MLN-8237: A dual inhibitor of aurora A and B in soft tissue sarcomas

Selective Aurora A-TPX2 Interaction Inhibitors Have In Vivo Efficacy as Targeted Antimitotic Agents

Aurora A kinase, a cell division regulator, is frequently overexpressed in various cancers, provoking genome instability and resistance to antimitotic chemotherapy. Localization and enzymatic activity of Aurora A are regulated by its interaction with the spindle assembly factor TPX2. We have used fragment-based, structure-guided lead discovery to develop small molecule inhibitors of the Aurora A-TPX2 protein-protein interaction (PPI). Our lead compound, CAM2602, inhibits Aurora A:TPX2 interaction, binding Aurora A with 19 nM affinity. CAM2602 exhibits oral bioavailability, causes pharmacodynamic biomarker modulation, and arrests the growth of tumor xenografts. CAM2602 acts by a novel mechanism compared to ATP-competitive inhibitors and is highly specific to Aurora A over Aurora B. Consistent with our finding that Aurora A overexpression drives taxane resistance, these inhibitors synergize with paclitaxel to suppress the outgrowth of pancreatic cancer cells. Our results provide a blueprint for targeting the Aurora A-TPX2 PPI for cancer therapy and suggest a promising clinical utility for this mode of action.

Nanogel enhances the efficacy of MLN8237 in treating hepatocellular carcinoma

MLN8237, a specific inhibitor of Aurora-A kinase, is proved to be a potential treatment strategy for hepatocellular carcinoma (HCC). Nanogels improve the efficacy of doxorubicin. Therefore, this study aims to investigate the increase in the effect of nanogels on MLN8237 in inhibiting HCC. Doxorubicin or MLN8237 was used as an anti-tumor drug models which were packaged by organic solvent volatilization method to obtain the doxorubicin-loaded nanogel and the MLN8237-loaded nanogel. Subsequently, CCK8 assay, cell cycle assay, apoptosis assay, real-time PCR, western blotting assay and animal experiments were used to detect the effects of MLN8237 nanogel on the proliferation, cell cycle, apoptosis, tumor growth, mRNA and protein levels of aurora-A and PUMA, and AKT phosphorylation levels in HCC cell lines. The results show that the nanogels can realize pH-regulated hydrophobicity reversal, have certain stability, and can realize lysosomal escape. Moreover, the MLN8237-loaded nanogel has a stronger ability to inhibit HCC cell proliferation, block cell cycle, promote apoptosis and inhibit tumor growth than free MLN8237 by suppressing aurora-A and AKT phosphorylation. In short, nanogel can enhance the efficacy of MLN8237.

Integrating a phenotypic screening with a structural simplification strategy to identify 4-phenoxy-quinoline derivatives to potently disrupt the mitotic localization of Aurora kinase B

We combined a mechanism-informed phenotypic screening (MIPS) assay with a structural simplification strategy to guide the discovery of compounds that disrupt the localization of the mitotic regulator, Aurora kinase B (AURKB), rather than inhibiting its catalytic activity. An initial hit 4-(4-methylthiophen-2-yl)-N-(4-(quinolin-4-yloxy)phenyl)phthalazin-1-amine was identified after screening an in-house library of small molecules and phenocopied the loss of function mutations in AURKB without inhibiting its catalytic activity. We isolated this hit compound activity to its 4-phenoxy-quinoline moiety. The fragment was further optimized into a class of new chemical entities that potently disrupt the mitotic localization of AURKB at low nanomolar concentrations and consequently elicit severe growth inhibition in diverse human cancer cell lines. A lead compound, N-(3-methoxy-5-(6-methoxyquinolin-4-yl)oxy)phenyl)acetamide possessed desirable pharmacokinetic properties such as AUC_0-∞: 227.15 [ng∙h/mL/(mg/kg)]; C_max: 3378.52 ng/mL T_1/2: 3.52 h; and F%: 42 % and produced the AURKB-inhibitory phenotypes in a mouse xenograft model. A lead compound is a powerful tool for interrogating the regulation of AURKB and has the potential to be further developed as a first-in-class oncology therapeutic.

