Aurora-A kinase is essential for bipolar spindle formation and early development

SOX9 is regulated by AURKA in response to Helicobacter pylori infection via EIF4E-mediated cap-dependent translation

Helicobacter pylori (H. pylori) infection is the main risk factor for gastric cancer. The SRY-Box Transcription Factor 9 (SOX9) serves as a marker of stomach stem cells. We detected strong associations between AURKA and SOX9 expression levels in gastric cancers. Utilizing in vitro and in vivo mouse models, we demonstrated that H. pylori infection induced elevated levels of both AURKA and SOX9 proteins. Notably, the SOX9 protein and transcription activity levels were dependent on AURKA expression. AURKA knockdown led to a reduction in the number and size of gastric gland organoids. Conditional knockout of AURKA in mice resulted in a decrease in SOX9 baseline level in AURKA-knockout gastric glands, accompanied by diminished SOX9 induction following H. pylori infection. We found an AURKA-dependent increase in EIF4E and cap-dependent translation with an AURKA-EIF4E-dependent increase in SOX9 polysomal RNA levels. Immunoprecipitation assays demonstrated binding of AURKA to EIF4E with a decrease in EIF4E ubiquitination. Immunohistochemistry analysis on tissue arrays revealed moderate to strong immunostaining of AURKA and SOX9 with a significant correlation in gastric cancer tissues. These findings elucidate the mechanistic role of AURKA in regulating SOX9 levels via cap-dependent translation in response to H. pylori infection in gastric tumorigenesis.

Deletion of Aurora kinase A prevents the development of polycystic kidney disease in mice

Aurora Kinase A (AURKA) promotes cell proliferation and is overexpressed in different types of polycystic kidney disease (PKD). To understand AURKA's role in regulating renal cyst development we conditionally deleted the gene in mouse models of Autosomal Dominant PKD (ADPKD) and Joubert Syndrome, caused by Polycystin 1 (Pkd1) and Inositol polyphosphate-5-phosphatase E (Inpp5e) mutations respectively. We show that while Aurka is dispensable for collecting duct development and homeostasis, its deletion prevents cyst formation in both disease models. Cross-comparison of transcriptional changes implicated AKT signaling in cyst prevention and we show that (i) AURKA and AKT physically interact, (ii) AURKA regulates AKT activity in a kinase-independent manner and (iii) inhibition of AKT can reduce disease severity. AKT activation also regulates Aurka expression, creating a feed-forward loop driving renal cystogenesis. We find that the AURKA kinase inhibitor Alisertib stabilises the AURKA protein, agonizing its cystogenic functions. These studies identify AURKA as a master regulator of renal cyst development in different types of PKD, functioning in-part via AKT.

Pentagamavunone-1 inhibits aggressive breast cancer cell proliferation through mitotic catastrophe and ROS-mediated activities: in vitro and in vivo studies

Pentagamavunone-1 (PGV-1), an analog of curcumin, has been studied for its cytotoxic effects in 4T1, MCF7, MCF7/HER2, and T47D breast cancer cells. Its antiproliferative effect is partly mediated through G2/M arrest; however, its molecular mechanism during cell cycle progression remains unknown. In this study, we aimed to determine whether PGV-1 has any anticancer effects on highly aggressive breast cancer cells, with a focus on cell cycle regulatory activity, reactive oxygen species (ROS) generation, and their mediated effects on cancer cells. MDA-MB-231 (triple-negative) and HCC1954 (overexpressed HER2) immortalized human breast cancer cells were used in the study. PGV-1 exhibited cytotoxic activity with an irreversible antiproliferative impact on treated cells and had good selectivity when tested in fibroblast cells. Oral PGV-1 administration suppressed tumor growth in a cell-derived xenograft mouse model. PGV-1 induced the phosphorylation of Aurora A kinase and PLK1 in MDA-MB-231 cells, while PLK1 and cyclin B1 phosphorylation were enhanced in the PGV-1-treated HCC1954 cells during prometaphase arrest. Intracellular ROS production was substantially higher upon PGV-1 treatment following mitotic arrest, and this activity caused impairment of mitochondrial respiration, induced senescence, and subsequently triggered early-to-late apoptosis. Collectively, these results suggest that the molecular mechanism of PGV-1 involves the regulation of mitotic kinases to cause cell cycle arrest and the enhancement of ROS production to impair mitochondrial activity and induce cellular senescence. The therapeutic activities demonstrated by PGV-1 in this study show its potential as an appealing candidate for chemotherapy in breast cancer treatment.

An emerging biomarker for the diagnosis and treatment of esophageal squamous cell carcinoma - Aurora A

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a prominent form of esophageal cancer. Aurora A (AURKA), an enzyme that phosphorylates serine and threonine, has a vital function in controlling the process of separating chromosomes during cell division. The contribution of this entity has been documented in the advancement of malignant proliferations, including tumors occurring in the breast, stomach, and ovaries.

METHODS

The potential molecular mechanism of AURKA is comprehensively examined through the analysis of bulk RNA-seq and single-cell RNA-seq data obtained from publicly available databases. This analysis encompasses various aspects such as expression levels, prognosis, and functional pathways, among others.

RESULTS

The upregulation of AURKA in ESCC has been found to be correlated with the overall survival of patients. The functional annotation and pathway enrichment analysis conducted in this study lead to the conclusion that AURKA participates in the regulation of a number of malignant processes connected to cell proliferation, such as cell cycle control, apoptosis, and the p53 signaling pathway. Additionally, AURKA has been found to be associated with drug sensitivity and has an impact on the infiltration of tumor-infiltrating immune cells in ESCC.

CONCLUSIONS

AURKA exhibits potential as a prognostic and therapeutic biomarker linked to the regulation of cell cycle and cell proliferation.

Single-cell profiling of Anopheles gambiae spermatogenesis defines the onset of meiotic silencing and premeiotic overexpression of the X chromosome

Understanding development and genetic regulation in the Anopheles gambiae germline is essential to engineer effective genetic control strategies targeting this malaria mosquito vector. These include targeting the germline to induce sterility or using regulatory sequences to drive transgene expression for applications such as gene drive. However, only very few germline-specific regulatory elements have been characterised with the majority showing leaky expression. This has been shown to considerably reduce the efficiency of current genetic control strategies, which rely on regulatory elements with more tightly restricted spatial and/or temporal expression. Meiotic silencing of the sex chromosomes limits the flexibility of transgene expression to develop effective sex-linked genetic control strategies. Here, we build on our previous study, dissecting gametogenesis into four distinct cell populations, using single-cell RNA sequencing to define eight distinct cell clusters and associated germline cell-types using available marker genes. We reveal overexpression of X-linked genes in a distinct cluster of pre-meiotic cells and document the onset of meiotic silencing of the X chromosome in a subcluster of cells in the latter stages of spermatogenesis. This study provides a comprehensive dataset, characterising the expression of distinct cell types through spermatogenesis and widening the toolkit for genetic control of malaria mosquitoes.

A phase I dose escalation, dose expansion and pharmacokinetic trial of gemcitabine and alisertib in advanced solid tumors and pancreatic cancer

PURPOSE

Aurora Kinase A (AKA) inhibition with gemcitabine represents a potentially synergistic cancer treatment strategy via mitotic catastrophe. The feasibility, safety, and preliminary efficacy of alisertib (MLN8237), an oral AKA inhibitor, with gemcitabine was evaluated in this open-label phase I trial with dose escalation and expansion.

