MLN8054, a small molecule inhibitor of aurora kinase a, sensitizes androgen-resistant prostate cancer to radiation

Mitotic kinase inhibitors as Therapeutic Interventions for Prostate Cancer: Evidence from In vitro Studies

Prostate cancer is one of the devastating diseases characterized by genetic changes leading to uncontrolled growth and metastasis of the cells of the prostate gland and affects men worldwide. Conventional hormonal and chemotherapeutic agents are effective in mitigating the disease if diagnosed at an early stage. All dividing eukaryotic cells require mitotic progression for the maintenance of genomic integrity in progeny populations. The protein kinases, upon activation and de-activation in an ordered fashion, lead to spatial and temporal regulation of the cell division process. The entry into mitosis along with the progression into sub-phases of mitosis is ensured due to the activity of mitotic kinases. These kinases include Polo-Like-Kinase 1 (PLK1), Aurora kinases, and Cyclin-Dependent-Kinase 1 (CDK1), among others. The mitotic kinases, among others, are usually overexpressed in many cancers and can be targeted using small molecule inhibitors to reduce the effects of these regulators on mechanisms, such as regulation of genomic integrity and mitotic fidelity. In this review, we attempted to discuss the appropriate functions of mitotic kinases revealed through cell culture studies and the impact of their respective inhibitors derived in pre-clinical studies. The review is designed to elucidate the growing field of small molecule inhibitors and their functional screening or mode of action at the cellular and molecular level in the context of Prostate Cancer. Therefore, studies performed specifically on cells of Prostatic-origin are narrated in this review, culminating in a comprehensive view of the specific field of mitotic kinases that can be targeted for therapy of Prostate cancer.

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.

Identification of Ferroptosis-Related Genes in Laryngeal Carcinoma Using an Integrated Bioinformatics Approach

Amaç: Hücre içi demir birikimi ve lipid peroksidasyonu ile karakterize edilen ferroptoz, tümör baskılanmasında önemli rol oynayabilen yeni tanımlanmış bir hücre ölüm şeklidir. Larengeal skuamöz hücreli karsinom (LSHK) ve ferroptozis arasındaki ilişki hakkında yapılan çalışmalar sınırlıdır. Bu çalışmanın amacı, LSHK' nin tanı, tedavisinde ve ferroptozis ile ilgili belirteçleri in siliko yöntemleri kullanarak saptamaktır.Yöntem: Ferroptoz ile ilgili genler, FerrDb veri tabanından elde edildi. The Cancer Genome Atlas (TCGA) veri setlerinden LSHK hastalarının mRNA ekspresyon verileri ve ferroptoz ile ilgili bazı genleri taramak için kullanıldı. LSHK ile ilgili GSE143224 ve GSE84957 mikrodizi veri setleri GEO veri tabanından elde edilmiştir. Tüm veri setleri kullanılarak ferroptoz ve LSHK ile ilişkili genleri elde etmek için örtüşen veriler kullanılmıştır. LSHK grubu ve normal kontroller arasındaki diferansiyel olarak eksprese edilen genler (DEG'ler) ve ferroptoz ile ilgili DEG'ler, biyoinformatik yöntemler kullanılarak analiz edildi. Daha sonra STRING ve Cytoscape yazılımları kullanılarak Gene Ontology (GO), KEGG ve protein-protein etkileşimi (PPE) ağı analizleri gerçekleştirilmiştir.Bulgular: Ferroptoz ile ilgili 259 gen, FerrDb veri tabanından alındı ve ferroptoz DEG'lerini tanımlamak için bunları TCGA-HNSC (523 örnek), GSE143224 (25 örnek) ve GSE84957 (18 örnek) ile analizleri yapıldı. Analiz sonrasında 13 adet yukarı regüle edilmiş (NOX4, BID, ABCC1, TNFAIP3, PANX1, SLC1A4, SLC3A2, FTL, TFRC, AURKA, HSF1, PML, CA9; p<0.05) ve 3 adet aşağı regüle edilmiş gen (CHAC1, LPIN1, MUC1; p<0.05) saptanmıştır. GO, KEGG ve PPE analizleri ile elde edilen hücresel stres, inflamasyon, oksidatif stres ve karsinogenez süreçlerine benzer sonuçlar (p<0.05) ile bu genlerin LSHK' nin ilerlemesinde rol oynayabileceğini göstermektedir.Sonuç: Sonuç olarak, bu çalışmada LSHK'de ferroptoz ile yakından ilişkili olan ve LSHK hastalarını sağlıklı kontrollerden ayırt edebilen 16 potansiyel gen saptanmıştır. Çalışmamız, LSHK’nin moleküler mekanizmasını ve terapötik hedeflerini keşfetmek için daha geniş bir fikir sağlayabilir.

