Preclinical validation of Aurora kinases-targeting drugs in osteosarcoma

Unraveling molecular aberrations and pioneering therapeutic strategies in osteosarcoma

Osteosarcoma, a rare primary bone cancer, presents diverse molecular aberrations that underscore its complexity. Despite the persistent endeavors by researchers, the limited amelioration in the five-year survival rate indicates that current therapeutic strategies prove inadequate in addressing the clinical necessities. Advancements in molecular profiling have facilitated an enhanced comprehension of the biology of osteosarcoma, offering a promising outlook for treatment. There is an urgent need to develop innovative approaches to address the complex challenges of osteosarcoma, ultimately contributing to enhanced patient outcomes. This review explores the nexus between osteosarcoma and cancer predisposition syndromes, intricacies in its somatic genome, and clinically actionable alterations. This review covers treatment strategies, including surgery, chemotherapy, immune checkpoint inhibitors (ICIs), and tyrosine kinase inhibitors (TKIs). Innovative treatment modalities targeting diverse pathways, including multi-target tyrosine kinases, cell cycle, PI3K/mTOR pathway, and DNA damage repair (DDR), offer promising interventions. This review also covers promising avenues, including antibody-drug conjugates (ADCs) and immunotherapy strategies, such as cytokines, adoptive cellular therapy (ACT), ICIs, and cancer vaccines. This comprehensive exploration contributes to a holistic understanding, offering guidance for clinical applications to advance the management of osteosarcoma.

Aurora-B: a novel biomarker in the invasion and metastasis of osteosarcoma

Osteosarcoma (OS), a primary human malignant tumor that affects the bones, mostly arises in children and adolescents. Even though surgical resection followed by radiotherapy and chemotherapy has improved the survival rate up to 60%, the long-term positive effect for most patients with OS is not satisfactory. Hence, elucidating the specific mechanisms involved in the pathogenesis of OS is particularly important. Aurora-B, a serine/threonine kinase, plays a crucial role in centrosome regulation, spindle formation and chromosomal separation during mitosis. It has been found that Aurora-B overexpression is related to the occurrence and development of several malignant tumors, including OS. This article summarizes the role of Aurora-B in the invasion and metastasis of OS.

Aurora B Inhibitors as Cancer Therapeutics

The Aurora kinases (A, B, and C) are a family of three isoform serine/threonine kinases that regulate mitosis and meiosis. The Chromosomal Passenger Complex (CPC), which contains Aurora B as an enzymatic component, plays a critical role in cell division. Aurora B in the CPC ensures faithful chromosome segregation and promotes the correct biorientation of chromosomes on the mitotic spindle. Aurora B overexpression has been observed in several human cancers and has been associated with a poor prognosis for cancer patients. Targeting Aurora B with inhibitors is a promising therapeutic strategy for cancer treatment. In the past decade, Aurora B inhibitors have been extensively pursued in both academia and industry. This paper presents a comprehensive review of the preclinical and clinical candidates of Aurora B inhibitors as potential anticancer drugs. The recent advances in the field of Aurora B inhibitor development will be highlighted, and the binding interactions between Aurora B and inhibitors based on crystal structures will be presented and discussed to provide insights for the future design of more selective Aurora B inhibitors.

Targeted therapy for osteosarcoma: a review

BACKGROUND

Osteosarcoma is a common primary malignant tumour of the bone that usually occurs in children and adolescents. It is characterised by difficult treatment, recurrence and metastasis, and poor prognosis. Currently, the treatment of osteosarcoma is mainly based on surgery and auxiliary chemotherapy. However, for recurrent and some primary osteosarcoma cases, owing to the rapid progression of disease and chemotherapy resistance, the effects of chemotherapy are poor. With the rapid development of tumour-targeted therapy, molecular-targeted therapy for osteosarcoma has shown promise.

PURPOSE

In this paper, we review the molecular mechanisms, related targets, and clinical applications of targeted osteosarcoma therapy. In doing this, we provide a summary of recent literature on the characteristics of targeted osteosarcoma therapy, the advantages of its clinical application, and development of targeted therapy in future. We aim to provide new insights into the treatment of osteosarcoma.

CONCLUSION

Targeted therapy shows potential in the treatment of osteosarcoma and may offer an important means of precise and personalised treatment in the future, but drug resistance and adverse effects may limit its application.

