Aurora A kinase regulates non-homologous end-joining and poly(ADP-ribose) polymerase function in ovarian carcinoma cells

Chromatin context-dependent effects of epigenetic drugs on CRISPR-Cas9 editing

The efficiency and outcome of CRISPR/Cas9 editing depends on the chromatin state at the cut site. It has been shown that changing the chromatin state can influence both the efficiency and repair outcome, and epigenetic drugs have been used to improve Cas9 editing. However, because the target proteins of these drugs are not homogeneously distributed across the genome, the efficacy of these drugs may be expected to vary from locus to locus. Here, we systematically analyzed this chromatin context-dependency for 160 epigenetic drugs. We used a human cell line with 19 stably integrated reporters to induce a double-stranded break in different chromatin environments. We then measured Cas9 editing efficiency and repair pathway usage by sequencing the mutational signatures. We identified 58 drugs that modulate Cas9 editing efficiency and/or repair outcome dependent on the local chromatin environment. For example, we find a subset of histone deacetylase inhibitors that improve Cas9 editing efficiency throughout all types of heterochromatin (e.g. PCI-24781), while others were only effective in euchromatin and H3K27me3-marked regions (e.g. apicidin). In summary, this study reveals that most epigenetic drugs alter CRISPR editing in a chromatin-dependent manner, and provides a resource to improve Cas9 editing more selectively at the desired location.

Aurora Kinase A inhibition enhances DNA damage and tumor cell death with 131I-MIBG therapy in high-risk neuroblastoma

BACKGROUND

Neuroblastoma is the most common extra-cranial pediatric solid tumor. 131I-metaiodobenzylguanidine (MIBG) is a targeted radiopharmaceutical highly specific for neuroblastoma tumors, providing potent radiotherapy to widely metastatic disease. Aurora kinase A (AURKA) plays a role in mitosis and stabilization of the MYCN protein in neuroblastoma. We aimed to study the impact of AURKA inhibitors on DNA damage and tumor cell death in combination with 131I-MIBG therapy in a pre-clinical model of high-risk neuroblastoma.

RESULTS

Using an in vivo model of high-risk neuroblastoma, we demonstrated a marked combinatorial effect of 131I-MIBG and alisertib on tumor growth. In MYCN amplified cell lines, the combination of radiation and an AURKA A inhibitor increased DNA damage and apoptosis and decreased MYCN protein levels.

CONCLUSION

The combination of AURKA inhibition with 131I-MIBG treatment is active in resistant neuroblastoma models.

Selective DNA-PK Inhibition Enhances Chemotherapy and Ionizing Radiation Activity in Soft-Tissue Sarcomas

PURPOSE

Patients with advanced soft-tissue sarcomas (STS) exhibit a poor prognosis and have few therapeutic options. DNA-dependent protein kinase (DNA-PK) catalytic subunit is a multifunctional serine-threonine protein kinase that plays a crucial role in DNA double-strand damage repair via nonhomologous end joining.

EXPERIMENTAL DESIGN

To investigate the therapeutic potential of DNA-PK targeting in STS, we first evaluated the prognostic value of DNA-PK expression in two large cohorts of patients with STS. We then used the potent and selective DNA-PK inhibitor AZD7648 compound to investigate the antitumor effect of the pharmacologic inhibition of DNA-PK in vitro via MTT, apoptosis, cell cycle, and proliferation assays. In vivo studies were performed with patient-derived xenograft models to evaluate the effects of AZD7648 in combination with chemotherapy or ionizing radiation on tumor growth. The mechanisms of sensitivity and resistance to DNA-PK inhibition were investigated by using a genome-wide CRISPR-Cas9 positive screen.

RESULTS

DNA-PK overexpression is significantly associated with poor prognosis in patients with sarcomas. Selective pharmacologic inhibition of DNA-PK strongly synergizes with radiation- and doxorubicin-based regimen in sarcoma models. By using a genome-wide CRISPR-Cas9 positive screen, we identified genes involved in sensitivity to DNA-PK inhibition.

CONCLUSIONS

DNA-PK inhibition deserves clinical investigation to improve response to current therapies in patients with sarcoma.

Aurora Kinase A inhibition enhances DNA damage and tumor cell death with 131I-MIBG therapy in high-risk neuroblastoma

Background

Neuroblastoma is the most common extra-cranial pediatric solid tumor. 131I-metaiodobenzylguanidine (MIBG) is a targeted radiopharmaceutical highly specific for neuroblastoma tumors, providing potent radiotherapy to widely metastatic disease. Aurora kinase A (AURKA) plays a role in mitosis and stabilization of the MYCN protein in neuroblastoma. Here we explore whether AURKA inhibition potentiates a response to MIBG therapy.