METHODS

Key inclusion criteria included advanced solid tumor with any number of prior chemotherapy regimens in the dose escalation phase, and advanced pancreatic adenocarcinoma with up to two prior chemotherapy regimens. Four dose levels (DLs 1-4) of alisertib (20, 30, 40, or 50 mg) were evaluated in 3 + 3 design with gemcitabine 1000 mg/m² on days 1, 8, and 15 in 28-day cycles.

RESULTS

In total, 21 subjects were treated in dose escalation and 5 subjects were treated in dose expansion at DL4. Dose-limiting toxicities were observed in 1 of 6 subjects each in DL3 and DL4. All subjects experienced treatment-related adverse events. Grade ≥ 3 treatment-related adverse events were observed in 73% of subjects, with neutropenia observed in 54%. Out of 22 subjects evaluable for response, 2 subjects (9%) had partial response and 14 subjects (64%) had stable disease. Median PFS was 4.1 months (95% CI 2.1-4.5). No significant changes in pharmacokinetic parameters for gemcitabine or its metabolite dFdU were observed with alisertib co-administration.

CONCLUSIONS

This trial established the recommended phase 2 dose of alisertib 50 mg to be combined with gemcitabine. Gemcitabine and alisertib are a feasible strategy with potential for disease control in multiple heavily pre-treated tumors, though gastrointestinal and hematologic toxicity was apparent.

WDR62 variants contribute to congenital heart disease by inhibiting cardiomyocyte proliferation

Background

Congenital heart disease (CHD) is the most common birth defect and has high heritability. Although some susceptibility genes have been identified, the genetic basis underlying the majority of CHD cases is still undefined.

Methods

A total of 1320 unrelated CHD patients were enrolled in our study. Exome‐wide association analysis between 37 tetralogy of Fallot (TOF) patients and 208 Han Chinese controls from the 1000 Genomes Project was performed to identify the novel candidate gene WD repeat‐containing protein 62 (WDR62). WDR62 variants were searched in another expanded set of 200 TOF patients by Sanger sequencing. Rescue experiments in zebrafish were conducted to observe the effects of WDR62 variants. The roles of WDR62 in heart development were examined in mouse models with Wdr62 deficiency. WDR62 variants were investigated in an additional 1083 CHD patients with similar heart phenotypes to knockout mice by multiplex PCR‐targeting sequencing. The cellular phenotypes of WDR62 deficiency and variants were tested in cardiomyocytes, and the molecular mechanisms were preliminarily explored by RNA‐seq and co‐immunoprecipitation.

Results

Seven WDR62 coding variants were identified in the 237 TOF patients and all were indicated to be loss of function variants. A total of 25 coding and 22 non‐coding WDR62 variants were identified in 80 (6%) of the 1320 CHD cases sequenced, with a higher proportion of WDR62 variation (8%) found in the ventricular septal defect (VSD) cohort. WDR62 deficiency resulted in a series of heart defects affecting the outflow tract and right ventricle in mouse models, including VSD as the major abnormality. Cell cycle arrest and an increased number of cells with multipolar spindles that inhibited proliferation were observed in cardiomyocytes with variants or knockdown of WDR62. WDR62 deficiency weakened the association between WDR62 and the cell cycle‐regulated kinase AURKA on spindle poles, reduced the phosphorylation of AURKA, and decreased expression of target genes related to cell cycle and spindle assembly shared by WDR62 and AURKA.

Conclusions

WDR62 was identified as a novel susceptibility gene for CHD with high variant frequency. WDR62 was shown to participate in the cardiac development by affecting spindle assembly and cell cycle pathway in cardiomyocytes.

Identification and Characterization of Natural and Semisynthetic Quinones as Aurora Kinase Inhibitors

Aurora kinases (Aurora A, B, and C) are a family of serine/threonine kinases that play critical roles during mitotic initiation and progression. Aurora A and B kinases are ubiquitously expressed, and their overexpression and/or amplification in many cancers have been associated with poor prognosis. Several inhibitors that target Aurora kinases A, B, or both have been developed during the past decade with efficacy in different in vitro and in vivo models for a variety of cancers. Recent studies have also identified Aurora A as a synthetic lethal target for different tumor suppressors, including RB1, SMARCA4, and ARID1A, which signifies the need for Aurora-A-selective inhibitors. Here, we report the screening of a small library of quinones (nine naphthoquinones, one orthoquinone, and one anthraquinone) in a biochemical assay for Aurora A kinase that resulted in the identification of several quinones as inhibitors. IC₅₀ determination against Aurora A and B kinases revealed the inhibition of both kinases with selectivity toward Aurora A. Two of the compounds, natural quinone naphthazarin (1) and a pseudo anthraquinone, 2-(chloromethyl)quinizarin (11), potently inhibited the proliferation of various cancer cell lines with IC₅₀ values ranging from 0.16 ± 0.15 to 1.7 ± 0.06 and 0.15 ± 0.04 to 6.3 ± 1.8 μM, respectively. Treatment of cancer cells with these compounds for 24 h resulted in abrogated mitosis and apoptotic cell death. Direct binding of both the compounds with Aurora A kinase was also confirmed through STD NMR analysis. Docking studies predicted the binding of both compounds to the ATP binding pocket of Aurora A kinase. We have, therefore, identified quinones as Aurora kinase inhibitors that can serve as a lead for future drug discovery endeavors.

Aurora kinase genetic polymorphisms: an association study in Down syndrome and spontaneous abortion

Aneuploidies, such as Down syndrome (DS), are the leading cause of pregnancy loss. Abnormalities in aurora kinase proteins result in genomic instability and aneuploidy, mainly in tumors. Thus, polymorphisms in Aurora kinase genes could influence the occurrence of DS and spontaneous abortion. A case-control study was conducted including 124 mothers of DS children (DSM) and 219 control mothers (CM) to investigate DS risk according to AURKA and AURKC polymorphisms. Genotyping was performed using TaqMan real-time PCR. The minor allele frequency (MAF) observed in AURKA rs2273535 was, respectively, 0.23 in DSM and 0.20 in CM, whereas the frequency of the AURKC rs758099 T allele was 0.32 in case and 0.33 in control mothers. Statistical analysis showed no significant difference in the distribution of genotypes and allele frequencies between DSM and CM. According to previous history of spontaneous abortion, the AURKA rs2273535 genotypes (TT + AT vs. AA: OR 2.54, 95% CI 1.13-5.71, p = 0.02; AT vs. AA: OR 2.39, 95% CI 1.03-5.51, p = 0.04; T vs. A: OR 2.08, 95% CI 1.12-3.90, p = 0.02) and AURKC rs758099 (TT vs. CC: OR 4.34, 95% CI 1.03-18.02, p = 0.04; TT + CT vs. CC: OR 2.52, 95% CI 1.02-6.23, p = 0.04; T vs. C: OR 2.03, 95% CI 1.09-3.80, p = 0.02) were observed as risk factors for spontaneous abortion in case mothers. Our study suggests a possible relationship between AURKA/AURKC variants and increased risk of spontaneous abortion within Down syndrome mothers.

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.

Mammalian SWI/SNF chromatin remodeler is essential for reductional meiosis in males

The mammalian SWI/SNF nucleosome remodeler is essential for spermatogenesis. Here, we identify a role for ARID2, a PBAF (Polybromo - Brg1 Associated Factor)-specific subunit, in meiotic division. Arid2cKO spermatocytes arrest at metaphase-I and are deficient in spindle assembly, kinetochore-associated Polo-like kinase1 (PLK1), and centromeric targeting of Histone H3 threonine3 phosphorylation (H3T3P) and Histone H2A threonine120 phosphorylation (H2AT120P). By determining ARID2 and BRG1 genomic associations, we show that PBAF localizes to centromeres and promoters of genes known to govern spindle assembly and nuclear division in spermatocytes. Consistent with gene ontology of target genes, we also identify a role for ARID2 in centrosome stability. Additionally, misexpression of genes such as Aurkc and Ppp1cc (Pp1γ), known to govern chromosome segregation, potentially compromises the function of the chromosome passenger complex (CPC) and deposition of H3T3P, respectively. Our data support a model where-in PBAF activates genes essential for meiotic cell division.