Current Status and Prospects of Targeted Therapy for Osteosarcoma

Osteosarcoma (OS) is a highly malignant tumor occurring in bone tissue with a high propensity to metastasize, and its underlying mechanisms remain largely elusive. The OS prognosis is poor, and improving the survival of OS patients remains a challenge. Current treatment methods such as surgical approaches, chemotherapeutic drugs, and immunotherapeutic drugs remain ineffective. As research progresses, targeted therapy is gradually becoming irreplaceable. In this review, several treatment modalities for osteosarcoma, such as surgery, chemotherapy, and immunotherapy, are briefly described, followed by a discussion of targeted therapy, the important targets, and new technologies for osteosarcoma treatment.

Impact of ABC Transporters in Osteosarcoma and Ewing's Sarcoma: Which Are Involved in Chemoresistance and Which Are Not?

The ATP-binding cassette (ABC) transporter superfamily consists of several proteins with a wide repertoire of functions. Under physiological conditions, ABC transporters are involved in cellular trafficking of hormones, lipids, ions, xenobiotics, and several other molecules, including a broad spectrum of chemical substrates and chemotherapeutic drugs. In cancers, ABC transporters have been intensely studied over the past decades, mostly for their involvement in the multidrug resistance (MDR) phenotype. This review provides an overview of ABC transporters, both related and unrelated to MDR, which have been studied in osteosarcoma and Ewing's sarcoma. Since different backbone drugs used in first-line or rescue chemotherapy for these two rare bone sarcomas are substrates of ABC transporters, this review particularly focused on studies that have provided findings that have been either translated to clinical practice or have indicated new candidate therapeutic targets; however, findings obtained from ABC transporters that were not directly involved in drug resistance were also discussed, in order to provide a more complete overview of the biological impacts of these molecules in osteosarcoma and Ewing's sarcoma. Finally, therapeutic strategies and agents aimed to circumvent ABC-mediated chemoresistance were discussed to provide future perspectives about possible treatment improvements of these neoplasms.

Advancing therapy for osteosarcoma

Improving the survival of patients with osteosarcoma has long proved challenging, although the treatment of this disease is on the precipice of advancement. The increasing feasibility of molecular profiling together with the creation of both robust model systems and large, well-annotated tissue banks has led to an increased understanding of osteosarcoma biology. The historical invariability of survival outcomes and the limited number of agents known to be active in the treatment of this disease facilitate clinical trials designed to identify efficacious novel therapies using small cohorts of patients. In addition, trial designs will increasingly consider the genetic background of the tumour through biomarker-based patient selection, thereby enriching for clinical activity. Indeed, osteosarcoma cells are known to express a number of surface proteins that might be of therapeutic relevance, including B7-H3, GD2 and HER2, which can be targeted using antibody-drug conjugates and/or adoptive cell therapies. In addition, immune-checkpoint inhibition might augment the latter approach by helping to overcome the immunosuppressive tumour microenvironment. In this Review, we provide a brief overview of current osteosarcoma therapy before focusing on the biological insights from the molecular profiling and preclinical modelling studies that have opened new therapeutic opportunities in this disease.

Drug Resistance in Osteosarcoma: Emerging Biomarkers, Therapeutic Targets and Treatment Strategies

Simple Summary

Despite the adoption of aggressive, multimodal treatment schedules, the cure rate of high-grade osteosarcoma (HGOS) has not significantly improved in the last 30 years. The most relevant problem preventing improvement in HGOS prognosis is drug resistance. Therefore, validated novel biomarkers that help to identify those patients who could benefit from innovative treatment options and the development of drugs enabling personalized therapeutic protocols are necessary. The aim of this review was to give an overview on the most relevant emerging drug resistance-related biomarkers, therapeutic targets and new agents or novel candidate treatment strategies, which have been highlighted and suggested for HGOS to improve the success rate of clinical trials.