Results

Using an in vivo model of high-risk neuroblastoma, we demonstrated a marked combinatorial effect of 131I-MIBG and alisertib on tumor growth. In MYCN amplified cell lines, the combination of radiation and an AURKA A inhibitor increased DNA damage and apoptosis and decreased MYCN protein levels.

Conclusion

The combination of AURKA inhibition with 131I-MIBG treatment is active in resistant neuroblastoma models and is a promising clinical approach in high-risk neuroblastoma.

Genetic and Functional Modifications Associated with Ovarian Cancer Cell Aggregation and Limited Culture Conditions

The aggregation of cancer cells provides a survival signal for disseminating cancer cells; however, the underlying molecular mechanisms have yet to be elucidated. Using qPCR gene arrays, this study investigated the changes in cancer-specific genes as well as genes regulating mitochondrial quality control, metabolism, and oxidative stress in response to aggregation and hypoxia in our progressive ovarian cancer models representing slow- and fast-developing ovarian cancer. Aggregation increased the expression of anti-apoptotic, stemness, epithelial-mesenchymal transition (EMT), angiogenic, mitophagic, and reactive oxygen species (ROS) scavenging genes and functions, and decreased proliferation, apoptosis, metabolism, and mitochondrial content genes and functions. The incorporation of stromal vascular cells (SVF) from obese mice into the spheroids increased DNA repair and telomere regulatory genes that may represent a link between obesity and ovarian cancer risk. While glucose had no effect, glutamine was essential for aggregation and supported proliferation of the spheroid. In contrast, low glucose and hypoxic culture conditions delayed adhesion and outgrowth capacity of the spheroids independent of their phenotype, decreased mitochondrial mass and polarity, and induced a shift of mitochondrial dynamics towards mitophagy. However, these conditions did not reduce the appearance of polarized mitochondria at adhesion sites, suggesting that adhesion signals that either reversed mitochondrial fragmentation or induced mitobiogenesis can override the impact of low glucose and oxygen levels. Thus, the plasticity of the spheroids' phenotype supports viability during dissemination, allows for the adaptation to changing conditions such as oxygen and nutrient availability. This may be critical for the development of an aggressive cancer phenotype and, therefore, could represent druggable targets for clinical interventions.

Combined TRIP13 and Aurora Kinase Inhibition Induces Apoptosis in Human Papillomavirus-Driven Cancers

PURPOSE

Human papillomavirus (HPV) causes >5% of cancers, but no therapies uniquely target HPV-driven cancers.

EXPERIMENTAL DESIGN

We tested the cytotoxic effect of 864 drugs in 16 HPV-positive and 17 HPV-negative human squamous cancer cell lines. We confirmed apoptosis in vitro and in vivo using patient-derived xenografts. Mitotic pathway components were manipulated with drugs, knockdown, and overexpression.

RESULTS

Aurora kinase inhibitors were more effective in vitro and in vivo in HPV-positive than in HPV-negative models. We hypothesized that the mechanism of sensitivity involves retinoblastoma (Rb) expression because the viral oncoprotein E7 leads to Rb protein degradation, and basal Rb protein expression correlates with Aurora inhibition-induced apoptosis. Manipulating Rb directly, or by inducing E7 expression, altered cells' sensitivity to Aurora kinase inhibitors. Rb affects expression of the mitotic checkpoint genes MAD2L1 and BUB1B, which we found to be highly expressed in HPV-positive patient tumors. Knockdown of MAD2L1 or BUB1B reduced Aurora kinase inhibition-induced apoptosis, whereas depletion of the MAD2L1 regulator TRIP13 enhanced it. TRIP13 is a potentially druggable AAA-ATPase. Combining Aurora kinase inhibition with TRIP13 depletion led to extensive apoptosis in HPV-positive cancer cells but not in HPV-negative cancer cells.

CONCLUSIONS

Our data support a model in which HPV-positive cancer cells maintain a balance of MAD2L1 and TRIP13 to allow mitotic exit and survival in the absence of Rb. Because it does not affect cells with intact Rb function, this novel combination may have a wide therapeutic window, enabling the effective treatment of Rb-deficient cancers.

