Down-Regulation of Insulin-Like Growth Factor I Receptor Activity by NVP-AEW541 Has an Antitumor Effect on Neuroblastoma Cells In vitro and In vivo

Preclinical Therapeutic Efficacy of RAF/MEK/ERK and IGF1R/AKT/mTOR Inhibition in Neuroblastoma

Activating mutations in the RAS/MAPK pathway are observed in relapsed neuroblastoma. Preclinical studies indicate that these tumors have an increased sensitivity to inhibitors of the RAS/MAPK pathway, such as MEK inhibitors. MEK inhibitors do not induce durable responses as single agents, indicating a need to identify synergistic combinations of targeted agents to provide therapeutic benefit. We previously showed preclinical therapeutic synergy between a MEK inhibitor, trametinib, and a monoclonal antibody specific for IGF1R, ganitumab in RAS-mutated rhabdomyosarcoma. Neuroblastoma cells, like rhabdomyosarcoma cells, are sensitive to the inhibition of the RAS/MAPK and IGF1R/AKT/mTOR pathways. We hypothesized that the combination of trametinib and ganitumab would be effective in RAS-mutated neuroblastoma. In this study, trametinib and ganitumab synergistically suppressed neuroblastoma cell proliferation and induced apoptosis in cell culture. We also observed a delay in tumor initiation and prolongation of survival in heterotopic and orthotopic xenograft models treated with trametinib and ganitumab. However, the growth of both primary and metastatic tumors was observed in animals receiving the combination of trametinib and ganitumab. Therefore, more preclinical work is necessary before testing this combination in patients with relapsed or refractory RAS-mutated neuroblastoma.

BET and CDK Inhibition Reveal Differences in the Proliferation Control of Sympathetic Ganglion Neuroblasts and Adrenal Chromaffin Cells

Neuroblastoma arising from the adrenal differ from ganglionic neuroblastoma both genetically and clinically, with adrenal tumors being associated with a more severe prognosis. The different tumor properties may be linked to specific tumor founder cells in adrenal and sympathetic ganglia. To address this question, we first set up cultures of mouse sympathetic neuroblasts and adrenal chromaffin cells. These cultures were then treated with various proliferation inhibitors to identify lineage-specific responses. We show that neuroblast and chromaffin cell proliferation was affected by WNT, ALK, IGF1, and PRC2/EZH2 signaling inhibitors to a similar extent. However, differential effects were observed in response to bromodomain and extraterminal (BET) protein inhibitors (JQ1, GSK1324726A) and to the CDK-7 inhibitor THZ1, with BET inhibitors preferentially affecting chromaffin cells, and THZ1 preferentially affecting neuroblasts. The differential dependence of chromaffin cells and neuroblasts on BET and CDK signaling may indicate different mechanisms during tumor initiation in sympathetic ganglia and adrenal.

Comparative Phosphoproteomics of Neuro-2a Cells under Insulin Resistance Reveals New Molecular Signatures of Alzheimer's Disease

Insulin in the brain is a well-known critical factor in neuro-development and regulation of adult neurogenesis in the hippocampus. The abnormality of brain insulin signaling is associated with the aging process and altered brain plasticity, and could promote neurodegeneration in the late stage of Alzheimer’s disease (AD). The precise molecular mechanism of the relationship between insulin resistance and AD remains unclear. The development of phosphoproteomics has advanced our knowledge of phosphorylation-mediated signaling networks and could elucidate the molecular mechanisms of certain pathological conditions. Here, we applied a reliable phosphoproteomic approach to Neuro2a (N2a) cells to identify their molecular features under two different insulin-resistant conditions with clinical relevance: inflammation and dyslipidemia. Despite significant difference in overall phosphoproteome profiles, we found molecular signatures and biological pathways in common between two insulin-resistant conditions. These include the integrin and adenosine monophosphate-activated protein kinase pathways, and we further verified these molecular targets by subsequent biochemical analysis. Among them, the phosphorylation levels of acetyl-CoA carboxylase and Src were reduced in the brain from rodent AD model 5xFAD mice. This study provides new molecular signatures for insulin resistance in N2a cells and possible links between the molecular features of insulin resistance and AD.

Proteomic investigation of Cbl and Cbl-b in neuroblastoma cell differentiation highlights roles for SHP-2 and CDK16

Neuroblastoma is a highly heterogeneous embryonal solid tumor of the sympathetic nervous system. As some tumors can be treated to undergo differentiation, investigating this process can guide differentiation-based therapies of neuroblastoma. Here, we studied the role of E3 ubiquitin ligases Cbl and Cbl-b in regulation of long-term signaling responses associated with extracellular signal-regulated kinase phosphorylation and neurite outgrowth, a morphological marker of neuroblastoma cell differentiation. Using quantitative mass spectrometry (MS)-based proteomics, we analyzed how the neuroblastoma cell line proteome, phosphoproteome, and ubiquitylome were affected by Cbl and Cbl-b depletion. To quantitatively assess neurite outgrowth, we developed a high-throughput microscopy assay that was applied in combination with inhibitor studies to pinpoint signaling underlying neurite outgrowth and to functionally validate proteins identified in the MS data sets. Using this combined approach, we identified a role for SHP-2 and CDK16 in Cbl/Cbl-b-dependent regulation of extracellular signal-regulated kinase phosphorylation and neurite outgrowth, highlighting their involvement in neuroblastoma cell differentiation.

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Multi-layered proteomics captures cellular changes induced by Cbl/Cbl-b depletion

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SHP-2 and CDK16 protein and phosphorylation levels increase upon Cbl/Cbl-b depletion

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SHP-2 and CDK16 regulate phospho-ERK and neurite outgrowth in neuroblastoma cells

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Inhibition of SHP-2 or CDK16 reverts Cbl/Cbl-b knockdown effects on differentiation

Advances in insulin-like growth factor biology and -directed cancer therapeutics

The insulin and insulin-like growth factor (IGF) family of proteins are part of a complex network that regulates cell proliferation and survival. While this system is undoubtedly important in prenatal development and postnatal cell growth, members of this family have been implicated in several different cancer types. Increased circulating insulin and IGF ligands have been linked to increased risk of cancer incidence. This observation has led to targeting the IGF system as a therapeutic strategy in a number of cancers. This chapter aims to describe the well-characterized biology of the IGF1R system, outline the rationale for targeting this system in cancer, summarize the clinical data as it stands, and discuss where we can go from here.

Two old drugs, NVP-AEW541 and GSK-J4, repurposed against the Toxoplasma gondii RH strain

Background

Toxoplasma gondii is a zoonotic pathogen that causes toxoplasmosis and leads to serious public health problems in developing countries. However, current clinical therapeutic drugs have some disadvantages, such as serious side effects, a long course of treatment and the emergence of drug-resistant strains. The urgent need to identify novel anti-Toxoplasma drugs has initiated the effective strategy of repurposing well-characterized drugs. As a principled screening for the identification of effective compounds against Toxoplasma gondii, in the current study, a collection of 666 compounds were screened for their ability to significantly inhibit Toxoplasma growth.

Methods

The inhibition of parasite growth was determined using a luminescence-based β-galactosidase activity assay. Meanwhile, the effect of compounds on the viability of host cells was measured using CCK8. To assess the inhibition of the selected compounds on discrete steps of the T. gondii lytic cycle, the invasion, intracellular proliferation and egress abilities were evaluated. Finally, a murine infection model of toxoplasmosis was used to monitor the protective efficacy of drugs against acute infection of a highly virulent RH strain.