Aurora Kinases as Therapeutic Targets in Head and Neck Cancer

ABSTRACT

The Aurora kinases (AURKA and AURKB) have attracted attention as therapeutic targets in head and neck squamous cell carcinomas. Aurora kinases were first defined as regulators of mitosis that localization to the centrosome (AURKA) and centromere (AURKB), governing formation of the mitotic spindle, chromatin condensation, activation of the core mitotic kinase CDK1, alignment of chromosomes at metaphase, and other processes. Subsequently, additional roles for Aurora kinases have been defined in other phases of cell cycle, including regulation of ciliary disassembly and DNA replication. In cancer, elevated expression and activity of Aurora kinases result in enhanced or neomorphic locations and functions that promote aggressive disease, including promotion of MYC expression, oncogenic signaling, stem cell identity, epithelial-mesenchymal transition, and drug resistance. Numerous Aurora-targeted inhibitors have been developed and are being assessed in preclinical and clinical trials, with the goal of improving head and neck squamous cell carcinoma treatment.

Precision Oncology, Signaling and Anticancer Agents in Cancer Therapeutics

BACKGROUND

The global alliance for genomics and healthcare facilities provides innovational solutions to expedite research and clinical practices for complex and incurable health conditions. Precision oncology is an emerging field explicitly tailored to facilitate cancer diagnosis, prevention and treatment based on patients' genetic profile. Advancements in "omics" techniques, next-generation sequencing, artificial intelligence and clinical trial designs provide a platform for assessing the efficacy and safety of combination therapies and diagnostic procedures.

METHOD

Data were collected from Pubmed and Google scholar using keywords: "Precision medicine", "precision medicine and cancer", "anticancer agents in precision medicine" and reviewed comprehensively.

RESULTS

Personalized therapeutics including immunotherapy, cancer vaccines, serve as a groundbreaking solution for cancer treatment. Herein, we take a measurable view of precision therapies and novel diagnostic approaches targeting cancer treatment. The contemporary applications of precision medicine have also been described along with various hurdles identified in the successful establishment of precision therapeutics.

CONCLUSION

This review highlights the key breakthroughs related to immunotherapies, targeted anticancer agents, and target interventions related to cancer signaling mechanisms. The success story of this field in context to drug resistance, safety, patient survival and in improving quality of life is yet to be elucidated. We conclude that, in the near future, the field of individualized treatments may truly revolutionize the nature of cancer patient care.

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.

Aurora Kinase A-YBX1 Synergy Fuels Aggressive Oncogenic Phenotypes and Chemoresistance in Castration-Resistant Prostate Cancer

Multifunctional protein YBX1 upregulation promotes castration-resistant prostate cancer (CRPC). However, YBX1 protein abundance, but not its DNA status or mRNA levels, predicts CRPC recurrence, although the mechanism remains unknown. Similarly, the mechanism by which YBX1 regulates androgen receptor (AR) signaling remains unclear. We uncovered the first molecular mechanism of YBX1 upregulation at a post-translational level. YBX1 was identified as an Aurora Kinase-A (AURKA) substrate using a chemical screen. AURKA phosphorylates YBX1 at two key residues, which stabilizes it and promotes its nuclear translocation. YBX1 reciprocates and stabilizes AURKA, thereby initiating a synergistic loop. Notably, phospho-resistant YBX1 is dominant-negative and fully inhibits epithelial to mesenchymal transition, chemoresistance, drug-resistance and tumorigenesis in vivo. Unexpectedly, we further observed that YBX1 upregulates AR post-translationally by preventing its ubiquitylation, but not by increasing its transcription as reported before. Uncovering YBX1-mediated AR stabilization is highly significant due to AR's critical role in both androgen-sensitive prostate cancer and CRPC. As YBX1 inhibitors are unknown, AURKA inhibitors provide a potent tool to degrade both YBX1 and AR simultaneously. Finally, this is the first study to show a reciprocal loop between YBX1 and its kinase, indicating that their concomitant inhibition will be act synergistically for CRPC therapy.

