Reactive oxygen species generation and increase in mitochondrial copy number: new insight into the potential mechanism of cytotoxicity induced by aurora kinase inhibitor, AZD1152-HQPA. Anticancer Drugs. 2017;28:841-851. [PMID: 28639950 DOI: 10.1097/cad.0000000000000523]

Antineoplastic effects of pharmacological inhibitors of aurora kinases in CSF3RT618I-driven cells

Myeloproliferative neoplasms (MPN) are consolidated as a relevant group of diseases derived from the malfunction of the hematopoiesis process and have as a particular attribute the increased proliferation of myeloid lineage. Among these, chronic neutrophilic leukemia (CNL) is distinguished, caused by the T618I mutation of the CSF3R gene, a trait that generates ligand-independent receptor activation and downstream JAK2/STAT signaling. Previous studies reported that mutations in BCR::ABL1 and JAK2V617F increased the expression of the aurora kinase A (AURKA) and B (AURKB) in Ba/F3 cells and their pharmacological inhibition displays antineoplastic effects in human BCR::ABL1 and JAK2V617F positive cells. Delimiting the current scenario, aspects related to the AURKA and AURKB as a potential target in CSF3RT618I-driven models is little known. In the present study, the cellular and molecular effects of pharmacological inhibitors of aurora kinases, such as aurora A inhibitor I, AZD1152-HQPA, and reversine, were evaluated in Ba/F3 expressing the CSF3RT618I mutation. AZD1152-HQPA and reversine demonstrated antineoplastic potential, causing a decrease in cell viability, clonogenicity, and proliferative capacity. At molecular levels, all inhibitors reduced histone H3 phosphorylation, aurora A inhibitor I and reversine reduced STAT5 phosphorylation, and AZD1152-HQPA and reversine induced PARP1 cleavage and γH2AX expression. Reversine more efficiently modulated genes associated with cell cycle and apoptosis compared to other drugs. In summary, our findings shed new insights into the use of AURKB inhibitors in the context of CNL.

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.

CK1 Is a Druggable Regulator of Microtubule Dynamics and Microtubule-Associated Processes

Protein kinases of the Casein Kinase 1 family play a vital role in the regulation of numerous cellular processes. Apart from functions associated with regulation of proliferation, differentiation, or apoptosis, localization of several Casein Kinase 1 isoforms to the centrosome and microtubule asters also implicates regulatory functions in microtubule dynamic processes. Being localized to the spindle apparatus during mitosis Casein Kinase 1 directly modulates microtubule dynamics by phosphorylation of tubulin isoforms. Additionally, site-specific phosphorylation of microtubule-associated proteins can be related to the maintenance of genomic stability but also microtubule stabilization/destabilization, e.g., by hyper-phosphorylation of microtubule-associated protein 1A and RITA1. Consequently, approaches interfering with Casein Kinase 1-mediated microtubule-specific functions might be exploited as therapeutic strategies for the treatment of cancer. Currently pursued strategies include the development of Casein Kinase 1 isoform-specific small molecule inhibitors and therapeutically useful peptides specifically inhibiting kinase-substrate interactions.

A Novel Ruthenium(II) Complex With Lapachol Induces G2/M Phase Arrest Through Aurora-B Kinase Down-Regulation and ROS-Mediated Apoptosis in Human Prostate Adenocarcinoma Cells

Lapachol is a well-studied natural product that has been receiving great interest due to its anticancer properties that target oxidative stress. In the present work, two novel lapachol-containing ruthenium(II) complexes [Ru(Lap)(dppm)(bipy)]PF6 (1) and [Ru(Lap)(dppm)(phen)]PF6 (2) [Lap = lapachol, dppm = 1,1'-bis(diphosphino)methane, bipy = 2,2'-bipyridine, phen = 1,10-phenantroline] were synthesized, fully characterized, and investigated for their cellular and molecular responses on cancer cell lines. We found that both complexes exhibited a potent cytotoxic effect in a panel of cancer cell lines in monolayer cultures, as well as in a 3D model of multicellular spheroids formed from DU-145 human prostate adenocarcinoma cells. Furthermore, the complex (2) suppressed the colony formation, induced G2/M-phase arrest, and downregulated Aurora-B. The mechanism studies suggest that complex (2) stimulate the overproduction of reactive oxygen species (ROS) and triggers caspase-dependent apoptosis as a result of changes in expression of several genes related to cell proliferation and caspase-3 and -9 activation. Interestingly, we found that N-acetyl-L-cysteine, a ROS scavenger, suppressed the generation of intracellular ROS induced by complex (2), and decreased its cytotoxicity, indicating that ROS-mediated DNA damage leads the DU-145 cells into apoptosis. Overall, we highlighted that coordination of lapachol to phosphinic ruthenium(II) compounds considerably improves the antiproliferative activities of resulting complexes granting attractive selectivity to human prostate adenocarcinoma cells. The DNA damage response to ROS seems to be involved in the induction of caspase-mediated cell death that plays an important role in the complexes' cytotoxicity. Upon further investigations, this novel class of lapachol-containing ruthenium(II) complexes might indicate promising chemotherapeutic agents for prostate cancer therapy.