Effects of Aurora kinase A on mouse decidualization via Stat3-plk1-cdk1 pathway

BACKGROUND

Decidualization is essential to the successful pregnancy in mice. The molecular mechanisms and effects of Aurora kinase A (Aurora A) remain poorly understood during pregnancy. This study is the first to investigate the expression and role of Aurora A during mouse decidualization.

METHODS

Quantitative real time polymerase chain reaction, western blotting and in situ hybridization were used to determine the expression of Aurora A in mouse uteri. Aurora A activity was inhibited by Aurora A inhibitor to explore the role of Aurora A on decidualization via regulating the Aurora A/Stat3/Plk1/Cdk1 signaling pathway.

RESULTS

Aurora A was strongly expressed at implantation sites compared with inter-implantation sites. Furthermore, Aurora A was also significantly increased in oil-induced deciduoma compared with control. Both Aurora A mRNA and protein were significantly increased under in vitro decidualization. Under in vitro decidualization, Prl8a2, a marker of mouse decidualization, was significantly decreased by TC-S 7010, an Aurora A inhibitor. Additionally, Prl8a2 was reduced by Stat3 inhibitor, Plk1 inhibitor and Cdk1 inhibitor, respectively. Moreover, the protein levels of p-Stat3, p-Plk1 and p-Cdk1 were suppressed by TC-S 7010. The protein levels of p-Stat3, p-Plk1 and p-Cdk1 were also suppressed by S3I-201, a Stat3 inhibitor). SBE 13 HCl (Plk1 inhibitor) could reduce the protein levels of p-Plk1 and p-Cdk1. Collectively, Aurora A could regulate Stat3/Plk1/Cdk1 signaling pathway.

CONCLUSION

Our study shows that Aurora A is expressed in decidual cells and should be important for mouse decidualization. Aurora A/Stat3/Plk1/Cdk1 signaling pathway may be involved in mouse decidualization.

Aurora a kinase (AURKA) is required for male germline maintenance and regulates sperm motility in the mouse

Aurora A kinase (AURKA) is an important regulator of cell division and is required for assembly of the mitotic spindle. We recently reported the unusual finding that this mitotic kinase is also found on the sperm flagellum. To determine its requirement in spermatogenesis, we generated conditional knockout animals with deletion of the Aurka gene in either spermatogonia or spermatocytes to assess its role in mitotic and postmitotic cells, respectively. Deletion of Aurka in spermatogonia resulted in disappearance of all developing germ cells in the testis, as expected given its vital role in mitotic cell division. Deletion of Aurka in spermatocytes reduced testis size, sperm count, and fertility, indicating disruption of meiosis or an effect on spermiogenesis in developing mice. Interestingly, deletion of Aurka in spermatocytes increased apoptosis in spermatocytes along with an increase in the percentage of sperm with abnormal morphology. Despite the increase in abnormal sperm, sperm from spermatocyte Aurka knockout mice displayed increased progressive motility. In addition, sperm lysate prepared from Aurka knockout animals had decreased protein phosphatase 1 (PP1) activity. Together, our results show that AURKA plays multiple roles in spermatogenesis, from mitotic divisions of spermatogonia to sperm morphology and motility.

SUMO proteases SENP3 and SENP5 spatiotemporally regulate the kinase activity of Aurora A

Precise chromosome segregation is mediated by a well-assembled mitotic spindle, which requires balance of the kinase activity of Aurora A (AurA, also known as AURKA). However, how this kinase activity is regulated remains largely unclear. Here, using in vivo and in vitro assays, we report that conjugation of SUMO2 with AurA at K258 in early mitosis promotes the kinase activity of AurA and facilitates the binding with its activator Bora. Knockdown of the SUMO proteases SENP3 and SENP5 disrupts the deSUMOylation of AurA, leading to increased kinase activity and abnormalities in spindle assembly and chromosome segregation, which could be rescued by suppressing the kinase activity of AurA. Collectively, these results demonstrate that SENP3 and SENP5 deSUMOylate AurA to render spatiotemporal control on its kinase activity in mitosis. This article has an associated First Person interview with the first author of the paper.

Aurora kinase A is essential for meiosis in mouse oocytes

The Aurora protein kinases are well-established regulators of spindle building and chromosome segregation in mitotic and meiotic cells. In mouse oocytes, there is significant Aurora kinase A (AURKA) compensatory abilities when the other Aurora kinase homologs are deleted. Whether the other homologs, AURKB or AURKC can compensate for loss of AURKA is not known. Using a conditional mouse oocyte knockout model, we demonstrate that this compensation is not reciprocal because female oocyte-specific knockout mice are sterile, and their oocytes fail to complete meiosis I. In determining AURKA-specific functions, we demonstrate that its first meiotic requirement is to activate Polo-like kinase 1 at acentriolar microtubule organizing centers (aMTOCs; meiotic spindle poles). This activation induces fragmentation of the aMTOCs, a step essential for building a bipolar spindle. We also show that AURKA is required for regulating localization of TACC3, another protein required for spindle building. We conclude that AURKA has multiple functions essential to completing MI that are distinct from AURKB and AURKC.

Hyaluronan-Mediated Motility Receptor Governs Chromosome Segregation by Regulating Microtubules Sliding Within the Bridging Fiber

Accurate segregation of chromosomes during anaphase relies on the central spindle and its regulators. A newly raised concept of the central spindle, the bridging fiber, shows that sliding of antiparallel microtubules (MTs) within the bridging fiber promotes chromosome segregation. However, the regulators of the bridging fiber and its regulatory mechanism on MTs sliding remain largely unknown. In this study, the non-motor microtubule-associated protein, hyaluronan-mediated motility receptor (HMMR), is identified as a novel regulator of the bridging fiber. It then identifies that HMMR regulates MTs sliding within the bridging fiber by cooperating with its binding partner HSET. By utilizing a laser-based cell ablation system and photoactivation approach, the study's results reveal that depletion of HMMR causes an inhibitory effect on MTs sliding within the bridging fiber and disrupts the forced uniformity on the kinetochore-attached microtubules-formed fibers (k-fibers). These are created by suppressing the dynamics of HSET, which functions in transiting the force from sliding of bridging MTs to the k-fiber. This study sheds new light on the novel regulatory mechanism of MTs sliding within the bridging fiber by HMMR and HSET and uncovers the role of HMMR in chromosome segregation during anaphase.

Alisertib inhibits migration and invasion of EGFR-TKI resistant cells by partially reversing the epithelial-mesenchymal transition

Epithelial growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been widely used in the clinical treatment of non-small cell lung cancer (NSCLC) patients with EGFR mutations. Previous studies have shown that Aurora kinase A (AURKA) is overexpressed in a broad spectrum of cancer cells, which can induce epithelial-mesenchymal transition (EMT) and contribute to the occurrence of acquired EGFR-TKI resistance. However, whether the inhibition of AURKA could overcome EGFR-TKI resistance or reverse the EMT in TKI-resistant NSCLC cells remains unclear. In the current study, we established three EGFR-TKI-resistant cell lines and analyzed their expression profiles by RNA sequencing. The results revealed that the EMT pathway is significantly upregulated in the three cell lines with EGFR-TKI resistance. The phosphorylation of AURKA at Thr 288 was also upregulated, suggesting that the activation of AURKA plays an important role in the occurrence of EGFR-TKI resistance. Interestingly, the AURKA inhibitor, alisertib treatment restored the susceptibility of resistant cells to EGFR-TKIs and partially reversed the EMT process, thereby reducing migration and invasion in EGFR-TKI-resistant cells. This study provides evidence that targeting AURKA signaling pathway by alisertib may be a novel approach for overcoming EGFR-TKI resistance and for the treatment of metastatic EGFR-TKIs in NSCLC patients.