Abstract

High-grade osteosarcoma (HGOS), the most common primary malignant tumor of bone, is a highly aggressive neoplasm with a cure rate of approximately 40–50% in unselected patient populations. The major clinical problems opposing the cure of HGOS are the presence of inherent or acquired drug resistance and the development of metastasis. Since the drugs used in first-line chemotherapy protocols for HGOS and clinical outcome have not significantly evolved in the past three decades, there is an urgent need for new therapeutic biomarkers and targeted treatment strategies, which may increase the currently available spectrum of cure modalities. Unresponsive or chemoresistant (refractory) HGOS patients usually encounter a dismal prognosis, mostly because therapeutic options and drugs effective for rescue treatments are scarce. Tailored treatments for different subgroups of HGOS patients stratified according to drug resistance-related biomarkers thus appear as an option that may improve this situation. This review explores drug resistance-related biomarkers, therapeutic targets and new candidate treatment strategies, which have emerged in HGOS. In addition to consolidated biomarkers, specific attention has been paid to the role of non-coding RNAs, tumor-derived extracellular vesicles, and cancer stem cells as contributors to drug resistance in HGOS, in order to highlight new candidate markers and therapeutic targets. The possible use of new non-conventional drugs to overcome the main mechanisms of drug resistance in HGOS are finally discussed.

Advances in targeted therapy for osteosarcoma based on molecular classification

Osteosarcoma, a highly malignant tumor, is characterized by widespread and recurrent chromosomal and genetic abnormalities. In recent years, a number of elaborated sequencing analyses have made it possible to cluster the osteosarcoma based on the identification of candidate driver genes and develop targeted therapy. Here, we reviewed recent next-generation genome sequencing studies and advances in targeted therapies for osteosarcoma based on molecular classification. First, we stratified osteosarcomas into ten molecular subtypes based on genetic changes. And we analyzed potential targeted therapies for osteosarcoma based on the identified molecular subtypes. Finally, the development of targeted therapies for osteosarcoma investigated in clinical trials were further summarized and discussed. Therefore, we indicated the importance of molecular classification on the targeted therapy for osteosarcoma. And the stratification of patients based on the genetic characteristics of osteosarcoma will help to obtain a better therapeutic response to targeted therapies, bringing us closer to the era of personalized medicine.

Elevated ABCB1 Expression Confers Acquired Resistance to Aurora Kinase Inhibitor GSK-1070916 in Cancer Cells

The emergence of multidrug resistance (MDR) has been a major issue for effective cancer chemotherapy as well as targeted therapy. One prominent factor that causes MDR is the overexpression of ABCB1 transporter. In the present study, we revealed that the Aurora kinase inhibitor GSK-1070916 is a substrate of ABCB1. GSK-1070916 is a newly developed inhibitor that is currently under clinical investigation. The cytotoxicity assay showed that overexpression of ABCB1 significantly hindered the anticancer effect of GSK-1070916 and the drug resistance can be abolished by the addition of an ABCB1 inhibitor. GSK-1070916 concentration-dependently stimulated ABCB1 ATPase activity. The HPLC drug accumulation assay suggested that the ABCB1-overexpressing cells had lower levels of intracellular GSK-1070916 compared with the parental cells. GSK-1070916 also showed high binding affinity to ABCB1 substrate-binding site in the computational docking analysis. In conclusion, our study provides strong evidence that ABCB1 can confer resistance to GSK-1070916, which should be taken into consideration in clinical setting.

Cisplatin Resistance in Osteosarcoma: In vitro Validation of Candidate DNA Repair-Related Therapeutic Targets and Drugs for Tailored Treatments

Treatment of high-grade osteosarcoma, the most common malignant tumor of bone, is largely based on administration of cisplatin and other DNA damaging drugs. Altered DNA repair mechanisms may thus significantly impact on either response or resistance to chemotherapy. In this study, by using a panel of human osteosarcoma cell lines, either sensitive or resistant to cisplatin, we assessed the value as candidate therapeutic targets of DNA repair-related factors belonging to the nucleotide excision repair (NER) or base excision repair (BER) pathways, as well as of a group of 18 kinases, which expression was higher in cisplatin-resistant variants compared to their parental cell lines and may be indirectly involved in DNA repair. The causal involvement of these factors in cisplatin resistance of human osteosarcoma cells was validated through gene silencing approaches and in vitro reversal of CDDP resistance. This approach highlighted a subgroup of genes, which value as promising candidate therapeutic targets was further confirmed by protein expression analyses. The in vitro activity of 15 inhibitor drugs against either these genes or their pathways was then analyzed, in order to identify the most active ones in terms of inherent activity and ability to overcome cisplatin resistance. NSC130813 (NERI02; F06) and triptolide, both targeting NER factors, proved to be the two most active agents, without evidence of cross-resistance with cisplatin. Combined in vitro treatments showed that NSC130813 and triptolide, when administered together with cisplatin, were able to improve its efficacy in both drug-sensitive and resistant osteosarcoma cells. This evidence may indicate an interesting therapeutic future option for treatment of osteosarcoma patients who present reduced responsiveness to cisplatin, even if possible effects of additive collateral toxicities must be carefully considered. Moreover, our study also showed that targeting protein kinases belonging to the mitogen-activated protein kinase (MAPK) or fibroblast growth factor receptor (FGFR) pathways might indicate new promising therapeutic perspectives in osteosarcoma, demanding for additional investigation.