Stabilization of AURKA by the E3 ubiquitin ligase CBLC in lung adenocarcinoma

CBL family proteins (CBL, CBLB and CBLC in mammals) are E3 ubiquitin ligases of protein tyrosine kinases. CBL mediates the lysosomal degradation of activated EGFR through K63-linked ubiquitination, while CBLC has an oncogenic function by positively regulating EGFR activation through K6 and K11-linked ubiquitination in EGFR mutant lung adenocarcinoma (LAD). Here, we used immunoprecipitation and mass spectrometry to study the CBLC interactome, and found that CBLC is also involved in cell cycle regulation by stabilizing Aurora kinase A (AURKA). CBLC interacted with the kinase domain of AURKA and positively regulated the stability of AURKA by conjugating monoubiquitination and K11/K63-linked polyubiquitination, which are protective from degrading K11/K48 polyubiquitination. CBLC depletion markedly decreased the half-life of AURKA in cycloheximide-treated LAD cells. When LAD cells were synchronized with double thymidine block at the G1/S boundary and then released into mitotic arrest, CBLC depletion delayed the accumulation and activation of AURKA and prevented cancer cells from entering mitosis. CBLC deficiency significantly delayed cell cycle progression, reduced the mitotic population, and increased apoptosis of LAD cells. Targeting CBLC inhibited tumor growth of LAD cells and enhanced their sensitivity to paclitaxel in xenograft models. Immunohistochemical staining of the tissue microarray also revealed a positive correlation between the expression of CBLC and AURKA in normal and LAD tissues, further supporting the positive regulation of AURKA expression by CBLC. In summary, these findings indicate that the oncogenic E3 ligase CBLC plays a role in mitotic entry by stabilizing AURKA via ubiquitination in LAD. This work demonstrates that targeting CBLC combined with paclitaxel might be a potential option for the treatment of LAD patients who have no available targeted therapies.

Aurora kinases in ovarian cancer

Aurora kinases (AURK) are key regulators of the mitotic spindle formation. AURK is frequently overexpressed in ovarian cancer and this overexpression has been frequently associated with prognosis in these tumours. Interestingly, AURK have been shown to interact with DNA repair mechanisms and other cell cycle regulators. These functions have brought light to Aurora family as a potential target for anticancer therapy. In the last years, two clinical trials with different AURK inhibitors have shown activity in epithelial and clear-cell ovarian cancer. Although there is a lack of predictive factors of AURK inhibition activity, recent trials have identified some candidates. This review will focus in the functions of the AURK family, its role as prognostic factor in epithelial ovarian cancer and potential clinical implications.

A Novel Five-Gene Signature for Prognosis Prediction in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) has been a global health issue and attracted wide attention due to its high incidence and poor outcomes. In this study, our purpose was to explore an effective prognostic marker for HCC. Five cohort profile datasets from GEO (GSE25097, GSE36376, GSE62232, GSE76427 and GSE101685) were integrated with TCGA-LIHC and GTEx dataset to identify differentially expressed genes (DEGs) between normal and cancer tissues in HCC patients, then 5 upregulated differentially expressed genes and 32 downregulated DEGs were identified as common DEGs in total. Next, we systematically explored the relationship between the expression of 37 common DEGs in tumor tissues and overall survival (OS) rate of HCC patients in TCGA and constructed a novel prognostic model composed of five genes (AURKA, PZP, RACGAP1, ACOT12 and LCAT). Furthermore, the predicted performance of the five-gene signature was verified in ICGC and another independent clinical samples cohort, and the results demonstrated that the signature performed well in predicting the OS rate of patients with HCC. What is more, the signature was an independent hazard factor for HCC patients when considering other clinical factors in the three cohorts. Finally, we found the signature was significantly associated with HCC immune microenvironment. In conclusion, the prognostic five-gene signature identified in our present study could efficiently classify patients with HCC into subgroups with low and high risk of longer overall survival time and help clinicians make decisions for individualized treatment.

Aurora kinase A, a synthetic lethal target for precision cancer medicine

Recent advances in high-throughput sequencing technologies and data science have facilitated the development of precision medicine to treat cancer patients. Synthetic lethality is one of the core methodologies employed in precision cancer medicine. Synthetic lethality describes the phenomenon of the interplay between two genes in which deficiency of a single gene does not abolish cell viability but combined deficiency of two genes leads to cell death. In cancer treatment, synthetic lethality is leveraged to exploit the dependency of cancer cells on a pathway that is essential for cell survival when a tumor suppressor is mutated. This approach enables pharmacological targeting of mutant tumor suppressors that are theoretically undruggable. Successful clinical introduction of BRCA-PARP synthetic lethality in cancer treatment led to additional discoveries of novel synthetic lethal partners of other tumor suppressors, including p53, PTEN, and RB1, using high-throughput screening. Recent work has highlighted aurora kinase A (AURKA) as a synthetic lethal partner of multiple tumor suppressors. AURKA is a serine/threonine kinase involved in a number of central biological processes, such as the G2/M transition, mitotic spindle assembly, and DNA replication. This review introduces synthetic lethal interactions between AURKA and its tumor suppressor partners and discusses the potential of AURKA inhibitors in precision cancer medicine.

A long-term survivor of metastatic neuroendocrine prostate cancer treated with multimodal therapy: genetic consideration from next-generation sequencing

It is still unclear whether cell-free DNA (cfDNA) can replace solid-tissue biopsy. A 59-year-old man developed castration-resistant prostate cancer with a liver metastasis. We performed a liver biopsy and collected a cfDNA sample. Although he underwent radiofrequency ablation, tumors recurred and he was transferred to another hospital. We performed next-generation sequencing using DNA from the biopsy tissue and cfDNA. BRCA2 p.T3033fs and AURKA F31I were detected in both the biopsy tissue and the cfDNA. cfDNA may be useful as a liquid biopsy for monitoring the gene profile of aggressive prostate cancer.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13691-021-00482-2.