CEP55 promotes cilia disassembly through stabilizing Aurora A kinase

Primary cilia protrude from the cell surface and have diverse roles during development and disease, which depends on the precise timing and control of cilia assembly and disassembly. Inactivation of assembly often causes cilia defects and underlies ciliopathy, while diseases caused by dysfunction in disassembly remain largely unknown. Here, we demonstrate that CEP55 functions as a cilia disassembly regulator to participate in ciliopathy. Cep55-/- mice display clinical manifestations of Meckel-Gruber syndrome, including perinatal death, polycystic kidneys, and abnormalities in the CNS. Interestingly, Cep55-/- mice exhibit an abnormal elongation of cilia on these tissues. Mechanistically, CEP55 promotes cilia disassembly by interacting with and stabilizing Aurora A kinase, which is achieved through facilitating the chaperonin CCT complex to Aurora A. In addition, CEP55 mutation in Meckel-Gruber syndrome causes the failure of cilia disassembly. Thus, our study establishes a cilia disassembly role for CEP55 in vivo, coupling defects in cilia disassembly to ciliopathy and further suggesting that proper cilia dynamics are critical for mammalian development.

CRISPR/Cas9 screening identifies a kinetochore-microtubule dependent mechanism for Aurora-A inhibitor resistance in breast cancer

Background

Overexpression of Aurora‐A (AURKA) is a feature of breast cancer and associates with adverse prognosis. The selective Aurora‐A inhibitor alisertib (MLN8237) has recently demonstrated promising antitumor responses as a single agent in various cancer types but its phase III clinical trial was reported as a failure since MLN8237 did not show an apparent effect in prolonging the survival of patients. Thus, identification of potential targets that could enhance the activity of MLN8237 would provide a rationale for drug combination to achieve better therapeutic outcome.

Methods

Here, we conducted a systematic synthetic lethality CRISPR/Cas9 screening of 507 kinases using MLN8237 in breast cancer cells and identified a number of targetable kinases that displayed synthetic lethality interactions with MLN8237. Then, we performed competitive growth assays, colony formation assays, cell viability assays, apoptosis assays, and xenograft murine model to evaluate the synergistic therapeutic effects of Haspin (GSG2) depletion or inhibition with MLN8237. For mechanistic studies, immunofluorescence was used to detect the state of microtubules and the localization of Aurora‐B and mitotic centromere‐associated kinesin (MCAK).

Results

Among the hits, we observed that Haspin depletion or inhibition marginally inhibited breast cancer cell growth but could substantially enhance the killing effects of MLN8237. Mechanistic studies showed that co‐treatment with Aurora‐A and Haspin inhibitors abolished the recruitment of Aurora‐B and mitotic centromere‐associated kinesin (MCAK) to centromeres which were associated with excessive microtubule depolymerization, kinetochore‐microtubule (KT‐MT) attachment failure, and severe mitotic catastrophe. We further showed that the combination of MLN8237 and the Haspin inhibitor CHR‐6494 synergistically reduced breast cancer cell viability and significantly inhibited both in vitro and in vivo tumor growth.

Conclusions

These findings establish Haspin as a synthetic lethal target and demonstrate CHR‐6494 as a potential combinational drug for promoting the therapeutic effects of MLN8237 on breast cancer.

DNA-PKcs inhibition impairs HDAC6-mediated HSP90 chaperone function on Aurora A and enhances HDACs inhibitor-induced cell killing by increasing mitotic aberrant spindle assembly

Combining targeted therapeutic agents is an attractive cancer treatment strategy associated with high efficacy and low toxicity. DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is an essential factor in DNA damage repair. Studies from us and others have revealed that DNA-PKcs also plays an important role in normal mitosis progression. Histone deacetylase (HDACs) inhibitors commonly lead to mitotic aberration and have been approved for treating various cancers in the clinic. We showed that DNA-PKcs depletion or kinase activity inhibition increases cancer cells' sensitivity to HDACs inhibitors in vitro and in vivo. DNA-PKcs deficiency significantly enhances HDACs inhibitors (HDACi)-induced mitotic arrest and is followed by apoptotic cell death. Mechanistically, we found that DNA-PKcs binds to HDAC6 and facilitates its acetylase activity. HDACi is more likely to impair HDAC6-induced deacetylation of HSP90 and abrogate HSP90's chaperone function on Aurora A, a critical mitotic kinase that regulates centrosome separation and mitotic spindle assembly in DNA-PKcs-deficient cells. Our current work indicates crosstalk between DNA-PKcs and HDACs signaling pathways, and highlights that the combined targeting of DNA-PKcs and HDACs can be used in cancer therapy. Abbreviations: DNA-PKcs, DNA-dependent protein kinase catalytic subunit, HDACs, Histone deacetylases, DSBs, DNA double-strand breaks, ATM, ataxia telangiectasia mutated, ATR, ATM-Rad3-related.

A first-in-human phase 1 and pharmacological study of TAS-119, a novel selective Aurora A kinase inhibitor in patients with advanced solid tumours

Background

This is a first-in-human study with TAS-119, an Aurora A kinase (AurA) inhibitor.

Methods

Patients with advanced, refractory, solid tumours were enrolled into 5 dose escalation cohorts (70–300 mg BID, 4 days on/3 days off, 3 out of 4 weeks or 4 out of 4 weeks). The expansion part consisted of patients with small-cell lung cancer, HER2-negative breast cancer, MYC-amplified/β-catenin-mutated (MT) tumours or other (basket cohort).

Results

In the escalation part (n = 34 patients), dose-limiting toxicities were one grade 3 nausea, two grade 2 and one grade 3 ocular toxicity and a combination of fatigue, ocular toxicity and nausea in one patient (all grade 2) at dose levels of 150, 200, 250 and 300 mg, respectively. Most frequent treatment-related adverse events were fatigue (32%), diarrhoea (24%) and ocular toxicity (24%). Toxicity grade ≥3 in ≥10% of patients were diarrhoea (15%) and increased lipase (12%). The maximum tolerated dose was 250 mg BID. Due to one additional grade 1 ocular toxicity, the RP2D was set at 200 mg BID (4 days on/3 days off, 3 out of 4 weeks), which was further explored in the expansion part (n = 40 patients). Target inhibition in paired skin biopsies was shown.

Conclusions

TAS-119 has a favourable and remarkably distinct safety profile from other AurA inhibitors.

Clinical trial registration

NCT02448589.

Principal Postulates of Centrosomal Biology. Version 2020

The centrosome, which consists of two centrioles surrounded by pericentriolar material, is a unique structure that has retained its main features in organisms of various taxonomic groups from unicellular algae to mammals over one billion years of evolution. In addition to the most noticeable function of organizing the microtubule system in mitosis and interphase, the centrosome performs many other cell functions. In particular, centrioles are the basis for the formation of sensitive primary cilia and motile cilia and flagella. Another principal function of centrosomes is the concentration in one place of regulatory proteins responsible for the cell's progression along the cell cycle. Despite the existing exceptions, the functioning of the centrosome is subject to general principles, which are discussed in this review.

