Insulin-like growth factor I receptor pathway inhibition by ADW742, alone or in combination with imatinib, doxorubicin, or vincristine, is a novel therapeutic approach in Ewing tumor

Establishment of platform for screening insulin-like growth factor-1 receptor inhibitors and evaluation of novel inhibitors

AIM

The insulin-like growth factor-1 receptor (IGF1R) is over-expressed in a wide variety of tumors and contributes to tumor cell proliferation, metastasis and drug resistance. The aim of this study was to establish a sensitive screening platform to identify novel IGF1R inhibitors.

METHODS

The catalytic domain of IGF1R was expressed using the Bac-to-Bac baculovirus expression system. The screening platform for IGF1R inhibitors was established based on ELISA. The binding profile of IGF1R with the inhibitors was predicted with molecular docking and then subjected to the surface plasmon resonance (SPR) approach. The growth inhibition of cancer cells by the inhibitors was assessed with MTT assay. Apoptosis was analyzed using flow cytometry and Western blotting.

RESULTS

A naturally occurring small molecule compound hematoxylin was identified as the most potent inhibitor (IC₅₀ value=1.8±0.1 μmol/L) within a library of more than 200 compounds tested. Molecular simulation predicted the possible binding mode of hematoxylin with IGF1R. An SPR assay further confirmed that hematoxylin bound directly to IGF1R with high binding affinity (Kd=4.2 × 10⁻⁶ mol/L). In HL-60 cancer cells, hematoxylin inactivated the phosphorylation of IGF1R and downstream signaling and therefore suppressed cell proliferation. Mechanistic studies revealed that hematoxylin induced apoptosis in HL-60 cells via both extrinsic and intrinsic pathways.

CONCLUSION

A simple, sensitive ELISA-based screening platform for identifying IGF1R inhibitors was established. Hematoxylin was identified as a promising IGF1R inhibitor with effective antitumor activity that deserves further investigation.

Activation of AMP-activated protein kinase is involved in vincristine-induced cell apoptosis in B16 melanoma cell

The molecular basis for induction of apoptosis in melanoma cells by vincristine remains unknown. Here we tested the potential involvement of AMP-activated protein kinase (AMPK) in this process. We found for the first time that vincristine induces AMPK activation (AMPKα, Thr 172) and Acetyl-CoA carboxylase (ACC, Ser 79) (a downstream molecular target of AMPK) phosphorylation in cultured melanoma cells in vitro. Reactive oxygen species (ROS) dependent LKB1 activation serves as the upstream signal for AMPK activation. AMPK inhibitor (compound C) or AMPKα siRNA knockdown inhibits vincristine induced B16 melanoma cell apoptosis, while AMPK activator 5-aminoimidazole-4-carboxamide-1-β-riboside (AICAR) enhances it. AMPK activation is involved in vincristine induced p53 phosphorylation and stabilization, the latter is known to mediate melanoma cell apoptosis. Further, activation of AMPK by vincristine inhibits mTOR Complex 1 (mTORC1) in B16 melanoma cells, which serves as another important mechanism to induce melanoma cell apoptosis. Our study provides new insights into understanding the cellular and molecular mechanisms of vincristine induced cancer cell death/apoptosis. We suggest that combining AMPK activator AICAR with vincristine may have potential to be used as a new therapeutic intervention against melanoma.

A novel oncogenic mechanism in Ewing sarcoma involving IGF pathway targeting by EWS/Fli1-regulated microRNAs

MicroRNAs (miRs) are a novel class of cellular bioactive molecules with critical functions in the regulation of gene expression in normal biology and disease. MiRs are frequently misexpressed in cancer, with potent biological consequences. However, relatively little is known about miRs in pediatric cancers, including sarcomas. Moreover, the mechanisms behind aberrant miR expression in cancer are poorly understood. Ewing sarcoma is an aggressive pediatric malignancy driven by EWS/Ets fusion oncoproteins, which are gain-of-function transcriptional regulators. We employed stable silencing of EWS/Fli1, the most common of the oncogenic fusions, and global miR profiling to identify EWS/Fli1-regulated miRs with oncogenesis-modifying roles in Ewing sarcoma. In this report, we characterize a group of miRs (100, 125b, 22, 221/222, 27a and 29a) strongly repressed by EWS/Fli1. Strikingly, all of these miRs have predicted targets in the insulin-like growth factor (IGF) signaling pathway, a pivotal driver of Ewing sarcoma oncogenesis. We demonstrate that miRs in this group negatively regulate the expression of multiple pro-oncogenic components of the IGF pathway, namely IGF-1, IGF-1 receptor, mammalian/mechanistic target of rapamycin and ribosomal protein S6 kinase A1. Consistent with tumor-suppressive functions, these miRs manifest growth inhibitory properties in Ewing sarcoma cells. Our studies thus uncover a novel oncogenic mechanism in Ewing sarcoma, involving post-transcriptional derepression of IGF signaling by the EWS/Fli1 fusion oncoprotein via miRs. This novel pathway may be amenable to innovative therapeutic targeting in Ewing sarcoma and other malignancies with activated IGF signaling.