Reversing tozasertib resistance in glioma through inhibition of pyruvate dehydrogenase kinases

Acquired resistance to conventional chemotherapeutic agents limits their effectiveness and can cause cancer treatment to fail. Because enzymes in the aurora kinase family are vital regulators of several mitotic events, we reasoned that targeting these kinases with tozasertib, a pan‐aurora kinase inhibitor, would not only cause cytokinesis defects, but also induce cell death in high‐grade pediatric and adult glioma cell lines. We found that tozasertib induced cell cycle arrest, increased mitochondrial permeability and reactive oxygen species generation, inhibited cell growth and migration, and promoted cellular senescence and pro‐apoptotic activity. However, sustained exposure to tozasertib at clinically relevant concentrations conferred resistance, which led us to examine the mechanistic basis for the emergence of drug resistance. RNA‐sequence analysis revealed a significant upregulation of the gene encoding pyruvate dehydrogenase kinase isoenzyme 4 (PDK4), a pyruvate dehydrogenase (PDH) inhibitory kinase that plays a crucial role in the control of metabolic flexibility under various physiological conditions. Upregulation of PDK1, PDK2, PDK3, or PDK4 protein levels was positively correlated with tozasertib‐induced resistance through inhibition of PDH activity. Tozasertib‐resistant cells exhibited increased mitochondrial mass as measured by 10‐N‐nonyl‐Acridine Orange. Inhibition of PDK with dichloroacetate resulted in increased mitochondrial permeability and cell death in tozasertib‐resistant glioma cell lines. Based on these results, we believe that PDK is a selective target for the tozasertib resistance phenotype and should be considered for further preclinical evaluations.

Inhibition of Aurora Kinase B activity disrupts development and differentiation of salivary glands

Little is known about the key molecules that regulate cell division during organogenesis. Here we determine the role of the cell cycle promoter aurora kinase B (AURKB) during development, using embryonic salivary glands (E-SGs) as a model. AURKB is a serine/threonine kinase that regulates key events in mitosis, which makes it an attractive target for tailored anticancer therapy. Many reports have elaborated on the role of AURKB in neoplasia and cancer; however, no previous study has shown its role during organ development. Our previous experiments have highlighted the essential requirement for AURKB during adult exocrine regeneration. To investigate if AURKB is similarly required for progression during embryonic development, we pharmacologically inhibited AURKB in developing submandibular glands (SMGs) at embryonic day (E)13.5 and E16.5, using the highly potent and selective drug Barasertib. Inhibition of AURKB interfered with the expansion of the embryonic buds. Interestingly, this effect on SMG development was also seen when the mature explants (E16.5) were incubated for 24 h with another cell cycle inhibitor Aphidicolin. Barasertib prompted apoptosis, DNA damage and senescence, the markers of which (cleaved caspase 3, γH2AX, SA-βgal and p21, respectively), were predominantly seen in the developing buds. In addition to a reduction in cell cycling and proliferation of the epithelial cells in response to AURKB inhibition, Barasertib treatment led to an excessive generation of reactive oxygen species (ROS) that resulted in downregulation of the acinar differentiation marker Mist1. Importantly, inhibition of ROS was able to rescue this loss of identity, with Mist1 expression maintained despite loss of AURKB. Together, these data identify AURKB as a key molecule in supporting embryonic development and differentiation, while inhibiting senescence-inducing signals during organogenesis.

Mitotic Poisons in Research and Medicine

Cancer is one of the greatest challenges of the modern medicine. Although much effort has been made in the development of novel cancer therapeutics, it still remains one of the most common causes of human death in the world, mainly in low and middle-income countries. According to the World Health Organization (WHO), cancer treatment services are not available in more then 70% of low-income countries (90% of high-income countries have them available), and also approximately 70% of cancer deaths are reported in low-income countries. Various approaches on how to combat cancer diseases have since been described, targeting cell division being among them. The so-called mitotic poisons are one of the cornerstones in cancer therapies. The idea that cancer cells usually divide almost uncontrolled and far more rapidly than normal cells have led us to think about such compounds that would take advantage of this difference and target the division of such cells. Many groups of such compounds with different modes of action have been reported so far. In this review article, the main approaches on how to target cancer cell mitosis are described, involving microtubule inhibition, targeting aurora and polo-like kinases and kinesins inhibition. The main representatives of all groups of compounds are discussed and attention has also been paid to the presence and future of the clinical use of these compounds as well as their novel derivatives, reviewing the finished and ongoing clinical trials.