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 A inhibition disrupts chromosome condensation and spindle assembly during the first embryonic division in pigs

As common overexpression of Aurora A in various tumours, much attention has focused on its function in inducing cancer, and its value in cancer therapeutics, considerably less is known regarding its role in the first cleavage division of mammalian embryos. Here, we highlight an indispensable role of Aurora A during the first mitotic division progression of pig embryos just after meiosis. The expression and spatiotemporal localization of Aurora A were initially assessed in pig embryos during the first mitotic division by Western blot analysis and indirect immunofluorescent staining. Then, the potential role of Aurora A was further evaluated using a highly selective Aurora A inhibitor, MLN8054, during this mitotic progression in pig embryos. Aurora A was found to express and exhibit a specific dynamic intracellular localization pattern during the first mitotic division in pig embryos. Aurora A was diffused in the cytoplasm at the prophase stage, and then exhibited a dynamic intracellular localization which was tightly associated with the chromosome and spindle dynamics throughout subsequent mitotic phases. Inhibition of Aurora A by MLN8054 treatment led to the failure of the first cleavage, with the majority of embryos being arrested in prophase of the mitotic division. Further subcellular structure examination showed that Aurora A inhibition not only led to the failure of spindle microtubule assembly, but also resulted in severe defects in chromosome condensation, accompanied by an obvious decrease in p-TACC3(S558) expression during the prophase of the first mitosis. Together, these results illustrated that Aurora A is crucial for both spindle assembly and chromosome condensation during the first mitotic division in pig embryos, and that the regulation of Aurora A may be associated with its effects on p-TACC3(S558) expression.

Aurora A Kinase Inhibition Destabilizes PAX3-FOXO1 and MYCN and Synergizes with Navitoclax to Induce Rhabdomyosarcoma Cell Death

The clinically aggressive alveolar rhabdomyosarcoma (RMS) subtype is characterized by expression of the oncogenic fusion protein PAX3-FOXO1, which is critical for tumorigenesis and cell survival. Here, we studied the mechanism of cell death induced by loss of PAX3-FOXO1 expression and identified a novel pharmacologic combination therapy that interferes with PAX3-FOXO1 biology at different levels. Depletion of PAX3-FOXO1 in fusion-positive (FP)-RMS cells induced intrinsic apoptosis in a NOXA-dependent manner. This was pharmacologically mimicked by the BH3 mimetic navitoclax, identified as top compound in a screen from 208 targeted compounds. In a parallel approach, and to identify drugs that alter the stability of PAX3-FOXO1 protein, the same drug library was screened and fusion protein levels were directly measured as a read-out. This revealed that inhibition of Aurora kinase A most efficiently negatively affected PAX3-FOXO1 protein levels. Interestingly, this occurred through a novel specific phosphorylation event in and binding to the fusion protein. Aurora kinase A inhibition also destabilized MYCN, which is both a functionally important oncogene and transcriptional target of PAX3-FOXO1. Combined treatment with an Aurora kinase A inhibitor and navitoclax in FP-RMS cell lines and patient-derived xenografts synergistically induced cell death and significantly slowed tumor growth. These studies identify a novel functional interaction of Aurora kinase A with both PAX3-FOXO1 and its effector MYCN, and reveal new opportunities for targeted combination treatment of FP-RMS. SIGNIFICANCE: These findings show that Aurora kinase A and Bcl-2 family proteins are potential targets for FP-RMS.

Randomized Phase II Study of Paclitaxel plus Alisertib versus Paclitaxel plus Placebo as Second-Line Therapy for SCLC: Primary and Correlative Biomarker Analyses

INTRODUCTION

We assessed the Aurora A kinase inhibitor, alisertib, plus paclitaxel (henceforth referred to as alisertib/paclitaxel) as second-line treatment for SCLC.

METHODS

In this double-blind study, patients with relapsed or refractory SCLC were stratified by relapse type (sensitive versus resistant or refractory) and brain metastases and randomized 1:1 to alisertib/paclitaxel or placebo plus paclitaxel (henceforth referred to as placebo/paclitaxel) in 28-day cycles. The primary end point was progression-free survival (PFS). Associations of c-Myc expression in tumor tissue (prespecified) and genetic alterations in circulating tumor DNA (retrospective) with clinical outcome were evaluated.

RESULTS

A total of 178 patients were enrolled (89 in each arm). The median PFS was 3.32 months with alisertib/paclitaxel versus 2.17 months with placebo/paclitaxel (hazard ratio [HR] = 0.77, 95% confidence limit [CI]: 0.557-1.067, p = 0.113 in the intent-to-treat population versus HR = 0.71, 95% CI: 0.509-0.985, p = 0.038 with corrected analysis applied). Among 140 patients with genetic alternations, patients with cell cycle regulator mutations (cyclin-dependent kinase 6 gene [CDK6], retinoblastoma-like 1 gene [RBL1], retinoblastoma-like 2 gene [RBL2], and retinoblastoma 1 gene [RB1]) had significantly improved PFS with alisertib/paclitaxel versus with placebo/paclitaxel (3.68 versus 1.80 months, respectively [HR = 0.395, 95% CI: 0.239-0.654, p = 0.0003]), and overall survival (7.20 versus 4.47 months, respectively [HR = 0.427, 95% CI: 0.259-0.704, p = 0.00085]). A subset of patients with c-Myc expression showed significantly improved PFS with alisertib/paclitaxel. The incidence of grade 3 or higher drug-related adverse events was 67% (58 patients) with alisertib/paclitaxel versus 22% (25 patients) with placebo/paclitaxel. Twelve patients (14%) versus 11 (12%) died on study, including four versus zero treatment-related deaths.

CONCLUSIONS

Efficacy signals were seen with alisertib/paclitaxel in relapsed or refractory SCLC. c-Myc expression and mutations in cell cycle regulators may be potential predictive biomarkers of alisertib efficacy; further prospective validations are warranted.

Novel Synergistic Combination of Mitotic Arrest and Promotion of Apoptosis for Treatment of Pancreatic Adenocarcinoma

The BCL-2 family of proteins, including anti-apoptotic members BCL-2, BCL-XL and MCL-1, are part of a complex network that controls apoptosis. BH3-mimetics such as ABT-263 inhibit anti-apoptotic BCL-2 proteins and have been developed as potential cancer therapeutics. Aurora Kinase A (AKA) is over-expressed in pancreatic cancer (PC) and controls G2-M transition during mitosis and AKA inhibitors have been developed that induce mitotic arrest. We hypothesized that mitotic arrest induced by AKA inhibition may sensitize PC to accelerated apoptosis by a BH3-mimetic. Our results demonstrated that ABT-263 plus MLN8237 treatment showed greater activity than either single drug alone, as well as strong synergism, in the inhibition of growth of pancreatic cell lines (AsPC-1, PANC-1, MIA PaCa-2, HPAF-II) and PC patient-derived organoids (PDOs). The higher efficacy of combination treatment was attributable to the higher levels of induction of apoptosis and reduction of MCL-1 in PC cells and PDOs. In addition, combination therapy was more effective than single drug in the suppression of tumor growth in AsPC-1 xenograft mouse models. Together, our findings suggest that combination therapy with ABT-263 and MLN8237 should be considered for further exploration as a novel treatment of deadly PC disease.