Targeting DNA damage response kinases in cancer therapy

Cancer cells die when their decimated DNA damage response (DDR) unsuccessfully handles DNA damage. This notion has been successfully exploited when targeting PARP (poly ADP-ribose polymerase) in homologous recombination-deficient cells. With the greater understanding of DDR achieved in the last decade, new cancer therapy targets within the DDR network have been identified. Intriguingly, many of the molecules that have advanced into clinical trials are inhibitors of DDR kinases. This special issue is devoted to discussing the mechanism of cell killing and the level of success that such inhibitors have reached in pre-clinical and clinical settings.

Targeting DNA Repair, Cell Cycle, and Tumor Microenvironment in B Cell Lymphoma

The DNA double-strand break (DSB) is the most cytotoxic lesion and compromises genome stability. In an attempt to efficiently repair DSBs, cells activate ATM kinase, which orchestrates the DNA damage response (DDR) by activating cell cycle checkpoints and initiating DSB repair pathways. In physiological B cell development, however, programmed DSBs are generated as intermediates for effective immune responses and the maintenance of genomic integrity. Disturbances of these pathways are at the heart of B cell lymphomagenesis. Here, we review the role of DNA repair and cell cycle control on B cell development and lymphomagenesis. In addition, we highlight the intricate relationship between the DDR and the tumor microenvironment (TME). Lastly, we provide a clinical perspective by highlighting treatment possibilities of defective DDR signaling and the TME in mantle cell lymphoma, which serves as a blueprint for B cell lymphomas.

BET, SRC, and BCL2 family inhibitors are synergistic drug combinations with PARP inhibitors in ovarian cancer

BACKGROUND

Homologous recombination deficiencies (HRD) are present in approximately half of epithelial ovarian cancers, for which PARP inhibitors (PARPi) are becoming a preferred treatment option. However, a considerable proportion of these carcinomas acquire resistance or harbour de novo resistance, posing a significant challenge to treatment.

METHODS

To identify new combinatorial therapeutics to overcome resistance to PARPi, we employed high-throughput conditional RNAi and drug screening of patient-derived ovarian cancer cells. To prioritise clinically relevant drug combinations, we integrated empirical validation with analysis of The Cancer Genome Atlas (TCGA) and Genomics of Drug Sensitivity in Cancer (GDSC) datasets to nominate candidate targets and drugs, reaching three main findings.

FINDINGS

Firstly, we found that the PARPi rucaparib enhanced the effect of BET inhibitors (CPI-203 & CPI-0610) irrespective of clinical subtype or HRD status. Additional drug combination screens identified that dasatinib, a non-receptor tyrosine kinase inhibitor, augmented the effects of rucaparib and BET inhibitors, proposing a potential broadly applicable triple-drug combination for high-grade serous and clear cell ovarian carcinomas. Secondly, rucaparib synergised with the BCL2 family inhibitor navitoclax, with preferential activity in ovarian carcinomas that harbour alterations in BRCA1/2, BARD1, or MSH2/6. Thirdly, we identified potentially antagonistic drug combinations between the PARPi rucaparib and vinca alkaloids, anthracyclines, and antimetabolites, cautioning their use in the clinic.

INTERPRETATION

These findings propose therapeutic strategies to address PARP inhibitor resistance using agents that are already approved or are in clinical development, with the potential for rapid translation to benefit a broad population of ovarian cancer patients.

The role of Aurora-A in human cancers and future therapeutics

Aurora-A is a mitotic serine/threonine-protein kinase and an oncogene. In normal cells, Aurora-A appears from G2 phase and localizes at the centrosome, where it participates in centrosome replication, isolation and maturation. Aurora-A also maintains Golgi apparatus structure and spindle assembly. Aurora-A undergoes ubiquitination-mediated degradation after the cell division phase. Aurora-A is abnormally expressed in tumor cells and promotes cell proliferation by regulating mitotic substrates, such as PP1, PLK1, TPX2, and LAST2, and affects other molecules through a non-mitotic pathway to promote cell invasion and metastasis. Some molecules in tumor cells also indirectly act on Aurora-A to regulate tumor cells. Aurora-A also mediates resistance to chemotherapy and radiotherapy and is involved in tumor immunotherapy. Clinical trials of Aurora-A molecular inhibitors are currently underway, and clinical transformation is just around the corner.

