A novel Aurora-A-mediated phosphorylation of p53 inhibits its interaction with MDM2

Aurora Kinase A Inhibition Potentiates Platinum and Radiation Cytotoxicity in Non-Small-Cell Lung Cancer Cells and Induces Expression of Alternative Immune Checkpoints

Despite major advances in non-small-cell lung cancer (NSCLC) treatment, the five-year survival rates for patients with non-oncogene-driven tumors remain low, necessitating combinatory approaches to improve outcomes. Our prior high-throughput RNAi screening identified Aurora kinase A (AURKA) as a potential key player in cisplatin resistance. In this study, we investigated AURKA's role in platinum and radiation sensitivity in multiple NSCLC cell lines and xenograft mouse models, as well as its effect on immune checkpoints, including PD-L1, B7x, B7-H3, and HHLA2. Of 94 NSCLC patient tumor specimens, 91.5% tested positive for AURKA expression, with 34% showing moderate-to-high levels. AURKA expression was upregulated following cisplatin treatment in NSCLC cell lines PC9 and A549. Both AURKA inhibition by alisertib and inducible AURKA knockdown potentiated the cytotoxic effects of cisplatin and radiation, leading to tumor regression in doxycycline-inducible xenograft mice. Co-treated cells exhibited increased DNA double-strand breaks, apoptosis, and senescence. Additionally, AURKA inhibition alone by alisertib increased PD-L1 and B7-H3 expression. In conclusion, our study demonstrates that AURKA inhibition enhances the efficacy of platinum-based chemotherapy in NSCLC cells and modulates the expression of multiple immune checkpoints. Therefore, combinatory regimens with AURKA inhibitors should be strategically designed and further studied within the evolving landscape of chemo-immunotherapy.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

The involvement of Aurora-A and p53 in oxaliplatin-resistant colon cancer cells

Resistance to chemotherapy is the deadlock in cancer treatment. In this study, we used wild-type LOVO (LOVO^WT ), a human colon cancer cell line, and the oxaliplatin-resistant sub-clone LOVO^OR cells to investigate the molecular mechanisms of the development of drug resistance in colon cancer. Compared with LOVO^WT cells, LOVO^OR cells had a high proliferation capacity and a high percentage on the G2/M phase. The expression and activation of Aurora-A, a critical kinase in G2/M phase, were higher in LOVO^OR cells than in LOVO^WT cells. The results from immunofluorescence indicated an irregular distribution of Aurora-A in LOVO^OR cells. To evaluate the importance of Aurora-A in oxaliplatin-resistant property of LOVO^OR cells, overexpression of Aurora-A in LOVO^WT cells and otherwise knockdown of Aurora-A in LOVO^OR cells were performed and followed by administration of oxaliplatin. The results indicated that Aurora-A might contribute to the resistance of LOVO^OR cells to oxaliplatin treatment by depressing p53 signaling. The specific findings in this study provide a possibility that targeting Aurora-A might be a solution for patients who have failed oxaliplatin treatment.

Emerging roles of Aurora-A kinase in cancer therapy resistance

Aurora kinase A (Aurora-A), a serine/threonine kinase, plays a pivotal role in various cellular processes, including mitotic entry, centrosome maturation and spindle formation. Overexpression or gene-amplification/mutation of Aurora-A kinase occurs in different types of cancer, including lung cancer, colorectal cancer, and breast cancer. Alteration of Aurora-A impacts multiple cancer hallmarks, especially, immortalization, energy metabolism, immune escape and cell death resistance which are involved in cancer progression and resistance. This review highlights the most recent advances in the oncogenic roles and related multiple cancer hallmarks of Aurora-A kinase-driving cancer therapy resistance, including chemoresistance (taxanes, cisplatin, cyclophosphamide), targeted therapy resistance (osimertinib, imatinib, sorafenib, etc.), endocrine therapy resistance (tamoxifen, fulvestrant) and radioresistance. Specifically, the mechanisms of Aurora-A kinase promote acquired resistance through modulating DNA damage repair, feedback activation bypass pathways, resistance to apoptosis, necroptosis and autophagy, metastasis, and stemness. Noticeably, our review also summarizes the promising synthetic lethality strategy for Aurora-A inhibitors in RB1, ARID1A and MYC gene mutation tumors, and potential synergistic strategy for mTOR, PAK1, MDM2, MEK inhibitors or PD-L1 antibodies combined with targeting Aurora-A kinase. In addition, we discuss the design and development of the novel class of Aurora-A inhibitors in precision medicine for cancer treatment.