Beyond targeting amplified MDM2 and CDK4 in well differentiated and dedifferentiated liposarcomas: From promise and clinical applications towards identification of progression drivers

Well differentiated and dedifferentiated liposarcomas (WDLPS and DDLPS) are tumors of the adipose tissue poorly responsive to conventional cytotoxic chemotherapy which currently remains the standard-of-care. The dismal prognosis of the DDLPS subtype indicates an urgent need to identify new therapeutic targets to improve the patient outcome. The amplification of the two driver genes MDM2 and CDK4, shared by WDLPD and DDLPS, has provided the rationale to explore targeting the encoded ubiquitin-protein ligase and cell cycle regulating kinase as a therapeutic approach. Investigation of the genomic landscape of WD/DDLPS and preclinical studies have revealed additional potential targets such as receptor tyrosine kinases, the cell cycle kinase Aurora A, and the nuclear exporter XPO1. While the therapeutic significance of these targets is being investigated in clinical trials, insights into the molecular characteristics associated with dedifferentiation and progression from WDLPS to DDLPS highlighted additional genetic alterations including fusion transcripts generated by chromosomal rearrangements potentially providing new druggable targets (e.g. NTRK, MAP2K6). Recent years have witnessed the increasing use of patient-derived cell and tumor xenograft models which offer valuable tools to accelerate drug repurposing and combination studies. Implementation of integrated "multi-omics" investigations applied to models recapitulating WD/DDLPS genetics, histologic differentiation and biology, will hopefully lead to a better understanding of molecular alterations driving liposarcomagenesis and DDLPS progression, as well as to the identification of new therapies tailored on tumor histology and molecular profile.

Selective Xi reactivation and alternative methods to restore MECP2 function in Rett syndrome

The human X-chromosome harbors only 4% of our genome but carries over 20% of genes associated with intellectual disability. Given that they inherit only one X-chromosome, males are more frequently affected by X-linked neurodevelopmental genetic disorders than females. However, despite inheriting two X-chromosomes, females can also be affected because X-chromosome inactivation enables only one of two X-chromosomes to be expressed per cell. For Rett syndrome and similar X-linked disorders affecting females, disease-specific treatments have remained elusive. However, a cure may be found within their own cells because every sick cell carries a healthy copy of the affected gene on the inactive X (Xi). Therefore, selective Xi reactivation may be a viable approach that would address the root cause of various X-linked disorders. Here, we discuss Rett syndrome and compare current approaches in the pharmaceutical pipeline to restore MECP2 function. We then focus on Xi reactivation and review available methods, lessons learned, and future directions.

Targetable Pathways in the Treatment of Retroperitoneal Liposarcoma

Liposarcoma (LPS) is the most prevalent soft tissue sarcoma histological subtype. When it occurs in the abdomen the overall survival rate is as low as 10% at 10 years and is fraught with high rates of recurrence, particularly for the more aggressive dedifferentiated subtype. Surgery remains the mainstay of treatment. Systemic therapies for the treatment of metastatic or unresectable disease have low response rates. Deep understanding of well-differentiated and de-differentiated LPS (WDLPS and DDLPS, respectively) oncologic drivers is necessary for the development of new efficacious targeted therapies for the management of this disease. This review discusses the current treatments under evaluation for retroperitoneal DDLPS and the potential targetable pathways in DDLPS.

Selective Inhibition of Aurora Kinase A by AK-01/LY3295668 Attenuates MCC Tumor Growth by Inducing MCC Cell Cycle Arrest and Apoptosis

Merkel cell carcinoma (MCC) is an often-lethal skin cancer with increasing incidence and limited treatment options. Although immune checkpoint inhibitors (ICI) have become the standard of care in advanced MCC, 50% of all MCC patients are ineligible for ICIs, and amongst those treated, many patients develop resistance. There is no therapeutic alternative for these patients, highlighting the urgent clinical need for alternative therapeutic strategies. Using patient-derived genetic insights and data generated in our lab, we identified aurora kinase as a promising therapeutic target for MCC. In this study, we examined the efficacy of the recently developed and highly selective AURKA inhibitor, AK-01 (LY3295668), in six patient-derived MCC cell lines and two MCC cell-line-derived xenograft mouse models. We found that AK-01 potently suppresses MCC survival through apoptosis and cell cycle arrest, particularly in MCPyV-negative MCC cells without RB expression. Despite the challenge posed by its short in vivo durability upon discontinuation, the swift and substantial tumor suppression with low toxicity makes AK-01 a strong potential candidate for MCC management, particularly in combination with existing regimens.