MicroRNA-mRNA networks define translatable molecular outcome phenotypes in osteosarcoma

There is a lack of well validated prognostic biomarkers in osteosarcoma, a rare, recalcitrant disease for which treatment standards have not changed in over 20 years. We performed microRNA sequencing in 74 frozen osteosarcoma biopsy samples, constituting the largest single center translationally analyzed osteosarcoma cohort to date, and we separately analyzed a multi-omic dataset from a large NCI supported national cooperative group cohort. We validated the prognostic value of candidate microRNA signatures and contextualized them in relevant transcriptomic and epigenomic networks. Our results reveal the existence of molecularly defined phenotypes associated with outcome independent of clinicopathologic features. Through machine learning based integrative pharmacogenomic analysis, the microRNA biomarkers identify novel therapeutics for stratified application in osteosarcoma. The previously unrecognized osteosarcoma subtypes with distinct clinical courses and response to therapy could be translatable for discerning patients appropriate for more intensified, less intensified, or alternate therapeutic regimens.

Systematic screening for potential therapeutic targets in osteosarcoma through a kinome-wide CRISPR-Cas9 library

Objective: Osteosarcoma is the most common primary malignant bone tumor. However, the survival of patients with osteosarcoma has remained unchanged during the past 30 years, owing to a lack of efficient therapeutic targets.

Methods: We constructed a kinome-targeting CRISPR-Cas9 library containing 507 kinases and 100 nontargeting controls and screened the potential kinase targets in osteosarcoma. The CRISPR screening sequencing data were analyzed with the Model-based Analysis of Genome-wide CRISPR/Cas9 Knockout (MAGeCK) Python package. The functional data were applied in the 143B cell line through lenti-CRISPR-mediated gene knockout. The clinical significance of kinases in the survival of patients with osteosarcoma was analyzed in the R2: Genomics Analysis and Visualization Platform.

Results: We identified 53 potential kinase targets in osteosarcoma. Among these targets, we analyzed 3 kinases, TRRAP, PKMYT1, and TP53RK, to validate their oncogenic functions in osteosarcoma. PKMYT1 and TP53RK showed higher expression in osteosarcoma than in normal bone tissue, whereas TRRAP showed no significant difference. High expression of all 3 kinases was associated with relatively poor prognosis in patients with osteosarcoma.

Conclusions: Our results not only offer potential therapeutic kinase targets in osteosarcoma but also provide a paradigm for functional genetic screening by using a CRISPR-Cas9 library, including target design, library construction, screening workflow, data analysis, and functional validation. This method may also be useful in potentially accelerating drug discovery for other cancer types.

Aurora B kinase as a novel molecular target for inhibition the growth of osteosarcoma

Osteosarcoma is the primary human malignant tumor affecting bone. This cancer most frequently arises in children and adolescents, with a second peak in those over the age of 50. Currently, surgery followed by radiotherapy and chemotherapy are the main treatments, but long-term positive effects are very poor. Aurora B kinase is a serine/threonine kinase that is a key regulator of cell cycle and mitosis. Tissue array analysis revealed that Aurora B kinase is overexpressed in osteosarcoma compared with normal bone tissue. We developed a compound, HOI-07 (i.e., (E)-3-((E)-4-(benzo[d] [1,3]dioxol-5-yl)-2-oxobut-3-en-1-ylidene)indolin-2-one), as a specific Aurora B kinase inhibitor and examined its effectiveness against osteosarcoma cell growth in this study. This compound inhibited Aurora B kinase activity in osteosarcoma and induced apoptosis, caused G2-M phase arrest, and attenuated osteosarcoma anchorage-independent cell growth. Moreover, knocking down the expression of Aurora B effectively reduced the sensitivity of osteosarcoma to HOI-07. Results of a xenograft mouse study indicated that HOI-07 treatment effectively suppressed the growth of 143B and KHOS xenografts, without affecting the body weight of mice. The expression of phosphorylated histone H3 (Ser10) was reduced in mice treated with HOI-07. Overall, we identified HOI-07 as a specific Aurora B kinase inhibitor for osteosarcoma treatment and this compound warrants further investigation.