Results

A total of 68 compounds demonstrated more than 70% parasite growth inhibition. After excluding compounds that impaired host cell viability, we further characterized two compounds, NVP-AEW541 and GSK-J4 HCl, which had IC₅₀ values for parasite growth of 1.17 μM and 2.37 μM, respectively. In addition, both compounds showed low toxicity to the host cell. Furthermore, we demonstrated that NVP-AEW541 inhibits tachyzoite invasion, while GSK-J4 HCl inhibits intracellular tachyzoite proliferation by halting cell cycle progression from G1 to S phase. These findings prompted us to analyse the efficacy of the two compounds in vivo by using established mouse models of acute toxoplasmosis. In addition to prolonging the survival time of mice acutely infected with T. gondii, both compounds had a remarkable ability to reduce the parasite burden of tissues.

Conclusions

Our findings suggest that both NVP-AEW541 and GSK-J4 could be potentially repurposed as candidate drugs against T. gondii infection.

Cell-Laden Hydrogel as a Clinical-Relevant 3D Model for Analyzing Neuroblastoma Growth, Immunophenotype, and Susceptibility to Therapies

High risk Neuroblastoma (NB) includes aggressive, metastatic solid tumors of childhood. The survival rate improved only modestly, despite the use of combination therapies including novel immunotherapies based on the antibody-mediated targeting of tumor-associated surface ligands. Treatment failures may be due to the lack of adequate in vitro models for studying, in a given patient, the efficacy of potential therapeutics, including those aimed to enhance anti-tumor immune responses. We here propose a 3D alginate-based hydrogel as extracellular microenvironment to evaluate the effects of the three-dimensionality on biological and immunological properties of NB cells. NB cell lines grown within the 3D alginate spheres presented spheroid morphology, optimal survival, and proliferation capabilities, and a reduced sensitivity to the cytotoxic effect of imatinib mesylate. 3D cultured NB cells were also evaluated for the constitutive and IFN-γ-induced expression of surface molecules capable of tuning the anti-tumor activity of NK cells including immune checkpoint ligands. In particular, IFN-γ induced de novo expression of high amounts of HLA-I molecules, which protected NB cells from the attack mediated by KIR/KIR-L matched NK cells. Moreover, in the 3D alginate spheres, the cytokine increased the expression of the immune checkpoint ligands PD-Ls and B7-H3 while virtually abrogating that of PVR, a ligand of DNAM-1 activating receptor, whose expression correlates with high susceptibility to NK-mediated killing. Our 3D model highlighted molecular features that more closely resemble the immunophenotypic variants occurring in vivo and not fully appreciated in classical 2D culture conditions. Thus, based on our results, 3D alginate-based hydrogels might represent a clinical-relevant cell culture platform where to test the efficacy of personalized therapeutic approaches aimed to optimize the current and innovative immune based therapies in a very systematic and reliable way.

A Combination CDK4/6 and IGF1R Inhibitor Strategy for Ewing Sarcoma

PURPOSE

Novel targeted therapeutics have transformed the care of subsets of patients with cancer. In pediatric malignancies, however, with simple tumor genomes and infrequent targetable mutations, there have been few new FDA-approved targeted drugs. The cyclin-dependent kinase (CDK)4/6 pathway recently emerged as a dependency in Ewing sarcoma. Given the heightened efficacy of this class with targeted drug combinations in other cancers, as well as the propensity of resistance to emerge with single agents, we aimed to identify genes mediating resistance to CDK4/6 inhibitors and biologically relevant combinations for use with CDK4/6 inhibitors in Ewing.

EXPERIMENTAL DESIGN

We performed a genome-scale open reading frame (ORF) screen in 2 Ewing cell lines sensitive to CDK4/6 inhibitors to identify genes conferring resistance. Concurrently, we established resistance to a CDK4/6 inhibitor in a Ewing cell line.

RESULTS

The ORF screen revealed IGF1R as a gene whose overexpression promoted drug escape. We also found elevated levels of phospho-IGF1R in our resistant Ewing cell line, supporting the relevance of IGF1R signaling to acquired resistance. In a small-molecule screen, an IGF1R inhibitor scored as synergistic with CDK4/6 inhibitor treatment. The combination of CDK4/6 inhibitors and IGF1R inhibitors was synergistic in vitro and active in mouse models. Mechanistically, this combination more profoundly repressed cell cycle and PI3K/mTOR signaling than either single drug perturbation.

CONCLUSIONS

Taken together, these results suggest that IGF1R inhibitors activation is an escape mechanism to CDK4/6 inhibitors in Ewing sarcoma and that dual targeting of CDK4/6 inhibitors and IGF1R inhibitors provides a candidate synergistic combination for clinical application in this disease.

Cell death in cancer in the era of precision medicine

Tumors constitute a large class of diseases that affect different organs and cell lineages. The molecular characterization of cancers of a given type has revealed an extraordinary heterogeneity in terms of genetic alterations and DNA mutations; heterogeneity that is further highlighted by single-cell DNA sequencing of individual patients. To address these issues, drugs that specifically target genes or altered pathways in cancer cells are continuously developed. Indeed, the genetic fingerprint of individual tumors can direct the modern therapeutic approaches to selectively hit the tumor cells while sparing the healthy ones. In this context, the concept of precision medicine finds a vast field of application. In this review, we will briefly list some classes of target drugs (Bcl-2 family modulators, Tyrosine Kinase modulators, PARP inhibitors, and growth factors inhibitors) and discuss the application of immunotherapy in tumors (T cell-mediated immunotherapy and CAR-T cells) that in recent years has drastically changed the prognostic outlook of aggressive cancers. We will also consider how apoptosis could represent a primary end point in modern cancer therapy and how "classic" chemotherapeutic drugs that induce apoptosis are still utilized in therapeutic schedules that involve the use of target drugs or immunotherapy to optimize the antitumor response.

Type I insulin-like growth factor receptor signaling in hematological malignancies

The insulin-like growth factor (IGF) signaling system plays key roles in the establishment and progression of different types of cancer. In agreement with this idea, substantial evidence has shown that the type I IGF receptor (IGF-IR) and its primary ligand IGF-I are important for maintaining the survival of malignant cells of hematopoietic origin. In this review, we discuss current understanding of the role of IGF-IR signaling in cancer with a focus on the hematological neoplasms. We also address the emergence of IGF-IR as a potential therapeutic target for the treatment of different types of cancer including plasma cell myeloma, leukemia, and lymphoma.

A dual-specific anti-IGF-1/IGF-2 human monoclonal antibody alone and in combination with temsirolimus for therapy of neuroblastoma

The insulin-like growth factors (IGFs), IGF-1 and IGF-2, have been implicated in the growth, survival and metastasis of a broad range of malignancies including pediatric tumors. They bind to the IGF receptor type 1 (IGF-1R) and the insulin receptor (IR) which are overexpressed in many types of solid malignancies. Activation of the IR by IGF-2 results in increased survival of tumor cells. We have previously identified a novel human monoclonal antibody, m708.5, which binds with high (pM) affinity to both human IGF-1 and IGF-2, and potently inhibits phosphorylation of the IGF-1R and the IR in tumor cells. m708.5 exhibited strong antitumor activity as a single agent against most cell lines derived from neuroblastoma, Ewing family of tumor, rhabdomyosarcoma and osteosarcoma. When tested in neuroblastoma cell lines, it showed strong synergy with temsirolimus and synergy with chemotherapeutic agents in vitro. In xenograft models, the combination of m708.5 and temsirolimus significantly inhibited neuroblastoma growth and prolonged mouse survival. Taken together, these results support the clinical development of m708.5 for pediatric solid tumors with potential for synergy with chemotherapy and mTOR inhibitors.