IGF1R signaling in Ewing sarcoma is shaped by clathrin-/caveolin-dependent endocytosis

Receptor endocytosis is critical for cell signaling. IGF1R mediates an autocrine loop that is de-regulated in Ewing Sarcoma (ES) cells. Here we study the impact of IGF1R internalization, mediated by clathrin and caveolin-1 (CAV1), in ES signaling. We used clathrin and CAV1-siRNA to interfere in clathrin- and caveolin-dependent endocytosis. Chlorpromazine (CPMZ) and methyl-beta-cyclo-dextrin (MCD) were also used in order to inhibit clathrin- and caveolin-dependent endocytosis, respectively. We analyzed IGF1R internalization and co-localization with clathrin and CAV1 upon ligand binding, as well as the status of the IGF1R pathway, cellular proliferation, and the apoptosis of interfered and inhibited ES cells. We performed a high-throughput tyrosine kinase phosphorylation assay to analyze the effects of combining the IGF1R tyrosine kinase inhibitor AEW541 (AEW) with CPMZ or MCD on the intracellular phospho-proteome. We observed that IGF1R is internalized upon ligand binding in ES cells and that this process is dependent on clathrin or CAV1. The blockage of receptor internalization inhibited AKT and MAPK phosphorylation, reducing the proliferative rate of ES cells and increasing the levels of apoptosis. Combination of AEW with CPMZ or MCD largely enhanced these effects. CAV1 and clathrin endocytosis controls IGF1R internalization and signaling and has a profound impact on ES IGF1R-promoted survival signaling. We propose the combination of tyrosine-kinase inhibitors with endocytosis inhibitors as a new therapeutic approach to achieve a stronger degree of receptor inhibition in this, or other neoplasms dependent on IGF1R signaling.

Targeting the Insulin-Like Growth Factor 1 Receptor in Ewing's Sarcoma: Reality and Expectations

Ewing's sarcoma family of tumours comprises a group of very aggressive diseases that are potentially curable with multimodality treatment. Despite the undoubted success of current treatment, approximately 30% of patients will relapse and ultimately die of disease. The insulin-like growth factor 1 receptor (IGF-1R) has been implicated in the genesis, growth, proliferation, and the development of metastatic disease in Ewing's sarcoma. In addition, IGF1-R has been validated, both in vitro and in vivo, as a potential therapeutic target in Ewing's sarcoma. Phase I studies of IGF-1R monoclonal antibodies reported several radiological and clinical responses in Ewing's sarcoma patients, and initial reports of several Phase II studies suggest that about a fourth of the patients would benefit from IGF-1R monoclonal antibodies as single therapy, with approximately 10% of patients achieving objective responses. Furthermore, these therapies are well tolerated, and thus far severe toxicity has been rare. Other studies assessing IGF-1R monoclonal antibodies in combination with traditional cytotoxics or other targeted therapies are expected. Despite, the initial promising results, not all patients benefit from IGF-1R inhibition, and consequently, there is an urgent need for the identification of predictive markers of response.

Small molecule inhibitors of the IGF-1R/IR axis for the treatment of cancer

INTRODUCTION

The IGF-1 receptor (IGF-1R) is a receptor tyrosine kinase and is well established as a key regulator of tumor cell growth and survival. There is also a growing body of data to support a role for the structurally and functionally related insulin receptor (IR) in human cancer. Bidirectional crosstalk between IGF-1R and IR is observed, where specific inhibition of either receptor confers a compensatory increase in the activity for the reciprocal receptor, therefore dual inhibition of both IGF-1R and IR may be important for optimal efficacy. The importance of IGF-1R and IR as targets in cancer is further underscored by their contribution to resistance against both cytotoxic and molecularly targeted anti-cancer therapeutics. Currently, both IGF-1R-neutralizing antibodies and small-molecule tyrosine kinase inhibitors of IGF-1R/IR are in clinical development.

AREAS COVERED

The importance of IGF-1R and IR as cancer targets and how IGF-1R/IR inhibitors may sensitize tumor cells to the anti-proliferative and pro-apoptotic effects of other anti-tumor agents. The potential advantages of small molecule IGF-1R/IR inhibitors compared with IGF-1R-specific neutralizing antibodies, and the characteristics of small-molecule IGF-1R inhibitors that have entered clinical development.

