Clinical Benefit to an Aurora A Kinase Inhibitor in a Patient with Metastatic Integrase Interactor 1-Deficient Carcinoma

Integrase interactor 1 (INI-1)-deficient carcinoma is a rare cancer characterized by the loss of the SWItch/Sucrose Non-Fermentable-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 gene (SMARCB1) and tends to follow an aggressive clinical course. There is no currently available standard therapy option, although a few promising treatment strategies, including enhancer of zeste homolog 2 (EZH2) inhibition, are under active investigation. This report describes a 30-year-old woman with INI-1-deficient carcinoma who progressed on combination chemotherapy and an EZH2 inhibitor. Next-generation-sequencing-based targeted cancer-related gene assay confirmed SMARCB1 loss and revealed other mutations in breast cancer 1 gene and checkpoint kinase 2 gene, which may have impacted her clinical course. After discussion at the molecular tumor board, she was offered alisertib, an aurora A kinase inhibitor, on a single-patient expanded-use program and achieved prolonged disease stabilization. Aurora A kinase inhibition may have an important role in the management of patients with INI-1-deficient tumors, warranting further evaluation in clinical studies. KEY POINTS: Loss of the SWItch/Sucrose Non-Fermentable-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 gene (SMARCB1), which encodes integrase interactor 1 (INI-1), is associated with various mesenchymal malignancies, but a few carcinomas with rhabdoid features have been recently described as a distinct entity.INI-1-deficient carcinoma can be very aggressive, and there is no known treatment option available.There are encouraging preliminary data with an enhancer of zeste homolog 2 inhibitor, tazematostat, in INI-1-deficient malignancies, including INI-1-deficient carcinomas.Loss of INI-1 can activate aurora A kinase (AurkA), and inhibition of AurkA by alisertib could be a viable option and warrants further investigation in this cancer.Clinical genomic profiling can confirm diagnosis of molecularly defined malignancy and provide insights on therapeutic options.

Chalcones Repressed the AURKA and MDR Proteins Involved in Metastasis and Multiple Drug Resistance in Breast Cancer Cell Lines

In the present investigation, trans-chalcone and licochalcone A were tested against MCF-7 and BT-20 breast cancer cell lines for anti-tumor activity. We found that both chalcones down regulated important genes associated to cancer development and inhibited cell migration of metastatic cells (BT-20). Finally, we observed that licochalcone A reduces the MDR-1 protein, while both chalcones suppress the AURKA protein in a dose-dependent manner. In conclusion, we observed the trans-chalcone and licochalcone A affected the cell viability of breast cancer cell lines MCF-7 and BT-20 and presents anti-metastatic and anti-resistance potential, by the repression of AUKA and MDR-1 proteins.

A phase II clinical trial of the Aurora and angiogenic kinase inhibitor ENMD-2076 for previously treated, advanced, or metastatic triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) remains an aggressive breast cancer subtype with limited treatment options. ENMD-2076 is a small-molecule inhibitor of Aurora and angiogenic kinases with proapoptotic and antiproliferative activity in preclinical models of TNBC.

METHODS

This dual-institution, single-arm, two-stage, phase II clinical trial enrolled patients with locally advanced or metastatic TNBC previously treated with one to three prior lines of chemotherapy in the advanced setting. Patients were treated with ENMD-2076 250 mg orally once daily with continuous dosing in 4-week cycles until disease progression or unacceptable toxicity occurred. The primary endpoint was 6-month clinical benefit rate (CBR), and secondary endpoints included progression-free survival, pharmacokinetic profile, safety, and biologic correlates in archival and fresh serial tumor biopsies in a subset of patients.

RESULTS

Forty-one patients were enrolled. The 6-month CBR was 16.7% (95% CI, 6-32.8%) and included two partial responses. The 4-month CBR was 27.8% (95% CI, 14-45.2%), and the average duration of benefit was 6.5 cycles. Common adverse events included hypertension, fatigue, diarrhea, and nausea. Treatment with ENMD-2076 resulted in a decrease in cellular proliferation and microvessel density and an increase in p53 and p73 expression, consistent with preclinical observations.

CONCLUSIONS

Single-agent ENMD-2076 treatment resulted in partial response or clinical benefit lasting more than 6 months in 16.7% of patients with pretreated, advanced, or metastatic TNBC. These results support the development of predictive biomarkers using archival and fresh tumor tissue, as well as consideration of mechanism-based combination strategies.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01639248 . Registered on July 12, 2012.