Recent Advancement in Atypical Lipomatous Tumor Research

After Evans and colleagues identified the lipomatous tumor with a well-differentiated liposarcoma in a subcutaneous location or within a muscle layer, namely, atypical lipomatous tumor (ALT), this malignancy has been investigated to clarify the characteristics of clinical behavior and genomic changes. As one of the important issues for clinicians, it is a hot topic of how to distinguish ALT from benign lipoma in the clinical aspect. Recent studies revealed novel findings to clarify the risk factor for the diagnosis of ALT and molecular targets for the treatment of ALT. Clinical characteristics of superficial-type ALT well reflect the subcutaneous location of the tumor and are slightly different compared to deep-type ALT, such as tumor size. In addition, there has been a recent discovery of novel findings in ALT-related genes, namely, HMG2A (high mobility group protein 2a), YEATS4 (YEATS domain containing 4), and CPM (Carboxypeptidase M). Recent updates on treatment for advanced ALT are well developed including immunotherapy and conducting clinical trials. Finally, this review introduces one of the hot topics of ALT research focused on epigenetic changes: their attention in recent updates on clinical characteristics and the novel discovery of related genes, treatment, and epigenetic modifications in atypical lipomatous tumors.

Recent researches for dual Aurora target inhibitors in antitumor field

Non-infectious and chronic diseases such as malignant tumors are now one of the main causes of human death. Its occurrence is a multi-factor, multi-step complex process with biological characteristics such as cell differentiation, abnormal proliferation, uncontrolled growth, and metastasis. It has been found that a variety of human malignant tumors are accompanied by over-expression and proliferation of Aurora kinase, which causes abnormalities in the mitotic process and is related to the instability of the genome that causes tumors. Therefore, the use of Aurora kinase inhibitors to target tumors is becoming a research hotspot. However, in cancer, because of the complexity of signal transduction system and the participation of different proteins and enzymes, the anticancer effect of selective single-target drugs is limited. After inhibiting one pathway, signal molecules can be conducted through other pathways, resulting in poor therapeutic effect of single-target drug treatment. Multi-target drugs can solve this problem very well. It can regulate the various links that cause disease at the same time without completely eliminating the relationship between the signal transmission systems, and it is not easy to cause drug resistance. Currently, studies have shown that Aurora dual-target inhibitors generated with the co-inhibition of Aurora and another target (such as CDK, PLK, JAK2, etc.) have better therapeutic effects on tumors. In this paper, we reviewed the studies of dual Aurora inhibitors that have been discovered in recent years.

Pan Aurora Kinase Inhibitor: A Promising Targeted-Therapy in Dedifferentiated Liposarcomas With Differential Efficiency Depending on Sarcoma Molecular Profile

Soft tissue sarcoma (STS) are rare and aggressive tumours. Their classification includes numerous histological subtypes of frequent poor prognosis. Liposarcomas (LPS) are the most frequent type among them, and the aggressiveness and deep localization of dedifferentiated LPS are linked to high levels of recurrence. Current treatments available today lead to five-year overall survival has remained stuck around 60%-70% for the past three decades. Here, we highlight a correlation between Aurora kinasa A (AURKA) and AURKB mRNA overexpression and a low metastasis - free survival. AURKA and AURKB expression analysis at genomic and protein level on a 9-STS cell lines panel highlighted STS heterogeneity, especially in LPS subtype. AURKA and AURKB inhibition by RNAi and drug targeting with AMG 900, a pan Aurora Kinase inhibitor, in four LPS cell lines reduces cell survival and clonogenic proliferation, inducing apoptosis and polyploidy. When combined with doxorubicin, the standard treatment in STS, aurora kinases inhibitor can be considered as an enhancer of standard treatment or as an independent drug. Kinome analysis suggested its effect was linked to the inhibition of the MAP-kinase pathway, with differential drug resistance profiles depending on molecular characteristics of the tumor. Aurora Kinase inhibition by AMG 900 could be a promising therapy in STS.