A Synthetic Pan-Aurora Kinase Inhibitor, 5-Methoxy-2-(2-methoxynaphthalen-1-yl)-4H-chromen-4-one, Triggers Reactive Oxygen Species-Mediated Apoptosis in HCT116 Colon Cancer Cells

Aurora kinases are Ser/Thr kinases that function as mitotic regulators. 5-Methoxy-2-(2-methoxynaphthalen-1-yl)-4H-chromen-4-one (DK1913) is a synthetic pan-Aurora kinase inhibitor. However, the mode of action of DK1913 concerning the induction of apoptosis is unclear. Here, we report that DK1913 triggered apoptosis, as revealed by flow cytometry and Annexin V staining. DK1913 enhanced the intracellular levels of reactive oxygen species (ROS) and stimulated the endoplasmic reticulum (ER) and genotoxic stress responses. We also found that DK1913 induced the loss of mitochondrial membrane potential, leading to the activation of caspase-9, caspase-7, and caspase-3. In addition, the antioxidant, butylated hydroxyanisole (BHA), abrogated DK1913-induced loss of mitochondrial membrane potential and activation of the caspase cascade. These findings demonstrate that pan-Aurora kinase inhibitor DK1913 triggers apoptosis through ROS-mediated ER and genotoxic stress responses.

Aurora kinase mRNA expression is reduced with increasing gestational age and in severe early onset fetal growth restriction

INTRODUCTION

Oxidative damage and biochemical ageing are implicated in placental dysfunction and potentially fetal death. Cellular senescence may play a role in the pathophysiology of fetal growth restriction (FGR) and preeclampsia (PE). Aurora kinases (AURKA, B and C) are important regulators of cellular division in mitosis and meiosis with implications in cellular senescence. We aimed to investigate whether aurora kinase expression is altered with placental dysfunction or placental ageing.

METHODS

Placenta and blood was obtained across gestation from pregnancies complicated by PE, FGR or both PE and FGR, as well as gestation-matched control samples. Expression of AURKA, B and C mRNA was examined using real time qPCR in both the placenta and maternal circulation.

RESULTS

Placental aurora kinase expression decreased as gestation progressed: AURKA and AURKB were significantly reduced at 37-40 weeks, whereas AURKC was significantly reduced at 34-37 weeks, when compared to <34 weeks. In the maternal circulation, the mRNA level of AURKB was significantly reduced at >40 weeks compared to <34 weeks gestation. A significant reduction in AURKC was seen in FGR pregnancies <34 weeks compared to gestation-matched controls.

CONCLUSION

Placental AURK expression is reduced with increased gestation. Circulating AURKB mRNA reduces at >40 weeks gestation, when compared to <34 weeks. AURKC is significantly reduced in placentas from pregnancies complicated by severe early onset (<34 weeks) FGR compared with gestation-matched controls. The functional role of aurora kinase in the placenta and in gestational age warrants further investigation.

Roles of cell fusion, hybridization and polyploid cell formation in cancer metastasis

Cell-cell fusion is a normal biological process playing essential roles in organ formation and tissue differentiation, repair and regeneration. Through cell fusion somatic cells undergo rapid nuclear reprogramming and epigenetic modifications to form hybrid cells with new genetic and phenotypic properties at a rate exceeding that achievable by random mutations. Factors that stimulate cell fusion are inflammation and hypoxia. Fusion of cancer cells with non-neoplastic cells facilitates several malignancy-related cell phenotypes, e.g., reprogramming of somatic cell into induced pluripotent stem cells and epithelial to mesenchymal transition. There is now considerable in vitro, in vivo and clinical evidence that fusion of cancer cells with motile leucocytes such as macrophages plays a major role in cancer metastasis. Of the many changes in cancer cells after hybridizing with leucocytes, it is notable that hybrids acquire resistance to chemo- and radiation therapy. One phenomenon that has been largely overlooked yet plays a role in these processes is polyploidization. Regardless of the mechanism of polyploid cell formation, it happens in response to genotoxic stresses and enhances a cancer cell’s ability to survive. Here we summarize the recent progress in research of cell fusion and with a focus on an important role for polyploid cells in cancer metastasis. In addition, we discuss the clinical evidence and the importance of cell fusion and polyploidization in solid tumors.

Aurora B kinase as a therapeutic target in acute lymphoblastic leukemia

PURPOSE

Acute lymphoblastic leukemia (ALL) is curable with standardized chemotherapy. However, the development of novel therapies is still required, especially for patients with relapsed or refractory disease. By utilizing an in vitro drug screening system, active molecular targeting agents against ALL were explored in this study.