High-Throughput Screening Identifies Kinase Inhibitors That Increase Dual Adeno-Associated Viral Vector Transduction In Vitro and in Mouse Retina

Retinal gene therapy based on adeno-associated viral (AAV) vectors is safe and efficient in humans. The low intrinsic DNA transfer capacity of AAV has been expanded by dual vectors where a large expression cassette is split in two halves independently packaged in two AAV vectors. Dual AAV transduction efficiency, however, is greatly reduced compared to that obtained with a single vector. As AAV intracellular trafficking and processing are negatively affected by phosphorylation, this study set to identify kinase inhibitors that can increase dual AAV vector transduction. By high-throughput screening of a kinase inhibitors library, three compounds were identified that increase AAV transduction in vitro, one of which has a higher effect on dual than on single AAV vectors. Importantly, the transduction enhancement is exerted on various AAV serotypes and is not transgene dependent. As kinase inhibitors are promiscuous, siRNA-mediated silencing of targeted kinases was performed, and AURKA and B, PLK1, and PTK2 were among those involved in the increase of AAV transduction levels. The study shows that kinase inhibitor administration reduces AAV serotype 2 (AAV2) capsid phosphorylation and increases the activity of DNA-repair pathways involved in AAV DNA processing. Importantly, the kinase inhibitor PF-00562271 improves dual AAV8 transduction in photoreceptors following sub-retinal delivery in mice. The study identifies kinase inhibitors that increase dual and single AAV transduction by modulating AAV entry and post-entry steps.

AURKA Suppresses Leukemic THP-1 Cell Differentiation through Inhibition of the KDM6B Pathway

Aberrations in histone modifications are being studied in mixed-lineage leukemia (MLL)-AF9-driven acute myeloid leukemia (AML). In this study, we focused on the regulation of the differentiation of the MLL-AF9 type AML cell line THP-1. We observed that, upon phorbol 12-myristate 13-acetate (PMA) treatment, THP-1 cells differentiated into monocytes by down-regulating Aurora kinase A (AURKA), resulting in a reduction in H3S10 phosphorylation. We revealed that the AURKA inhibitor alisertib accelerates the expression of the H3K27 demethylase KDM6B, thereby dissociating AURKA and YY1 from the KDM6B promoter region. Using Flow cytometry, we found that alisertib induces THP-1 differentiation into monocytes. Furthermore, we found that treatment with the KDM6B inhibitor GSK-J4 perturbed the PMA-mediated differentiation of THP-1 cells. Thus, we discovered the mechanism of AURKA-KDM6B signaling that controls the differentiation of THP-1 cells, which has implications for biotherapy for leukemia.

Global assessment of its network dynamics reveals that the kinase Plk1 inhibits the phosphatase PP6 to promote Aurora A activity

Polo-like kinase 1 (Plk1) is an essential protein kinase that promotes faithful mitotic progression in eukaryotes. The subcellular localization and substrate interactions of Plk1 are tightly controlled and require its binding to phosphorylated residues. To identify phosphorylation-dependent interactions within the Plk1 network in human mitotic cells, we performed quantitative proteomics on HeLa cells cultured with kinase inhibitors or expressing a Plk1 mutant that was deficient in phosphorylation-dependent substrate binding. We found that many interactions were abolished upon kinase inhibition; however, a subset was protected from phosphatase opposition or was unopposed, resulting in persistent interaction of the substrate with Plk1. This subset includes phosphoprotein phosphatase 6 (PP6), whose activity toward Aurora kinase A (Aurora A) was inhibited by Plk1. Our data suggest that this Plk1-PP6 interaction generates a feedback loop that coordinates and reinforces the activities of Plk1 and Aurora A during mitotic entry and is terminated by the degradation of Plk1 during mitotic exit. Thus, we have identified a mechanism for the previously puzzling observation of the Plk1-dependent regulation of Aurora A.

Primary Cilia Are Dysfunctional in Obese Adipose-Derived Mesenchymal Stem Cells

Adipose-derived mesenchymal stem cells (ASCs) have crucial functions, but their roles in obesity are not well defined. We show here that ASCs from obese individuals have defective primary cilia, which are shortened and unable to properly respond to stimuli. Impaired cilia compromise ASC functionalities. Exposure to obesity-related hypoxia and cytokines shortens cilia of lean ASCs. Like obese ASCs, lean ASCs treated with interleukin-6 are deficient in the Hedgehog pathway, and their differentiation capability is associated with increased ciliary disassembly genes like AURKA. Interestingly, inhibition of Aurora A or its downstream target the histone deacetylase 6 rescues the cilium length and function of obese ASCs. This work highlights a mechanism whereby defective cilia render ASCs dysfunctional, resulting in diseased adipose tissue. Impaired cilia in ASCs may be a key event in the pathogenesis of obesity, and its correction might provide an alternative strategy for combating obesity and its associated diseases.