Aurora A-Selective Inhibitor LY3295668 Leads to Dominant Mitotic Arrest, Apoptosis in Cancer Cells, and Shows Potent Preclinical Antitumor Efficacy

Although Aurora A, B, and C kinases share high sequence similarity, especially within the kinase domain, they function distinctly in cell-cycle progression. Aurora A depletion primarily leads to mitotic spindle formation defects and consequently prometaphase arrest, whereas Aurora B/C inactivation primarily induces polyploidy from cytokinesis failure. Aurora B/C inactivation phenotypes are also epistatic to those of Aurora A, such that the concomitant inactivation of Aurora A and B, or all Aurora isoforms by nonisoform-selective Aurora inhibitors, demonstrates the Aurora B/C-dominant cytokinesis failure and polyploidy phenotypes. Several Aurora inhibitors are in clinical trials for T/B-cell lymphoma, multiple myeloma, leukemia, lung, and breast cancers. Here, we describe an Aurora A-selective inhibitor, LY3295668, which potently inhibits Aurora autophosphorylation and its kinase activity in vitro and in vivo, persistently arrests cancer cells in mitosis, and induces more profound apoptosis than Aurora B or Aurora A/B dual inhibitors without Aurora B inhibition-associated cytokinesis failure and aneuploidy. LY3295668 inhibits the growth of a broad panel of cancer cell lines, including small-cell lung and breast cancer cells. It demonstrates significant efficacy in small-cell lung cancer xenograft and patient-derived tumor preclinical models as a single agent and in combination with standard-of-care agents. LY3295668, as a highly Aurora A-selective inhibitor, may represent a preferred approach to the current pan-Aurora inhibitors as a cancer therapeutic agent.

Discovery of Inhibitors of Aurora/PLK Targets as Anticancer Agents

Aurora and polo-like kinases control the G2/M phase in cell mitosis, which are both considered as crucial targets for cancer cell proliferations. Here, naphthalene-based Aurora/PLK coinhibitors as leading compounds were designed through in silico approach, and a total of 36 derivatives were synthesized. One candidate (AAPK-25) was selected under in vitro cell based high throughput screening with an IC50 value = 0.4 μM to human colon cancer cell HCT-116. A kinome scan assay showed that AAPK-25 was remarkably selective to both Aurora and PLK families. The relevant genome pathways were also depicted by microarray based gene expression analysis. Furthermore, validated from a set of in vitro and in vivo studies, AAPK-25 significantly inhibited the development of the colon cancer growth and prolonged the median survival time at the end of the administration (p < 0.05). To sum up, AAPK-25 has a great potential to be developed for a chemotherapeutic agent in clinical use.

RACK1 affects the progress of G2/M by regulating Aurora-A

Aurora-A is a serine/threonine kinase, which is overexpressed in multiple human cancers and plays a key role in tumorigenesis and tumor development. In this study, we found that the receptor of activated C-kinase1 (RACK1), an important regulator of biological functions, interacted with Aurora-A and co-localized with Aurora-A at centrosomes. Moreover, RACK1 induces the auto-phosphorylation of Aurora-A in vitro and in vivo. Depletion of RACK1 impaired the activation of Aurora-A in late G2 phase, then inhibited the mitotic entry and leaded to multi-polarity, severe chromosome alignment defects, or centrosome amplification. Taken together, these results suggest that RACK1 is a new partner of Aurora-A and play a critical role in the regulation of the Aurora-A activity during mitosis, which may provide a basis for future anticancer studies targeting Aurora-A.

Precision Oncology in Sarcomas: Divide and Conquer

Sarcomas are a heterogeneous group of rare malignancies that exhibit remarkable heterogeneity, with more than 50 subtypes recognized. Advances in next-generation sequencing technology have resulted in the discovery of genetic events in these mesenchymal tumors, which in addition to enhancing understanding of the biology, have opened up avenues for molecularly targeted therapy and immunotherapy. This review focuses on how incorporation of next-generation sequencing has affected drug development in sarcomas and strategies for optimizing precision oncology for these rare cancers. In a significant percentage of soft tissue sarcomas, which represent up to 40% of all sarcomas, specific driver molecular abnormalities have been identified. The challenge to evaluate these mutations across rare cancer subtypes requires the careful characterization of these genetic alterations to further define compelling drivers with therapeutic implications. Novel models of clinical trial design also are needed. This shift would entail sustained efforts by the sarcoma community to move from one-size-fits-all trials, in which all sarcomas are treated similarly, to divide-and-conquer subtype-specific strategies.