Aurora kinases and DNA damage response

It is well established that Aurora kinases perform critical functions during mitosis. It has become increasingly clear that the Aurora kinases also perform a myriad of non-mitotic functions including DNA damage response. The available evidence indicates that inhibition Aurora kinase A (AURKA) may contribute to the G₂ DNA damage checkpoint through AURKA's functions in PLK1 and CDC25B activation. Both AURKA and Aurora kinase B (AURKB) are also essential in mitotic DNA damage response that guard against DNA damage-induced chromosome segregation errors, including the control of abscission checkpoint and prevention of micronuclei formation. Dysregulation of Aurora kinases can trigger DNA damage in mitosis that is sensed in the subsequent G₁ by a p53-dependent postmitotic checkpoint. Aurora kinases are themselves linked to the G₁ DNA damage checkpoint through p53 and p73 pathways. Finally, several lines of evidence provide a connection between Aurora kinases and DNA repair and apoptotic pathways. Although more studies are required to provide a comprehensive picture of how cells respond to DNA damage, these findings indicate that both AURKA and AURKB are inextricably linked to pathways guarding against DNA damage. They also provide a rationale to support more detailed studies on the synergism between small-molecule inhibitors against Aurora kinases and DNA-damaging agents in cancer therapies.

Emerging serine-threonine kinase inhibitors for treating ovarian cancer

Introduction: Ovarian cancer is the leading cause of gynecologic cancer death, owing to high rates of incurable, recurrent disease after initial treatment. Serine threonine kinases (STKs) have been proposed as potential therapeutic targets in ovarian cancer because of their role in the initiation and progression of cancers. Experience in non-ovarian cancers suggests that STK inhibitors are active against tumors with specific molecular alterations.Areas covered: This review discusses STK inhibitors in active development in phase II/III clinical trials for ovarian cancer. PubMed and ClinicalTrials.gov were systematically searched to identify STK inhibitor trials for ovarian cancer; active development was confirmed via Pharmaprojects. Available data regarding the efficacy and safety of these compounds are explored.Expert opinion: STK inhibitors currently in development have modest activity as single agents and are unlikely to achieve approval as monotherapy for unselected ovarian cancer patients. Combination trials of STK inhibitors with chemotherapy and/or targeted therapies have suggested an acceptable efficacy/toxicity ratio for certain combinations but confirmatory studies are needed. Carefully designed trials, especially those including somatic molecular analysis, may help identify the subsets of patients most likely to benefit from these therapeutic strategies and determine the role of STK inhibitors in the evolving landscape of precision oncology.

Wise Management of Ovarian Cancer: On the Cutting Edge

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer mortality among women. Two-thirds of patients present at advanced stage at diagnosis, and the estimated 5 year survival rate is 20-40%. This heterogeneous group of malignancies has distinguishable etiology and molecular biology. Initially, single-gene sequencing was performed to identify germline DNA variations associated with EOC. However, hereditary EOC syndrome can be explained by germline pathogenic variants (gPVs) in several genes. In this regard, next-generation sequencing (NGS) changed clinical diagnostic testing, allowing assessment of multiple genes simultaneously in a faster and cheaper manner than sequential single gene analysis. As we move into the era of personalized medicine, there is evidence that poly (ADP-ribose) polymerase (PARP) inhibitors exploit homologous recombination (HR) deficiency, especially in breast cancer gene 1 and 2 (BRCA1/2) mutation carriers. Furthermore, extensive preclinical data supported the development of aurora kinase (AURK) inhibitors in specific tumor types, including EOC. Their efficacy may be optimized in combination with chemotherapeutic or other molecular agents. The efficacy of metformin in ovarian cancer prevention is under investigation. Certain mutations, such as ARID1A mutations, and alterations in the phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR pathway, which are specific in ovarian clear cell carcinoma (OCCC) and endometrioid ovarian carcinoma (EnOC), may offer additional therapeutic targets in these clinical entities. Malignant ovarian germ cell tumors (MOGCTs) are rare and randomized trials are extremely challenging for the improvement of the existing management and development of novel strategies. This review attempts to offer an overview of the main aspects of ovarian cancer, catapulted from the molecular mechanisms to therapeutic considerations.