The Four Homeostasis Knights: In Balance upon Post-Translational Modifications

A cancer outcome is a multifactorial event that comes from both exogenous injuries and an endogenous predisposing background. The healthy state is guaranteed by the fine-tuning of genes controlling cell proliferation, differentiation, and development, whose alteration induces cellular behavioral changes finally leading to cancer. The function of proteins in cells and tissues is controlled at both the transcriptional and translational level, and the mechanism allowing them to carry out their functions is not only a matter of level. A major challenge to the cell is to guarantee that proteins are made, folded, assembled and delivered to function properly, like and even more than other proteins when referring to oncogenes and onco-suppressors products. Over genetic, epigenetic, transcriptional, and translational control, protein synthesis depends on additional steps of regulation. Post-translational modifications are reversible and dynamic processes that allow the cell to rapidly modulate protein amounts and function. Among them, ubiquitination and ubiquitin-like modifications modulate the stability and control the activity of most of the proteins that manage cell cycle, immune responses, apoptosis, and senescence. The crosstalk between ubiquitination and ubiquitin-like modifications and post-translational modifications is a keystone to quickly update the activation state of many proteins responsible for the orchestration of cell metabolism. In this light, the correct activity of post-translational machinery is essential to prevent the development of cancer. Here we summarize the main post-translational modifications engaged in controlling the activity of the principal oncogenes and tumor suppressors genes involved in the development of most human cancers.

Combination of AURKA inhibitor and HSP90 inhibitor to treat breast cancer with AURKA overexpression and TP53 mutations

Breast cancer is the most common cancer among women worldwide. Researches show that Aurora kinase A (AURKA) is highly expressed in approximately 73% of breast cancer patients, which induces drug resistance in breast cancer patients and decreases the median survival time. AURKA regulates spindle assembly, centrosome maturation, and chromosome alignment. AURKA overexpression affects the occurrence and development of breast cancer. Besides AURKA overexpression, heat shock protein 90 (HSP90) maintains the survival and proliferation of tumor cells by stabilizing the structure of oncoproteins, including P53 mutants (mtP53). TP53 mutations accounted for approximately 13%, 40%, 80%, 33%, 71%, and 82% of luminal A, Luminal B, Luminal C, normal basal-like, HER2-amplified, and basal-like breast cancers, respectively. TP53 mutation can aggravate cell genome instability and enhance the invasion, migration, and resistance of cancer cell. This review describes the research status of AURKA and HSP90 in breast cancer, summarizes the structure, function, and the chaperone cycle of HSP90, elaborates the interrelation between HSP90, mtP53, P53, and AURKA, and proposes the combination of HSP90 inhibitor and AURKA inhibitor to treat breast cancer. Targeting AURKA and HSP90 to treat cancer with AURKA overexpression and TP53 mutations will help improve the specificity and efficiency of breast cancer treatment and solve the problem of drug resistance.

Post-Translational Modifications of p53 in Ferroptosis: Novel Pharmacological Targets for Cancer Therapy

The tumor suppressor p53 is a well-known cellular guardian of genomic integrity that blocks cell cycle progression or induces apoptosis upon exposure to cellular stresses. However, it is unclear how the remaining activities of p53 are regulated after the abrogation of these routine activities. Ferroptosis is a form of iron- and lipid-peroxide-mediated cell death; it is particularly important in p53-mediated carcinogenesis and corresponding cancer prevention. Post-translational modifications have clear impacts on the tumor suppressor function of p53. Here, we review the roles of post-translational modifications in p53-mediated ferroptosis, which promotes the elimination of tumor cells. A thorough understanding of the p53 functional network will be extremely useful in future strategies to identify pharmacological targets for cancer therapy.