Preclinical evaluation of the Aurora kinase inhibitors AMG 900, AZD1152-HQPA, and MK-5108 on SW-872 and 93T449 human liposarcoma cells

Liposarcoma is a malignant soft tissue tumor that originates from adipose tissue and is one of the most frequently diagnosed soft tissue sarcomas in humans. There is great interest in identifying novel chemotherapeutic options for treating liposarcoma based upon molecular alterations in the cancer cells. The Aurora kinases have been identified as promising chemotherapeutic targets based on their altered expression in many human cancers and cellular roles in mitosis and cytokinesis. In this study, we investigated the effects of an Aurora kinase A inhibitor (MK-5108), an Aurora kinase B inhibitor (AZD1152-HQPA), and a pan-Aurora kinase inhibitor (AMG 900) on undifferentiated SW-872 and well-differentiated 93T449 human liposarcoma cells. Treatment of the SW-872 and 93T449 cells with MK-5108 (0-1000 nM), AZD1152-HQPA (0-1000 nM), and AMG 900 (0-1000 nM) for 72 h resulted in a dose-dependent decrease in the total viable cell number. Based upon the EC₅₀ values, the potency of the three Aurora kinase inhibitors in the SW-872 cells was as follows: AMG 900 (EC₅₀ = 3.7 nM) > AZD1152-HQPA (EC₅₀ = 43.4 nM) > MK-5108 (EC₅₀ = 309.0 nM), while the potency in the 93T449 cells was as follows: AMG 900 (EC₅₀ = 6.5 nM) > AZD1152-HQPA (EC₅₀ = 74.5 nM) > MK-5108 (EC₅₀ = 283.6 nM). The percentage of polyploidy after 72 h of drug treatment (0-1000 nM) was determined by propidium iodide staining and flow cytometric analysis. AMG 900 caused a significant increase in polyploidy starting at 25 nM in the SW-872 and 93T449 cells, and AZD1152-HQPA caused a significant increase starting at 100 nM in the SW-872 cells and 250 nM in the 93T449 cells. The Aurora kinase A inhibitor MK-5108 did not significantly increase the percentage of polyploid cells at any of the doses tested in either cell line. The expression of Aurora kinase A and B was evaluated in the SW-872 cells versus differentiated adipocytes and human mesenchymal stem cells by real-time RT-PCR and Western blot analysis. Aurora kinase A and B mRNA expression was significantly increased in the SW-872 cells versus the differentiated adipocytes and human mesenchymal stem cells. Western blot analysis revealed a ~ 48 kDa immunoreactive band for Aurora kinase A that was not present in the differentiated adipocytes or the human mesenchymal stem cells. A ~ 39 kDa immunoreactive band for Aurora kinase B was detected in the SW-872 cells, differentiated adipocytes, and human mesenchymal stem cells. A smaller immunoreactive band for Aurora kinase B was detected in the SW-872 cells but not in the differentiated adipocytes and human mesenchymal stem cells, and this may reflect the expression of a truncated splice variant of Aurora kinase B that has been associated with poor patient prognosis. The 93T449 cells demonstrated decreased expression of Aurora kinase A and B mRNA and protein compared to the SW-872 cells, and also expressed the truncated form of Aurora kinase B. The results of these in vitro studies indicate that Aurora kinase inhibitors should be further investigated as possible chemotherapeutic agents for human liposarcoma.

Plk4 and Aurora A cooperate in the initiation of acentriolar spindle assembly in mammalian oocytes

Establishing the bipolar spindle in mammalian oocytes after their prolonged arrest is crucial for meiotic fidelity and subsequent development. In contrast to somatic cells, the first meiotic spindle assembles in the absence of centriole-containing centrosomes. Ran-GTP can promote microtubule nucleation near chromatin, but additional unidentified factors are postulated for the activity of multiple acentriolar microtubule organizing centers in the oocyte. We now demonstrate that partially overlapping, nonredundant functions of Aurora A and Plk4 kinases contribute to initiate acentriolar meiosis I spindle formation. Loss of microtubule nucleation after simultaneous chemical inhibition of both kinases can be significantly rescued by drug-resistant Aurora A alone. Drug-resistant Plk4 can enhance Aurora A-mediated rescue, and, accordingly, Plk4 can phosphorylate and potentiate the activity of Aurora A in vitro. Both kinases function distinctly from Ran, which amplifies microtubule growth. We conclude that Aurora A and Plk4 are rate-limiting factors contributing to microtubule growth as the acentriolar oocyte resumes meiosis.