Relationship between insulin-like growth factor-1 receptor and human papillomavirus in patients with oropharyngeal cancer

BACKGROUND

Human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (SCC) is associated with better prognosis than HPV-negative oropharyngeal SCC. The purpose of this study was to assess the expression of insulin-like growth factor-1 receptor (IGF-1R) in patients with oropharyngeal SCC, its relationship to HPV status and various clinical parameters, and its relationship with clinical outcome.

METHODS

The study subjects were 59 patients with oropharyngeal SCC. IGF-1R expression was examined by immunohistochemistry in paraffin-embedded tumor tissues. HPV status was evaluated by in situ hybridization (ISH) in the same tissues.

RESULTS

IGF-1R did not correlate with clinical parameters, but IGF-1R expression was more common in HPV-negative tumors than in HPV-positive tumors. The prognosis was poorer in patients of the IGF-1R-positive group than in the IGF-1R-negative group.

CONCLUSION

The results suggested that IGF-1R expression in oropharyngeal SCC correlated with poor prognosis in HPV-negative patients. Treatment targeting IGF-1R could potentially improve the survival of patients with HPV-negative oropharyngeal SCC.

Molecular mechanisms of chemoresistance in osteosarcoma (Review)

Due to the emergence of adjuvant and neoadjuvant chemotherapy, the survival rate has been greatly improved in osteosarcoma (OS) patients with localized disease. However, this survival rate has remained unchanged over the past 30 years, and the long-term survival rate for OS patients with metastatic or recurrent disease remains poor. To a certain extent, the reason behind this may be ascribed to the chemoresistance to anti-OS therapy. Chemoresistance in OS appears to be mediated by numerous mechanisms, which include decreased intracellular drug accumulation, drug inactivation, enhanced DNA repair, perturbations in signal transduction pathways, apoptosis- and autophagy-related chemoresistance, microRNA (miRNA) dysregulation and cancer stem cell (CSC)-mediated drug resistance. In addition, methods employed to circumvent these resistance mechanism have been shown to be effective in the treatment of OS. However, almost all the current studies on the mechanisms of chemoresistance in OS are in their infancy. Further studies are required to focus on the following aspects: i) Improving the delivery of efficacy through novel delivery patterns; ii) improving the understanding of the signal transduction pathways that regulate the proliferation and growth of OS cells; iii) elucidating the signaling pathways of autophagy and its association with apoptosis in OS cells; iv) utilizing high-throughput miRNA expression analysis to identify miRNAs associated with chemoresistance in OS; and v) identifying the role that CSCs play in tumor metastasis and in-depth study of the mechanism of chemoresistance in the CSCs of OS.

Phase 2 trial of cixutumumab in children, adolescents, and young adults with refractory solid tumors: a report from the Children's Oncology Group

PURPOSE

This phase 2 study was designed to assess the efficacy of single agent cixutumumab (IMC-A12) and gain further information about associated toxicities and pharmacodynamics in children, adolescents, and young adults with recurrent or refractory solid tumors.

PATIENTS AND METHODS

Patients with relapsed or refractory solid tumors were treated with 9 mg/kg of cixutumumab as a 1-hour IV infusion once weekly. Strata included: osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, neuroblastoma (evaluable disease), neuroblastoma (measurable disease), Wilms tumor, adrenocortical carcinoma, synovial sarcoma, hepatoblastoma, and retinoblastoma. Correlative studies in consenting patients included an assessment of c-peptide, IGFBP-3, IGF-1, IGF-2, hGH, and insulin in consenting patients.

RESULTS

One hundred sixteen patients with 114 eligible having a median age of 12 years (range, 2-30) were enrolled. Five patients achieved a partial response: 4/20 with neuroblastoma (evaluable only) and 1/20 with rhabdomyosarcoma. Fourteen patients had stable disease for a median of 10 cycles. Hematologic and non-hematologic toxicities were generally mild and infrequent. Serum IGF-1 and IGFBP-3 increased in response to therapy with cixutumumab.

CONCLUSION

Cixutumumab is well tolerated in children with refractory solid tumors. Limited objective single-agent activity of cixutumumab was observed; however, prolonged stable disease was observed in 15% of patients. Ongoing studies are evaluating the toxicity and benefit of cixutumumab in combination with other agents that inhibit the IGF pathway.

Vertical blockade of the IGFR- PI3K/Akt/mTOR pathway for the treatment of hepatocellular carcinoma: the role of survivin

BACKGROUND

To explore whether combining inhibitors that target the insulin-like growth factor receptor (IGFR)/PI3K/Akt/mTOR signaling pathway (vertical blockade) can improve treatment efficacy for hepatocellular carcinoma (HCC).

METHODS

HCC cell lines (including Hep3B, Huh7, and PLC5) and HUVECs (human umbilical venous endothelial cells) were tested. The molecular targeting therapy agents tested included NVP-AEW541 (IGFR kinase inhibitor), MK2206 (Akt inhibitor), BEZ235 (PI3K/mTOR inhibitor), and RAD001 (mTOR inhibitor). Potential synergistic antitumor effects were tested by median dose-effect analysis in vitro and by xenograft HCC models. Apoptosis was analyzed by flow cytometry (sub-G1 fraction analysis) and Western blotting. The activities of pertinent signaling pathways and expression of apoptosis-related proteins were measured by Western blotting.

RESULTS

Vertical blockade induced a more sustained inhibition of PI3K/Akt/mTOR signaling activities in all the HCC cells and HUVEC tested. Synergistic apoptosis-inducing effects, however, varied among different cell lines and drug combinations and were most prominent when NVP-AEW541 was combined with MK2206. Using an apoptosis array, we identified survivin as a potential downstream mediator. Over-expression of survivin in HCC cells abolished the anti-tumor synergy between NVP-AEW541 and MK2206, whereas knockdown of survivin improved the anti-tumor effects of all drug combinations tested. In vivo by xenograft studies confirmed the anti-tumor synergy between NVP-AEW541 and MK2206 and exhibited acceptable toxicity profiles.

CONCLUSIONS

Vertical blockade of the IGFR/PI3K/Akt/mTOR pathway has promising anti-tumor activity for HCC. Survivin expression may serve as a biomarker to predict treatment efficacy.

Insulin receptor (IR) and insulin-like growth factor receptor 1 (IGF-1R) signaling systems: novel treatment strategies for cancer

Insulin and insulin-like growth factor (IGF) signaling system, commonly known for fine-tuning numerous biological processes, has lately made its mark as a much sought-after therapeutic targets for diabetes and cancer. These receptors make an attractive anticancer target owing to their overexpression in variety of cancer especially in prostate and breast cancer. Inhibitors of IGF signaling were subjected to clinical cancer trials with the main objective to confirm the effectiveness of these receptors as a therapeutic target. However, the results that these trials produced proved to be disappointing as the role played by the cross talk between IGF and insulin receptor (IR) signaling pathways at the receptor level or at downstream signaling level became more lucid. Therapeutic strategy for IGF-1R and IR inhibition mainly encompasses three main approaches namely receptor blockade with monoclonal antibodies, tyrosine kinase inhibition (ATP antagonist and non-ATP antagonist), and ligand neutralization via monoclonal antibodies targeted to ligand or recombinant IGF-binding proteins. Other drug-discovery approaches are employed to target IGF-1R, and IR includes antisense oligonucleotides and recombinant IGF-binding proteins. However, therapies with monoclonal antibodies and tyrosine kinase inhibition targeting the IGF-1R are not evidenced to be satisfactory as expected. Factors that are duly held responsible for the unsuccessfulness of these therapies include (a) the existence of the IR isoform A overexpressed on a variety of cancers, enhancing the mitogenic signals to the nucleus leading to the endorsement of cell growth, (b) IGF-1R and IR that form hybrid receptors sensitive to the stimulation of all three IGF axis ligands, and (c) IGF-1R and IR that also have the potential to form hybrid receptors with other tyrosine kinase to potentiate the cellular transformation, tumorigenesis, and tumor vascularization. This mini review is a concerted effort to explore and fathom the well-recognized roles of the IRA signaling system in human cancer phenotype and the main strategies that have been so far evaluated to target the IR and IGF-1R.