Genome-Informed Targeted Therapy for Osteosarcoma

Osteosarcoma is a highly aggressive cancer for which treatment has remained essentially unchanged for more than 30 years. Osteosarcoma is characterized by widespread and recurrent somatic copy-number alterations (SCNA) and structural rearrangements. In contrast, few recurrent point mutations in protein-coding genes have been identified, suggesting that genes within SCNAs are key oncogenic drivers in this disease. SCNAs and structural rearrangements are highly heterogeneous across osteosarcoma cases, suggesting the need for a genome-informed approach to targeted therapy. To identify patient-specific candidate drivers, we used a simple heuristic based on degree and rank order of copy-number amplification (identified by whole-genome sequencing) and changes in gene expression as identified by RNA sequencing. Using patient-derived tumor xenografts, we demonstrate that targeting of patient-specific SCNAs leads to significant decrease in tumor burden, providing a road map for genome-informed treatment of osteosarcoma. SIGNIFICANCE: Osteosarcoma is treated with a chemotherapy regimen established 30 years ago. Although osteosarcoma is genomically complex, we hypothesized that tumor-specific dependencies could be identified within SCNAs. Using patient-derived tumor xenografts, we found a high degree of response for "genome-matched" therapies, demonstrating the utility of a targeted genome-informed approach.This article is highlighted in the In This Issue feature, p. 1.

The Effect of Aurora Kinase Inhibitor on Adhesion and Migration in Human Breast Cancer Cells and Clinical Implications

Background

The Aurora kinase family is comprised of highly conserved serine/threonine protein kinases that are known to be crucial in the regulation of the cell cycle. Aberrant expression of Aurora kinases has been demonstrated in certain malignancies. We aimed to examine the expression of Aurora kinases in human breast cancer tissues and to investigate the cellular impact of Aurora kinases inhibitor on breast cancer cells.

Methods

The expression of Aurora kinase A/B/C was individually examined in tumor specimens (n = 106) and normal tissues (n = 29) from breast cancer patients using quantitative real-time PCR (Q-PCR) and immunohistochemistry. Cells were treated with the corresponding inhibitor, and then migration and adhesion were evaluated by electric cell impedance sensing assay. The proliferation of breast cancer cells treated with the inhibitor was examined using in vitro models.

Results

High levels of Aurora kinase B and C were found in the tumor tissues from breast cancer patients, but low levels of Aurora kinase A were seen in normal tissues at the mRNA level and immunohistochemistry. The mRNA expression level of Aurora kinase B and C had a negative correlation with grade staging, staging and survival rate in breast cancer patients, whilst Aurora kinase A exhibited a converse expression. The inhibitor ZM447439 promoted adhesion of the human breast cancer cell line MDA-MB-231 and inhibited the migration of MCF-7 human breast cancer cells.

Conclusion

Taken together, the expression of Aurora kinase B and C was down-regulated in breast tumor tissues but Aurora kinase A was not. Aurora kinase may have a key role in the progression and metastasis of breast cancer.

Re-calculating! Navigating through the osteosarcoma treatment roadblock

The survival rates for patients with osteosarcoma have remained almost static for the past three decades. Current standard of care therapy includes chemotherapies such as doxorubicin, cisplatin, and methotrexate along with complete surgical resection and surgery with or without ifosfamide and etoposide for relapse, though outcomes are hoped to be improved through clinical trials. Additionally, increased understanding of the genetics, signaling pathways and microenvironmental factors driving the disease have led to the identification of promising agents and potential paths towards translation of an exciting array of novel targeted therapies. Here, we review the mechanism of action of these emerging therapies and how, with clinical translation, they can potentially improve the survival rates for osteosarcoma patients in the near future.