Imbalance of the spindle-assembly checkpoint promotes spindle poison-mediated cytotoxicity with distinct kinetics

Disrupting microtubule dynamics with spindle poisons activates the spindle-assembly checkpoint (SAC) and induces mitotic cell death. However, mitotic exit can occur prematurely without proper chromosomal segregation or cytokinesis by a process termed mitotic slippage. It remains controversial whether mitotic slippage increases the cytotoxicity of spindle poisons or the converse. Altering the SAC induces either mitotic cell death or mitotic slippage. While knockout of MAD2-binding protein p31^comet strengthened the SAC and promoted mitotic cell death, knockout of TRIP13 had the opposite effect of triggering mitotic slippage. We demonstrated that mitotic slippage prevented mitotic cell death caused by spindle poisons, but reduced subsequent long-term survival. Weakening of the SAC also reduced cell survival in response to spindle perturbation insufficient for triggering mitotic slippage, of which mitotic exit was characterized by displaced chromosomes during metaphase. In either mitotic slippage or mitotic exit with missegregated chromosomes, cell death occurred only after one cell cycle following mitotic exit and increased progressively during subsequent cell cycles. Consistent with these results, transient inhibition of the SAC using an MPS1 inhibitor acted synergistically with spindle perturbation in inducing chromosome missegregation and cytotoxicity. The specific temporal patterns of cell death after mitotic exit with weakened SAC may reconcile the contradictory results from many previous studies.

MLN8237 treatment in an orthoxenograft murine model for malignant peripheral nerve sheath tumors

OBJECTIVE

Malignant peripheral nerve sheath tumors (MPNSTs) are soft-tissue sarcomas arising from peripheral nerves. MPNSTs have increased expression of the oncogene aurora kinase A, leading to enhanced cellular proliferation. This makes them extremely aggressive with high potential for metastasis and a devastating prognosis; 5-year survival estimates range from a dismal 15% to 60%. MPNSTs are currently treated with resection (sometimes requiring limb amputation) in combination with chemoradiation, both of which demonstrate limited effectiveness. The authors present the results of immunohistochemical, in vitro, and in vivo analyses of MLN8237 for the treatment of MPNSTs in an orthoxenograft murine model.

METHODS

Immunohistochemistry was performed on tumor sections to confirm the increased expression of aurora kinase A. Cytotoxicity analysis was then performed on an MPNST cell line (STS26T) to assess the efficacy of MLN8237 in vitro. A murine orthoxenograft MPNST model transfected to express luciferase was then developed to assess the efficacy of aurora kinase A inhibition in the treatment of MPNSTs in vivo. Mice with confirmed tumor on in vivo imaging were divided into 3 groups: 1) controls, 2) mice treated with MLN8237, and 3) mice treated with doxorubicin/ifosfamide. Treatment was carried out for 32 days, with imaging performed at weekly intervals until postinjection day 42. Average bioluminescence among groups was compared at weekly intervals using 1-way ANOVA. A survival analysis was performed using Kaplan-Meier curves.

RESULTS

Immunohistochemical analysis showed robust expression of aurora kinase A in tumor cells. Cytotoxicity analysis revealed STS26T susceptibility to MLN8237 in vitro. The group receiving treatment with MLN8237 showed a statistically significant difference in tumor size compared with the control group starting at postinjection day 21 and persisting until the end of the study. The MLN8237 group also showed decreased tumor size compared with the doxorubicin/ifosfamide group at the conclusion of the study (p = 0.036). Survival analysis revealed a significantly increased median survival in the MLN8237 group (83 days) compared with both the control (64 days) and doxorubicin/ifosfamide (67 days) groups. A hazard ratio comparing the 2 treatment groups showed a decreased hazard rate in the MLN8237 group compared with the doxorubicin/ifosfamide group (HR 2.945; p = 0.0134).

CONCLUSIONS

The results of this study demonstrate that MLN8237 is superior to combination treatment with doxorubicin/ifosfamide in a preclinical orthoxenograft murine model. These data have major implications for the future of MPNST research by providing a robust murine model as well as providing evidence that MLN8237 may be an effective treatment for MPNSTs.

Microtubule polyglutamylation and acetylation drive microtubule dynamics critical for platelet formation

Background

Upon maturation in the bone marrow, polyploid megakaryocytes elongate very long and thin cytoplasmic branches called proplatelets. Proplatelets enter the sinusoids blood vessels in which platelets are ultimately released. Microtubule dynamics, bundling, sliding, and coiling, drive these dramatic morphological changes whose regulation remains poorly understood. Microtubule properties are defined by tubulin isotype composition and post-translational modification patterns. It remains unknown whether microtubule post-translational modifications occur in proplatelets and if so, whether they contribute to platelet formation.