EXPERT OPINION

Because of compensatory crosstalk between IGF-1R and IR, dual IGF-1R and IR tyrosine kinase inhibitors may have superior anti-tumor activity compared to anti-IGF-1R specific antibodies. The clinical success for IGF-1R/IR inhibitors may ultimately be dependent upon our ability to correctly administer these agents to the right niche patient subpopulation using single agent therapy, when appropriate, or using the right combination therapy.

Discovery of an Orally Efficacious Imidazo[5,1-f][1,2,4]triazine Dual Inhibitor of IGF-1R and IR

This report describes the investigation of a series of 5,7-disubstituted imidazo[5,1-f][1,2,4]triazine inhibitors of insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor (IR). Structure-activity relationship exploration and optimization leading to the identification, characterization, and pharmacological activity of compound 9b, a potent, selective, well-tolerated, and orally bioavailable dual inhibitor of IGF-1R and IR with in vivo efficacy in tumor xenograft models, is discussed.

Small is beautiful: insulin-like growth factors and their role in growth, development, and cancer

Insulin-like growth factors were discovered more than 50 years ago as mediators of growth hormone that effect growth and differentiation of bone and skeletal muscle. Interest of the role of insulin-like growth factors in cancer reached a peak in the 1990s, and then waned until the availability in the past 5 years of monoclonal antibodies and small molecules that block the insulin-like growth factor 1 receptor. In this article, we review the history of insulin-like growth factors and their role in growth, development, organism survival, and in cancer, both epithelial cancers and sarcomas. Recent developments regarding phase I to II clinical trials of such agents are discussed, as well as potential studies to consider in the future, given the lack of efficacy of one such monoclonal antibody in combination with cytotoxic chemotherapy in a first-line study in metastatic non-small-cell lung adenocarcinoma. Greater success with these agents clinically is expected when combining the agents with inhibitors of other cell signaling pathways in which cross-resistance has been observed.

The emerging role of insulin-like growth factor 1 receptor (IGF1r) in gastrointestinal stromal tumors (GISTs)

Recent years have seen a growing interest in insulin-like growth factor 1 receptor (IGF1R) in medical oncology. Interesting data have been reported also on IGF1r in gastrointestinal stromal tumors (GISTs) especially in children and in young adult patients whose disease does not harbour mutations on KIT and PDGFRA and are poorly responsive to conventional therapies. However, it is too early to reach conclusions on IGF1R as a novel therapeutic target in GIST because the receptor's biological role is still to be defined and the clinical significance in patients needs to be studied in larger studies. We update and comment the current literature on IGF1R in GISTs and discuss the future perspectives in this promising field.

Imatinib plus low-dose doxorubicin in patients with advanced gastrointestinal stromal tumors refractory to high-dose imatinib: a phase I-II study by the Spanish Group for Research on Sarcomas

BACKGROUND

In KIT-expressing Ewing sarcoma cell lines, the addition of doxorubicin to imatinib increases apoptosis, compared with imatinib or doxorubicin alone. On the basis of these in vitro data, the authors conducted a phase 1-2 trial of doxorubicin with imatinib in patients with gastrointestinal sarcoma tumors refractory to high-dose imatinib therapy.

METHODS

Patients with metastatic gastrointestinal sarcoma tumor resistant to imatinib at 400 mg by mouth (p.o.) twice a day were eligible for this multicenter study, and received imatinib (400 mg p.o. every day [q.d.]) concomitantly with doxorubicin 15-20 mg/m2/weekly for 4 cycles (monthly cycles), followed by imatinib (400 mg p.o. q.d.) maintenance in nonprogressive patients. Spiral computed tomography and positron emission tomography with F18-fluorodeoxyglucose were done basally and after 2 months of therapy to evaluate response. An in vitro study assessed the effect of combining imatinib and doxorubicin.

RESULTS

Twenty-six patients with progressive gastrointestinal sarcoma tumor were entered in the study. Treatment was well tolerated. Three (14%) of 22 evaluable patients had partial responses per Response Evaluation Criteria in Solid Tumors, and 8 (36%) had clinical benefit (partial response or stable disease for >or=6 months). Median progression-free survival (PFS) was 100 days (95% confidence interval [CI], 62-138), and median survival was 390 days (95% CI, 264-516). Interestingly, PFS was 211 days (95% CI, 52-370) in patients with wild type (WT) KIT and 82 days (95% CI, 53-111) in non-WT patients (10 mutant, 6 not assessed). A synergistic effect on cell line proliferation and apoptosis was found with imatinib and doxorubicin combination.