Targeting CDKs with Roscovitine Increases Sensitivity to DNA Damaging Drugs of Human Osteosarcoma Cells

Cyclin-dependent kinase 2 (CDK2) has been reported to be essential for cell proliferation in several human tumours and it has been suggested as an appropriate target to be considered in order to enhance the efficacy of treatment regimens based on the use of DNA damaging drugs. We evaluated the clinical impact of CDK2 overexpression on a series of 21 high-grade osteosarcoma (OS) samples profiled by using cDNA microarrays. We also assessed the in vitro efficacy of the CDKs inhibitor roscovitine in a panel of drug-sensitive and drug-resistant human OS cell lines. OS tumour samples showed an inherent overexpression of CDK2, and high expression levels at diagnosis of this kinase appeared to negatively impact on clinical outcome. CDK2 expression also proved to be relevant for in vitro OS cells growth. These findings indicated CDK2 as a promising candidate therapeutic marker for OS and therefore we assessed the efficacy of the CDKs-inhibitor roscovitine in both drug-sensitive and -resistant OS cell lines. All cell lines resulted to be responsive to roscovitine, which was also able to increase the activity of cisplatin and doxorubicin, the two most active DNA damaging drugs used in OS chemotherapy. Our results indicated that combined treatment with conventional OS chemotherapeutic drugs and roscovitine may represent a new candidate intervention approach, which may be considered to enhance tumour cell sensitivity to DNA damaging drugs.

MEK inhibition induces apoptosis in osteosarcoma cells with constitutive ERK1/2 phosphorylation

Conventional high-grade osteosarcoma is the most common primary bone cancer with relatively high incidence in young people. Recurrent and metastatic tumors are difficult to treat. We performed a kinase inhibitor screen in two osteosarcoma cell lines, which identified MEK1/2 inhibitors. These inhibitors were further validated in a panel of six osteosarcoma cell lines. Western blot analysis was performed to assess ERK activity and efficacy of MEK inhibition. A 3D culture system was used to validate results from 2D monolayer cultures. Gene expression analysis was performed to identify differentially expressed gene signatures in sensitive and resistant cell lines. Activation of the AKT signaling network was explored using Western blot and pharmacological inhibition. In the screen, Trametinib, AZD8330 and TAK-733 decreased cell viability by more than 50%. Validation in six osteosarcoma cell lines identified three cell lines as resistant and three as sensitive to the inhibitors. Western blot analysis of ERK activity revealed that sensitive lines had high constitutive ERK activity. Treatment with the three MEK inhibitors in a 3D culture system validated efficacy in inhibition of osteosarcoma viability. MEK1/2 inhibition represents a candidate treatment strategy for osteosarcomas displaying high MEK activity as determined by ERK phosphorylation status.

Targeting protein kinases to reverse multidrug resistance in sarcoma

Sarcomas are a group of cancers that arise from transformed cells of mesenchymal origin. They can be classified into over 50 subtypes, accounting for approximately 1% of adult and 15% of pediatric cancers. Wide surgical resection, radiotherapy, and chemotherapy are the most common treatments for the majority of sarcomas. Among these therapies, chemotherapy can palliate symptoms and prolong life for some sarcoma patients. However, sarcoma cells can have intrinsic or acquired resistance after treatment with chemotherapeutics drugs, leading to the development of multidrug resistance (MDR). MDR attenuates the efficacy of anticancer drugs and results in treatment failure for sarcomas. Therefore, overcoming MDR is an unmet need for sarcoma therapy. Certain protein kinases demonstrate aberrant expression and/or activity in sarcoma cells, which have been found to be involved in the regulation of sarcoma cell progression, such as cell cycle, apoptosis, and survival. Inhibiting these protein kinases may not only decrease the proliferation and growth of sarcoma cells, but also reverse their resistance to chemotherapeutic drugs to subsequently reduce the doses of anticancer drugs and decrease drug side-effects. The discovery of novel strategies targeting protein kinases opens a door to a new area of sarcoma research and provides insight into the mechanisms of MDR in chemotherapy. This review will focus on the recent studies in targeting protein kinase to reverse chemotherapeutic drug resistance in sarcoma.

