Aurora kinase-A overexpression in mouse mammary epithelium induces mammary adenocarcinomas harboring genetic alterations shared with human breast cancer

Aurora Kinase A proximity map reveals centriolar satellites as regulators of its ciliary function

Aurora kinase A (AURKA) is a conserved kinase that plays crucial roles in numerous cellular processes. Although AURKA overexpression is frequent in human cancers, its pleiotropic functions and multifaceted regulation present challenges in its therapeutic targeting. Key to overcoming these challenges is to identify and characterize the full range of AURKA interactors, which are often weak and transient. Previous proteomic studies were limited in monitoring dynamic and non-mitotic AURKA interactions. Here, we generate the proximity interactome of AURKA in asynchronous cells, which consists of 440 proteins involving multiple biological processes and cellular compartments. Importantly, AURKA has extensive proximate and physical interactions to centriolar satellites, key regulators of the primary cilium. Loss-of-function experiments identify satellites as negative regulators of AURKA activity, abundance, and localization in quiescent cells. Notably, loss of satellites activates AURKA at the basal body, decreases centrosomal IFT88 levels, and causes ciliogenesis defects. Collectively, our results provide a resource for dissecting spatiotemporal regulation of AURKA and uncover its proteostatic regulation by satellites as a new mechanism for its ciliary functions.

Bora phosphorylation substitutes in trans for T-loop phosphorylation in Aurora A to promote mitotic entry

Polo-like kinase 1 (Plk1) is instrumental for mitotic entry and progression. Plk1 is activated by phosphorylation on a conserved residue Thr210 in its activation segment by the Aurora A kinase (AURKA), a reaction that critically requires the co-factor Bora phosphorylated by a CyclinA/B-Cdk1 kinase. Here we show that phospho-Bora is a direct activator of AURKA kinase activity. We localize the key determinants of phospho-Bora function to a 100 amino acid region encompassing two short Tpx2-like motifs and a phosphoSerine-Proline motif at Serine 112, through which Bora binds AURKA. The latter substitutes in trans for the Thr288 phospho-regulatory site of AURKA, which is essential for an active conformation of the kinase domain. We demonstrate the importance of these determinants for Bora function in mitotic entry both in Xenopus egg extracts and in human cells. Our findings unveil the activation mechanism of AURKA that is critical for mitotic entry.

Use of signals of positive and negative selection to distinguish cancer genes and passenger genes

A major goal of cancer genomics is to identify all genes that play critical roles in carcinogenesis. Most approaches focused on genes positively selected for mutations that drive carcinogenesis and neglected the role of negative selection. Some studies have actually concluded that negative selection has no role in cancer evolution. We have re-examined the role of negative selection in tumor evolution through the analysis of the patterns of somatic mutations affecting the coding sequences of human genes. Our analyses have confirmed that tumor suppressor genes are positively selected for inactivating mutations, oncogenes, however, were found to display signals of both negative selection for inactivating mutations and positive selection for activating mutations. Significantly, we have identified numerous human genes that show signs of strong negative selection during tumor evolution, suggesting that their functional integrity is essential for the growth and survival of tumor cells.

PROTAC-mediated degradation reveals a non-catalytic function of AURORA-A kinase

The mitotic kinase AURORA-A is essential for cell cycle progression and is considered a priority cancer target. While the catalytic activity of AURORA-A is essential for its mitotic function, recent reports indicate an additional non-catalytic function, which is difficult to target by conventional small molecules. We therefore developed a series of chemical degraders (PROTACs) by connecting a clinical kinase inhibitor of AURORA-A to E3 ligase-binding molecules (e.g. thalidomide). One degrader induced rapid, durable and highly specific degradation of AURORA-A. In addition ,we found that the degrader complex was stabilized by cooperative binding between AURORA-A and CEREBLON. Degrader-mediated AURORA-A depletion caused an S-phase defect, which is not the cell cycle effect observed upon kinase inhibition, supporting an important non-catalytic function of AURORA-A during DNA replication. AURORA-A degradation induced rampant apoptosis in cancer cell lines, and thus represents a versatile starting point for developing new therapeutics to counter AURORA-A function in cancer.