Quantitative phosphoproteomic analysis identifies activation of the RET and IGF-1R/IR signaling pathways in neuroblastoma

Neuroblastoma is an embryonal tumor of childhood with a heterogenous clinical presentation that reflects differences in activation of complex biological signaling pathways. Protein phosphorylation is a key component of cellular signal transduction and plays a critical role in processes that control cancer cell growth and survival. We used shotgun LC/MS to compare phosphorylation between a human MYCN amplified neuroblastoma cell line (NB10), modeling a resistant tumor, and a human neural precursor cell line (NPC), modeling a normal baseline neural crest cell. 2181 unique phosphorylation sites representing 1171 proteins and 2598 phosphopeptides were found. Protein kinases accounted for 6% of the proteome, with a predominance of tyrosine kinases, supporting their prominent role in oncogenic signaling pathways. Highly abundant receptor tyrosine kinase (RTK) phosphopeptides in the NB10 cell line relative to the NPC cell line included RET, insulin-like growth factor 1 receptor/insulin receptor (IGF-1R/IR), and fibroblast growth factor receptor 1 (FGFR1). Multiple phosphorylated peptides from downstream mediators of the PI3K/AKT/mTOR and RAS pathways were also highly abundant in NB10 relative to NPC. Our analysis highlights the importance of RET, IGF-1R/IR and FGFR1 as RTKs in neuroblastoma and suggests a methodology that can be used to identify potential novel biological therapeutic targets. Furthermore, application of this previously unexploited technology in the clinic opens the possibility of providing a new wide-scale molecular signature to assess disease progression and prognosis.

Neuroblastoma: developmental biology, cancer genomics and immunotherapy

Neuroblastoma is a solid tumour that arises from the developing sympathetic nervous system. Over the past decade, our understanding of this disease has advanced tremendously. The future challenge is to apply the knowledge gained to developing risk-based therapies and, ultimately, improving outcome. In this Review we discuss the key discoveries in the developmental biology, molecular genetics and immunology of neuroblastoma, as well as new translational tools for bringing these promising scientific advances into the clinic.

Cell survival signaling in neuroblastoma

Neuroblastoma is the most common extracranial solid tumor of childhood and is responsible for over 15% of pediatric cancer deaths. Neuroblastoma tumorigenesis and malignant transformation is driven by overexpression and dominance of cell survival pathways and a lack of normal cellular senescence or apoptosis. Therefore, manipulation of cell survival pathways may decrease the malignant potential of these tumors and provide avenues for the development of novel therapeutics. This review focuses on several facets of cell survival pathways including protein kinases (PI3K, AKT, ALK, and FAK), transcription factors (NF-κB, MYCN and p53), and growth factors (IGF, EGF, PDGF, and VEGF). Modulation of each of these factors decreases the growth or otherwise hinders the malignant potential of neuroblastoma, and many therapeutics targeting these pathways are already in the clinical trial phase of development. Continued research and discovery of effective modulators of these pathways will revolutionize the treatment of neuroblastoma.

Targeting the insulin-like growth factor-1 receptor in human cancer

The insulin-like growth factor (IGF) signaling system plays a crucial role in human cancer and the IGF-1 receptor (IGF-1R) is an attractive drug target against which a variety of novel anti-tumor agents are being developed. Deregulation of the IGF signaling pathway frequently occurs in human cancer and involves the establishment of autocrine loops comprising IGF-1 or IGF-2 and/or IGF-1R over-expression. Epidemiologic studies have documented a link between elevated IGF levels and the development of solid tumors, such as breast, colon, and prostate cancer. Anti-cancer strategies targeting the IGF signaling system involve two main approaches, namely neutralizing antibodies and small molecule inhibitors of the IGF-1R kinase activity. There are numerous reports describing anti-tumor activity of these agents in pre-clinical models of major human cancers. In addition, multiple clinical trials have started to evaluate the safety and efficacy of selected IGF-1R inhibitors, in combination with standard chemotherapeutic regimens or other targeted agents in cancer patients. In this mini review, I will discuss the role of the IGF signaling system in human cancer and the main strategies which have been so far evaluated to target the IGF-1R.

The type 1 insulin-like growth factor receptor signalling system and targeted tyrosine kinase inhibition in cancer

Type 1 insulin-like growth factor receptor (IGF1R) signalling plays a critical role in normal cell growth, and in cancer development and progression. IGF1R and the insulin-like growth factors 1 and 2 (IGF1 and IGF2) are involved in various aspects of the malignant phenotype, suggesting that IGF1R is a potential target for cancer therapy. IGF1R is particularly important in the establishment and maintenance of the transformed phenotype, in mediating proliferation, and for the survival of tumour cells with anchorage-independent growth. IGF1R also exerts antiapoptotic activity and has a substantial influence on the control of the cell and body size. This property enables transformed cells to form macroscopic tumours and to survive the process of detachment required for metastasis. Pharmaceutical companies are investigating molecules that target IGF1R, including specific low molecular weight tyrosine kinase inhibitors and monoclonal antibodies, both of which possess various advantages and display different activity profiles. This review article focuses on the preclinical and clinical development of low molecular weight IGF1R tyrosine kinase inhibitors. It is critical to pursue a thorough molecular analysis of the metabolic activity of IGF1R to avoid possible side-effects of its inhibition.

Novel agents targeting the IGF-1R/PI3K pathway impair cell proliferation and survival in subsets of medulloblastoma and neuroblastoma

The receptor tyrosine kinase (RTK)/phosphoinositide 3-kinase (PI3K) pathway is fundamental for cancer cell proliferation and is known to be frequently altered and activated in neoplasia, including embryonal tumors. Based on the high frequency of alterations, targeting components of the PI3K signaling pathway is considered to be a promising therapeutic approach for cancer treatment. Here, we have investigated the potential of targeting the axis of the insulin-like growth factor-1 receptor (IGF-1R) and PI3K signaling in two common cancers of childhood: neuroblastoma, the most common extracranial tumor in children and medulloblastoma, the most frequent malignant childhood brain tumor. By treating neuroblastoma and medulloblastoma cells with R1507, a specific humanized monoclonal antibody against the IGF-1R, we could observe cell line-specific responses and in some cases a strong decrease in cell proliferation. In contrast, targeting the PI3K p110α with the specific inhibitor PIK75 resulted in broad anti-proliferative effects in a panel of neuro- and medulloblastoma cell lines. Additionally, sensitization to commonly used chemotherapeutic agents occurred in neuroblastoma cells upon treatment with R1507 or PIK75. Furthermore, by studying the expression and phosphorylation state of IGF-1R/PI3K downstream signaling targets we found down-regulated signaling pathway activation. In addition, apoptosis occurred in embryonal tumor cells after treatment with PIK75 or R1507. Together, our studies demonstrate the potential of targeting the IGF-1R/PI3K signaling axis in embryonal tumors. Hopefully, this knowledge will contribute to the development of urgently required new targeted therapies for embryonal tumors.