CONCLUSIONS

Low-dose chemobiotherapy combination showed promising activity in heavily pretreated gastrointestinal sarcoma tumor patients, especially in those with WT-KIT genotype.

Biological rationale and current clinical experience with anti-insulin-like growth factor 1 receptor monoclonal antibodies in treating sarcoma: twenty years from the bench to the bedside

Two decades have elapsed since insulin-like growth factor-1 receptor (IGF-1R) signaling was initially implicated in sarcoma biology to the first clinical experience of IGF-1R blockade in sarcoma. During these 21 years, the IGF pathway and its key mediator IGF-1R have been implicated in the genesis, growth, proliferation, metastasis, and resistance to conventional treatment in several sarcoma subtypes. In addition, IGF-1R has been validated, both in vitro and in vivo, as a target for the treatment of sarcoma. Several radiologic and clinical responses to IGF-1R monoclonal antibodies have been reported in Ewing sarcoma patients enrolled in early clinical studies. Furthermore, these therapies were well tolerated, and thus far severe toxicity has been rare. The early clinical evidence of antitumor activity has supported the initiation of various phase II clinical trials in Ewing and other sarcoma subtypes, the results of which are eagerly awaited, as well as studies assessing IGF-1R monoclonal antibodies in combination with traditional cytotoxics or other targeted therapies. Despite these encouraging results, not all patients benefit from IGF-1R inhibition and consequently there is an urgent need for the identification of predictive markers of response.

Past, present and future of therapies in pediatric sarcomas

Limited progress has been made over the past 30 years in improving the outcome of patients with high-risk pediatric sarcomas. The 5-year overall survival rate remains at 20% or less with metastatic sarcomas. Therefore, current and future research is focused on the identification and development of molecular or biological agents targeting the pathogenic pathways in sarcomas, either alone or in combination with conventional chemotherapy. To this end, the most promising activity has been seen with IGF-1 receptor antibodies and mTOR inhibitors. Other agents of interest are oncolytic viruses, epigenetic modulators (e.g., histone deacetylase inhibitors), immune modulators (e.g., muramyl tripeptide phosphatidylethanolamine) and other biological agents (e.g., trabectedin). In addition to the development of novel drugs, the other major area of recent focus is developing immune therapies, such as dendritic cell vaccines and adoptive immunotherapy for treating pediatric sarcomas. This article discusses the successes, the failures and the future direction of these therapies.

Imatinib mesylate in children and adolescents with cancer

Imatinib is an inhibitor of the BCR-ABL fusion gene product that characterizes chronic myeloid leukemia (CML), and of the related tyrosine kinases c-KIT and platelet-derived growth factor (PDGF) receptor. The drug is now included as front-line therapy for CML and Philadelphia chromosome-positive acute lymphoblastic leukemia in children and adolescents, though valid concerns about serious late sequelae remain unresolved and are important issues for further study. European and North American consortia have conducted phase I and II clinical trials of imatinib in children and adolescents with brain and other solid tumors that have provided little evidence of efficacy.

The clinical relevance of molecular genetics in soft tissue sarcomas

Bone and soft tissue sarcomas are an infrequent and heterogeneous group of mesenchymal tumors including more than a hundred different entities attending to histologic patterns. Research into the molecular aspects of sarcomas has increased greatly in the last few years. This enormous amount of knowledge has allowed, for instance, to refine the classification of sarcomas, improve the diagnosis, and increase the number of therapeutical targets available, most of them under preclinical evaluation. However, other important key issues, such as sarcomagenesis and the cell of origin of sarcomas, remain unresolved. From a molecular point of view, these neoplasias are grouped into 2 main types: (a) sarcomas showing relatively simple karyotypes and translocations, which originate gene fusions (eg, EWS-FLI1 in Ewing sarcoma) or point mutations (eg, c-kit in the gastrointestinal tumors) and (b) sarcomas showing unspecific gene alterations, very complex karyotypes, and no translocations. The discovery of the early mechanisms involved in the genesis of sarcomas, the more relevant signaling pathways, and the development of genetically engineered mouse models could also provide a new individualized therapeutic strategy against these tumors. This review describes the clinical application of some of the molecular alterations found in sarcomas, some advances in the field of sarcomagenesis, and the development of animal models.