Inhibition of Aurora Kinase A Induces Necroptosis in Pancreatic Carcinoma

BACKGROUND & AIMS

Induction of nonapoptotic cell death could be an approach to eliminate apoptosis-resistant tumors. We investigated necroptosis-based therapies in mouse models of pancreatic ductal adenocarcinoma cancer (PDAC).

METHODS

We screened 273 commercially available kinase inhibitors for cytotoxicity against a human PDAC cell line (PANC1). We evaluated the ability of the aurora kinase inhibitor CCT137690 to stimulate necroptosis in PDAC cell lines (PANC1, PANC2.03, CFPAC1, MiaPaCa2, BxPc3, and PANC02) and the HEK293 cell line, measuring loss of plasma membrane integrity, gain in cell volume, swollen organelles, and cytoplasmic vacuoles. We tested the effects of CCT137690 in colon formation assays, and the effects of the necroptosis (necrostatin-1 and necrosulfonamide), apoptosis, autophagy, and ferroptosis inhibitors. We derived cells from tumors that developed in Pdx1-Cre;K-RasG12D/+;p53R172H/+ (KPC) mice. Genes encoding proteins in cell death pathways were knocked out, knocked down, or expressed from transgenes in PDAC cell lines. Athymic nude or B6 mice were given subcutaneous injections of PDAC cells or tail-vein injections of KPC tumor cells. Mice were given CCT137690 (80 mg/kg) or vehicle and tumor growth was monitored; tumor tissues were collected and analyzed by immunohistochemistry. We compared gene expression levels between human pancreatic cancer tissues (n = 130) with patient survival times using the online R2 genomics analysis and visualization platform.

RESULTS

CCT137690 induced necrosis-like death in PDAC cell lines and reduced colony formation; these effects required RIPK1, RIPK3, and MLKL, as well as inhibition of aurora kinase A (AURKA). AURKA interacted directly with RIPK1 and RIPK3 to reduce necrosome activation. AURKA-mediated phosphorylation of glycogen synthase kinase 3 beta (GSK3β) at serine 9 inhibited activation of the RIPK3 and MLKL necrosome. Mutations in AURKA (D274A) or GSK3β (S9A), or pharmacologic inhibitors of RIPK1 signaling via RIPK3 and MLKL, reduced the cytotoxic activity of CCT137690 in PDAC cells. Oral administration of CCT137690 induced necroptosis and immunogenic cell death in subcutaneous and orthotopic tumors in mice, and reduced tumor growth and tumor cell phosphorylation of AURKA and GSK3β. CCT137690 increased survival times of mice with orthotopic KPC PDACs and reduced tumor growth, stroma, and metastasis. Increased expression of AURKA and GSK3β mRNAs associated with shorter survival times of patients with pancreatic cancer.

CONCLUSIONS

We identified the aurora kinase inhibitor CCT137690 as an agent that induces necrosis-like death in PDAC cells, via RIPK1, RIPK3, and MLKL. CCT137690 slowed growth of orthotopic tumors from PDAC cells in mice, and expression of AURKA and GSK3β associate with patient survival times. AURKA might be targeted for treatment of pancreatic cancer.

Dynamic Equilibrium of the Aurora A Kinase Activation Loop Revealed by Single-Molecule Spectroscopy

The conformation of the activation loop (T-loop) of protein kinases underlies enzymatic activity and influences the binding of small-molecule inhibitors. By using single-molecule fluorescence spectroscopy, we have determined that phosphorylated Aurora A kinase is in dynamic equilibrium between a DFG-in-like active T-loop conformation and a DFG-out-like inactive conformation, and have measured the rate constants of interconversion. Addition of the Aurora A activating protein TPX2 shifts the equilibrium towards an active T-loop conformation whereas addition of the inhibitors MLN8054 and CD532 favors an inactive T-loop. We show that Aurora A binds TPX2 and MLN8054 simultaneously and provide a new model for kinase conformational behavior. Our approach will enable conformation-specific effects to be integrated into inhibitor discovery across the kinome, and we outline some immediate consequences for structure-based drug discovery.