ABCG2 impairs the activity of the aurora kinase inhibitor tozasertib but not of alisertib

BACKGROUND

Recently, we have shown that the ATP-binding cassette (ABC) transporter ABCB1 interferes with the anti-cancer activity of the pan-aurora kinase inhibitor tozasertib (VX680, MK-0457) but not of the aurora kinase A and B inhibitor alisertib (MLN8237). Preliminary data had suggested tozasertib also to be a substrate of the ABC transporter ABCG2, another ABC transporter potentially involved in cancer cell drug resistance. Here, we studied the effect of ABCG2 on the activity of tozasertib and alisertib.

RESULTS

The tozasertib concentration that reduces cell viability by 50% (IC50) was dramatically increased in ABCG2-transduced UKF-NB-3(ABCG2) cells (48.8-fold) compared to UKF-NB-3 cells and vector-transduced control cells. The ABCG2 inhibitor WK-X-34 reduced tozasertib IC50 to the level of non-ABCG2-expressing UKF-NB-3 cells. Furthermore, ABCG2 depletion from UKF-NB-3(ABCG2) cells using another lentiviral vector expressing an shRNA against the bicistronic mRNA of ABCG2 and eGFP largely re-sensitised these cells to tozasertib. In contrast, alisertib activity was not affected by ABCG2 expression.

CONCLUSIONS

Tozasertib but not alisertib activity is affected by ABCG2 expression. This should be considered within the design and analysis of experiments and clinical trials investigating these compounds.

Advances in emerging drugs for osteosarcoma

INTRODUCTION

Osteosarcoma (OS), the most common primary malignant bone tumor, is currently treated with pre- and postoperative chemotherapy in association with the surgical removal of the tumor. Conventional treatments allow to cure about 60 - 65% of patients with primary tumors and only 20 - 25% of patients with recurrent disease. New treatment approaches and drugs are therefore highly warranted to improve prognosis.

AREAS COVERED

This review focuses on the therapeutic approaches that are under development or clinical evaluation in OS. Information was obtained from different and continuously updated data bases, as well as from literature searches, in which particular relevance was given to reports and reviews on new targeted therapies under clinical investigation in high-grade OS.

EXPERT OPINION

OS is a heterogeneous tumor, with a great variability in treatment response between patients. It is therefore unlikely that a single therapeutic tool will be uniformly successful for all OS patients. This claims for the validation of new treatment approaches together with biologic/(pharmaco)genetic markers, which may select the most appropriate subgroup of patients for each treatment approach. Since some promising novel agents and treatment strategies are currently tested in Phase I/II/III clinical trials, we may hope that new therapies with superior efficacy and safety profiles will be identified in the next few years.

Targeting polo-like kinase 1 by NMS-P937 in osteosarcoma cell lines inhibits tumor cell growth and partially overcomes drug resistance

BACKGROUND

Polo-like kinase 1 (PLK1) has emerged as a prognostic factor in various neoplasms, but only scarce data have been reported for high-grade osteosarcoma (OS). In this study, we assessed PLK1 expression and the efficacy of PLK1 inhibitor NMS-P937 in OS.

METHODS

PLK1 expression was assessed on 21 OS clinical samples and on a panel of human OS cell lines. In vitro efficacy of NMS-P937 was evaluated on nine drug-sensitive and six drug-resistant human OS cell lines, either as single agent or in combination with the drugs used in chemotherapy for OS.

RESULTS

PLK1 expression was higher in OS clinical samples and cell lines compared to normal human tissue. A higher PLK1 expression at diagnosis appeared to be associated with an unfavourable clinical outcome. PLK1 silencing produced growth inhibition, cell cycle retardation and apoptosis induction in human OS cell lines. NMS-P937 proved to be highly active in both drug-sensitive and drug-resistant cell lines, with the only exception of ABCB1-overexpressing, Doxorubicin (DX)-resistant variants. However, in these cells, the association of NMS-P937 with DX was able to revert DX-resistance by negatively interfering with ABCB1 transport activity. NMS-P937 was also able to decrease clonogenic and migration ability of human OS cell lines.

CONCLUSION

PLK1 can be proposed as a new candidate target for OS. Targeting PLK1 in OS with NMS-P937 in association with conventional chemotherapeutic drugs may be a new interesting therapeutic option, since this approach has proved to be active against drug resistant cells.