It’s Getting Complicated—A Fresh Look at p53-MDM2-ARF Triangle in Tumorigenesis and Cancer Therapy

Anti-tumorigenic mechanisms mediated by the tumor suppressor p53, upon oncogenic stresses, are our bodies’ greatest weapons to battle against cancer onset and development. Consequently, factors that possess significant p53-regulating activities have been subjects of serious interest from the cancer research community. Among them, MDM2 and ARF are considered the most influential p53 regulators due to their abilities to inhibit and activate p53 functions, respectively. MDM2 inhibits p53 by promoting ubiquitination and proteasome-mediated degradation of p53, while ARF activates p53 by physically interacting with MDM2 to block its access to p53. This conventional understanding of p53-MDM2-ARF functional triangle have guided the direction of p53 research, as well as the development of p53-based therapeutic strategies for the last 30 years. Our increasing knowledge of this triangle during this time, especially through identification of p53-independent functions of MDM2 and ARF, have uncovered many under-appreciated molecular mechanisms connecting these three proteins. Through recognizing both antagonizing and synergizing relationships among them, our consideration for harnessing these relationships to develop effective cancer therapies needs an update accordingly. In this review, we will re-visit the conventional wisdom regarding p53-MDM2-ARF tumor-regulating mechanisms, highlight impactful studies contributing to the modern look of their relationships, and summarize ongoing efforts to target this pathway for effective cancer treatments. A refreshed appreciation of p53-MDM2-ARF network can bring innovative approaches to develop new generations of genetically-informed and clinically-effective cancer therapies.

Aurora kinases in ovarian cancer

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

Integrated pan-cancer of AURKA expression and drug sensitivity analysis reveals increased expression of AURKA is responsible for drug resistance

Introduction

The AURKA gene encodes a protein kinase involved in cell cycle regulation and plays an oncogenic role in many cancers. The main objective of this study is to analyze AURKA expression in 13 common cancers and its role in prognostic and drug resistance.

Method

Using the cancer genome atlas (TCGA) as well as CCLE and GDSC data, the level of AURKA gene expression and its role in prognosis and its association with drug resistance were evaluated, respectively. In addition, the expression level of AURKA was assessed in colorectal cancer (CRC) and gastric cancer (GC) samples. Besides, using Gene Expression Omnibus (GEO) data, drugs that could affect the expression level of this gene were also identified.

Results

The results indicated that the expression level of AURKA gene in 13 common cancers increased significantly compared to normal samples or it survived poorly (HR >1, p < 0.01) in lung, prostate, kidney, bladder, and uterine cancers. Also, the gene expression data showed increased expression in CRC and GC samples compared to normal ones. The level of AURKA was significantly associated with the resistance to SB 505124, NU‐7441, and irinotecan drugs (p < 0.01). Eventually, GEO data showed that JQ1, actinomycin D1, and camptothecin could reduce the expression of AURKA gene in different cancer cell lines (logFC < 1, p < 0.01).

Conclusion

Increased expression of AURKA is observed in prevalent cancers and associated with poor prognostic and the development of drug resistance. In addition, some chemotherapy drugs can reduce the expression of this gene.

Deciphering the PTM codes of the tumor suppressor p53

The genome guardian p53 functions as a transcription factor that senses numerous cellular stresses and orchestrates the corresponding transcriptional events involved in determining various cellular outcomes, including cell cycle arrest, apoptosis, senescence, DNA repair, and metabolic regulation. In response to diverse stresses, p53 undergoes multiple posttranslational modifications (PTMs) that coordinate with intimate interdependencies to precisely modulate its diverse properties in given biological contexts. Notably, PTMs can recruit ‘reader’ proteins that exclusively recognize specific modifications and facilitate the functional readout of p53. Targeting PTM–reader interplay has been developing into a promising cancer therapeutic strategy. In this review, we summarize the advances in deciphering the ‘PTM codes’ of p53, focusing particularly on the mechanisms by which the specific reader proteins functionally decipher the information harbored within these PTMs of p53. We also highlight the potential applications of intervention with p53 PTM–reader interactions in cancer therapy and discuss perspectives on the ‘PTMomic’ study of p53 and other proteins.

Co-relation with novel phosphorylation sites of IκBα and necroptosis in breast cancer cells

Background

Phosphorylation of NF-kappaB inhibitor alpha (IκBα) is key to regulation of NF-κB transcription factor activity in the cell. Several sites of IκBα phosphorylation by members of the IκB kinase family have been identified, but phosphorylation of the protein by other kinases remains poorly understood. We investigated a new phosphorylation site on IκBα and identified its biological function in breast cancer cells.