Repression of malignant tumor progression upon pharmacologic IGF1R blockade in a mouse model of insulinoma

NVP-AEW541, a specific ATP-competitive inhibitor of the insulin-like growth factor-1 receptor (IGF1R) tyrosine kinase, has been reported to interfere with tumor growth in various tumor transplantation models. We have assessed the efficacy of NVP-AEW541 in repressing tumor growth and tumor progression in the Rip1Tag2 transgenic mouse model of pancreatic β-cell carcinogenesis. In addition, we have tested NVP-AEW541 in Rip1Tag2;RipIGF1R double-transgenic mice which show accelerated tumor growth and increased tumor malignancy compared with Rip1Tag2 single-transgenic mice. Previously, we have shown that high levels of IGF-2, a high-affinity ligand for IGF1R, are required for Rip1Tag2 tumor cell survival and tumor growth. Unexpectedly, treatment of Rip1Tag2 mice with NVP-AEW541 in prevention and intervention trials neither did affect tumor growth nor tumor cell proliferation and apoptosis. Yet, it significantly repressed progression to tumor malignancy, that is, the rate of the transition from differentiated adenoma to invasive carcinoma. Treatment of Rip1Tag2;RipIGF1R double-transgenic mice resulted in moderately reduced tumor volumes and increased rates of tumor cell apoptosis. Sustained expression of IGF-2 and of the IGF-2-binding form of insulin receptor (IR-A) in tumor cells suggests a compensatory role of IR-A upon IGF1R blockade. The results indicate that inhibition of IGF1R alone is not sufficient to efficiently block insulinoma growth and imply an overlapping role of IGF1R and insulin receptor in executing mitogenic and survival stimuli elicited by IGF-2. The reduction of tumor invasion upon IGF1R blockade on the other hand indicates a critical function of IGF1R signaling for the acquisition of a malignant phenotype.

Nuclear targeting of IGF-1 receptor in orbital fibroblasts from Graves' disease: apparent role of ADAM17

Insulin-like growth factor-1 receptor (IGF-1R) comprises two subunits, including a ligand binding domain on extra- cellular IGF-1Rα and a tyrosine phosphorylation site located on IGF-1Rβ. IGF-1R is over-expressed by orbital fibroblasts in the autoimmune syndrome, Graves' disease (GD). When activated by IGF-1 or GD-derived IgG (GD-IgG), these fibroblasts produce RANTES and IL-16, while those from healthy donors do not. We now report that IGF-1 and GD-IgG provoke IGF-1R accumulation in the cell nucleus of GD fibroblasts where it co-localizes with chromatin. Nuclear IGF-1R is detected with anti-IGF-1Rα-specific mAb and migrates to approximately 110 kDa, consistent with its identity as an IGF-1R fragment. Nuclear IGF-1R migrating as a 200 kDa protein and consistent with an intact receptor was undetectable when probed with either anti-IGF-1Rα or anti-IGF-1Rβ mAbs. Nuclear redistribution of IGF-1R is absent in control orbital fibroblasts. In GD fibroblasts, it can be abolished by an IGF-1R-blocking mAb, 1H7 and by physiological concentrations of glucocorticoids. When cell-surface IGF-1R is cross-linked with ¹²⁵I IGF-1, ¹²⁵I-IGF-1/IGF-1R complexes accumulate in the nuclei of GD fibroblasts. This requires active ADAM17, a membrane associated metalloproteinase, and the phosphorylation of IGF-1R. In contrast, virally encoded IGF-1Rα/GFP fusion protein localizes equivalently in nuclei in both control and GD fibroblasts. This result suggests that generation of IGF-1R fragments may limit the accumulation of nuclear IGF-1R. We thus identify a heretofore-unrecognized behavior of IGF-1R that appears limited to GD-derived fibroblasts. Nuclear IGF-1R may play a role in disease pathogenesis.

New strategies in refractory and recurrent neuroblastoma: translational opportunities to impact patient outcome

Neuroblastoma remains responsible for a disproportionate amount of childhood cancer morbidity and mortality despite recent significant advances in understanding the genetic basis of tumor initiation and progression. About half of newly diagnosed patients can be reliably identified as having tumors of low malignant potential, and these children have cure rates of greater than 95% with little or no cytotoxic therapy. On the other hand, the other half of neuroblastomas typically present in an explosive fashion with widely metastatic disease, and reliable tumor-specific biomarkers have been defined for this phenotype as well. Empiric approaches to high-risk neuroblastoma therapy have relied on dramatic escalation of chemotherapy dose intensity and, recently, the incorporation of targeted immunotherapy, but nearly 50% of children with high-risk disease will be refractory to therapy or suffer a relapse, both of which are invariably fatal. Future improvements in high-risk neuroblastoma outcomes will require the identification of disease and patient-specific oncogenic vulnerabilities that can be leveraged therapeutically. Rational development of novel approaches to neuroblastoma therapy requires forward-thinking strategies to unequivocally prove activity in the relapse setting and, ultimately, efficacy in curing patients when integrated into frontline treatment plans.

Phase I/II trial and pharmacokinetic study of cixutumumab in pediatric patients with refractory solid tumors and Ewing sarcoma: a report from the Children's Oncology Group

PURPOSE

A phase I/II study of cixutumumab (IMC-A12) in children with refractory solid tumors was conducted. This study was designed to assess the toxicities, pharmacokinetics, and pharmacodynamics of cixutumumab in children to determine a recommended phase II dose and to assess antitumor activity in Ewing sarcoma (ES).

PATIENTS AND METHODS

Pediatric patients with relapsed or refractory solid tumors were treated with cixutumumab as a 1-hour intravenous infusion once per week. Two dose levels-6 and 9 mg/kg-were evaluated using a standard three-plus-three cohort design. Patients with refractory ES were treated in an expanded phase II cohort at each dose level.

RESULTS

Forty-seven eligible patients with a median age of 15 years (range, 4 to 28 years) were enrolled. Twelve patients were treated in the dose-finding phase. Hematologic and nonhematologic toxicities were generally mild and infrequent. Dose-limiting toxicities included grade 4 thrombocytopenia at 6 mg/kg and grade 3 dehydration at 9 mg/kg. Mean trough concentration (± standard deviation) at 9 mg/kg was 106 ± 57 μg/mL, which exceeded the effective trough concentration of 60 μg/mL observed in xenograft models. Three patients with ES had confirmed partial responses: one of 10 at 6 mg/kg and two of 20 at 9 mg/kg. Serum insulin-like growth factor I (IGF-I) levels consistently increased after one dose of cixutumumab. Tumor IGF-I receptor expression by immunohistochemistry did not correlate with response in patients with ES.

CONCLUSION

Cixutumumab is well tolerated in children with refractory solid tumors. The recommended phase II dose is 9 mg/kg. Limited single-agent activity of cixutumumab was seen in ES.

Insulin-like growth factor-type 1 receptor inhibitor NVP-AEW541 enhances radiosensitivity of PTEN wild-type but not PTEN-deficient human prostate cancer cells

PURPOSE

During the past decade, many clinical trials with both monoclonal antibodies and small molecules that target the insulin-like growth factor-type 1 receptor (IGF-1R) have been launched. Despite the important role of IGF-1R signaling in radioresistance, studies of such agents in combination with radiotherapy are lagging behind. Therefore, the aim of this study was to investigate the effect of the small molecule IGF-1R kinase inhibitor NVP-AEW541 on the intrinsic radioresistance of prostate cancer cells.

METHODS AND MATERIALS

The effect of NVP-AEW541 on cell proliferation, cell viability, IGF-1R signaling, radiosensitivity, cell cycle distribution, and double strand break repair was determined in three human prostate cancer cell lines (PC3, DU145, 22Rv1). Moreover, the importance of the PTEN pathway status was explored by means of transfection experiments with constitutively active Akt or inactive kinase-dead Akt.