Identification of LIMK2 as a therapeutic target in castration resistant prostate cancer

This study identified LIMK2 kinase as a disease-specific target in castration resistant prostate cancer (CRPC) pathogenesis, which is upregulated in response to androgen deprivation therapy, the current standard of treatment for prostate cancer. Surgical castration increases LIMK2 expression in mouse prostates due to increased hypoxia. Similarly, human clinical specimens showed highest LIMK2 levels in CRPC tissues compared to other stages, while minimal LIMK2 was observed in normal prostates. Most notably, inducible knockdown of LIMK2 fully reverses CRPC tumorigenesis in castrated mice, underscoring its potential as a clinical target for CRPC. We also identified TWIST1 as a direct substrate of LIMK2, which uncovered the molecular mechanism of LIMK2-induced malignancy. TWIST1 is strongly associated with CRPC initiation, progression and poor prognosis. LIMK2 increases TWIST1 mRNA levels upon hypoxia; and stabilizes TWIST1 by direct phosphorylation. TWIST1 also stabilizes LIMK2 by inhibiting its ubiquitylation. Phosphorylation-dead TWIST1 acts as dominant negative and fully prevents EMT and tumor formation in vivo, thereby highlighting the significance of LIMK2-TWIST1 signaling axis in CRPC. As LIMK2 null mice are viable, targeting LIMK2 should have minimal collateral toxicity, thereby improving the overall survival of CRPC patients.

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

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

Mitosis inhibitors in anticancer therapy: When blocking the exit becomes a solution

Current microtubule-targeting agents (MTAs) remain amongst the most important antimitotic drugs used against a broad range of malignancies. By perturbing spindle assembly, MTAs activate the spindle assembly checkpoint (SAC), which induces mitotic arrest and subsequent apoptosis. However, besides toxic side effects and resistance, mitotic slippage and failure in triggering apoptosis in various cancer cells are limiting factors of MTAs efficacy. Alternative strategies to target mitosis without affecting microtubules have, thus, led to the identification of small molecules, such as those that target spindle Kinesins, Aurora and Polo-like kinases. Unfortunately, these so-called second-generation of antimitotics, encompassing mitotic blockers and mitotic drivers, have failed in clinical trials. Our recent understanding regarding the mechanisms of cell death during a mitotic arrest pointed out apoptosis as the main variable, providing an opportunity to control the cell fates and influence the effectiveness of antimitotics. Here, we provide an overview on the second-generation of antimitotics, and discuss possible strategies that exploit SAC activity, mitotic slippage/exit and apoptosis induction, in order to improve the efficacy of anticancer strategies that target mitosis.

Aurora-A affects radiosenstivity in cervical squamous cell carcinoma and predicts poor prognosis

BACKGROUND

Definitive radiation therapy (RT) (with or without cisplatin-based chemotherapy) is one of the most effective treatments for cervical squamous cell carcinoma (CSCC), but efficacy is limited due to resistance. In the present study, we investigated the relationship between the expression of Aurora kinase A (Aurora-A, AURKA)and response to RT in patients with CSCC.

METHODS

The expression of Aurora-A in biopsy specimens of untreated primary tumors in 129 Uyghur patients with CSCC was investigated immunohistochemically. Primary treatment in these patients was definitive radical RT, which consisted of pelvic RT plus brachytherapy (total point A dose:70-85 Gy) (with or without cisplatin-based chemotherapy). The prognostic value of tumoral Aurora-A expression and patients' clinical outcomes were evaluated.

RESULTS

Aurora-A expression was significantly associated with lymph node metastasis (P<0.001), large tumor size (P<0.001), low hemoglobin (Hb) level (P=0.011) and recurrence (P<0.001), but not other clinicopathological factors. Definitive RT was unfavorable in patients with high Aurora-A expression (P < 0.001). In 129 enrolled patients, lymph node metastasis, large tumor size, low Hb level, and AURKA overexpression were prognostic factors for both recurrent free survival (RFS) and overall survival (OS) in univariate analysis. However, only high AURKA expression was an adverse independent risk factor for both RFS (hazard ratio, 3.953; 95% CI, 1.473-10.638; P = 0.006) and OS (hazard ratio 9.091; 95%CI 2.597-32.258; P<0.001) in multivariate analyses.

CONCLUSIONS

Aurora-A may serve as a predictive biomarker of radiation response and a therapeutic target to reverse radiation therapy resistance.