Methods

Previously, we observed that aurora kinase (AURK) binds IκBα in the cell. To identify the domains of IκBα essential for phosphorylation by AURK, we performed kinase assays with a series of IκBα truncation mutants. AURK significantly promoted activation of IκBα at serine 32 but not serine 36; by contrast, IκB kinase (IKK) family proteins activated both of these residues. We also confirmed phosphorylation of IκBα by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) and nano-liquid chromatography hybrid quadrupole orbitrap mass spectrometer (nanoLC-MS/MS; Q-Exactive).

Results

We identified two novel sites of serine phosphorylation, S63 and S262. Alanine substitution of S63 and S262 (S63A and S262A) of IκBα inhibited proliferation and suppressed p65 transcription activity. In addition, S63A and/or S262A of IκBα regulated apoptotic and necroptotic effects in breast cancer cells.

Conclusions

Phosphorylation of IκBα by AURK at novel sites is related to the apoptosis and necroptosis pathways in breast cancer cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08304-7.

Curcumin Rescues Doxorubicin Responsiveness via Regulating Aurora a Signaling Network in Breast Cancer Cells

BACKGROUND

Insensitivity towards anthracycline drugs like doxorubicin poses a significant challenge in the treatment of breast cancer. Among several factors, Aurora A (a mitotic serine threonine kinase) plays crucial roles in acquiring non-responsiveness towards doxorubicin. However, the mechanisms underlying need to be elucidated. The present study was therefore designed to evaluate the underlying mechanisms of Aurora A mediated doxorubicin insensitivity in MCF-7Dox/R, an isolated resistant-subline of MCF-7 (breast adenocarcinoma cell line). Effect of curcumin, a natural phytochemical in restoring doxorubicin sensitivity by targeting Aurora A was assessed furthermore.

METHODS

A doxorubicin resistant subline (MCF-7Dox/R) was isolated from the parental MCF-7 cells by treating the cell with gradual step-wise increasing concentration of the drug. Expressions of Aurora A and its target proteins (Akt, IκBα and NFκB) were assessed in both parental and MCF-7Dox/R cells. Both the cell lines were pretreated with curcumin prior to doxorubicin treatment. Cellular proliferation rate was measured using BrdU (5-bromo-2'-deoxyuridine) assay kit. Intracellular doxorubicin accumulation was estimated spectrofluorimetrically. Cellular uptake of curcumin (spectrophotometric and spectrofluorimetric method) and its nuclear localization was confirmed by confocal microscopic study. Protein expressions were determined by western blot analysis. Localization of Aurora A was ascertained by immunofluorescence assay. To explore the possible outcome of impact of curcumin on Aurora A, cell-cycle distribution and apoptosis were performed subsequently.

RESULTS

Higher expressions of Aurora A in MCF-7Dox/R cells led to phosphorylation of Akt as well as IκBα. Phosphorylated IκBα preceded release of NFκB. Phospho-Akt, NFκB consequentially decreased doxorubicin accumulation by enhancing the expressions of ABCG2 and Pgp1 respectively. Curcumin by regulating Aurora A and its target molecules sensitized resistant subline towards doxorubicin mediated G2/M-arrest and apoptosis.

CONCLUSION

Molecular targeting of Aurora A by curcumin restores chemosensitivity by increasing the efficacy of doxorubicin in breast cancer.<br />.

OTUD6A Is an Aurora Kinase A-Specific Deubiquitinase

Aurora kinases are serine/threonine kinases required for cell proliferation and are overexpressed in many human cancers. Targeting Aurora kinases has been a therapeutic strategy in cancer treatment. Here, we attempted to identify a deubiquitinase (DUB) that regulates Aurora kinase A (Aurora-A) protein stability and/or kinase activity as a potential cancer therapeutic target. Through pull-down assays with the human DUB library, we identified OTUD6A as an Aurora-A-specific DUB. OTUD6A interacts with Aurora-A through OTU and kinase domains, respectively, and deubiquitinates Aurora-A. Notably, OTUD6A promotes the protein half-life of Aurora-A and activates Aurora-A by increasing phosphorylation at threonine 288 of Aurora-A. From qPCR screening, we identified and validated that the cancer gene CKS2 encoding Cyclin-dependent kinases regulatory subunit 2 is the most upregulated cell cycle regulator when OTUD6A is overexpressed. The results suggest that OTUD6A may serve as a therapeutic target in human cancers.