The anticancer effects of cinobufagin on hepatocellular carcinoma Huh‑7 cells are associated with activation of the p73 signaling pathway

The Na⁺/K⁺-ATPase inhibitor cinobufagin exhibits numerous anticancer effects on hepatocellular carcinoma (HCC) cells expressing wild-type p53 via inhibition of aurora kinase A (AURKA) and activation of p53 signaling. However, the effects of cinobufagin on HCC cells expressing mutant p53 remain unclear. In the present study, the anticancer effects of cinobufagin were investigated on HCC Huh-7 cells with mutant p53, and the effects of AURKA overexpression or inhibition on the anticancer effects of cinobufagin were analyzed. Viability, cell cycle progression and apoptosis of cells were determined using an MTT assay, flow cytometry and Hoechst 33342 staining, respectively. The expression levels of p53 and p73 signaling-associated proteins were investigated via western blot analysis. The results demonstrated that the expression levels of AURKA, B-cell lymphoma 2 (Bcl-2), cyclin-dependent kinase 1, cyclin B1, proliferating cell nuclear antigen and heterogeneous nuclear ribonucleoprotein K, as well as the phosphorylation of p53 and mouse double minute 2 homolog, were significantly decreased in Huh-7 cells treated with 5 µmol/l cinobufagin for 24 h. Conversely, the expression levels of Bcl-2-associated X protein, p21, p53 upregulated modulator of apoptosis and phorbol-12-myristate-13-acetate-induced protein 1, were significantly increased by cinobufagin treatment. Overexpression or inhibition of AURKA suppressed or promoted the anticancer effects of cinobufagin on Huh-7 cells, respectively. These results indicated that cinobufagin may induce anticancer effects on Huh-7 cells via the inhibition of AURKA and p53 signaling, and via the activation of p73 signaling, in an AURKA-dependent manner.

High Expression of Human AugminComplex Submit 3 Indicates Poor Prognosis and Associates with Tumor Progression in Hepatocellular Carcinoma

The function of human augmin complex unit 3(Haus3), a component of the HAU augmin-like complex, in various cancers is not clear. This study aims to elucidate the clinical significance and the role of Haus3 in tumor progression of hepatocellular carcinoma (HCC). We analyzed the expression of Haus3 in 50 HCC patients from The Cancer Genome Atlas and 137 HCC patients in our hospital. Compared with adjacent normal tissue, Haus3 expression assessed by immunohistochemical staining was dramatically increased in tumor tissues. A high level of Haus3 expression was significantly correlated with large tumor size (p=0.025) and tumor multiplicity (p=0.004). Univariate and multivariate survival analysis showed thatexpression of Haus3 was an independent prognostic factor for overall survival ofHCCpatients. Western blot analysis showed that Haus3 regulated the phosphorylation of PLK1-T210 and activity of the Cdk1/cyclin B1 complex, indicating that Haus3 disrupted G2/M phase arrest. In immunofluorescence studies, expression of Haus3 correlated with the level ofα-tubulin and γ-tubulin. In summary, Haus3 plays a vital role in regulatingtheactivityof PLK2-T210 and Cdk1/cyclin B1 complex in G2/M phasetransition and the expression of tubulins to ensure normal mitotic progression. Our data suggest that Haus3 might be a promising prognostic biomarker and molecular target of HCC.

AURKA rs8173 G>C Polymorphism Decreases Wilms Tumor Risk in Chinese Children

Wilms tumor is the most common type of renal malignancy in children. Previous studies have demonstrated that single nucleotide polymorphisms (SNPs) in the AURKA gene could predispose to several human malignancies. We recruited 145 cases and 531 cancer-free controls to investigate whether AURKA gene variants modify Wilms tumor susceptibility. Three AURKA SNPs (rs1047972 C>T, rs2273535 T>A, and rs8173 G>C) were genotyped by the Taqman methodology. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of association between AURKA SNPs and Wilms tumor risk. We found that only the rs8173 G>C polymorphism was significantly associated with Wilms tumor risk (GC vs. GG: adjusted OR (AOR) = 0.50, 95% CI = 0.35-0.73, P=0.0002; GC/CC vs. GG: AOR = 0.60, 95% CI = 0.42-0.88, P=0.008). Stratification analysis revealed that rs8173 GC/CC genotypes were associated with Wilms tumor risk among children aged >18 months (AOR = 0.56, 95% CI = 0.34-0.93, P=0.024), male children (AOR = 0.54, 95% CI = 0.33-0.90, P=0.017), and children with clinical stage III + IV diseases (AOR = 0.56, 95% CI = 0.35-0.90, P=0.017). Haplotype analysis indicated that the CAG haplotype was significantly associated with increased Wilms tumor risk. In conclusion, our findings indicated that the AURKA rs8173 G>C polymorphism was associated with decreased Wilms tumor risk in Chinese children.