EGFR-Aurka Signaling Rescues Polarity and Regeneration Defects in Dystrophin-Deficient Muscle Stem Cells by Increasing Asymmetric Divisions

Loss of dystrophin expression in Duchenne muscular dystrophy (DMD) causes progressive degeneration of skeletal muscle, which is exacerbated by reduced self-renewing asymmetric divisions of muscle satellite cells. This, in turn, affects the production of myogenic precursors and impairs regeneration and suggests that increasing such divisions may be beneficial. Here, through a small-molecule screen, we identified epidermal growth factor receptor (EGFR) and Aurora kinase A (Aurka) as regulators of asymmetric satellite cell divisions. Inhibiting EGFR causes a substantial shift from asymmetric to symmetric division modes, whereas EGF treatment increases asymmetric divisions. EGFR activation acts through Aurka to orient mitotic centrosomes, and inhibiting Aurka blocks EGF stimulation-induced asymmetric division. In vivo EGF treatment markedly activates asymmetric divisions of dystrophin-deficient satellite cells in mdx mice, increasing progenitor numbers, enhancing regeneration, and restoring muscle strength. Therefore, activating an EGFR-dependent polarity pathway promotes functional rescue of dystrophin-deficient satellite cells and enhances muscle force generation.

Centrosome Amplification and Tumorigenesis: Cause or Effect?

Centrosome amplification is a feature of multiple tumour types and has been postulated to contribute to both tumour initiation and tumour progression. This chapter focuses on the mechanisms by which an increase in centrosome number might lead to an increase or decrease in tumour progression and the role of proteins that regulate centrosome number in driving tumorigenesis.

Allosteric Small-Molecule Serine/Threonine Kinase Inhibitors

Deregulation of protein kinase activity has been linked to many diseases ranging from cancer to AIDS and neurodegenerative diseases. Not surprisingly, drugging the human kinome - the complete set of kinases encoded by the human genome - has been one of the major drug discovery pipelines. Majority of the approved clinical kinase inhibitors target the ATP binding site of kinases. However, the remarkable sequence and structural similarity of ATP binding pockets of kinases make selective inhibition of kinases a daunting task. To circumvent these issues, allosteric inhibitors that target sites other than the orthosteric ATP binding pocket have been developed. The structural diversity of the allosteric sites allows these inhibitors to have higher selectivity, lower toxicity and improved physiochemical properties and overcome drug resistance associated with the use of conventional kinase inhibitors. In this chapter, we will focus on the allosteric inhibitors of selected serine/threonine kinases, outline the benefits of using these inhibitors and discuss the challenges and future opportunities.

The α-Aurora Kinases Function in Vascular Development in Arabidopsis

The Aurora kinases are serine/threonine kinases with conserved functions in mitotic cell division in eukaryotes. In Arabidopsis, Aurora kinases play important roles in primary meristem maintenance, but their functions in vascular development are still elusive. We report a dominant xdi-d mutant showing the xylem development inhibition (XDI) phenotype. Gene identification and transgenic overexpression experiments indicated that the activation of the Arabidopsis Aurora 2 (AtAUR2) gene is responsible for the XDI phenotype. In contrast, the aur1-2 aur2-2 double mutant plants showed enhanced differentiation of phloem and xylem cells, indicating that the Aurora kinases negatively affect xylem differentiation. The transcript levels of key regulatory genes in vascular cell differentiation, i.e. ALTERED PHLOEM DEVELOPMENT (APL), VASCULAR-RELATED NAC-DOMAIN 6 (VND6) and VND7, were higher in the aur1-2 aur2-2 double mutant and lower in xdi-d mutants compared with the wild-type plants, further supporting the functions of α-Aurora kinases in vascular development. Gene mutagenesis and transgenic studies showed that protein phosphorylation and substrate binding, but not protein dimerization and ubiquitination, are critical for the biological function of AtAUR2. These results indicate that α-Aurora kinases play key roles in vascular cell differentiation in Arabidopsis.

Induction of Mitotic Catastrophe via Inhibition of Aurora B by Ionizing Radiation With Additive of Mulberry Water Extract in Human Bladder Cancer Cells

Mulberry fruit water extract (MWE) has been reported to synergistically enhance the cytotoxic effect of paclitaxel by promoting mitotic catastrophe to induce apoptosis in bladder cancer cells in our previous work. The aim of this study was to evaluate and to mechanistically explore the effects of MWE on bladder cancer responses to ionizing radiation (IR) by treating TSGH 8301 bladder carcinoma cells with MWE after exposing to IR. The results of MTT assay showed a synergistic cytotoxicity of IR with the co-treatment of MWE (IR/MWE) by inducing G2/M phase arrest as demonstrated by flow cytometry analysis in TSGH 8301, HT1367 and HT1197 bladder carcinoma cells lines. The IR/MWE-treated cells expressed increased levels of the G2/M phase arrest-related proteins cdc2/cyclin B1 and displayed giant multinucleated morphology, a typical characteristic of mitotic catastrophe. Immunofluorescent confocal microscopy revealed that the combined strategy inhibited Aurora B phosphorylation through Ras/Raf/MEK/ERK signaling cascade as demonstrated by Western blotting analysis. IR/MWE also caused an inhibitory effect on Plk1 and the subsequent downstream regulator RhoA repression and Cep55 induction, which would influence cell cycle progression in the early steps of cytokinesis. A profound tumor growth suppression and inactivation of Aurora B activity in the tumor tissues by IR/MWE treatment were confirmed in the TSGH 8301 xenograft model in vivo. These data demonstrated that MWE could be an effective auxiliary to synergize with radiation on the anticancer efficacy by promoting mitotic catastrophe through inhibition of Aurora B, providing a novel and effective therapeutic option for bladder cancer management.

Potent effects of roniciclib alone and with sorafenib against well-differentiated thyroid cancer

Activation of cyclin-dependent kinase activity is frequently observed in many human cancers; therefore, cyclin-dependent kinases that promote cell cycle transition and cell proliferation may be potential targets in the treatment of malignancy. The therapeutic effects of roniciclib, a cyclin-dependent kinase inhibitor for papillary and follicular thyroid cancer (designated as well-differentiated thyroid cancer), were investigated in this study. Roniciclib inhibited cell proliferation in two papillary and two follicular thyroid cancer cell lines in a dose-dependent manner. Roniciclib activated caspase-3 activity and induced apoptosis. Cell cycle progression was arrested in the G2/M phase. Roniciclib treatment in vivo retarded the growth of two well-differentiated thyroid tumors in xenograft models in a dose-dependent fashion. Furthermore, the combination of roniciclib with sorafenib was more effective than either single treatment in a follicular thyroid cancer xenograft model. Acceptable safety profiles appeared in animals treated with either roniciclib alone or roniciclib and sorafenib combination therapy. These findings support roniciclib as a potential drug for the treatment of patients with well-differentiated thyroid cancer.

The functional diversity of Aurora kinases: a comprehensive review

Aurora kinases are serine/threonine kinases essential for the onset and progression of mitosis. Aurora members share a similar protein structure and kinase activity, but exhibit distinct cellular and subcellular localization. AurA favors the G2/M transition by promoting centrosome maturation and mitotic spindle assembly. AurB and AurC are chromosome-passenger complex proteins, crucial for chromosome binding to kinetochores and segregation of chromosomes. Cellular distribution of AurB is ubiquitous, while AurC expression is mainly restricted to meiotically-active germ cells. In human tumors, all Aurora kinase members play oncogenic roles related to their mitotic activity and promote cancer cell survival and proliferation. Furthermore, AurA plays tumor-promoting roles unrelated to mitosis, including tumor stemness, epithelial-to-mesenchymal transition and invasion. In this review, we aim to understand the functional interplay of Aurora kinases in various types of human cells, including tumor cells. The understanding of the functional diversity of Aurora kinases could help to evaluate their relevance as potential therapeutic targets in cancer.