Drug Targeting of Genomic Instability in Multiple Myeloma

Genomic instability can be observed at both chromosomal and chromatin levels. Instability at the macro level includes centrosome abnormalities (CA) resulting in numerical as well as structural chromosomal changes, whereas instability at the micro level is characterized by defects in DNA repair pathways resulting in microsatellite instability (MIN) or mutations. Genomic instability occurs during carcinogenesis without impairing survival and growth, though the precise mechanisms remain unclear. Solid tumors arising from most cells of epithelial origin are characterized by genomic instability which renders them resistant to chemotherapy and radiotherapy. This instability is also observed in 25% of myeloma patients and has been shown to be highly prognostic, independently of the international staging system (ISS). However, a biomarker of aberrant DNA repair and loss of heterozygosity (LOH), was only observed at a frequency of 5% in newly diagnosed patients. Several new molecules targeting the pathways involved in genomic instability are under development and some have already entered clinical trials. Poly(ADP-ribose) polymerase-1 (PARP) inhibitors have been FDA-approved for the treatment of breast cancer type 1 susceptibility protein (BRCA1)-mutated metastatic breast cancer, as well as ovarian and lung cancer. Topoisomerase inhibitors and epigenetic histone modification-targeting inhibitors, such as HDAC (Histone Deacetylase) inhibitors which are novel agents that can target genomic instability. Several of the small molecule inhibitors targeting chromosomal level instability such as PARP, Akt, Aurora kinase, cyclin dependent kinase or spindle kinase inhibitors have been tested in mouse models and early phase I/II trials. ATM, ATR kinase inhibitors and DNA helicase inhibitors are also promising novel agents. However, most of these drugs are not effective as single agents but appear to act synergistically with DNA damaging agents such as radiotherapy, platinum derivatives, immunomodulators, and proteasome inhibitors. In this review, new drugs targeting genomic instability and their mechanisms of action will be discussed.

Insights into the non-mitotic functions of Aurora kinase A: more than just cell division

AURKA is a serine/threonine kinase overexpressed in several cancers. Originally identified as a protein with multifaceted roles during mitosis, improvements in quantitative microscopy uncovered several non-mitotic roles as well. In physiological conditions, AURKA regulates cilia disassembly, neurite extension, cell motility, DNA replication and senescence programs. In cancer-like contexts, AURKA actively promotes DNA repair, it acts as a transcription factor, promotes cell migration and invasion, and it localises at mitochondria to regulate mitochondrial dynamics and ATP production. Here we review the non-mitotic roles of AURKA, and its partners outside of cell division. In addition, we give an insight into how structural data and quantitative fluorescence microscopy allowed to understand AURKA activation and its interaction with new substrates, highlighting future developments in fluorescence microscopy needed to better understand AURKA functions in vivo. Last, we will recapitulate the most significant AURKA inhibitors currently in clinical trials, and we will explore how the non-mitotic roles of the kinase may provide new insights to ameliorate current pharmacological strategies against AURKA overexpression.

Pharmacological ascorbate induces 'BRCAness' and enhances the effects of Poly(ADP-Ribose) polymerase inhibitors against BRCA1/2 wild-type ovarian cancer

The promise of poly(ADP-ribose) polymerase inhibitors (PARPis) in the management of epithelial ovarian cancer (EOC) is hampered by the limited clinical activity against BRCA wild-type or homologous recombination-proficient EOC. In order to decrease the resistance and increase the efficacy of PARPis, combination treatments of pharmacological ascorbate and PARPis in preclinical BRCA wild-type EOC models were investigated. The cytotoxicity of pharmacological ascorbate, olaparib and veliparib in a panel of BRCA1/2 wild-type EOC cell lines were measured using MTT assays. Poly(ADP-ribose) levels were quantified using chemiluminescent ELISA. The expression of proteins involved in DNA damage and DNA double-strand breaks (DSBs) repair pathways were assessed by western blotting. The in vivo efficacy of pharmacological ascorbate, olaparib and their combination was evaluated in an intraperitoneal xenograft mouse model of BRCA1/2 wild-type EOC. Pharmacological ascorbate induced H₂O₂-dependent cytotoxicity in BRCA1/2 wild-type EOC cells. SHIN3 and OVCAR5 cells were resistant to olaparib and veliparib treatment; however, the combination of ascorbate with olaparib or veliparib significantly enhanced cell death. Pharmacological ascorbate enhanced the effects olaparib or veliparib by downregulating the expression of BRCA1, BRCA2 and RAD51. Consequently, the combination of pharmacological ascorbate and olaparib potently enhanced DNA DSBs and significantly decreased tumor burden, ascites volume and the number of tumor cells in ascites in mice bearing BRCA1/2 wild-type ovarian cancer xenografts. The combination of pharmacological ascorbate and PARPis may be a promising therapeutic approach worth clinical investigation in patients with BRCA wild-type or PARPi-resistant EOC.

Targeting DNA Replication Stress and DNA Double-Strand Break Repair for Optimizing SCLC Treatment

Small cell lung cancer (SCLC), accounting for about 15% of all cases of lung cancer worldwide, is the most lethal form of lung cancer. Despite an initially high response rate of SCLC to standard treatment, almost all patients are invariably relapsed within one year. Effective therapeutic strategies are urgently needed to improve clinical outcomes. Replication stress is a hallmark of SCLC due to several intrinsic factors. As a consequence, constitutive activation of the replication stress response (RSR) pathway and DNA damage repair system is involved in counteracting this genotoxic stress. Therefore, therapeutic targeting of such RSR and DNA damage repair pathways will be likely to kill SCLC cells preferentially and may be exploited in improving chemotherapeutic efficiency through interfering with DNA replication to exert their functions. Here, we summarize potentially valuable targets involved in the RSR and DNA damage repair pathways, rationales for targeting them in SCLC treatment and ongoing clinical trials, as well as possible predictive biomarkers for patient selection in the management of SCLC.