Targeting AURKA in Cancer: molecular mechanisms and opportunities for Cancer therapy

Aurora kinase A (AURKA) belongs to the family of serine/threonine kinases, whose activation is necessary for cell division processes via regulation of mitosis. AURKA shows significantly higher expression in cancer tissues than in normal control tissues for multiple tumor types according to the TCGA database. Activation of AURKA has been demonstrated to play an important role in a wide range of cancers, and numerous AURKA substrates have been identified. AURKA-mediated phosphorylation can regulate the functions of AURKA substrates, some of which are mitosis regulators, tumor suppressors or oncogenes. In addition, enrichment of AURKA-interacting proteins with KEGG pathway and GO analysis have demonstrated that these proteins are involved in classic oncogenic pathways. All of this evidence favors the idea of AURKA as a target for cancer therapy, and some small molecules targeting AURKA have been discovered. These AURKA inhibitors (AKIs) have been tested in preclinical studies, and some of them have been subjected to clinical trials as monotherapies or in combination with classic chemotherapy or other targeted therapies.

Aurora kinases and DNA damage response

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

Inhibition of Aurora A enhances radiosensitivity in selected lung cancer cell lines

Background

In mammalian cells, Aurora serine/threonine kinases (Aurora A, B, and C) are expressed in a cell cycle-dependent fashion as key mitotic regulators required for the maintenance of chromosomal stability. Aurora-A (AURKA) has been proven to be an oncogene in a variety of cancers; however, whether its expression relates to patient survival and the association with radiotherapy remains unclear in non-small cell lung cancer (NSCLC).

Methods

Here, we first analyzed AURKA expression in 63 NSCLC tumor samples by immunohistochemistry (IHC) and used an MTS assay to compare cell survival by targeting AURKA with MLN8237 (Alisertib) in H460 and HCC2429 (P53-competent), and H1299 (P53-deficient) cell lines. The radiosensitivity of MLN8237 was further evaluated by clonogenic assay. Finally, we examined the effect of combining radiation and AURKA inhibition in vivo with a xenograft model and explored the potential mechanism.

Results

We found that increased AURKA expression correlated with decreased time to progression and overall survival (p = 0.0447 and 0.0096, respectively). AURKA inhibition using 100 nM MLN8237 for 48 h decreases cell growth in a partially P53-dependent manner, and the survival rates of H460, HCC2429, and H1299 cells were 56, 50, and 77%, respectively. In addition, the survival of H1299 cells decreased 27% after ectopic restoration of P53 expression, and the radiotherapy enhancement was also influenced by P53 expression (DER H460 = 1.33; HCC2429 = 1.35; H1299 = 1.02). Furthermore, tumor growth of H460 was delayed significantly in a subcutaneous mouse model exposed to both MLN8237 and radiation.

Conclusions

Taken together, our results confirmed that the expression of AURKA correlated with decreased NSCLC patient survival, and it might be a promising inhibition target when combined with radiotherapy, especially for P53-competent lung cancer cells. Modulation of P53 function could provide a new option for reversing cell resistance to the AURKA inhibitor MLN8237, which deserves further investigation.

p53 modifications: exquisite decorations of the powerful guardian

The last 40 years have witnessed how p53 rose from a viral binding protein to a central factor in both stress responses and tumor suppression. The exquisite regulation of p53 functions is of vital importance for cell fate decisions. Among the multiple layers of mechanisms controlling p53 function, posttranslational modifications (PTMs) represent an efficient and precise way. Major p53 PTMs include phosphorylation, ubiquitination, acetylation, and methylation. Meanwhile, other PTMs like sumoylation, neddylation, O-GlcNAcylation, adenosine diphosphate (ADP)-ribosylation, hydroxylation, and β-hydroxybutyrylation are also shown to play various roles in p53 regulation. By independent action or interaction, PTMs affect p53 stability, conformation, localization, and binding partners. Deregulation of the PTM-related pathway is among the major causes of p53-associated developmental disorders or diseases, especially in cancers. This review focuses on the roles of different p53 modification types and shows how these modifications are orchestrated to produce various outcomes by modulating p53 activities or targeted to treat different diseases caused by p53 dysregulation.