The small molecule inhibitor YK-4-279 disrupts mitotic progression of neuroblastoma cells, overcomes drug resistance and synergizes with inhibitors of mitosis

Neuroblastoma is a biologically and clinically heterogeneous pediatric malignancy that includes a high-risk subset for which new therapeutic agents are urgently required. As well as MYCN amplification, activating point mutations of ALK and NRAS are associated with high-risk and relapsing neuroblastoma. As both ALK and RAS signal through the MEK/ERK pathway, we sought to evaluate two previously reported inhibitors of ETS-related transcription factors, which are transcriptional mediators of the Ras-MEK/ERK pathway in other cancers. Here we show that YK-4-279 suppressed growth and triggered apoptosis in nine neuroblastoma cell lines, while BRD32048, another ETV1 inhibitor, was ineffective. These results suggest that YK-4-279 acts independently of ETS-related transcription factors. Further analysis reveals that YK-4-279 induces mitotic arrest in prometaphase, resulting in subsequent cell death. Mechanistically, we show that YK-4-279 inhibits the formation of kinetochore microtubules, with treated cells showing a broad range of abnormalities including multipolar, fragmented and unseparated spindles, together leading to disrupted progression through mitosis. Notably, YK-4-279 does not affect microtubule acetylation, unlike the conventional mitotic poisons paclitaxel and vincristine. Consistent with this, we demonstrate that YK-4-279 overcomes vincristine-induced resistance in two neuroblastoma cell-line models. Furthermore, combinations of YK-4-279 with vincristine, paclitaxel or the Aurora kinase A inhibitor MLN8237/Alisertib show strong synergy, particularly at low doses. Thus, YK-4-279 could potentially be used as a single-agent or in combination therapies for the treatment of high-risk and relapsing neuroblastoma, as well as other cancers.

Effects of rifampin, itraconazole and esomeprazole on the pharmacokinetics of alisertib, an investigational aurora a kinase inhibitor in patients with advanced malignancies

Aim Two studies investigated the effect of gastric acid reducing agents and strong inducers/inhibitors of CYP3A4 on the pharmacokinetics of alisertib, an investigational Aurora A kinase inhibitor, in patients with advanced malignancies. Methods In Study 1, patients received single doses of alisertib (50 mg) in the presence and absence of either esomeprazole (40 mg once daily [QD]) or rifampin (600 mg QD). In Study 2, patients received single doses of alisertib (30 mg) in the presence and absence of itraconazole (200 mg QD). Blood samples for alisertib and 2 major metabolites were collected up to 72 h (Study 1) and 96 h (Study 2) postdose. Area under the curve from time zero extrapolated to infinity (AUC_0-inf) and maximum concentrations (C_max) were calculated and compared using analysis of variance to estimate least squares (LS) mean ratios and 90% confidence intervals (CIs). Results The LS mean ratios (90% CIs) for alisertib AUC_0-inf and C_max in the presence compared to the absence of esomeprazole were 1.28 (1.07, 1.53) and 1.14 (0.97, 1.35), respectively. The LS mean ratios (90% CIs) for alisertib AUC_0-inf and C_max in the presence compared to the absence of rifampin were 0.53 (0.41, 0.70) and 1.03 (0.84, 1.26), respectively. The LS mean ratios (90% CIs) for alisertib AUC_0-inf and C_max in the presence compared to the absence of itraconazole were 1.39 (0.99, 1.95) and 0.98 (0.82, 1.19), respectively. Conclusions The use of gastric acid reducing agents, strong CYP3A inhibitors or strong metabolic enzyme inducers should be avoided in patients receiving alisertib.

A moving target: structure and disorder in pursuit of Myc inhibitors

The Myc proteins comprise a family of ubiquitous regulators of gene expression implicated in over half of all human cancers. They interact with a large number of other proteins, such as transcription factors, chromatin-modifying enzymes and kinases. Remarkably, few of these interactions have been characterized structurally. This is at least in part due to the intrinsically disordered nature of Myc proteins, which adopt a defined conformation only in the presence of binding partners. Owing to this behaviour, crystallographic studies on Myc proteins have been limited to short fragments in complex with other proteins. Most recently, we determined the crystal structure of Aurora-A kinase domain bound to a 28-amino acid fragment of the N-Myc transactivation domain. The structure reveals an α-helical segment within N-Myc capped by two tryptophan residues that recognize the surface of Aurora-A. The kinase domain acts as a molecular scaffold, independently of its catalytic activity, upon which this region of N-Myc becomes ordered. The binding site for N-Myc on Aurora-A is disrupted by certain ATP-competitive inhibitors, such as MLN8237 (alisertib) and CD532, and explains how these kinase inhibitors are able to disrupt the protein-protein interaction to affect Myc destabilization. Structural studies on this and other Myc complexes will lead to the design of protein-protein interaction inhibitors as chemical tools to dissect the complex pathways of Myc regulation and function, which may be developed into Myc inhibitors for the treatment of cancer.