The Aurora kinase A inhibitor TC-A2317 disrupts mitotic progression and inhibits cancer cell proliferation

Mitotic progression is crucial for the maintenance of chromosomal stability. A proper progression is ensured by the activities of multiple kinases. One of these enzymes, the serine/threonine kinase Aurora A, is required for proper mitosis through the regulation of centrosome and spindle assembly. In this study, we functionally characterized a newly developed Aurora kinase A inhibitor, TC-A2317. In human lung cancer cells, TC-A2317 slowed proliferation by causing aberrant formation of centrosome and microtubule spindles and prolonging the duration of mitosis. Abnormal mitotic progression led to accumulation of cells containing micronuclei or multinuclei. Furthermore, TC-A2317–treated cells underwent apoptosis, autophagy or senescence depending on cell type. In addition, TC-A2317 inactivated the spindle assembly checkpoint triggered by paclitaxel, thereby exacerbating mitotic catastrophe. Consistent with this, the expression level of Aurora A in tumors was inversely correlated with survival in lung cancer patients. Collectively, these data suggest that inhibition of Aurora kinase A using TC-A2317 is a promising target for anti-cancer therapeutics.

The p38 MAPK inhibitor BIRB796 enhances the antitumor effects of VX680 in cervical cancer

VX680 is a potent and selective inhibitor that targets the Aurora kinase family. The p38 mitogen-activated protein kinase (MAPK) regulates a large number of cellular pathways and plays an important role in the regulation of cell survival and apoptosis. This study aimed to evaluate the effect of VX680 on cervical cancer cells and investigate whether the effects on apoptosis are enhanced by the ablation of p38 MAPK activation. The results suggested that VX680 inhibited the proliferation of cervical cancer cells by causing G2/M phase arrest and endoreduplication and that the apoptotic effect was attenuated by the activation of p38 MAPK. However, the addition of BIRB796, which is an important p38 MAPK inhibitor, effectively eliminated the expression of p-p38 and hence significantly enhanced the cell death induced by VX680 in vitro. Further study demonstrated that BIRB796 cooperated with VX680 to suppress cervical cancer cell growth in a mouse xenograft model. Taken together, our results demonstrated that VX680 induced cell cycle arrest and endoreduplication in human cervical cancer cells. Combined treatment with VX680 and BIRB796 synergistically inhibited tumor growth both in vitro and in vivo. Dual blockade of Aurora kinases and p38 MAPK is therefore a promising strategy for cervical cancer treatment.

Aurora-A Kinase: A Potent Oncogene and Target for Cancer Therapy

The Aurora kinase family is comprised of three serine/threonine kinases, Aurora-A, Aurora-B, and Aurora-C. Among these, Aurora-A and Aurora-B play central roles in mitosis, whereas Aurora-C executes unique roles in meiosis. Overexpression or gene amplification of Aurora kinases has been reported in a broad range of human malignancies, pointing to their role as potent oncogenes in tumorigenesis. Aurora kinases therefore represent promising targets for anticancer therapeutics. A number of Aurora kinase inhibitors (AKIs) have been generated; some of which are currently undergoing clinical evaluation. Recent studies have unveiled novel unexpected functions of Aurora kinases during cancer development and the mechanisms underlying the anticancer actions of AKIs. In this review, we discuss the most recent advances in Aurora-A kinase research and targeted cancer therapy, focusing on the oncogenic roles and signaling pathways of Aurora-A kinases in promoting tumorigenesis, the recent preclinical and clinical AKI data, and potential alternative routes for Aurora-A kinase inhibition.

The Aurora kinase inhibitors in cancer research and therapy

Compounds that affect enzymatic function of kinases are valuable for the understanding of the complex biochemical processes in cells. Aurora kinases (AURKs) play a key role in the control of the mitosis. These kinases are frequently deregulated in different human cancers: overexpression, amplifications, translocations and deletions were reported in many cancer cell lines as well as patient tissues. These findings steered a rigorous hunt for small-molecule AURK inhibitors not only for research purposes as well as for therapeutic uses. In this review, we describe a number of AURK inhibitors and their use in cancer research and/or therapy. We hope to assist researchers and clinicians in deciding which inhibitor is most appropriate for their specific purpose. The review will also provide a broad overview of the clinical studies performed with some of these inhibitors (if such studies have been performed).

Aurora kinase A in gastrointestinal cancers: time to target

Gastrointestinal (GI) cancers are a major cause of cancer-related deaths. During the last two decades, several studies have shown amplification and overexpression of Aurora kinase A (AURKA) in several GI malignancies. These studies demonstrated that AURKA not only plays a role in regulating cell cycle and mitosis, but also regulates a number of key oncogenic signaling pathways. Although AURKA inhibitors have moved to phase III clinical trials in lymphomas, there has been slower progress in GI cancers and solid tumors. Ongoing clinical trials testing AURKA inhibitors as a single agent or in combination with conventional chemotherapies are expected to provide important clinical information for targeting AURKA in GI cancers. It is, therefore, imperative to consider investigations of molecular determinants of response and resistance to this class of inhibitors. This will improve evaluation of the efficacy of these drugs and establish biomarker based strategies for enrollment into clinical trials, which hold the future direction for personalized cancer therapy. In this review, we will discuss the available data on AURKA in GI cancers. We will also summarize the major AURKA inhibitors that have been developed and tested in pre-clinical and clinical settings.