Results

Here, we show that in proplatelets from mouse megakaryocytes, microtubules are both acetylated and polyglutamylated. To bypass the difficulties of working with differentiating megakaryocytes, we used a cell model that allowed us to test the functions of these modifications. First, we show that α2bβ3integrin signaling in D723H cells is sufficient to induce β1tubulin expression and recapitulate the specific microtubule behaviors observed during proplatelet elongation and platelet release. Using this model, we found that microtubule acetylation and polyglutamylation occur with different spatio-temporal patterns. We demonstrate that microtubule acetylation, polyglutamylation, and β1tubulin expression are mandatory for proplatelet-like elongation, swelling formation, and cytoplast severing. We discuss the functional importance of polyglutamylation of β1tubulin-containing microtubules for their efficient bundling and coiling during platelet formation.

Conclusions

We characterized and validated a powerful cell model to address microtubule behavior in mature megakaryocytes, which allowed us to demonstrate the functional importance of microtubule acetylation and polyglutamylation for platelet release. Furthermore, we bring evidence of a link between the expression of a specific tubulin isotype, the occurrence of microtubule post-translational modifications, and the acquisition of specific microtubule behaviors. Thus, our findings could widen the current view of the regulation of microtubule behavior in cells such as osteoclasts, spermatozoa, and neurons, which express distinct tubulin isotypes and display specific microtubule activities during differentiation.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0584-6) contains supplementary material, which is available to authorized users.

AURKA induces EMT by regulating histone modification through Wnt/β-catenin and PI3K/Akt signaling pathway in gastric cancer

Gastric cancer, a highly invasive and aggressive malignancy, is the third leading cause of death from cancer worldwide. Genetic association studies have successfully revealed several important genes consistently associated with gastric cancer to date. However, these robust gastric cancer-associated genes do not fully elucidate the mechanisms underlying the development and progression of the disease. In the present study, we performed an alternative approach, a gene expression-based genome-wide association study (eGWAS) across 13 independent microarray experiments (including 251 gastric cancer cases and 428 controls), to identify top candidates (p<0.00001). Additionally, we conducted gene ontology analysis, pathway analysis and network analysis and identified aurora kinase A (AURKA) as our candidate. We observed that MLN8237, which is a specific inhibitor of AURKA, decreased the β-catenin and the phosphorylation of Akt1 and GSK-3β, as well as blocked the Akt and Wnt signaling pathways. Furthermore, MLN8237 arrested the cells in the G2/M phase. The activity of Wnt and Akt signaling pathways affected the level of histone methylation significantly, and we supposed that MLN8237 affected the level of histone methylation through these two signaling pathways. Additionally, the treatment of MLN8237 influenced the level of H3K4 me1/2/3 and H3K27 me1/2/3. Chip data on cell lines suggested that MLN8237 increases the level of H3K27 me3 on the promoter of Twist and inhibits EMT (epithelial-mesenchymal transition). In summary, AURKA is a potential therapeutic target in gastric cancer and induces EMT through histone methylation.

Clinical and Molecular Spectrum of Liposarcoma

Liposarcomas are rare malignant tumors of adipocytic differentiation. The classification of liposarcomas into four principal subtypes reflects the distinct clinical behavior, treatment sensitivity, and underlying biology encompassed by these diseases. Increasingly, clinical management decisions and the development of investigational therapeutics are informed by an improved understanding of subtype-specific molecular pathology. Well-differentiated liposarcoma is the most common subtype and is associated with indolent behavior, local recurrence, and insensitivity to radiotherapy and chemotherapy. Dedifferentiated liposarcoma represents focal progression of well-differentiated disease into a more aggressive, metastasizing, and fatal malignancy. Both of these subtypes are characterized by recurrent amplifications within chromosome 12, resulting in the overexpression of disease-driving genes that have been the focus of therapeutic targeting. Myxoid liposarcoma is characterized by a pathognomonic chromosomal translocation that results in an oncogenic fusion protein, whereas pleomorphic liposarcoma is a karyotypically complex and especially poor-prognosis subtype that accounts for less than 10% of liposarcoma diagnoses. A range of novel pharmaceutical agents that aim to target liposarcoma-specific biology are under active investigation and offer hope of adding to the limited available treatment options for recurrent or inoperable disease.

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.