Cell cycle proteins as promising targets in cancer therapy

Cancer is characterized by uncontrolled tumour cell proliferation resulting from aberrant activity of various cell cycle proteins. Therefore, cell cycle regulators are considered attractive targets in cancer therapy. Intriguingly, animal models demonstrate that some of these proteins are not essential for proliferation of non-transformed cells and development of most tissues. By contrast, many cancers are uniquely dependent on these proteins and hence are selectively sensitive to their inhibition. After decades of research on the physiological functions of cell cycle proteins and their relevance for cancer, this knowledge recently translated into the first approved cancer therapeutic targeting of a direct regulator of the cell cycle. In this Review, we focus on proteins that directly regulate cell cycle progression (such as cyclin-dependent kinases (CDKs)), as well as checkpoint kinases, Aurora kinases and Polo-like kinases (PLKs). We discuss the role of cell cycle proteins in cancer, the rationale for targeting them in cancer treatment and results of clinical trials, as well as the future therapeutic potential of various cell cycle inhibitors.

SMARCA4-inactivating mutations increase sensitivity to Aurora kinase A inhibitor VX-680 in non-small cell lung cancers

Mutations in the SMARCA4/BRG1 gene resulting in complete loss of its protein (BRG1) occur frequently in non-small cell lung cancer (NSCLC) cells. Currently, no single therapeutic agent has been identified as synthetically lethal with SMARCA4/BRG1 loss. We identify AURKA activity as essential in NSCLC cells lacking SMARCA4/BRG1. In these cells, RNAi-mediated depletion or chemical inhibition of AURKA induces apoptosis and cell death in vitro and in xenograft mouse models. Disc large homologue-associated protein 5 (HURP/DLGAP5), required for AURKA-dependent, centrosome-independent mitotic spindle assembly is essential for the survival and proliferation of SMARCA4/BRG1 mutant but not of SMARCA4/BRG1 wild-type cells. AURKA inhibitors may provide a therapeutic strategy for biomarker-driven clinical studies to treat the NSCLCs harbouring SMARCA4/BRG1-inactivating mutations.

A simple and rapid UHPLC-MS/MS method for the quantitation of the dual aurora kinase A/B inhibitor SCH-1473759 in murine plasma

The Aurora kinase family facilitates cell division through various processes and is overexpressed in a wide variety of human cancers, leading to aneuploidy. For that reason, these enzymes are currently targets of a rising class of anticancer drugs, with some molecules already in therapeutic use. In this study, a new UHPLC-MS/MS method was developed and validated to quantitate a new pan Aurora kinase inhibitor still in preclinical development, SCH-1473759. This bioanalytical method employed a liquid-liquid extraction from plasma using ethyl acetate before evaporation. Calibration range encompassed 0.5-2500ng/mL. The inter- and intra-day accuracy and precision were assessed over five quality control levels; all within limits required by the FDA guidelines. Assay applicability was demonstrated in a first-in-animals study with oral administration, where the maximum plasma concentration (34ng/mL) occurred at 1h, the half-life (1h) was consistent with a previous IV study, and oral bioavailability was poor (F=0.002).

A high-throughput small molecule screen identifies synergism between DNA methylation and Aurora kinase pathways for X reactivation

X-chromosome inactivation is a mechanism of dosage compensation in which one of the two X chromosomes in female mammals is transcriptionally silenced. Once established, silencing of the inactive X (Xi) is robust and difficult to reverse pharmacologically. However, the Xi is a reservoir of >1,000 functional genes that could be potentially tapped to treat X-linked disease. To identify compounds that could reactivate the Xi, here we screened ∼367,000 small molecules in an automated high-content screen using an Xi-linked GFP reporter in mouse fibroblasts. Given the robust nature of silencing, we sensitized the screen by "priming" cells with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5azadC). Compounds that elicited GFP activity include VX680, MLN8237, and 5azadC, which are known to target the Aurora kinase and DNA methylation pathways. We demonstrate that the combinations of VX680 and 5azadC, as well as MLN8237 and 5azadC, synergistically up-regulate genes on the Xi. Thus, our work identifies a synergism between the DNA methylation and Aurora kinase pathways as being one of interest for possible pharmacological reactivation of the Xi.

A Phase I/II Study of the Investigational Drug Alisertib in Combination With Abiraterone and Prednisone for Patients With Metastatic Castration-Resistant Prostate Cancer Progressing on Abiraterone

Lessons Learned

Patients with metastatic castration-resistant prostate cancer did not tolerate the combination of alisertib with abiraterone and prednisone.