Current concepts in clinical radiation oncology

Based on its potent capacity to induce tumor cell death and to abrogate clonogenic survival, radiotherapy is a key part of multimodal cancer treatment approaches. Numerous clinical trials have documented the clear correlation between improved local control and increased overall survival. However, despite all progress, the efficacy of radiation-based treatment approaches is still limited by different technological, biological, and clinical constraints. In principle, the following major issues can be distinguished: (1) The intrinsic radiation resistance of several tumors is higher than that of the surrounding normal tissue, (2) the true patho-anatomical borders of tumors or areas at risk are not perfectly identifiable, (3) the treatment volume cannot be adjusted properly during a given treatment series, and (4) the individual heterogeneity in terms of tumor and normal tissue responses toward irradiation is immense. At present, research efforts in radiation oncology follow three major tracks, in order to address these limitations: (1) implementation of molecularly targeted agents and 'omics'-based screening and stratification procedures, (2) improvement of treatment planning, imaging, and accuracy of dose application, and (3) clinical implementation of other types of radiation, including protons and heavy ions. Several of these strategies have already revealed promising improvements with regard to clinical outcome. Nevertheless, many open questions remain with individualization of treatment approaches being a key problem. In the present review, the current status of radiation-based cancer treatment with particular focus on novel aspects and developments that will influence the field of radiation oncology in the near future is summarized and discussed.

Aurora-A: a potential DNA repair modulator

It is well-known that overexpression of Aurora-A promotes tumorigenesis, but the role of Aurora-A in the development of cancer has not been fully investigated. Recent studies indicate that Aurora-A may confer cancer cell chemo- and radioresistance through dysregulation of cell cycle progression and DNA damage response. Direct evidences from literatures suggest that Aurora-A inhibits pRb, p53, p21(waf1/cip1), and p27(cip/kip) but enhances Plk1, CDC25, CDK1, and cyclin B1 to repeal cell cycle checkpoints and to promote cell cycle progression. Other studies indicate that Aurora-A suppresses BRCA1, BRCA2, RAD51, poly(ADP ribose) polymerase (PARP), and gamma-H2AX to dysregulate DNA damage response. Aurora-A may also interact with RAS and Myc to control DNA repair indirectly. In this review, we summarized the potential role of Aurora-A in DNA repair from the current literatures and concluded that Aurora-A may function as a DNA repair modulator to control cancer cell radio- and chemosensitivity, and that Aurora-A-associated DNA repair molecules may be considered for targeted cancer therapy.

Pretherapeutic drug evaluation by tumor xenografting in anaplastic thyroid cancer

BACKGROUND

Despite various attempts at modifying usual treatment modalities, anaplastic thyroid cancer (ATC) is still associated with unfavorable prognosis. Results of preclinical investigations are often of limited transferability to clinical tumor biology. Individualized multimodal treatment regimens, including novel growth-inhibiting drugs, might be a future option.

METHODS

Tumor tissue, freshly prepared from a patient operated for ATC, was xenotransplanted to nude mice. While the patient obtained a hyperfractionated external beam radiation, mice carrying xenotransplanted tumors were randomized (n = 6) and treated by multikinase inhibitors (sorafenib [S]: vascular endothelial growth factor receptor [VEGF-R], platelet derived growth factor receptor, RET; vandetanib [V]: VEGF-R, endothelial growth factor receptor [EGF-R]; and MLN8054 [M]: Aurora kinases [AK]). Antiproliferative, antiangiogenic, and proapoptotic effects were evaluated.

RESULTS

Treatment of successfully xenotransplanted fresh ATC tumor tissue by multikinase inhibitors and aurora kinase inhibitor reduced the tumor volume up to 61% depending on the drug and time of application (3 wk of treatment: 46% [M], 34% [V], 30% [S]; 5 wk of treatment: 61% [S]). Tumor cell proliferation (BrdU) was reduced between 34% and 58% [S] and [V]. Reduction of tumor vascularity was between 67% [V] and 33% [S] and was accompanied by decreased EGF-R/VEGF-R2 receptor activity [V/V,S]. Tumor cell apoptosis (caspase 3 activity) increased up to 2.4-fold [S].