RESULTS

NVP-AEW541 inhibited cell proliferation and decreased cell viability in a time-and dose-dependent manner in all three cell lines. Radiosensitization was observed in the PTEN wild-type cell lines DU145 and 22Rv1 but not in the PTEN-deficient PC3 cell line. NVP-AEW541-induced radiosensitization coincided with downregulation of phospho-Akt levels and high levels of residual double strand breaks. The importance of PTEN status in the radiosensitization effect was confirmed by transfection experiments with constitutively active Akt or inactive kinase-dead Akt.

CONCLUSIONS

NVP-AEW541 enhances the effect of ionizing radiation in PTEN wild-type, but not in PTEN-deficient, prostate cancer cells. Proper patient selection based on the PTEN status of the tumor will be critical to the achievement of optimal results in clinical trials in which the combination of radiotherapy and this IGF-1R inhibitor is being explored.

Enhanced efficacy of IGF1R inhibition in pediatric glioblastoma by combinatorial targeting of PDGFRα/β

Pediatric glioblastoma (pGBM), although rare, is one of the leading causes of cancer-related deaths in children, with tumors essentially refractory to existing treatments. We have identified IGF1R to be a potential therapeutic target in pGBM due to gene amplification and high levels of IGF2 expression in some tumor samples, as well as constitutive receptor activation in pGBM cell lines. To evaluate the therapeutic potential of strategies targeting the receptor, we have carried out in vitro and in vivo preclinical studies using the specific IGF1R inhibitor NVP-AEW541. A modest inhibitory effect was seen in vitro, with GI(50) values of 5 to 6 μmol/L, and concurrent inhibition of receptor phosphorylation. Specific targeting of IGF1R with short interfering RNA decreased cell viability, diminished downstream signaling through phosphoinositide 3-kinase (PI3K), and induced G(1) arrest, effects mimicked by NVP-AEW541, both in the absence and presence of IGF2. Hallmarks of PI3K inhibition were observed after treatment with NVP-AEW541 by expression profiling and Western blot analysis. Phospho-receptor tyrosine kinase (RTK) arrays showed phosphorylation of platelet-derived growth factor receptor (PDGFR) α/β in pGBM cells, suggesting coactivation of an alternative RTK pathway. Treatment of KNS42 with the PDGFR inhibitor imatinib showed additional effects targeting the mitogen-activated protein kinase pathway, and cotreatment of the PDGFR inhibitor imatinib with NVP-AEW541 resulted in a highly synergistic interaction in vitro and increased efficacy after 14 days therapy in vivo compared with either agent alone. These data provide evidence that inhibition of IGF1R, in combination with other targeted agents, may be a useful and novel therapeutic strategy in pGBM.

IGF-1R expression predicts clinical outcome in patients with locally advanced oral squamous cell carcinoma

To assess the expression of IGF-1R in oral cavity squamous cell carcinoma patients, to explore its relation with clinical and pathologic prognostic factors and its role in predicting clinical outcome. One hundred and thirty-one consecutive patients suffering from oral cavity squamous cell carcinoma were included in this study from July 1989 to April 2005. Follow-up was closed in May 2010. The mean follow-up for survivors was 110.26±47.42 months. Patients were staged following the TNM classification. Patients in tumour stages I and II were referred to surgery. Patients in stages III-IV were referred to postoperative radiotherapy. Radiation therapy was administered up to a mean dose of 62.13±7.74 Gy in 1.8-2 Gy fractions. IGF-1R expression was studied by immunohistochemistry in paraffin-embedded tumour tissue. IGF-1R was expressed in 101 patients (77.1%). IGF-1R expression was related to tumour grade (P=0.012). Tumour stage was the most important prognostic factor for survival. Low (negative and fairly) IGF-1R tumour expression was correlated to better long-term Local Disease Free Survival (P=0.016), Disease-Free Survival (P=0.029), and Survival (P=0.009) in patients achieving tumour stages III-IV. Low IGF-1R expression was related to better long-term control in patients suffering locally advanced oral carcinoma.

Therapy innovations: tyrosine kinase inhibitors for the treatment of pancreatic neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) show limited sensitivity to cytotoxic agents, requiring the search for novel therapies. Recently, data from a phase III trial demonstrated that sunitinib produces a clinically significant improvement in progression-free survival in patients with unresectable, advanced, or metastatic GEP-NETs. Based on this finding, sunitinib became the first targeted drug approved for the treatment of GEP-NETs, paving the way for the approval of other anticancer agents in this drug-orphan disease. To date, results of trials involving other multitargeted tyrosine kinase inhibitors, such as sorafenib, the monoclonal antibody bevacizumab, and insulin-like growth factor 1 receptor inhibitors, have also shown promising results, and some are already being studied in phase III trials. This review updates the results of ongoing trials using inhibitors of growth factors and tyrosine kinase receptors involved in the carcinogenesis of GEP-NETs.

Anti-insulin-like growth factor 1 receptor antibody EM164 (murine AVE1642) exhibits anti-tumour activity alone and in combination with temozolomide against neuroblastoma

Insulin-like growth factor 1 receptor (IGF-1R) is overexpressed in many tumours and contributes to tumourigenicity, cell proliferation, metastasis and resistance, thus representing a promising therapeutic target. The human IGF-1R antagonistic monoclonal antibody EM164 (murine AVE1642) has shown activity in adult cancers and is being evaluated in patients with advanced malignancies. We investigated the EM164 for its therapeutic potential against childhood neuroblastoma. EM164 at 0.07, 0.7 and 7 μg/mL exhibited anti-proliferative activity against all nine cell lines tested in (3)H-thymidine incorporation assay in vitro. Cell proliferation after EM164 exposure ranged between 24% and 80% compared to controls. Sensitivity was independent from culture serum conditions, intensity of IGF-1R expression and IGF-II secretion, although associated with inhibition of AKT activation. In vivo, EM164 administered intravenously at 40 mg/kg twice weekly for 4 weeks yielded significant tumour growth delays (TGD) of 13.4d in advanced stage IGR-N91 and 12.9 d in SK-N-AS tumours compared to controls (p = 0.02 and p = 0.0059, respectively). Simultaneous treatment of EM164 0.7 μg/mL and temozolomide resulted in enhanced activity in vitro. In vivo, treatment with temozolomide at the maximum tolerated dose (100mg/kg/d for 5 consecutive days) and EM164 yielded a significantly greater TGD of 29.1d (p<0.01) and two complete tumour regressions (CR) compared to 18.1d (p = ns) and one CR for EM164 alone and 16.1d (p = ns) for temozolomide alone. Our results demonstrate the potential of the anti-IGF-1R antibody alone and in combination with alkylating agents and support the therapeutic development of the AVE1642 for aggressive neuroblastoma.

PI3K/PTEN/Akt pathway status affects the sensitivity of high-grade glioma cell cultures to the insulin-like growth factor-1 receptor inhibitor NVP-AEW541

IGF-1 receptor signaling contributes to the growth of many solid tumors, including glioblastoma. This study analyzed the sensitivity of 8 glioblastoma cultures to the IGF-1 receptor inhibitor NVP-AEW541. Growth reduction, caused by a combination of antiproliferative and proapoptotic effects, varied between 20% and 100%. Growth-inhibitory effects of IGF-1 receptor siRNA were also demonstrated in 2 of the cultures. Activating mutations in PIK3CA were found in 2 cultures, and 2 other cultures displayed ligand-independent Akt phosphorylation. Growth inhibition was significantly reduced in cultures with PIK3CA mutations or ligand-independent Akt phosphorylation. PTEN siRNA experiments supported the notion that the status of the PI3K/PTEN/Akt pathway is involved in determining NVP-AEW541 sensitivity. Combination treatments with either PI3 kinase or mTOR inhibitors together with NVP-AEW541 were performed. These experiments demonstrated the effects of NVP-AEW541 in cells not responding to mono-treatment with the IGF-1 receptor inhibitor, when used together with either of the 2 other inhibitors. Together, the studies support continued clinical development of IGF-1 receptor antagonists for glioblastomas and identify links between PI3K/PTEN/Akt status and sensitivity to mono-treatment with NVP-AEW541. Furthermore, the studies suggest that NVP-AEW541 is also active together with PI3 kinase and mTOR inhibitors in cultures with a dysregulated PI3K/PTEN/Akt pathway. These studies should assist in future clinical development of IGF-1 receptor antagonists for glioblastoma and other tumors.