Heterogeneity in sarcoma cell lines reveals enhanced motility of tetraploid versus diploid cells

Soft tissue sarcomas with complex genomics are very heterogeneous tumors lacking simple prognosis markers or targeted therapies. Overexpression of a subset of mitotic genes from a signature called CINSARC is of bad prognosis, but the significance of this signature remains elusive. Here we precisely measure the cell cycle and mitosis duration of sarcoma cell lines and we found that the mitotic gene products overexpression does not reflect variation in the time spent during mitosis or G2/M. We also found that the CINSARC cell lines, we studied, are composed of a mixture of aneuploid, diploid, and tetraploid cells that are highly motile in vitro. After sorting diploid and tetraploid cells, we showed that the tetraploid cell clones do not possess a proliferative advantage, but are strikingly more motile and invasive than their diploid counterparts. This is correlated with higher levels of mitotic proteins overexpression. Owing that mitotic proteins are almost systematically degraded at the end of mitosis, we propose that it is the abnormal activity of the mitotic proteins during interphase that boosts the sarcoma cells migratory properties by affecting their cytoskeleton. To test this hypothesis, we designed a screen for mitotic or cytoskeleton protein inhibitors affecting the sarcoma cell migration potential independently of cytotoxic activities. We found that inhibition of several mitotic kinases drastically impairs the CINSARC cell invasive and migratory properties. This finding could provide a handle by which to selectively inhibit the most invasive cells.

Uterine sarcoma part III-Targeted therapy: The Taiwan Association of Gynecology (TAG) systematic review

Uterine sarcoma is a very aggressive and highly lethal disease. Even after a comprehensive staging surgery or en block cytoreduction surgery followed by multimodality therapy (often chemotherapy and/or radiation therapy), many patients relapse or present with distant metastases, and finally die of diseases. The worst outcome of uterine sarcomas is partly because of their rarity, unknown etiology, and highly divergent genetic aberration. Uterine sarcomas are often classified into four distinct subtypes, including uterine leiomyosarcoma, low-grade uterine endometrial stromal sarcoma, high-grade uterine endometrial stromal sarcoma, and undifferentiated uterine sarcoma. Currently, evidence from tumor biology found that these tumors showed alternation and/or mutation of genomes and the intracellular signal pathway. In addition, some preclinical studies showed promising results for targeting receptor tyrosine kinase signaling, phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway, various kinds of growth factor pathways, Wnt/beta-catenin signaling pathway, transforming growth factor β/bone morphogenetic protein signal pathway, aurora kinase A, MDM2 proto-oncogene, histone deacetylases, sex hormone receptors, certain types of oncoproteins, and/or loss of tumor suppressor genes. The current review is attempted to summarize the recurrent advance of targeted therapy for uterine sarcomas.

Recent translational research into targeted therapy for liposarcoma

Liposarcomas (LPS) are among the most common soft tissue sarcomas, originating from adipocytes. Treatment for LPS typically involves surgical resection and radiation therapy, while the use of conventional cytotoxic chemotherapy for unresectable or metastatic LPS remains controversial. This review summarizes the results of recent translational research and trials of novel therapies targeting various genetic and molecular aberrations in different subtypes of LPS. Genetic aberrations such as the 12q13-15 amplicon, genetic amplification of MDM2, CDK4, TOP2A, PTK7, and CHEK1, point mutations in CTNNB1, CDH1, FBXW7, and EPHA1, as the fusion of FUS-DDIT3/EWSR1-DDIT3 are involved in the pathogenesis LPS and represent potential therapeutic candidates. Tyrosine kinase inhibitors targeting MET, AXL, IGF1R, EGFR, VEGFR2, PDGFR-β and Aurora kinase are effective in certain types of LPS. Abnormalities in the PI3K/Akt signaling pathway deregulation of C/EBP-α and its partner PPAR-γ, and the interaction between calreticulin (CRT) and CD47 are also promising therapeutic targets. These promising new approaches may help to supplement existing treatments for LPS.