Aurora kinase A localises to mitochondria to control organelle dynamics and energy production

Many epithelial cancers show cell cycle dysfunction tightly correlated with the overexpression of the serine/threonine kinase Aurora A (AURKA). Its role in mitotic progression has been extensively characterised, and evidence for new AURKA functions emerges. Here, we reveal that AURKA is located and imported in mitochondria in several human cancer cell lines. Mitochondrial AURKA impacts on two organelle functions: mitochondrial dynamics and energy production. When AURKA is expressed at endogenous levels during interphase, it induces mitochondrial fragmentation independently from RALA. Conversely, AURKA enhances mitochondrial fusion and ATP production when it is over-expressed. We demonstrate that AURKA directly regulates mitochondrial functions and that AURKA over-expression promotes metabolic reprogramming by increasing mitochondrial interconnectivity. Our work paves the way to anti-cancer therapeutics based on the simultaneous targeting of mitochondrial functions and AURKA inhibition.

Structures called mitochondria power cells by turning oxygen and sugar into chemical energy. Each cell can have thousands of mitochondria, which work together to supply changing energy demands. They can fuse together or break apart, forming networks that change size and produce different amounts of energy. Getting the balance right is crucial; if energy levels are too low, the cell will not be able to grow and divide. If energy levels are too high, the cell can grow at a faster rate, which can contribute to the cell becoming cancerous.

Although we know that mitochondria provide energy, it is not clear how they communicate to fine-tune the supply. Some clues come from cancer cells that seem dependent on their mitochondria for survival. In these cells, levels of a protein called AURKA are higher than normal. AURKA helps cells to divide, and it interacts with many different proteins. This complexity makes it difficult to work out exactly what AURKA does, but it is possible that it plays a role in energy supply.

Bertolin et al. have now investigated whether mitochondria use AURKA to communicate inside human breast cancer cells. Tagging AURKA proteins with a fluorescent marker revealed that it accumulates inside mitochondria. Once it gets there, AURKA changes the shape of the mitochondria, which has dramatic effects on their capacity to produce energy. At normal levels, AURKA causes the mitochondria to fragment, breaking apart into smaller pieces. This maintains their energy output at a normal level. If AURKA levels are too high, the mitochondria fuse together and produce more energy. This means AURKA could help to fuel fast-growing cancer cells.

Current drugs that aim to treat cancer by blocking the activity of AURKA show poor results. This is partly due to the fact that the protein has so many different roles in the cell. Finding that AURKA affects mitochondria is the first step in understanding one of its unknown roles. It also suggests the possibility of developing new drugs to change how mitochondria make energy in cancer cells that contain high levels of AURKA.

Functions and therapeutic potential of protein phosphatase 1: Insights from mouse genetics

Protein phosphatase 1 (PP1) catalyzes more than half of all phosphoserine/threonine dephosphorylation reactions in mammalian cells. In vivo PP1 does not exist as a free catalytic subunit but is always associated with at least one regulatory PP1-interacting protein (PIP) to generate a large set of distinct holoenzymes. Each PP1 complex controls the dephosphorylation of only a small subset of PP1 substrates. We screened the literature for genetically engineered mouse models and identified models for all PP1 isoforms and 104 PIPs. PP1 itself and at least 49 PIPs were connected to human disease-associated phenotypes. Additionally, phenotypes related to 17 PIPs were clearly linked to altered PP1 function, while such information was lacking for 32 other PIPs. We propose structural reverse genetics, which combines structural characterization of proteins with mouse genetics, to identify new PP1-related therapeutic targets. The available mouse models confirm the pleiotropic action of PP1 in health and diseases.

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Four protein phosphatases 1 (PP1) isoforms and >200 PP1-interacting proteins (PIPs)

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Genetically engineered mice of 49 PIPs display human disease-associated phenotypes.

