib and palbociclib, have transformed the lives of patients with ER+/HER2− metastatic breast cancer (BC). However, most patients will eventually progress on treatment. The discovery of novel targets and optimization of therapy beyond CDK4/6i is an area of ongoing investigation. We conducted a comprehensive evaluation in CDK4/6i resistant BC cells and aimed to discover novel markers of resistance for therapeutic application. Methods: The ER+/HER2− BC cell lines, MCF7 and T47D were chronically treated with increasing dose of ribociclib (R), abemaciclib (A) or palbociclib (P) over 8 months (0-600nM). CDK4/6i resistant cell lines (MCF7RR, MCF7RA, MCF7RP, T47DRR, TD7DRA, T47DRP) were isolated. CDK4/6i resistant and sensitive cells were evaluated for spheroid forming ability, cell cycle progression, apoptosis, cross resistance to other CDK4/6i, whole genome RNA sequencing, and cisplatin/volasertib (PLK1 inhibitor)/barasertib (Arora kinase B inhibitor) sensitivity. In addition, immunohistochemical evaluation of PLK1 and Aurora kinase B expression was completed in a clinical cohort of 4000 early-stage BC specimens. Results: MCF7RR, MCF7RA, MCF7RP, T47DRR, TD7DRA, T47DRP cells manifested aggressive phenotypes with increased spheroid forming ability, progressed through G1/S phase of cell cycle despite CDK4/6i treatment and were resistant to apoptosis. Cross resistance to other CDK4/6is and cisplatin resistance was evident. Whole genome RNA sequencing revealed upregulation of several genes involved in cell cycle regulation, cell signalling, immune regulation, metabolic reprogramming and others across all resistant models compared to controls. Polo-like kinase 1 and Aurora kinase B were consistently overexpressed in MCF7RR, MCF7RA and MCF7RP cells compared to controls. Whereas CDKN4B and TGFβ were upregulated in T47DRR, TD7DRA, T47DRP cells compared to controls. MCF7RR, MCF7RA and MCF7RP cells, whilst resistant to CDK4/6i, remain sensitive to volasertib (PLK1 inhibitor) and barasertib (Aurora Kinase B inhibitor) therapy which was associated with G2/M cell cycle arrest and increased apoptosis. In clinical cohorts, PLK1/CDK4 and PLK1/CDK6 co-expression influence clinical outcomes in BC patients. Conclusion: In ER+/ HER2− BCs, pathways to resistance to CDK4/6i therapy are complex and diverse. PLK1 or Aurora Kinase B targeting could be an attractive therapeutic strategy in certain CDK4/6i resistant ER+ BCs. Citation Format: Srinivasan Madhusudan, Mashael Algethami, Ahmed Shoqafi, Shatha Alqahtani, Jennie N Jeyapalan, Ahmad ALtayyar, Ayat Lashen, Emad A Rakha, Nigel P Mongan. Evaluation of ribociclib, abemaciclib and palbociclib resistance in ER+ breast cancer cells reveal novel therapeutic opportunities in ER+/HER2- breast cancers [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P3-02-23.

Breast cancer (BCa) is one of the most commonly diagnosed malignancies worldwide and is clinically heterogenous. BCa is classified into distinct histopathological and molecular subtypes that inform diagnosis, treatment, and prognosis. Although therapeutic advances, particularly targeted therapies, have improved outcomes, metastatic BCa remains an unmet clinical need. In addition, treatment options remain limited especially for triple negative BCa (TNBC). There is an urgent need to develop novel approaches that can prevent, delay, or reverse disease progression in these patients. The roles of genetic and epigenetic alterations in BCa are well established. Emerging evidence highlights the dysregulation of epitranscriptomic mechanisms involving covalent RNA modifications as a contributing factor in BCa pathogenesis. Notably, recent evidence supports functional crosstalk between epigenetic and epitranscriptomic processes with potential clinical and therapeutic relevance. This review explores key epitranscriptomic RNA modifications, m6A, m6Am, m5C, m7G, and m1A in the context of BCa. The functional consequences of the epitranscriptomic regulators ("writers," "erasers", and "readers") are discussed alongside the accumulating evidence of their contribution to cancer development and progression. This review considers how RNA modifications and their regulators might serve as biomarkers or therapeutic targets and offers new directions for translational research and clinical intervention in BCa.

Cyclin-dependent kinase 2 (CDK2) is a key cell cycle regulator, with essential roles during G1/S transition. The clinicopathological significance of CDK2 in ductal carcinomas in situ (DCIS) and early-stage invasive breast cancers (BCs) remains largely unknown. Here, we evaluated CDK2’s protein expression in 479 BC samples and 216 DCIS specimens. Analysis of CDK2 transcripts was completed in the METABRIC cohort (n = 1980) and TCGA cohort (n = 1090), respectively. A high nuclear CDK2 protein expression was significantly associated with aggressive phenotypes, including a high tumour grade, lymph vascular invasion, a poor Nottingham prognostic index (all p-values < 0.0001), and shorter survival (p = 0.006), especially in luminal BC (p = 0.009). In p53-mutant BC, high nuclear CDK2 remained linked with worse survival (p = 0.01). In DCIS, high nuclear/low cytoplasmic co-expression showed significant association with a high tumour grade (p = 0.043), triple-negative and HER2-enriched molecular subtypes (p = 0.01), Comedo necrosis (p = 0.024), negative ER status (p = 0.004), negative PR status (p < 0.0001), and a high proliferation index (p < 0.0001). Tumours with high CDK2 transcripts were more likely to have higher expressions of genes involved in the cell cycle, homologous recombination, and p53 signaling. We provide compelling evidence that high CDK2 is a feature of aggressive breast cancers. The clinical evaluation of CDK2 inhibitors in early-stage BC patients will have a clinical impact.