Growth factors as active participants in carcinogenesis: a perspective

Growth factors are low molecular peptides active in the stimulation of cell proliferation and in the regulation of embryonic development and cellular differentiation. Significant progress has been made in developing effective strategies to treat human malignancies with new chemical compounds based on a rationale directed against various components of signaling pathways. Many of these drugs target a growth factor receptor--for instance, in the form of monoclonal antibodies or inhibitors of tyrosine kinases, such as monoclonal antibodies against epidermal growth factor receptors used in treating certain types of breast cancer. Imatinib mesylate [Gleevec]) is an excellent example of mediators of signal transduction, such as tyrosine kinases. Growth factors proper are used to ameliorate various and sometimes fatal side effects of cytotoxic and/or myelosuppressive chemotherapy. Basic characteristics of several growth families are discussed with therapeutic modalities based on growth factor activity or, more often, inhibition of such activity.

Treatment of biliary tract cancer with NVP-AEW541: Mechanisms of action and resistance

AIM: To investigate in vitro treatment with NVP-AEW541, a small molecule inhibitor of insulin-like growth factor-1 receptor (IGF-1R), in biliary tract cancer (BTC), since this disease is associated with a poor prognosis due to wide resistance to chemotherapeutic agents and radiotherapy.

METHODS: Cell growth inhibition by NVP-AEW541 was studied in vitro in 7 human BTC cell lines by automated cell counting. In addition, the anti-tumoral mechanism of NVP-AEW541 was studied by Western blotting, cell cycle analysis and reverse transcription-polymerase chain reaction (RT-PCR). Anti-tumoral drug effect in combination with gemcitabine, 5-fluorouracil (5-FU) and Polo-like kinase 1 inhibitor BI2536 was also studied.

RESULTS: In vitro treatment with NVP-AEW541 suppressed growth in all human BTC cell lines, however response was lower in gallbladder cancer. Treatment with NVP-AEW541 was associated with dephosphorylation of IGF-1R and AKT. In contrast, phosphorylation of p42/p44 and Stat3 and expression of Bcl-xL were inconsistently downregulated. In addition, treated cells showed cell cycle arrest at the G1/S-checkpoint and an increase in sub-G1 peak. Moreover, IGF-1R and its ligands IGF-1 and IGF-2 were co-expressed in RT-PCR, suggesting an autocrine loop of tumor cell activation. Combined with gemcitabine, NVP-AEW541 exerted synergistic effects, particularly at low concentrations, while effects of combination with 5-FU or BI 2536 were only additive.

CONCLUSION: Our findings suggest that NVP-AEW541 is active against BTC in vitro and potentiates the efficacy of gemcitabine.

Activity of tyrosine kinase inhibitor Dasatinib in neuroblastoma cells in vitro and in orthotopic mouse model

Stage 4 neuroblastoma (NB) is a devastating childhood cancer whose poor outcome has remained essentially unchanged in the last 20 years. Receptor tyrosine kinases have important roles in the control of proliferation, differentiation and apoptosis of NB cells. Thus, we tested the activity of second-generation tyrosine kinase inhibitor Dasatinib in human NB cell lines in vitro and in an orthotopic mouse model. Dasatinib inhibited cell viability with an IC(50) in the submicromolar range in 7 of 10 tested cell lines. In sensitive cells, Dasatinib reduced anchorage-independent growth and, in some instances, induced senescence and apoptosis. In HTLA-230 cells, Dasatinib treatment caused down-regulation of c-Kit and c-Src phosphorylation in conjunction with strong inhibition of Erk1/2 and Akt activity. To test the efficacy of Dasatinib in vivo, HTLA-230 and SY5Y cells were orthotopically injected in the adrenal gland of nude mice and drug treatments carried out until day 40. In mice injected with HTLA-230 cells, tumour growth was significantly inhibited at the dose of 30 mg/(kg day) when treatment was started 7 days after injection. In animals injected with SY5Y cells that were exquisitely sensitive in vitro (IC(50)= 92 nM), the antitumour effect of Dasatinib was observed at the dose of 60 mg/(kg day) but only when treatment was started 1 day after injection. However, the anti-tumour effect of Dasatinib in vivo was partial in both orthotopic models, emphasizing the importance of testing candidate new drugs in animal environments closely mimicking the human tumour.

Novel insulin-like growth factor-methotrexate covalent conjugate inhibits tumor growth in vivo at lower dosage than methotrexate alone

The insulin-like growth factor receptor is overexpressed on many types of cancer cells and has been implicated in metastasis and resistance to apoptosis. We report here the development of a novel covalent conjugate that contains the antifolate drug methotrexate coupled to an engineered variant of insulin-like growth factor-1 (IGF-1), long-R3-IGF-1, which was designed to target methotrexate to tumor cells that overexpress the membrane IGF-1 receptor. The IGF-methotrexate conjugate was found to contain at least 4 methotrexate molecules per IGF-1 protein. The IGF-methotrexate conjugate bound to MCF7 breast cancer cells with greater than 3.3-fold higher affinity than unconjugated long-R3-IGF-1 in a competition binding assay against radiolabeled wild-type IGF-1. Compared with free methotrexate, the IGF-methotrexate conjugate required slightly higher concentrations to inhibit the in vitro growth of the human prostate cancer cell line LNCaP. In vivo, however, in a mouse xenograft model using LNCaP cells, the IGF-methotrexate conjugate was more effective than free methotrexate even at a 6.25-fold lower molar dosage. Similarly, MCF7 xenografts were inhibited more effectively by the IGF-methotrexate conjugate than free methotrexate, even at a 4-fold lower molar dosage. Our results suggest that the targeting of the IGF receptor on tumor cells and tumor-related tissues with IGF-chemotherapy conjugates may substantially increase the specific drug localization and therapeutic effect in the tumor.

Sensitivity of breast cancer cell lines to the novel insulin-like growth factor-1 receptor (IGF-1R) inhibitor NVP-AEW541 is dependent on the level of IRS-1 expression

To investigate the potential value of targeting insulin-like growth factor-1 receptor (IGF-1R) in breast cancer, we examined the effects of NVP-AEW541, a selective small-molecule inhibitor of the IGF-1R tyrosine kinase, in a panel of 16 breast cancer cell lines. All cell lines expressed IGF-1R, but MCF-7 expressed much higher levels of insulin receptor substrate-1 (IRS-1) than the others. NVP-AEW541 was more potent at inhibiting growth of MCF-7 cells as compared to the others (IC(50), 1 microM vs. approximately 7 microM). Comparing MCF-7 to T47D cells, which express IGF-1R at a level identical to MCF-7 but have less than 1/30 the amount of IRS-1, NVP-AEW541 caused cell-cycle arrest at the G1-S boundary, reduced in vitro cell migration, and enhanced the cytotoxic effects of vinorelbine and paclitaxel in MCF-7, but not in T47D. While NVP-AEW541 decreased the phosphorylation of IGF-1R in both cell lines, it inhibited phosphorylation of Akt and disrupted the IRS-1/PI3K complex only in MCF-7. These findings suggest that inhibiting IGF-1R may be an effective therapeutic strategy for breast cancers that co-express IGF-1R and IRS-1 at high levels.