The EGF/hnRNP Q1 axis is involved in tumorigenesis via the regulation of cell cycle-related genes

Heterogeneous nuclear ribonucleoprotein (hnRNP) Q1, an RNA-binding protein, has been implicated in many post-transcriptional processes, including RNA metabolism and mRNA splicing and translation. However, the role of hnRNP Q1 in tumorigenesis remains unclear. We previously performed RNA immunoprecipitation (RIP)-seq analysis to identify hnRNP Q1-interacting mRNAs and found that hnRNP Q1 targets a group of genes that are involved in mitotic regulation, including Aurora-A. Here, we demonstrate that altering the hnRNP Q1 level influences the expression of the Aurora-A protein, but not its mRNA. Stimulation with epidermal growth factor (EGF) enhances both binding between hnRNP Q1 and Aurora-A mRNA as well as the efficacy of the hnRNP Q1-induced translation of Aurora-A mRNA. The EGF/hnRNP Q1-induced translation of Aurora-A mRNA is mediated by the mTOR and ERK pathways. In addition, we show that hnRNP Q1 up-regulates the translation of a group of spindle assembly checkpoint (SAC) genes. hnRNP Q1 overexpression is positively correlated with the levels of Aurora-A and the SAC genes in human colorectal cancer tissues. In summary, our data suggest that hnRNP Q1 plays an important role in regulating the expression of a group of cell cycle-related genes. Therefore, it may contribute to tumorigenesis by up-regulating the translation of these genes in colorectal cancer.

An RNA-binding protein contributes to cancer by boosting the protein-making potential of various genes involved in the cell cycle and cell division. Researchers in Taiwan led by Liang-Yi Hung from the National Cheng Kung University in Tainan, Taiwan, previously showed that a cancer-causing protein implicated in tumors of the colon and elsewhere gets induced by both an RNA-binding protein called hnRNP Q1 and a growth factor called EGF. Now, they have demonstrated that these two molecules work in concert to boost the efficiency by which the RNA encoding the cancer-causing protein gets translated into the protein. They also showed that hnRNP Q1 serves a similar RNA-modulating function for several genes involved in spindle checkpoint during cell division. Together, the findings point to hnRNP Q1 as a potential target for future anti-cancer drugs.

TP53 mutations, expression and interaction networks in human cancers

Although the associations of p53 dysfunction, p53 interaction networks and oncogenesis have been widely explored, a systematic analysis of TP53 mutations and its related interaction networks in various types of human cancers is lacking. Our study explored the associations of TP53 mutations, gene expression, clinical outcomes, and TP53 interaction networks across 33 cancer types using data from The Cancer Genome Atlas (TCGA). We show that TP53 is the most frequently mutated gene in a number of cancers, and its mutations appear to be early events in cancer initiation. We identified genes potentially repressed by p53, and genes whose expression correlates significantly with TP53 expression. These gene products may be especially important nodes in p53 interaction networks in human cancers. This study shows that while TP53-truncating mutations often result in decreased TP53 expression, other non-truncating TP53 mutations result in increased TP53 expression in some cancers. Survival analyses in a number of cancers show that patients with TP53 mutations are more likely to have worse prognoses than TP53-wildtype patients, and that elevated TP53 expression often leads to poor clinical outcomes. We identified a set of candidate synthetic lethal (SL) genes for TP53, and validated some of these SL interactions using data from the Cancer Cell Line Project. These predicted SL genes are promising candidates for experimental validation and the development of personalized therapeutics for patients with TP53-mutated cancers.