Histone H1 (H.H1) is involved in chromatin organisation and gene regulation and is overexpressed in many malignant tumours, including breast cancer (BC). This study proposed and evaluated the prognostic role of H.H1 expression in BC.H.H1 mRNA expression was evaluated in publicly available BC dataset bc-GenExMiner database (n=4421). H.H1 protein expression was assessed immunohistochemically in a well-characterised early-stage BC cohort (n=1311), and associations with clinicopathological data and survival outcomes were evaluated.At the mRNA level, there was a significant association between high H.H1 mRNA and basal-like BC subtype and with poor outcome. The association with shorter survival was observed in the whole cohort and in the basal-like class. H.H1 protein expression was detected in both tumour cells and surrounding stroma. Total expression was detected in 72% of the cases including 28% in tumour cell nuclei and 44% in the stroma. There was strong association between high tumour H.H1 expression and triple-negative BC (TNBC) subtype (p=0.007) and with shorter survival (p=0.019), independent of other variables including tumour size, histologic tumour grade, and lymph node status.H.H1 expression is associated with poor prognosis in BC. Given poor prognostic role of H.H1 in TNBC, it may represent a potential therapeutic target for patients with this aggressive disease.

Cyclin-dependent kinases (CDK2, CDK4, CDK6), cyclin D1, cyclin E1 and phosphorylated retinoblastoma (pRB1) are key regulators of the G1/S cell cycle checkpoint and may influence platinum response in ovarian cancers. CDK2/4/6 inhibitors are emerging targets in ovarian cancer therapeutics. In the current study, we evaluated the prognostic and predictive significance of the CDK2/4/6–cyclin D1/E1–pRB1 axis in clinical ovarian cancers (OC). The CDK2/4/6, cyclin D1/E1 and RB1/pRB1 protein expression were investigated in 300 ovarian cancers and correlated with clinicopathological parameters and patient outcomes. CDK2/4/6, cyclin D1/E1 and RB1 mRNA expression were evaluated in the publicly available ovarian TCGA dataset. We observed nuclear and cytoplasmic staining for CDK2/4/6, cyclins D1/E1 and RB1/pRB1 in OCs with varying percentages. Increased nuclear CDK2 and nuclear cyclin E1 expression was linked with poor progression-free survival (PFS) and a shorter overall survival (OS). Nuclear CDK6 was associated with poor OS. The cytoplasmic expression of CDK4, cyclin D1 and cyclin E1 also has predictive and/or prognostic significance in OCs. In the multivariate analysis, nuclear cyclin E1 was an independent predictor of poor PFS. Tumours with high nuclear cyclin E1/high nuclear CDK2 have a worse PFS and OS. Detailed bioinformatics in the TCGA cohort showed a positive correlation between cyclin E1 and CDK2. We also showed that cyclin-E1-overexpressing tumours are enriched for genes involved in insulin signalling and release. Our data not only identified the prognostic/predictive significance of these key cell cycle regulators but also demonstrate the importance of sub-cellular localisation. CDK2 targeting in cyclin-E1-amplified OCs could be a rational approach.

N6-methyladenosine (m6A) is the most common internal RNA modification and is involved in regulation of RNA and protein expression. AlkB family member 5 (ALKBH5) is a m6A demethylase. Given the important role of m6A in biological mechanisms, m6A and its regulators, have been implicated in many disease processes, including cancer. However, the contribution of ALKBH5 to invasive breast cancer (BC) remains poorly understood. The aim of this study was to evaluate the clinicopathological value of ALKBH5 in BC. Publicly available data were used to investigate ALKBH5 mRNA alterations, prognostic significance, and association with clinical parameters at the genomic and transcriptomic level. Differentially expressed genes (DEGs) and enriched pathways with low or high ALKBH5 expression were investigated. Immunohistochemistry (IHC) was used to assess ALKBH5 protein expression in a large well-characterised BC series (n = 1327) to determine the clinical significance and association of ALKBH5 expression. Reduced ALKBH5 mRNA expression was significantly associated with poor prognosis and unfavourable clinical parameters. ALKBH5 gene harboured few mutations and/or copy number alternations, but low ALKBH5 mRNA expression was seen. Patients with low ALKBH5 mRNA expression had a number of differentially expressed genes and enriched pathways, including the cytokine-cytokine receptor interaction pathway. Low ALKBH5 protein expression was significantly associated with unfavourable clinical parameters associated with tumour progression including larger tumour size and worse Nottingham Prognostic Index group. This study implicates ALKBH5 in BC and highlights the need for further functional studies to decipher the role of ALKBH5 and RNA m6A methylation in BC progression.