Alisertib (MLN8237), a selective Aurora-A kinase inhibitor, induces apoptosis in human tongue squamous cell carcinoma cell both in vitro and in vivo

Aurora-A kinases are overexpressed in many cancer tissues and cells. Alisertib is an investigational, orally administered, selective, small-molecule Aurora-A kinase inhibitor with preclinical activity against a broad range of tumors. Our study was aimed to detect the effects of alisertib on human tongue squamous cell carcinoma (HTSCC). Treatment of a human tongue squamous cell carcinoma cell line, HSC-3, with alisertib to inhibition of Aurora-A kinases reduced proliferation and induced apoptosis, which was accompanied by activation of the ATM/Chk2/p53 pathway. In vivo, inhibition of Aurora-A kinases in established xenografted tumors decreased tumor size and weight. Kaplan-Meyer survival analysis demonstrated that the cumulative survival time of mice without Aurora-A kinases was significantly longer than those with Aurora-A kinases. Our data provide the basis for developing alisertib to treat human tongue squamous cell carcinoma.

Translational biology of osteosarcoma

For the past 30 years, improvements in the survival of patients with osteosarcoma have been mostly incremental. Despite evidence of genomic instability and a high frequency of chromothripsis and kataegis, osteosarcomas carry few recurrent targetable mutations, and trials of targeted agents have been generally disappointing. Bone has a highly specialized immune environment and many immune signalling pathways are important in bone homeostasis. The success of the innate immune stimulant mifamurtide in the adjuvant treatment of non-metastatic osteosarcoma suggests that newer immune-based treatments, such as immune checkpoint inhibitors, may substantially improve disease outcome.

Aurora kinases as targets in drug-resistant neuroblastoma cells

Aurora kinase inhibitors displayed activity in pre-clinical neuroblastoma models. Here, we studied the effects of the pan-aurora kinase inhibitor tozasertib (VX680, MK-0457) and the aurora kinase inhibitor alisertib (MLN8237) that shows some specificity for aurora kinase A over aurora kinase B in a panel of neuroblastoma cell lines with acquired drug resistance. Both compounds displayed anti-neuroblastoma activity in the nanomolar range. The anti-neuroblastoma mechanism included inhibition of aurora kinase signalling as indicated by decreased phosphorylation of the aurora kinase substrate histone H3, cell cycle inhibition in G2/M phase, and induction of apoptosis. The activity of alisertib but not of tozasertib was affected by ABCB1 expression. Aurora kinase inhibitors induced a p53 response and their activity was enhanced in combination with the MDM2 inhibitor and p53 activator nutlin-3 in p53 wild-type cells. In conclusion, aurora kinases are potential drug targets in therapy-refractory neuroblastoma, in particular for the vast majority of p53 wild-type cases.

Aurora kinase inhibitor patents and agents in clinical testing: an update (2011 - 2013)

INTRODUCTION

Aurora kinase A, B and C, members of serine/threonine kinase family, are key regulators of mitosis. As Aurora kinases are overexpressed in many of the human cancers, small-molecule inhibitors of Aurora kinase have emerged as a possible treatment option for cancer.

AREAS COVERED

In 2009 and 2011, the literature pertaining to Aurora kinase inhibitors and their patents was reviewed. Here, the aim is to update the information for Aurora kinase inhibitors in clinical trials and the patents filed between the years 2011 and 2013. Pubmed, Scopus®, Scifinder®, USPTO, EPO and www.clinicaltrials.gov databases were used for searching the literature and patents for Aurora kinase inhibitors.

EXPERT OPINION

Even though both Aurora sub-type selective as well as pan-selective inhibitors show preclinical and clinical efficacy, so far no Aurora kinase inhibitor has been approved for clinical use. Particularly, dose-limiting toxicity (neutropenia) is a key issue that needs to be addressed. Preliminary evidence suggests that the use of selective Aurora A inhibitors could avoid Aurora B-mediated neutropenia in clinical settings. Also, use of adjunctive agents such as granulocyte stimulating factor to overcome neutropenia associated with Aurora B inhibition could be an answer to overcome the toxicity and bring Aurora inhibitors to market in the future.