Phase I study combining the aurora kinase a inhibitor alisertib with mFOLFOX in gastrointestinal cancer

Overexpression and cellular mis-localization of aurora kinase A (AURKA) in gastrointestinal cancers results in chromosomal instability, activation of multiple oncogenic pathways, and inhibition of pro-apoptotic signaling. Inhibition of AURKA causes mitotic delays, severe chromosome congression, and activation of p53/p73 leading to cell death. Our preclinical data showed cooperative activity with the AURKA inhibitor alisertib and platinum agents in cell lines and xenografts, and suggested an optimal treatment window. Therefore, this study was designed to determine the maximum-tolerated dose (MTD) of alisertib in combination with modified FOLFOX (mFOLFOX), as this is a standard platinum-based therapy for gastrointestinal cancers. Standard 3 + 3 dose escalation was used, where the starting dose of alisertib was 10 mg twice daily (Days 1-3), with leucovorin (400 mg/m²) and oxaliplatin (85 mg/m²) on Day 2 followed by continuous 46-h 5-FU (2400 mg/m²) infusion on Days 2-4 in 14-day cycles. Fourteen patients with advanced gastrointestinal cancers were enrolled and two doses explored; two patients were not evaluable for dose-limiting toxicity (DLT) and replaced. Two patients experienced DLTs at 20 mg of alisertib (Grade 3 fatigue (n = 2); Grade 3 nausea, vomiting, dehydration with hospitalization (n = 1)). MTD was 10 mg alisertib with 85 mg/m² oxaliplatin and 2400 mg/m² 5-FU. Most frequent toxicities were nausea (57%), diarrhea, fatigue, neuropathy, and vomiting (43%), and anorexia and anemia (36%); most were Grade 1-2. One patient with colorectal cancer had a partial response of 12 evaluable patients, and four patients had stable disease. Alisertib in combination with mFOLFOX did not demonstrate unexpected side effects, but the regimen was only tolerable at the lowest dose investigated.

Centrosome aberrations and chromosome instability contribute to tumorigenesis and intra-tumor heterogeneity

Centrosomes serve as the major microtubule organizing centers in cells and thereby contribute to cell shape, polarity, and motility. Also, centrosomes ensure equal chromosome segregation during mitosis. Centrosome aberrations arise when the centrosome cycle is deregulated, or as a result of cytokinesis failure. A long-standing postulate is that centrosome aberrations are involved in the initiation and progression of cancer. However, this notion has been a subject of controversy because until recently the relationship has been correlative. Recently, it was shown that numerical or structural centrosome aberrations can initiate tumors in certain tissues in mice, as well as invasion. Particularly, we will focus on centrosome amplification and chromosome instability as drivers of intra-tumor heterogeneity and their consequences in cancer. We will also discuss briefly the controversies surrounding this theory to highlight the fact that the role of both centrosome amplification and chromosome instability in cancer is highly context-dependent. Further, we will discuss single-cell sequencing as a novel technique to understand intra-tumor heterogeneity and some therapeutic approaches to target chromosome instability.

Activation of S6 signaling is associated with cell survival and multinucleation in hyperplastic skin after epidermal loss of AURORA-A Kinase

The role of mitosis in the progression of precancerous skin remains poorly understood. To address this question, we deleted the mitotic Kinase Aurora-A (Aur-A) in hyperplastic mutant p53 mouse skin as an experimental tool to study the G2/M transition in precancerous keratinocytes and AUR-A's role in this process. Epidermal Aur-A deletion (Aur-A^epiΔ) led to marked keratinocyte enlargement, pleomorphism, multinucleation, and  attenuated induction of cell death. This phenotype was characteristic of slippage after a stalled mitosis. We also observed altered or impaired epidermal differentiation, indicative of a partial skin barrier defect. The upregulation of mTOR/PI3K signaling was implicated as a mechanism by which keratinocytes may evade cell death after AUR-A deficiency. This was evidenced by the ectopic expression of the pathway readout, p-S6, in the basal layer of Aur-A^epiΔ skin and its mitotic upregulation in isolated keratinocytes. We further tested whether our findings were extended to skin carcinoma cells. The chemical inhibition of AUR-A led to a similar mitotic delay, polyploidy/multinucleation, and attenuated cell death in skin cancer cell lines. Moreover, inhibition of mTOR/PI3K signaling ameliorated the effects caused by the deficiency of AUR-A activity but was also associated with the persistence of mitotic p-S6 detection in surviving cancer cells. These results show the induction of multinucleation/polyploidy may be a compensatory state in keratinocytes that allows for cellular survival and maintenance of partial barrier function in face of aberrant cell division or differentiation. Moreover, mTOR/PI3K signaling is active in the mitosis of hyperplastic keratinocytes expressing mutant p53 and is further enhanced by stalled mitosis, indicating a potential resistance mechanism to the use of anti-mitotic drugs in the treatment of skin cancers.

Activity of roniciclib in medullary thyroid cancer

Altered cyclin-dependent kinase activity is observed in many human malignancies. Cyclin-dependent kinases that promote cell cycle progression may be promising targets in the treatment of cancer. The therapeutic effects of roniciclib, a cyclin-dependent kinase inhibitor for medullary thyroid cancer were investigated in the present study. Roniciclib inhibited medullary thyroid cancer cell proliferation in a dose-dependent manner. Roniciclib induced caspase-3 activity and contributed to apoptosis. Cell cycle progression was arrested in the G2 phase. In vivo, roniciclib treatment retarded the growth of tumors of medullary thyroid cancer xenografts. In addition, roniciclib in combination with sorafenib was more effective than either single treatment in a xenograft model. No morbidity was observed in animals treated with single roniciclib therapy and combination treatment of roniciclib and sorafenib. These data provide a rationale for clinical assessment of using roniciclib in the treatment of patients with medullary thyroid cancer.

Aurora kinase A interacts with H-Ras and potentiates Ras-MAPK signaling

In cancer, upregulated Ras promotes cellular transformation and proliferation in part through activation of oncogenic Ras-MAPK signaling. While directly inhibiting Ras has proven challenging, new insights into Ras regulation through protein-protein interactions may offer unique opportunities for therapeutic intervention. Here we report the identification and validation of Aurora kinase A (Aurora A) as a novel Ras binding protein. We demonstrate that the kinase domain of Aurora A mediates the interaction with the N-terminal domain of H-Ras. Further more, the interaction of Aurora A and H-Ras exists in a protein complex with Raf-1. We show that binding of H-Ras to Raf-1 and subsequent MAPK signaling is enhanced by Aurora A, and requires active H-Ras. Thus, the functional linkage between Aurora A and the H-Ras/Raf-1 protein complex may provide a mechanism for Aurora A's oncogenic activity through direct activation of the Ras/MAPK pathway.

Comparative transcriptome analysis reveals a regulatory network of microRNA-29b during mouse early embryonic development

MicroRNAs are endogenous ~22 nt RNAs that regulate gene expression by translational inhibition and mRNA destabilization. MicroRNA-29b (miR-29b) is essential for progression of mouse embryos past preimplantation development; however, details of the underlying regulatory network remain to be elucidated. Here, we used RNA sequencing to identify changes in the transcriptome of mouse embryos in response to miR-29b inhibition. Morula-stage embryos that had been subject to miR-29b inhibition throughout preimplantation development exhibited significant expression changes in 870 genes compared with controls. Among 405 genes that were downregulated, 30 genes encoded factors with known essential function during early embryonic development, including the pluripotent stem cell factor Nanog. We identified 19 genes encoding putative miR-29b target transcripts. These included Zbtb40, Hbp1, Ccdc117, Ypel2, Klf4, and Tmed9, which are upregulated at the 4-cell state of mouse development concomitant with miR-29b downregulation. Luciferase reporter analysis confirmed that Zbtb40, Hbp1, Ccdc117, Ypel2, and Klf4 transcripts are direct targets of miR-29b. These results suggest that miR-29b decreases the mRNA levels of several target genes during early mouse development, including the gene encoding the reprogramming factor Klf4. We hypothesize that inhibition of miR-29b causes overexpression of its target genes, triggering downstream signaling networks to decrease the expression of genes that are essential for embryonic development. In conclusion, miR-29b controls an extensive regulatory network in early mouse embryos, which comprises reprogramming factors and molecular regulators of post-transcriptional modification processes.