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The use of structural reverse genetics to identify the PP1-dependent phenotypes

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Various interaction sites in PP1:PIP complexes suit for therapeutic targeting.

CSF-1/CSF-1R axis is associated with epithelial/mesenchymal hybrid phenotype in epithelial-like inflammatory breast cancer

Inflammatory breast cancer (IBC) is a rare subtype of breast cancer, accounting for 8–10% of breast cancer-associated deaths in the US. Clinical hallmarks of IBC include tumor emboli in lymphatic vessels and E-cadherin overexpression, which supports a type of metastasis referred to as cell cluster-based metastasis, prevalent in IBC. In contrast, we previously reported epithelial-to-mesenchymal transition (EMT)-based progression of IBC, utilizing in vivo xenografts and in vitro Matrigel culture models. To address these two contradictory concepts of IBC metastasis, we used Matrigel culture to induce EMT in a panel of IBC cells. Results revealed Matrigel culture induced vimentin expression in SUM149 and SUM190 IBC cells at the transcriptional and protein levels while maintaining the expression of E-cadherin, a phenomenon referred to as partial EMT. Transcriptional profiling revealed that expression of colony-stimulating factor 1 (CSF-1) was induced in Matrigel culture. When the receptor tyrosine kinase of CSF-1 (CSF-1R) was inhibited by CSF-1R inhibitor BLZ945, the partial EMT was reversed in a dose-dependent manner, indicating that the CSF-1/CSF-1R axis plays a key role in controlling partial EMT. This observation may help reconcile the two contradictory theories of IBC metastasis, EMT vs cell cluster-based metastasis.

Variations in the AURKA Gene: Biomarkers for the Development and Progression of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a liver malignancy and a major cause of cancer mortality worldwide. AURKA (aurora kinase A) is a mitotic serine/threonine kinase that functions as an oncogene and plays a critical role in hepatocarcinogenesis. We report on the association between 4 single nucleotide polymorphisms (SNPs) of the AURKA gene (rs1047972, rs2273535, rs2064836, and rs6024836) and HCC susceptibility as well as clinical outcomes in 312 patients with HCC and in 624 cancer-free controls. We found that carriers of the TT allele of the variant rs1047972 were at greater risk of HCC compared with wild-type (CC) carriers. Moreover, carriers of at least one A allele in rs2273535 were less likely to progress to stage III/IV disease, develop large tumors or be classified into Child-Pugh class B or C. Individuals with at least one G allele at AURKA SNP rs2064863 were at lower risk of developing large tumors or progressing to Child-Pugh grade B or C. Our results indicate that genetic variations in the AURKA gene may serve as an important predictor of early-stage HCC and be a reliable biomarker for the development of HCC.

Association between the functional polymorphism Ile31Phe in the AURKA gene and susceptibility of hepatocellular carcinoma in chronic hepatitis B virus carriers

Aurora kinase A (AURKA) is a serine threonine kinase which affects chromosomal separation and mitotic spindle stability through interaction with the centrosome during mitosis. Two functional nonsynonymous polymorphisms of the AURKA gene (Ile31Phe and Val57Ile) have been reported recently. We analyzed the association between the two polymorphisms and risk of the occurrence of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) in the Guangxi population consisting of 348 patients with HCC and 359 control subjects, and then validated the significant association in the Guangdong population consisting of 440 cases and 456 controls. All of the participants were of Chinese origin and HBV carriers. The two polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism assay or Sequenom MassARRAY iPLEX platform. In the Guangxi population, carriers of the AURKA 31Phe allele (Ile/Phe + Phe/Phe) were significantly associated with decreased susceptibility to HBV-related HCC when compared with noncarriers (Ile/Ile) (odds ratio [OR] = 0.63, 95% confidence interval [CI] = 0.46-0.86, P = 3.4 × 10^-3). On the contrary, no significant association was found between Val57Ile and HBV-related HCC occurrence. The association of Ile31Phe with HBV-related HCC occurrence was confirmed in the Guangdong population (OR = 0.64, 95% CI = 0.49-0.83, P = 8.0 × 10^-4). The pooled analysis gave a joint P value of 5.5 × 10^-6 (joint OR = 0.63, 95% CI = 0.52-0.77). Our findings suggest that AURKA Ile31Phe may play a role in mediating the susceptibility to HBV-related HCC among Chinese.