Cisplatin-resistant cancer cells are sensitive to Aurora kinase A inhibition by alisertib

De novo and acquired resistance to platinum therapy such as cisplatin (CDDP) is a clinical challenge in gastric cancer treatment. Aberrant expression and activation of aurora kinase A (AURKA) and eukaryotic translation initiation factor 4E (eIF4E) are detected in several cancer types. Herein, we investigated the role of AURKA in CDDP resistance in gastric cancer. Western blot analysis demonstrated overexpression of AURKA and phosphorylation of eIF4E in acquired and de novo CDDP‐resistant gastric cancer models. Inhibition of AURKA with MLN8237 (alisertib) alone or in combination with CDDP significantly suppressed viability of CDDP‐resistant cancer cells (P < 0.01). Additionally, inhibition or knockdown of AURKA decreased protein expression of p‐eIF4E (S209), HDM2, and c‐MYC in CDDP‐resistant cell models. This was associated with a significant decrease in cap‐dependent translation levels (P < 0.01). In vivo tumor xenografts data corroborated these results and confirmed that inhibition of AURKA was sufficient to overcome CDDP resistance in gastric cancer. Our data demonstrate that AURKA promotes acquired and de novo resistance to CDDP through regulation of p‐eIF4E (S209), c‐MYC, HDM2, and cap‐dependent translation. Targeting AURKA could be an effective therapeutic approach to overcome CDDP resistance in refractory gastric cancer and possibly other cancer types.

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.

Abrogation of AuroraA-TPX2 by novel natural inhibitors: molecular dynamics-based mechanistic analysis

INTRODUCTION

Cancer is characterized by uncontrolled cell growth and genetic instabilities. The human Aurora-A kinase protein plays a crucial role in spindle assembly during mitosis and is activated by another candidate oncogene, targeting protein for Xklp2 (TPX2). It has been proposed that dissociation of Aurora A-TPX2 complex leads to disruption of mitotic spindle apparatus, thereby preventing cell division and further tumor growth.

MATERIALS AND METHODS

A large natural compound library was docked against the active site of Aurora A-TPX2 complex. The protein-ligand complexes were subjected to molecular dynamics simulation to ascertain their binding stability. The drug properties of the compounds were analyzed to observe their drug-like properties.

RESULTS

The virtual screening of natural compound library yielded two high scoring compounds, the first compound CTOM [ZINC ID: 38143674] (Glide score: -9.49) was stable for 17 ns while the second TTOM (Glide score: -9.07) was stable for 15 ns. While CTOM interacted with His280, Thr288 of Aurora A and Tyr34, Lys38 of TPX2, TTOM interacted with Arg285 and Arg286 in addition to the residues involved with CTOM.

CONCLUSIONS

We report two natural compounds as potential drugs leads for the disruption of this complex. These ligands show a preferable docking score and have many drugs like properties within in the range of 95% of known drugs. The study provides evidence that CTOM and TTOM can efficiently inhibit the TPX2-mediated activation of Aurora A. Thus, it paves way for an elaborate investigation and establishes the importance of computational approaches as time- and cost-effective techniques.

Role of Aurora-A in Ovarian Cancer: A Meta-Analysis

BACKGROUND

Recently, several studies have examined associations between Aurora-A expression and clinical outcome in patients with ovarian cancer, but yielded conflicting results with respect to survival. Therefore, the aim of this study was to evaluate the prognostic significance of Aurora-A in ovarian cancer by performing a meta-analysis.

METHODS

PubMed, Cochrane library, Web of Science, Embase, Medline and Chinese BioMed Database (CBM) databases were searched systematically and only articles in which Aurora-A expression was detected by immunohistochemical staining were included. Hazard ratios (HRs) with 95% confidence intervals (CIs) were extracted and pooled for overall survival (OS) and disease-free survival (DFS).

RESULTS

Our results show that the pooled HR for OS was 1.40 (95% CI 0.82-1.98, p < 0.01) by univariate analysis in 7 articles (1,028) and 0.32 (95% CI 0.04-0.615, p = 0.23) by multivariate analysis in 3 studies (155). The association between Aurora-A expression and DFS was also statistically significant in 5 studies (HR = 1.14, 95% CI 0.50-1.78, p < 0.01).

CONCLUSION

This present meta-analysis suggests that the Aurora-A expression may be associated with poor prognosis in patients with ovarian cancer. Furthermore, studies of larger scale and well-matched regimes are warranted to confirm the findings in the future.