The role of IGF-1R in pediatric malignancies

The insulin-like growth factor (IGF) family consists of ligands (IGF-I, IGF-II, insulin), several receptors (including IGF-1R), and six binding proteins (IGFBP-1 through IGFBP-6). Members of this family regulate key cellular activities and they also play an important role in the development and progression of both adult and childhood cancers. Binding of a ligand to the receptor leads to its activation, followed by signal transduction along several pathways. In some childhood malignancies, IGF-1R can be activated by endocrine, autocrine, or paracrine mechanisms. Although mutations in IGF-1R have not been identified, this signaling pathway is upregulated in many childhood cancers. These findings have led to the development of a host of IGF-1R signaling modulators that are currently being tested in clinical trials. This review explores the role of IGF-1R in a range of childhood malignancies.

Targeted medical therapy of biliary tract cancer: recent advances and future perspectives

The limited efficacy of cytotoxic therapy for advanced biliary tract and gallbladder cancers emphasizes the need for novel and more effective medical treatment options. A better understanding of the specific biological features of these neoplasms led to the development of new targeted therapies, which take the abundant expression of several growth factors and cognate tyrosine kinase receptors into account. This review will briefly summarize the status and future perspectives of antiangiogenic and growth factor receptor-based pharmacological approaches for the treatment of biliary tract and gallbladder cancers. In view of multiple novel targeted approaches, the rationale for innovative therapies, such as combinations of growth factor (receptor)-targeting agents with cytotoxic drugs or with other novel anticancer drugs will be highlighted.

Expression of insulin-like growth factor-II and its receptor in pediatric and adult adrenocortical tumors

BACKGROUND

Adrenocortical tumors are heterogeneous neoplasms with incompletely understood pathogenesis. IGF-II overexpression has been consistently demonstrated in adult adrenocortical carcinomas.

OBJECTIVES

The objective of the study was to analyze expression of IGF-II and its receptor (IGF-IR) in pediatric and adult adrenocortical tumors and the effects of a selective IGF-IR kinase inhibitor (NVP-AEW541) on adrenocortical tumor cells.

PATIENTS

Fifty-seven adrenocortical tumors (37 adenomas and 20 carcinomas) from 23 children and 34 adults were studied.

METHODS

Gene expression was determined by quantitative real-time PCR. Cell proliferation and apoptosis were analyzed in NCI H295 cells and a new cell line established from a pediatric adrenocortical adenoma.

RESULTS

IGF-II transcripts were overexpressed in both pediatric adrenocortical carcinomas and adenomas. Otherwise, IGF-II was mainly overexpressed in adult adrenocortical carcinomas (270.5 +/- 130.2 vs. 16.1 +/- 13.3; P = 0.0001). IGF-IR expression was significantly higher in pediatric adrenocortical carcinomas than adenomas (9.1 +/- 3.1 vs. 2.6 +/- 0.3; P = 0.0001), whereas its expression was similar in adult adrenocortical carcinomas and adenomas. IGF-IR expression was a predictor of metastases in pediatric adrenocortical tumors in univariate analysis (hazard ratio 1.84; 95% confidence interval 1.28-2.66; P = 0.01). Furthermore, NVP-AEW541 blocked cell proliferation in a dose- and time-dependent manner in both cell lines through a significant increase of apoptosis.

CONCLUSION

IGF-IR overexpression was a biomarker of pediatric adrenocortical carcinomas. Additionally, a selective IGF-IR kinase inhibitor had antitumor effects in adult and pediatric adrenocortical tumor cell lines, suggesting that IGF-IR inhibitors represent a promising therapy for human adrenocortical carcinoma.

Establishment of atypical-teratoid/rhabdoid tumor (AT/RT) cell cultures from disseminated CSF cells: a model to elucidate biology and potential targeted therapeutics

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant central nervous system neoplasm that usually affects infants and young children. In this report, we describe culture conditions that enabled the sustained growth of tumor cells obtained from the cerebrospinal fluid (CSF) of an infant with AT/RT. These cells retained the morphological and biomarker characteristics of the original tumor. A screening of receptor tyrosine kinases identified the presence of phosphorylated ErbB4, Insulin-R, PDGFR and IGF-IR, which appear to depend on Hsp90 to maintain their active form. IGF-IR activity is consistent with data from other established AT/RT cell lines. Inhibition of IGF-IR by the small molecular weight inhibitor AEW541 led to growth suppression of cultured AT/RT cells. In addition, neutralizing antibodies to IGF-II also inhibited the growth of these cells suggesting a potential autocrine function for this cytokine. We also compared cultured AT/RT cells to established cell lines to identify consistent drug sensitivity patterns among these cells. In addition to previously described cell lines and xenograft models, continuous culture of CSF derived cells may also provide an effective way to study the biology of AT/RT and to identify potential targets for future therapeutics for this tumor.

Synergic antitumoral effect of an IGF-IR inhibitor and trastuzumab on HER2-overexpressing breast cancer cells

BACKGROUND

Receptor tyrosine kinases play an important role in breast cancer. One of them, the type I insulin-like growth factor, has been linked to resistance to trastuzumab (Herceptin), an agent that targets human epidermal growth factor receptor 2. Here, we show that the insulin-like growth factor-I receptor (IGF-IR) antagonist NVP-AEW541 inhibits proliferation of breast cancer cells and synergizes with trastuzumab.

PATIENTS AND METHODS

Patient samples and breast cancer cell lines were evaluated for IGF-IR expression or activation by western blotting. 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT) uptake assays and Annexin V staining were used for the analyses of cell proliferation/apoptosis. Biochemical and genomic studies were carried out to gain insights into the mechanism of action of NVP-AEW541.

RESULTS

The IGF-IR was expressed above normal levels in a number of breast cancer samples. Activation of this receptor was inhibited by NVP-AEW541 that also decreased cell proliferation and increased apoptosis. NVP-AEW541 decreased the amount of pAkt and increased the level of p27. Combination studies with several drugs used in the breast cancer clinic showed that NVP-AEW541 synergistically increased the action of trastuzumab.

CONCLUSIONS

Our results show the anti-breast cancer action of NVP-AEW541 and support the clinical development of anti-IGF-IR agents, especially in combination with trastuzumab.

AKT pathway in neuroblastoma and its therapeutic implication

Neuroblastoma is a frequent pediatric tumor with a poor outcome in spite of aggressive treatment, even with autologous hematopoietic stem cell transplantation. The overall cure rate of 40% is unsatisfactory and new therapeutic strategies are urgently needed. AKT is a major mediator of survival signals that protect cells from apoptosis and regulate cell proliferation. The AKT signaling network is considered a key determinant of the biological aggressiveness of these tumors. In this article, the authors discuss the relation between activators of AKT in neuroblastoma, in particular, growth factors such as IGF-1, TRK, GDNF, VEGF and EGF, and their effects on tumoral proliferation, differentiation and apoptosis. Numerous other proteins interact with AKT in neuroblastoma. Several are relatively well characterized, such as PTEN and retinoic acid; others are new and potentially interesting, such as PKC and anaplastic lymphoma kinase. Specific inhibition of AKT has been studied, such as with LY249002, with significant effects on cell progression and apoptosis in tumoral cells. Moreover, a series of new drugs, such as geldanamycin and rapamycin, directly modify the expression of AKT in tumoral cells. Few specific inhibitors of AKT are available; less specific inhibitors are probably unsuitable therapeutic options in neuroblastoma. Drugs with a direct or indirect inhibitory effect on the AKT pathway, used alone or in combination with other drugs, seem to hold great promise as a new therapeutic modality in neuroblastoma.