Combined effect of genetic polymorphisms of AURKA and environmental factors on oral cancer development in Taiwan

Background

Oral squamous cell carcinoma (OSCC) is the sixth and fourth most common cause of cancer death in men worldwide and in Taiwan, respectively. AURKA, which encodes a centrosome-related serine/threonine kinase, is frequently amplified and overexpressed in many human cancers, particularly advanced OSCC. We conducted a hospital-based case-control study to estimate AURKA single-nucleotide polymorphisms (SNPs) and environmental risk factors to determine OSCC susceptibility and clinicopathological characteristics.

Methodology/Principal findings

We enrolled a total of 876 OSCC patients and 1200 controls. Four SNPs of AURKA, namely rs1047972, rs2273535, rs2064863, and rs6024836, were analyzed using real-time polymerase chain reaction (PCR). Among the 1420 smokers, the AURKA polymorphism carriers with the betel nut chewing habit had a higher risk of oral cancer than AURKA wild-type (WT) carriers without the betel nut chewing habit. Patients with the AURKA rs2064863 gene had a 1.365-fold higher risk of stage III or IV OSCC (95% confidence interval [CI] 1.029–1.811) than those with the rs2064863 WT gene. Furthermore, carriers of the AURKA rs1047972/rs2273535/rs2064863 C-A-T haplotype had a 1.736-fold (95% CI 1.110–2.715) higher risk of OSCC than controls (C-T-T, the most common haplotype). Among patients with the betel quid chewing habit, carriers of other haplotypes (C-T-T, C-A-G, T-A-T, T-A-G, T-T-T, and C-T-G) had a 12.857-fold (95% CI 10.731–15.404) increased risk, and carriers of the C-A-T haplotype had the highest risk (AOR: 31.120; 95% CI 13.864–69.850) of OSCC, compared with those without the betel quid chewing who harbored other haplotypes.

Conclusions

In conclusion, betel nut chewing combined with the AURKA C-A-T haplotypes lead to a high risk of OSCC. These findings reveal a novel genetic-environmental predisposition for oral tumorigenesis.

Functional Significance of Aurora Kinases-p53 Protein Family Interactions in Cancer

Aurora kinases play critical roles in regulating spindle assembly, chromosome segregation, and cytokinesis to ensure faithful segregation of chromosomes during mitotic cell division cycle. Molecular and cell biological studies have revealed that Aurora kinases, at physiological levels, orchestrate complex sequential cellular processes at distinct subcellular locations through functional interactions with its various substrates. Aberrant expression of Aurora kinases, on the other hand, cause defects in mitotic spindle assembly, checkpoint response activation, and chromosome segregation leading to chromosomal instability. Elevated expression of Aurora kinases correlating with chromosomal instability is frequently detected in human cancers. Recent genomic profiling of about 3000 human cancer tissue specimens to identify various oncogenic signatures in The Cancer Genome Atlas project has reported that recurrent amplification and overexpression of Aurora kinase-A characterize distinct subsets of human tumors across multiple cancer types. Besides the well-characterized canonical pathway interactions of Aurora kinases in regulating assembly of the mitotic apparatus and chromosome segregation, growing evidence also supports the notion that deregulated expression of Aurora kinases in non-canonical pathways drive transformation and genomic instability by antagonizing tumor suppressor and exacerbating oncogenic signaling through direct interactions with critical proteins. Aberrant expression of the Aurora kinases–p53 protein family signaling axes appears to be critical in the abrogation of p53 protein family mediated tumor suppressor pathways frequently deregulated during oncogenic transformation process. Recent findings reveal the existence of feedback regulatory loops in mRNA expression and protein stability of these protein families and their consequences on downstream effectors involved in diverse physiological functions, such as mitotic progression, checkpoint response pathways, as well as self-renewal and pluripotency in embryonic stem cells. While these investigations have focused on the functional consequences of Aurora kinase protein family interactions with wild-type p53 family proteins, those involving Aurora kinases and mutant p53 remain to be elucidated. This article presents a comprehensive review of studies on Aurora kinases–p53 protein family interactions along with a prospective view on the possible functional consequences of Aurora kinase–mutant p53 signaling pathways in tumor cells. Additionally, we also discuss therapeutic implications of these findings in Aurora kinases overexpressing subsets of human tumors.