There was no clear signal indicating that adding alisertib might be beneficial for those patients progressing on abiraterone.

Background.

We hypothesized that Aurora A kinase (AK) contributes to castrate resistance in prostate cancer (PCa) and that inhibiting AK with alisertib can resensitize PCa cells to androgen receptor (AR) inhibitor abiraterone.

Methods.

This was a phase I/II trial to determine the safety and efficacy of alisertib when given in combination with abiraterone plus prednisone (AP). Metastatic castration-resistant prostate cancer (mCRPC) patients were treated with dose escalation (alisertib at 30, 40, and 50 mg orally b.i.d., days 1–7 every 21 days) per standard 3+3 design.

Results.

Nine of 43 planned subjects were enrolled. The maximum tolerated dose (MTD) was not reached, and the dose-limiting toxicities (DLTs) included neutropenic fever (1 of 9), neutropenia (1 of 9), fatigue with memory impairment (1 of 9), and diarrhea/mucositis (1 of 9). No prostate-specific antigen (PSA) decrease or circulating tumor cell (CTC) changes were observed during the study. Pharmacodynamically, adding alisertib did not affect total testosterone or dehydroepiandrosterone (DHEA) levels. There was some change in neuroendocrine markers after therapy. Mean duration on study was 2.5 months. The trial was terminated early.

Conclusion.

A tolerable dose of alisertib in combination with AP in mCRPC was not established in this study. There was no clear signal indicating that alisertib might be beneficial for patients with mCRPC progressing on abiraterone.

Aurora A Kinase Amplifies a Midzone Phosphorylation Gradient to Promote High-Fidelity Cytokinesis

During cytokinesis, aurora B kinase (ABK) relocalizes from centromeres to the spindle midzone, where it is thought to provide a spatial cue for cytokinesis. While global ABK inhibition in Drosophila S2 cells results in macro- and multi-nucleated large cells, mislocalization of midzone ABK (mABK) by depletion of Subito (Drosophila MKLP2) does not cause notable cytokinesis defects. Subito depletion was, therefore, used to investigate the contribution of other molecules and redundant pathways to cytokinesis in the absence of mABK. Inhibiting potential polar relaxation pathways via removal of centrosomes (CNN RNAi) or a kinetochore-based phosphatase gradient (Sds22 RNAi) did not result in cytokinesis defects on their own or in combination with loss of mABK. Disruption of aurora A kinase (AAK) activity resulted in midzone assembly defects, but did not significantly affect contractile ring positioning or cytokinesis. Live-cell imaging of a Förster resonance energy transfer (FRET)-based aurora kinase phosphorylation sensor revealed that midzone substrates were less phosphorylated in AAK-inhibited cells, despite the fact that midzone levels of active phosphorylated ABK (pABK) were normal. Interestingly, in the absence of mABK, an increased number of binucleated cells were observed following AAK inhibition. The data suggest that equatorial stimulation rather than polar relaxation mechanisms is the major determinant of contractile ring positioning and high-fidelity cytokinesis in Drosophila S2 cells. Furthermore, we propose that equatorial stimulation is mediated primarily by the delivery of factors to the cortex by noncentrosomal microtubules (MTs), as well as a midzone-derived phosphorylation gradient that is amplified by the concerted activities of mABK and a soluble pool of AAK.

Preclinical Evaluation of Combined Targeted Approaches in Malignant Rhabdoid Tumors

BACKGROUND/AIM

Rhabdoid tumors (RT) are aggressive pediatric tumors, which show poor prognosis despite use of multimodal intensive therapy. In these tumors, several different oncogenic pathways and epigenetic regulators (like CDK4/6-cyclinD-Rb-signaling, EZH2, histone deacetylases) are contemporaneously deregulated as a consequence of biallelic SMARCB1/SNF5/INI1 alterations. Since these tumors are highly resistant to current therapies, alternative treatment strategies are urgently required.

MATERIALS AND METHODS

In this study, we evaluated cytotoxic effects (by MTT tests) of small molecular compounds, which specifically target these deregulated pathways, using either single-drug or combined approaches. Half-maximal inhibitory concentration (IC50) and combined index (CI) were calculated.

RESULTS

All target-directed inhibitors blocked cell growth of three different rhabdoid tumor cell lines in vitro. Several combinations of those target-specific drugs synergistically inhibited cell proliferation of rhabdoid tumors.

CONCLUSION

Supporting earlier reports, combined target-directed approaches are a promising tool for the therapy of malignant rhabdoid tumors.