Defining and Modulating 'BRCAness'

The concept of 'BRCAness' defines the pathogenesis and vulnerability of multiple cancers. The canonical definition of BRCAness is a defect in homologous recombination repair, mimicking BRCA1 or BRCA2 loss. In turn, BRCA-deficient cells utilize error-prone DNA-repair pathways, causing increased genomic instability, which may be responsible for their sensitivity to DNA damaging agents and poly-(ADP)-ribose polymerase inhibitors (PARPis). However, recent work has expanded the mechanistic basis of BRCAness, to include defects in replication fork protection (RFP). Here, we broaden the definition of BRCAness to include RFP and regulatory mechanisms that cause synthetic lethality with PARPis. We highlight these recent discoveries, which include mechanisms of RFP regulation, DNA damage checkpoint proteins, as well as kinases that regulate BRCA1/2 function. Importantly, many of these emerging mechanisms may be targeted for inhibition with small molecule inhibitors, thus inducing BRCAness in a much larger subset of BRCA-proficient tumors, with significant translational potential.

Expression of RRBP1 in epithelial ovarian cancer and its clinical significance

Hematopoietic pre-B cell leukemia transcription factor (PBX)-interacting protein (RRBP1) has been shown to participate in various aspects of malignancies. The clinical significance of RRBP1 and its involvement in the epithelial ovarian cancer have yet to be studied. The aim of the present study was to investigate the expression of RRBP1 in epithelial ovarian cancer (EOC) and its relationship with clinical characteristics and prognosis. We evaluated the mRNA and protein expression levels of RRBP1 by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (n=45). Immunohistochemistry and data analysis were used to examine the relationship between the expression level of RRBP1 and the clinicopathological features and prognosis of epithelial ovarian cancer. RRBP1 was highly expressed in EOC (P<0.001). The specimens were obtained from 108 patients undergoing surgery to treat epithelial ovarian cancer. RRBP1 expression was obviously related to Federation International of Gynecologie and Obstetrigue (FIGO) stage (P<0.001), histological grade (P=0.021), histological type (P=0.004), and lymph node metastasis (P=0.012) but was not related to patient age (P=0.385) or preoperative carbohydrate antigen125 (CA125) level (P=0.238). Univariate analysis showed that the prognosis of the epithelial ovarian cancer patients was related to the age of the patients, the FIGO stage, and the expression level of RRBP1 (P<0.05). Patients with higher RRBP1 expression had significantly worse overall survival (OS) (P=0.003) and disease-free survival (DFS) (P<0.001). Multivariate survival analysis proved that RRBP1 was an independent predictor of OS (P=0.003) and DFS (P<0.001). RRBP1 plays an important role in predicting the prognosis of EOC. These results show that RRBP1 is a potential target for the treatment of epithelial ovarian cancer.

A new role for Drosophila Aurora-A in maintaining chromosome integrity

Aurora-A is a conserved mitotic kinase overexpressed in many types of cancer. Growing evidence shows that Aurora-A plays a crucial role in DNA damage response (DDR) although this aspect has been less characterized. We isolated a new aur-A mutation, named aur-A⁹⁴⁹, in Drosophila, and we showed that it causes chromosome aberrations (CABs). In addition, aur-A⁹⁴⁹ mutants were sensitive to X-ray treatment and showed impaired γ-H2Av foci dissolution kinetics. To identify the pathway in which Aur-A works, we conducted an epistasis analysis by evaluating CAB frequencies in double mutants carrying aur-A⁹⁴⁹ mutation combined to mutations in genes related to DNA damage response (DDR). We found that mutations in tefu (ATM) and in the histone variant H2Av were epistatic over aur-A⁹⁴⁹ indicating that Aur-A works in DDR and that it is required for γ-H2Av foci dissolution. More interestingly, we found that a mutation in lig4, a gene belonging to the non-homologous end joining (NHEJ) repair pathway, was epistatic over aur-A⁹⁴⁹. Based on studies in other systems, which show that phosphorylation is important to target Lig4 for degradation, we hypothesized that in aur-A⁹⁴⁹ mutant cells, there is a persistence of Lig4 that could be, in the end, responsible for CABs. Finally, we observed a synergistic interaction between Aur-A and the homologous recombination (HR) repair system component Rad 51 in the process that converts chromatid deletions into isochromatid deletions. Altogether, these data indicate that Aur-A depletion can elicit chromosome damage. This conclusion should be taken into consideration, since some anticancer therapies are aimed at reducing Aurora-A expression.