METHODS

By the in vitro drug sensitivity test, 81 agents with various actions were screened for their cytotoxicity in a panel of 22 ALL cell lines and ALL clinical samples. The drug effect score (DES) was calculated from the dose-response of each drug for comparison among drugs or samples. Normal peripheral blood mononuclear cells were also applied onto the drug screening to provide the reference control values. The drug combination effect was screened based on the Bliss independent model, and validated by the improved isobologram method.

RESULTS

On sensitivity screening in a cell line panel, barasertib-HQPA which is an active metabolite of barasertib, an aurora B kinase inhibitor, alisertib, an aurora A kinase inhibitor, and YM155, a survivin inhibitor, were effective against the broadest range of ALL cells. The DES of barasertib-HQPA was significantly higher in ALL clinical samples compared to the reference value. There were significant correlations in DES between barasertib-HQPA and vincristine or docetaxel. In the drug combination assay, barasertib-HQPA and eribulin showed additive to synergistic effects.

CONCLUSION

Aurora B kinase was identified to be an active therapeutic target in a broad range of ALL cells. Combination therapy of barasertib and a microtubule-targeting drug is of clinical interest.

Comprehensive pharmacogenomic profiling of human papillomavirus-positive and -negative squamous cell carcinoma identifies sensitivity to aurora kinase inhibition in KMT2D mutants

To address the unmet need for effective biomarker-driven targeted therapy for human papillomavirus (HPV)-associated head and neck squamous cell carcinoma (HNSCC) and cervical cancer, we conducted a high-throughput drug screen using 1122 compounds in 13 HPV-positive and 11 matched HPV-negative cell lines. The most effective drug classes were inhibitors of polo-like kinase, proteasomes, histone deacetylase, and Aurora kinases. Treatment with a pan-Aurora inhibitor, danusertib, led to G2M arrest and apoptosis in vitro. Furthermore, danusertib decreased tumor size compared with controls in patient derived xenograft models of HNSCC. To identify biomarkers predicting response, we determined associations between mutations and drug sensitivity. Our data and the Genomics of Drug Sensitivity in Cancer database showed that cancer cells with KMT2D mutations were more sensitive to Aurora kinase inhibitors than were cells without mutations. Knockdown of KMT2D in wild-type cells led to increased Aurora kinase inhibitor-induced apoptosis. We identified Aurora kinase inhibitors as effective and understudied drugs in HNSCC and CESC. This is the first published study to demonstrate that mutations in KMT2D, which are common in many cancers, correlate with drug sensitivity in two independent datasets.

Deguelin, an Aurora B Kinase Inhibitor, Exhibits Potent Anti-Tumor Effect in Human Esophageal Squamous Cell Carcinoma

Aurora B kinase has emerged as a key regulator of mitosis and deregulation of Aurora B activity is closely related to the development and progression of human cancers. In the present study, we found that Aurora B is overexpressed in human esophageal squamous cell carcinoma (ESCC), high levels of Aurora B protein were associated with a worse overall survival rate in ESCC patients. Depleting of Aurora B blunted the malignant phenotypes in ESCC cells. Importantly, we demonstrated that a natural compound, deguelin, has a profound anti-tumor effect on ESCC via inhibiting Aurora B activity. Deguelin potently inhibited in vitro Aurora B kinase activity. The in silico docking study further indicated that deguelin was docked into the ATP-binding pocket of Aurora B. Inhibition of Aurora B activity attenuated growth of ESCC cells, resulted in G2/M cell cycle arrest, polyploidy cells formation, and apoptosis induction. Knocking down of Aurora B decreased the sensitivity of ESCC cells to deguelin. The in vivo results showed that deguelin blocked the phosphorylation of histone H3 and inhibited the growth of ESCC tumor xenografts. Overall, we identified deguelin as an effective Aurora B inhibitor, which deserves further studies in other animal models and ESCC treatment.

Mitochondrial DNA in Telocytes

Telocyte (TC) is a new identified interstitial cell type with a small nuclear and one or several long and thin prolongations with enlargements on them. They were found in many mammals including humans, mouse, rats, dogs, and monkeys and play vital roles in many physiological and pathological conditions. The ultrastructure of mitochondria was observed in TCs, and the alterations were found in TCs from inflammatory ureter tissue. MtDNA is associated with mitochondria normal functions and involved in physiological and pathological processes. However, mitochondria and mtDNA in TCs were not investigated deeply. This review will introduce the origin, distribution, morphology, and functions of TCs and the distribution and functions of TC mitochondria in order to improve a better understanding of the potential functions of mtDNA in TCs.