Prognostic importance of Aurora Kinases and mitotic spindle genes transcript levels in Myelodysplastic syndrome

Myelodysplastic syndrome (MDS) are a heterogeneous group of clonal disease characterized by insufficiency of bone marrow, increase of apoptosis and increased risk of acute leukemia progression. Proteins related to the mitotic spindle (AURKA, AURKB, TPX2), to the mitotic checkpoint (MAD2, CDC20) and the regulation of the cell cycle (p21) are directly related to chromosomal stability and tumor development. This study aimed to evaluate the mRNA expression levels of these genes in 101 MDS patients using a real-time PCR methodology. We identified that CDC20 expression are increased in patients with dysmegakaryopoiesis (p=0.024), thrombocytopenia (p=0.000) and high-risk patients (p=0.014, 0.018) MAD2 expression are decreased in patients with 2 or 3 cytopenias (p=0.000) and neutrophil below 800/mm³. TPX2 is also overexpressed in patients presenting dysmegakaryopoiesis (p=0.009). A decrease in AURKA and AURKB expression were observed in patients with altered karyotype (p=0.000), who presented dysplasia in 3 lineages (p=0.000; 0.017) and hemoglobin inferior to 8g/dL (p=0.024). The expression of AURKA, AURKB and MAD2 (p=0.000; 0.001; 0.025) were decreased in patients with hypoplastic MDS, associated with high frequency of chromosomal alterations and high mortality rate. This study reaffirms the importance of aurora kinases and mitotic spindle genes to the pathogenesis and clinical evolution of MDS.

Aurora kinases: novel therapy targets in cancers

Aurora kinases, a family of serine/threonine kinases, consisting of Aurora A (AURKA), Aurora B (AURKB) and Aurora C (AURKC), are essential kinases for cell division via regulating mitosis especially the process of chromosomal segregation. Besides regulating mitosis, Aurora kinases have been implicated in regulating meiosis. The deletion of Aurora kinases could lead to failure of cell division and impair the embryonic development. Overexpression or gene amplification of Aurora kinases has been clarified in a number of cancers. And a growing number of studies have demonstrated that inhibition of Aurora kinases could potentiate the effect of chemotherapies. For the past decades, a series of Aurora kinases inhibitors (AKIs) developed effectively repress the progression and growth of many cancers both in vivo and in vitro, suggesting that Aurora kinases could be a novel therapeutic target. In this review, we'll first briefly present the structure, localization and physiological functions of Aurora kinases in mitosis, then describe the oncogenic role of Aurora kinases in tumorigenesis, we shall finally discuss the outcomes of AKIs combination with conventional therapy.

Computationally-guided optimization of small-molecule inhibitors of the Aurora A kinase-TPX2 protein-protein interaction

Free energy perturbation theory, in combination with enhanced sampling of protein-ligand binding modes, is evaluated in the context of fragment-based drug design, and used to design two new small-molecule inhibitors of the Aurora A kinase-TPX2 protein-protein interaction.

Effects of roniciclib in preclinical models of anaplastic thyroid cancer

Many human cancers have altered cyclin-dependent kinase activity. Inhibition of cyclin-dependent kinases may arrest cell cycle progression and represents an important strategy in the treatment of malignancies. We evaluated the therapeutic effects of roniciclib, a cyclin-dependent kinase inhibitor, as a treatment for anaplastic thyroid cancer. Roniciclib inhibited anaplastic thyroid cancer cell proliferation in a dose-dependent manner. Roniciclib activated caspase-3 activity and induced apoptosis. Cell cycle progression was arrested in G2/M phase. In vivo, the growth of anaplastic thyroid cancer xenograft tumors was retarded by roniciclib treatment without evidence of toxicity. These data provide a rationale for further clinical evaluation using roniciclib in the treatment of patients with anaplastic thyroid cancer.

A cyclin-dependent kinase inhibitor, dinaciclib in preclinical treatment models of thyroid cancer

Background

We explored the therapeutic effects of dinaciclib, a cyclin-dependent kinase (CDK) inhibitor, in the treatment of thyroid cancer.

Materials and methods

Seven cell lines originating from three pathologic types of thyroid cancer (papillary, follicular and anaplastic) were studied. The cytotoxicity of dinaciclib was measured using a lactate dehydrogenase assay. The expression of proteins associated with cell cycle and apoptosis was assessed using Western blot analysis and immunofluorescence microscopy. Cell cycle distribution was measured by flow cytometry and immunofluorescence microscopy. Apoptosis and caspase-3 activity were measured by flow cytometry and fluorometric assay. Mice bearing flank anaplastic thyroid cancer (ATC) were treated with intraperitoneal injections of dinaciclib.

Results

Dinaciclib inhibited thyroid cancer cell proliferation in a dose-dependent manner. Dinaciclib had a low median-effect dose (≤ 16.0 nM) to inhibit cell proliferation in seven thyroid cancer cell lines. Dinaciclib decreased CDK1, cyclin B1, and Aurora A expression, induced cell cycle arrest in the G2/M phase, and induced accumulation of prophase mitotic cells. Dinaciclib decreased Mcl-1, Bcl-x_L and survivin expression, activated caspase-3 and induced apoptosis. In vivo, the growth of ATC xenograft tumors was retarded in a dose-dependent fashion with daily dinaciclib treatment. Higher-dose dinaciclib (50 mg/kg) caused slight, but significant weight loss, which was absent with lower-dose dinaciclib (40 mg/kg) treatment.

Conclusions

Dinaciclib inhibited thyroid cancer proliferation both in vitro and in vivo. These findings support dinaciclib as a potential drug for further studies in clinical trials for the treatment of patients with refractory thyroid cancer.

Aurora-A promotes the establishment of spindle assembly checkpoint by priming the Haspin-Aurora-B feedback loop in late G2 phase

Aurora-A kinase functions mainly in centrosome maturation, separation and spindle formation. It has also been found to be amplified or overexpressed in a range of solid tumors, which is linked with tumor progression and poor prognosis. Importantly, Aurora-A inhibitors are being studied in a number of ongoing clinical trials. However, whether and how Aurora-A has a role in the regulation of the mitotic checkpoint is controversial. Additionally, the function of nuclear-accumulated Aurora-A in late G2 phase is not clear. Here we show that knockout, inhibition or blockade of the nuclear entry of Aurora-A severely decreased the centromere localization of Aurora-B and the phosphorylation of histone H3 threonine 3 (H3T3-ph) mediated by the kinase Haspin in late G2 phase. We further reveal that nuclear-accumulated Aurora-A phosphorylates Haspin at multiple sites at its N-terminus and that this promotes H3T3-ph and the rapid recruitment to the centromere of the chromosomal passenger complex. In addition, Aurora-A facilitates the association of Aurora-B with their common substrates: Haspin and Plk1. Notably, these functions of Aurora-A are mostly independent of Plk1. Thus we demonstrate that, in late G2 and prophase, Aurora-A phosphorylates Haspin to trigger the Haspin-H3T3-ph-Aurora-B positive feedback loop that supports the timely establishment of the chromosomal passenger complex and the mitotic checkpoint before spindle assembly.