Identifying genes as potential prognostic indicators in patients with serous ovarian cancer resistant to carboplatin using integrated bioinformatics analysis

Serous ovarian cancer (SOC) accounts for >50% of all epithelial ovarian cancers. However, patients with SOC present with various degrees of response to platinum‑based chemotherapy and, thus, their survival may differ. The present study aimed to identify the candidate genes involved in the carcinogenesis and drug resistance of SOC by analyzing the microarray datasets GDS1381 and GDS3592. GDS1381 and GDS3592 were downloaded from the Gene Expression Omnibus database (https://www.ncbi.nlm.nih.gov/gds/). A total of 219 differentially expressed genes (DEGs) were identified. Potential genes that may predict the response to carboplatin and, thus, the prognosis of SOC were analyzed. The enriched functions and pathways of DEGs included extracellular region, extracellular space and extracellular exosome, among others. Upon screening the upregulated and downregulated genes on the connectivity map, 10 small‑molecule drugs were identified that may be helpful in improving drug sensitivity in patients with ovarian cancer. A total of 30 hub genes were screened for further analysis after constructing the protein‑to‑protein interaction network. Through survival analysis, comparison of genes across numerous analyses, and immunohistochemistry, GNAI1, non‑structural maintenance of chromosomes (non‑SMC) condensin I complex subunit H (NCAPH), matrix metallopeptidase 9 (MMP9), aurora kinase A (AURKA) and enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) were identified as the key molecules that may be involved in the carcinogenesis and carboplatin resistance of SOC. In conclusion, GNAI1, NCAPH, MMP9, AURKA and EZH2 should be examined in further studies for the possibility of their participation in the carcinogenesis and carboplatin response of SOC.

The BET inhibitor INCB054329 reduces homologous recombination efficiency and augments PARP inhibitor activity in ovarian cancer

OBJECTIVE

Homologous recombination (HR)-proficient ovarian tumors have poorer clinical outcomes and show resistance to poly ADP ribose polymerase inhibitors (PARPi). A subset of HR-proficient ovarian tumors show amplification in bromodomain and extra-terminal (BET) genes such as BRD4. We aimed to test the hypothesis that BRD4 inhibition sensitizes ovarian cancer cells to PARPi by reducing HR efficiency and increasing DNA damage.

METHODS

HR-proficient ovarian cancer cell lines (OVCAR-3, OVCAR-4, SKOV-3, UWB1.289+BRCA1) were treated with BRD4-targeting siRNA, novel (INB054329, INCB057643) and established (JQ1) BET inhibitors (BETi) and PARPi (olaparib, rucaparib). Cell growth and viability were assessed by sulforhodamine B assays in vitro, and in SKOV-3 and ovarian cancer patient-derived xenografts in vivo. DNA damage and repair (pH2AX, RAD51 and BRCA1 foci formation, and DRGFP HR reporter activity), apoptosis markers (cleaved PARP, cleaved caspase-3, Bax) and proliferation markers (PCNA, Ki67) were assessed by immunofluorescence and western blot.

RESULTS

In cultured cells, inhibition of BRD4 by siRNA or INCB054329 reduced expression and function of BRCA1 and RAD51, reduced HR reporter activity, and sensitized the cells to olaparib-induced growth inhibition, DNA damage induction and apoptosis. Synergy was observed between all BETi tested and PARPi. INCB054329 and olaparib also co-operatively inhibited xenograft tumor growth, accompanied by reduced BRCA1 expression and proliferation, and increased apoptosis and DNA damage.

CONCLUSIONS

These results provide strong rationale for using BETi to extend therapeutic efficacy of PARPi to HR-proficient ovarian tumors and could benefit a substantial number of women diagnosed with this devastating disease.

Developing a genetic signature to predict drug response in ovarian cancer

There is a lack of personalized treatment options for women with recurrent platinum-resistant ovarian cancer. Outside of bevacizumab and a group of poly ADP-ribose polymerase inhibitors, few options are available to women that relapse. We propose that efficacious drug combinations can be determined via molecular characterization of ovarian tumors along with pre-established pharmacogenomic profiles of repurposed compounds. To that end, we selectively performed multiple two-drug combination treatments in ovarian cancer cell lines that included reactive oxygen species inducers and HSP90 inhibitors. This allowed us to select cell lines that exhibit disparate phenotypes of proliferative inhibition to a specific drug combination of auranofin and AUY922. We profiled altered mechanistic responses from these agents in both reactive oxygen species and HSP90 pathways, as well as investigated PRKCI and lncRNA expression in ovarian cancer cell line models. Generation of dual multi-gene panels implicated in resistance or sensitivity to this drug combination was produced using RNA sequencing data and the validity of the resistant signature was examined using high-density RT-qPCR. Finally, data mining for the prevalence of these signatures in a large-scale clinical study alluded to the prevalence of resistant genes in ovarian tumor biology. Our results demonstrate that high-throughput viability screens paired with reliable in silico data can promote the discovery of effective, personalized therapeutic options for a currently untreatable disease.