CONCLUSIONS

Successful in vivo evaluation of novel drugs in xenotransplanted fresh tumor tissue allows in-time (while patient receives standard treatment) prospective analysis for possible additional clinical application. However, technical specifications have to be taken into account to obtain stable in vivo tumor growth. Based on the individual results, a tailored clinical drug application seems possible.

Selective enhancing effect of early mitotic inhibitor 1 (Emi1) depletion on the sensitivity of doxorubicin or X-ray treatment in human cancer cells

Chemotherapy and radiation in addition to surgery has proven useful in a number of different cancer types, but the effectiveness in normal tissue cannot be avoided in these therapies. To improve the effectiveness of these therapies selectively in cancer tissue is important for avoiding side effects. Early mitotic inhibitor 1 (Emi1) is known to have the function to inhibit anaphase-promoting complex/cyclosome ubiquitin ligase complex, which ubiquitylates the cell cycle-related proteins. It recently has been shown that Emi1 knockdown prevents transition from S to G2 phase by down-regulating geminin via anaphase-promoting complex/cyclosome activation. At present, anticancer drugs for targeting DNA synthesis to interfere with rapidly dividing cells commonly are used. As Emi1 depletion interferes with completion of DNA synthesis in cancer cells, we thought that Emi1 knockdown might enhance the sensitivity for anticancer agents. Here, we confirmed that Emi1 siRNA induced polyploidy for preventing transition from S to G2 phase in several cancer cell lines. Then, we treated Emi1 depleted cells with doxorubicin. Interestingly, increased apoptotic cells were observed after doxorubicin treatment in Emi1 siRNA-treated cancer cells. In addition, Emi1 depletion enhanced the sensitivity of x-ray irradiation in cancer cells. Importantly, synergistic effect of Emi1 knockdown in these combination therapies was not observed in normal cells. These results suggest that Emi1 siRNA can be a useful tool for enhancing of sensitivity of cancer cells to anticancer reagents and radiation.

Antimitotic agents for the treatment of patients with metastatic castrate-resistant prostate cancer

INTRODUCTION

Metastatic castrate-resistant prostate cancer (mCRPC) is the second deadliest cancer in men. The group of taxanes, which target microtubules of mitotic cells, is currently the only chemotherapy which has proven to increase overall survival in mCRPC patients. Other mitotic inhibitors are being explored for their clinical potential in mCRPC treatment.

AREAS COVERED

In this review, we summarize recent developments in the application of mitotic inhibitors for mCRPC from a clinical perspective. The four main groups of mitotic inhibitors currently being tested in clinical trials are microtubule-inhibitors, polo-like kinase 1 inhibitors, aurora kinase inhibitors and kinesin-spindle protein inhibitors. Compounds of these groups of inhibitors that are in clinical development for mCRPC are discussed. For this extensive overview, relevant literature was searched in PubMed and retrieved from clinicaltrials.gov and presentations at ASCO/AACR meetings.

EXPERT OPINION

In general, mitotic inhibitors are clinically well tolerated but exert limited antitumor activity compared to preclinical study results. However, efficacy of mitotic inhibitors is improving, either by personalizing treatment, by introducing more active compounds, by decreasing resistance of cancer cells against mitotic inhibitors or by using mitotic inhibitors in combination therapies.

Radiosensitization in prostate cancer: mechanisms and targets

Prostate cancer is the second most commonly diagnosed cancer in American men over the age of 45 years and is the third most common cause of cancer related deaths in American men. In 2012 it is estimated that 241,740 men will be diagnosed with prostate cancer and 28,170 men will succumb to prostate cancer. Currently, radiation therapy is one of the most common definitive treatment options for localized prostate cancer. However, significant number of patients undergoing radiation therapy will develop locally persistent/recurrent tumours. The varying response rates to radiation may be due to 1) tumor microenvironment, 2) tumor stage/grade, 3) modality used to deliver radiation, and 4) dose of radiation. Higher doses of radiation has not always proved to be effective and have been associated with increased morbidity. Compounds designed to enhance the killing effects of radiation, radiosensitizers, have been extensively investigated over the past decade. The development of radiosensitizing agents could improve survival, improve quality of life and reduce costs, thus benefiting both patients and healthcare systems. Herin, we shall review the role and mechanisms of various agents that can sensitize tumours, specifically prostate cancer.