Resveratrol inhibits cell cycle progression by targeting Aurora kinase A and Polo-like kinase 1 in breast cancer cells

The Aurora protein kinase (AURKA) and the Polo-like kinase-1 (PLK1) activate the cell cycle, and they are considered promising druggable targets in cancer therapy. However, resistance to chemotherapy and to specific small‑molecule inhibitors is common in cancer patients; thus alternative therapeutic approaches are needed to overcome clinical resistance. Here, we showed that the dietary compound resveratrol suppressed the cell cycle by targeting AURKA and PLK1 kinases. First, we identified genes modulated by resveratrol using a genome-wide analysis of gene expression in MDA-MB-231 breast cancer cells. Transcriptional profiling indicated that 375 genes were modulated at 24 h after resveratrol intervention, whereas 579 genes were regulated at 48 h. Of these, 290 genes were deregulated in common at 24 and 48 h. Interestingly, a significant decrease in the expression of genes involved in the cell cycle, DNA repair, cytoskeleton organization, and angiogenesis was detected. In particular, AURKA and PLK1 kinases were downregulated by resveratrol at 24 h. In addition the BRCA1 gene, an AURKA/PLK1 inhibitor, was upregulated at 24 h of treatment. Moreover, two well-known resveratrol effectors, cyclin D1 (CCND1) and cyclin B1 (CCNB1), were also repressed at both times. Congruently, we found that resveratrol impaired G1/S phase transition in both MDA-MB-231 and MCF-7 cells. By western blot assays, we confirmed that resveratrol suppressed AURKA, CCND1 and CCNB1 at 24 and 48 h. In summary, we showed for the first time that resveratrol regulates cell cycle progression by targeting AURKA and PLK1. Our findings highlight the potential use of resveratrol as an adjuvant therapy for breast cancer.

Preclinical testing of selective Aurora kinase inhibitors on a medullary thyroid carcinoma-derived cell line

Deregulated expression of the Aurora kinases (Aurora-A, B, and C) is thought to be involved in cell malignant transformation and genomic instability in several cancer types. Over the last decade, a number of small-molecule inhibitors of Aurora kinases have been developed, which have proved to efficiently restrain malignant cell growth and tumorigenicity. Regarding medullary thyroid carcinoma (MTC), we previously showed the efficacy of a pan-Aurora kinase inhibitor (MK-0457) in impairing growth and survival of the MTC-derived cell line TT. In the present study, we sought to establish if one of the Aurora kinases might represent a preferential target for MTC therapy. The effects of selective inhibitors of Aurora-A (MLN8237) and Aurora-B (AZD1152) were analyzed on TT cell proliferation, apoptosis, cell cycle, and ploidy. The two inhibitors reduced TT cell proliferation in a time- and dose-dependent manner, with IC50 of 19.0 ± 2.4 nM for MLN8237 and 401.6 ± 44.1 nM for AZD1152. Immunofluorescence experiments confirmed that AZD1152 inhibited phosphorylation of histone H3 (Ser10) by Aurora-B, while it did not affect Aurora-A autophosphorylation. MLN8237 inhibited Aurora-A autophosphorylation as expected, but at concentrations required to achieve the maximum antiproliferative effects it also abolished H3 (Ser10) phosphorylation. Cytofluorimetry experiments showed that both inhibitors induced accumulation of cells in G2/M phase and increased the subG0/G1 fraction and polyploidy. Finally, both inhibitors triggered apoptosis. We demonstrated that inhibition of either Aurora-A or Aurora-B has antiproliferative effects on TT cells, and thus it would be worthwhile to further investigate the therapeutical potential of Aurora kinase inhibitors in MTC treatment.

MYCN Transforms Prostate Epithelium to Neuroendocrine Prostate Cancer

Overexpression of MYCN in normal basal prostate cells drives formation of metastatic NEPC.

N-Myc Drives Neuroendocrine Prostate Cancer Initiated from Human Prostate Epithelial Cells

MYCN amplification and overexpression are common in neuroendocrine prostate cancer (NEPC). However, the impact of aberrant N-Myc expression in prostate tumorigenesis and the cellular origin of NEPC have not been established. We define N-Myc and activated AKT1 as oncogenic components sufficient to transform human prostate epithelial cells to prostate adenocarcinoma and NEPC with phenotypic and molecular features of aggressive, late-stage human disease. We directly show that prostate adenocarcinoma and NEPC can arise from a common epithelial clone. Further, N-Myc is required for tumor maintenance, and destabilization of N-Myc through Aurora A kinase inhibition reduces tumor burden. Our findings establish N-Myc as a driver of NEPC and a target for therapeutic intervention.