Bioinformatics study of cancer-related mutations within p53 phosphorylation site motifs

p53 protein has about thirty phosphorylation sites located at the N- and C-termini and in the core domain. The phosphorylation sites are relatively less mutated than other residues in p53. To understand why and how p53 phosphorylation sites are rarely mutated in human cancer, using a bioinformatics approaches, we examined the phosphorylation site and its nearby flanking residues, focusing on the consensus phosphorylation motif pattern, amino-acid correlations within the phosphorylation motifs, the propensity of structural disorder of the phosphorylation motifs, and cancer mutations observed within the phosphorylation motifs. Many p53 phosphorylation sites are targets for several kinases. The phosphorylation sites match 17 consensus sequence motifs out of the 29 classified. In addition to proline, which is common in kinase specificity-determining sites, we found high propensity of acidic residues to be adjacent to phosphorylation sites. Analysis of human cancer mutations in the phosphorylation motifs revealed that motifs with adjacent acidic residues generally have fewer mutations, in contrast to phosphorylation sites near proline residues. p53 phosphorylation motifs are mostly disordered. However, human cancer mutations within phosphorylation motifs tend to decrease the disorder propensity. Our results suggest that combination of acidic residues Asp and Glu with phosphorylation sites provide charge redundancy which may safe guard against loss-of-function mutations, and that the natively disordered nature of p53 phosphorylation motifs may help reduce mutational damage. Our results further suggest that engineering acidic amino acids adjacent to potential phosphorylation sites could be a p53 gene therapy strategy.

Identification of potential synthetic lethal genes to p53 using a computational biology approach

BACKGROUND

Identification of genes that are synthetic lethal to p53 is an important strategy for anticancer therapy as p53 mutations have been reported to occur in more than half of all human cancer cases. Although genome-wide RNAi screening is an effective approach to finding synthetic lethal genes, it is costly and labor-intensive.

METHODS

To illustrate this approach, we identified potentially druggable genes synthetically lethal for p53 using three microarray datasets for gene expression profiles of the NCI-60 cancer cell lines, one next-generation sequencing (RNA-Seq) dataset from the Cancer Genome Atlas (TCGA) project, and one gene expression data from the Cancer Cell Line Encyclopedia (CCLE) project. We selected the genes which encoded kinases and had significantly higher expression in the tumors with functional p53 mutations (somatic mutations) than in the tumors without functional p53 mutations as the candidates of druggable synthetic lethal genes for p53. We identified important regulatory networks and functional categories pertinent to these genes, and performed an extensive survey of literature to find experimental evidence that support the synthetic lethality relationships between the genes identified and p53. We also examined the drug sensitivity difference between NCI-60 cell lines with functional p53 mutations and NCI-60 cell lines without functional p53 mutations for the compounds that target the kinases encoded by the genes identified.

RESULTS

Our results indicated that some of the candidate genes we identified had been experimentally verified to be synthetic lethal for p53 and promising targets for anticancer therapy while some other genes were putative targets for development of cancer therapeutic agents.

CONCLUSIONS

Our study indicated that pre-screening of potential synthetic lethal genes using gene expression profiles is a promising approach for improving the efficiency of synthetic lethal RNAi screening.

Aurora B prevents delayed DNA replication and premature mitotic exit by repressing p21(Cip1)

Aurora kinase B is a critical component of the chromosomal passenger complex, which is involved in the regulation of microtubule-kinetochore attachments and cytokinesis. By using conditional knockout cells and chemical inhibition, we show here that inactivation of Aurora B results in delayed G(1)/S transition and premature mitotic exit. Aurora B deficiency results in delayed DNA replication in cultured fibroblasts as well as liver cells after hepatectomy. This is accompanied by increased transcription of the cell cycle inhibitor p21 (Cip1). Lack of Aurora B does not prevent mitotic entry but results in a premature exit from prometaphase in the presence of increased p21(Cip1)-Cdk1 inactive complexes. Aurora B-null cells display reduced degradation of cyclin B1, suggesting the presence of phenomenon known as adaptation to the mitotic checkpoint, previously described in yeast. Elimination of p21(Cip1) rescues Cdk1 activity and prevents premature mitotic exit in Aurora B-deficient cells. These results suggest that Aurora B represses p21(Cip1), preventing delayed DNA replication, Cdk inhibition and premature mitotic exit. The upregulation of p21(Cip1) observed after inhibition of Aurora B may have important implications in cell cycle progression, tetraploidy, senescence or cancer therapy.