Molecular mechanism and therapeutic implications of selinexor (KPT-330) in liposarcoma

Exportin-1 mediates nuclear export of multiple tumor suppressor and growth regulatory proteins. Aberrant expression of exportin-1 is noted in human malignancies, resulting in cytoplasmic mislocalization of its target proteins. We investigated the efficacy of selinexor against liposarcoma cells both in vitro and in vivo. Exportin-1 was highly expressed in liposarcoma samples and cell lines as determined by immunohistochemistry, western blot, and immunofluorescence assay. Knockdown of endogenous exportin-1 inhibited proliferation of liposarcoma cells. Selinexor also significantly decreased cell proliferation as well as induced cell cycle arrest and apoptosis of liposarcoma cells. The drug also significantly decreased tumor volumes and weights of liposarcoma xenografts. Importantly, selinexor inhibited insulin-like growth factor 1 (IGF1) activation of IGF-1R/AKT pathway through upregulation of insulin-like growth factor binding protein 5 (IGFBP5). Further, overexpression and knockdown experiments showed that IGFBP5 acts as a tumor suppressor and its expression was restored upon selinexor treatment of liposarcoma cells. Selinexor decreased aurora kinase A and B levels in these cells and inhibitors of these kinases suppressed the growth of the liposarcoma cells. Overall, our study showed that selinexor treatment restored tumor suppressive function of IGFBP5 and inhibited aurora kinase A and B in liposarcoma cells supporting the usefulness of selinexor as a potential therapeutic strategy for the treatment of this cancer.

Phosphorylation of MAP65-1 by Arabidopsis Aurora Kinases Is Required for Efficient Cell Cycle Progression

Aurora kinases are key effectors of mitosis. Plant Auroras are functionally divided into two clades. The alpha Auroras (Aurora1 and Aurora2) associate with the spindle and the cell plate and are implicated in controlling formative divisions throughout plant development. The beta Aurora (Aurora3) localizes to centromeres and likely functions in chromosome separation. In contrast to the wealth of data available on the role of Aurora in other kingdoms, knowledge on their function in plants is merely emerging. This is exemplified by the fact that only histone H3 and the plant homolog of TPX2 have been identified as Aurora substrates in plants. Here we provide biochemical, genetic, and cell biological evidence that the microtubule-bundling protein MAP65-1-a member of the MAP65/Ase1/PRC1 protein family, implicated in central spindle formation and cytokinesis in animals, yeasts, and plants-is a genuine substrate of alpha Aurora kinases. MAP65-1 interacts with Aurora1 in vivo and is phosphorylated on two residues at its unfolded tail domain. Its overexpression and down-regulation antagonistically affect the alpha Aurora double mutant phenotypes. Phospho-mutant analysis shows that Aurora contributes to the microtubule bundling capacity of MAP65-1 in concert with other mitotic kinases.

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.

Phase II study of MLN8237 (Alisertib) in advanced/metastatic sarcoma

BACKGROUND

Aurora kinase A (AURKA) is commonly overexpressed in sarcoma. The inhibition of AURKA by shRNA or by a specific AURKA inhibitor blocks in vitro proliferation of multiple sarcoma subtypes. MLN8237 (alisertib) is a novel oral adenosine triphosphate-competitive AURKA inhibitor.

PATIENTS AND METHODS

This Cancer Therapy Evaluation Program-sponsored phase II study of alisertib was conducted through the Alliance for Clinical Trials in Oncology (A091102). Patients were enrolled into histology-defined cohorts: (i) liposarcoma, (ii) leiomyosarcoma, (iii) undifferentiated sarcoma, (iv) malignant peripheral nerve sheath tumor, or (v) other. Treatment was alisertib 50 mg PO b.i.d. d1-d7 every 21 days. The primary end point was response rate; progression-free survival (PFS) was secondary. One response in the first 9 patients expanded enrollment in a cohort to 24 using a Simon two-stage design.

RESULTS

Seventy-two patients were enrolled at 24 sites [12 LPS, 10 LMS, 11 US, 10 malignant peripheral nerve sheath tumor (MPNST), 29 Other]. The median age was 55 years; 54% were male; 58%/38%/4% were ECOG PS 0/1/2. One PR expanded enrollment to the second stage in the other sarcoma cohort. The histology-specific cohorts ceased at the first stage. There were two confirmed PRs in the other cohort (both angiosarcoma) and one unconfirmed PR in dedifferentiated chondrosarcoma. Twelve-week PFS was 73% (LPS), 44% (LMS), 36% (US), 60% (MPNST), and 38% (Other). Grade 3-4 adverse events: oral mucositis (12%), anemia (14%), platelet count decreased (14%), leukopenia (22%), and neutropenia (42%).

CONCLUSIONS

Alisertib was well tolerated. Occasional responses, yet prolonged stable disease, were observed. Although failing to meet the primary RR end point, PFS was promising.

TRIAL REGISTRATION ID

NCT01653028.