Inhibition of the insulin-like growth factor I receptor by epigallocatechin gallate blocks proliferation and induces the death of Ewing tumor cells

The insulin-like growth factor I receptor (IGFIR) has emerged as a key therapeutic target in many human malignancies, including childhood cancers such as Ewing family tumors (EFT). In this study, we show that IGFIR is constitutively activated in EFTs and that the major catechin derivative found in green tea, (-)-epigallocatechin gallate (EGCG), can inhibit cell proliferation and survival of EFT cells through the inhibition of IGFIR activity. Treatment of EFT cell lines with EGCG blocked the autophosphorylation of IGFIR tyrosine residues and inhibited its downstream pathways including phosphoinositide 3-kinase-Akt, Ras-Erk, and Jak-Stat cascades. EGCG treatment was associated with dose- and time-dependent inhibition of cellular proliferation, viability, and anchorage-independent growth, as well as with the induction of cell cycle arrest and apoptosis. Apoptosis in EFT cells by EGCG correlated with altered expression of Bcl-2 family proteins, including increased expression of proapoptotic Bax and decreased expression of prosurvival Bcl2, Bcl-XL, and Mcl-1 proteins. Our results provide further evidence that IGFIR is an attractive therapeutic target in EFTs and that EGCG is an effective inhibitor of this receptor tyrosine kinase. EGCG may be a useful agent for targeting IGFIR, either alone or in combination, with other potentially more toxic IGFIR inhibitors for the management of EFTs.

Targets for cancer therapy in childhood sarcomas

Development of chemotherapeutic treatment modalities resulted in a dramatic increase in the survival of children with many types of cancer. Still, in case of some pediatric cancer entities including rhabdomyosarcoma, osteosarcoma and Ewing's sarcoma, survival of patients remains dismal and novel treatment approaches are urgently needed. Therefore, based on the concept of targeted therapy, numerous potential targets for the treatment of these cancers have been evaluated pre-clinically or in some cases even clinically during the last decade. This review gives an overview over many different potential therapeutic targets for treatment of these childhood sarcomas, including receptor tyrosine kinases, intracellular signaling molecules, cell cycle and apoptosis regulators, proteasome, hsp90, histone deacetylases, angiogenesis regulators and sarcoma specific fusion proteins. The large number of potential therapeutic targets suggests that improved comparability of pre-clinical models might be necessary to prioritize the most effective ones for future clinical trials.

Synergistic antitumor effect of melatonin with several chemotherapeutic drugs on human Ewing sarcoma cancer cells: potentiation of the extrinsic apoptotic pathway

Ewing sarcoma, the second most frequent bone cancer type, affects mainly adolescents, who have a survival of 50% 5 yr after diagnosis. Current treatments include a combination of surgery, radiotherapy and chemotherapy, which present potential serious side effects. Melatonin, a natural molecule without relevant side effects, has been previously shown to induce cytotoxicity in SK-N-MC cells, a Ewing sarcoma cell line. Here, we found that there is a synergy in the antitumor effect when melatonin (50 mum-1 mm) is combined with vincristine at the concentration of 5-10 nm or with ifosfamide at the range of 100 mum-1 mm. This synergism is due to the potentiation of cell death, particularly to the potentiation of apoptosis, i.e., mainly the extrinsic apoptotic pathway. There is a significant increase in the activation of caspase-3, -8, -9 and Bid when melatonin is combined with vincristine or ifosfamide compared to the individual treatments. Finally, there is also a potentiation of the early free radical production, likely dependent on the extrinsic apoptosis pathway activation, when the drugs are combined with melatonin. Other proteins which are related to this pathway including mitogen-activated protein kinase or protein kinase B/Akt are not involved in apoptosis induced by these agents separately or when combined. The results shown here together with the facts that: (i) no relevant side effects have been reported for melatonin and (ii) melatonin has a cytoprotective effect on noncancer cells, opens the door for a new approach in the treatment of the Ewing sarcoma family of tumors.

Advances in Ewing's sarcoma research: where are we now and what lies ahead?

Ewing's sarcoma family tumors (EFT) are characterized by specific chromosomal translocations, which lead to EWS/ETS transcription factors. Elucidation of EWS/ETS target gene networks within the context of other signaling pathways, together with the identification of the initiating cell, and the development of genetically engineered mice will hopefully lead to biology-based therapeutic strategies for these tumors.

Stable interference of EWS-FLI1 in an Ewing sarcoma cell line impairs IGF-1/IGF-1R signalling and reveals TOPK as a new target

BACKGROUND

Ewing sarcoma is a paradigm of solid tumour -bearing chromosomal translocations resulting in fusion proteins that act as deregulated transcription factors. Ewing sarcoma translocations fuse the EWS gene with an ETS transcription factor, mainly FLI1. Most of the EWS-FLI1 target genes still remain unknown and many have been identified in heterologous model systems.

METHODS

We have developed a stable RNA interference model knocking down EWS-FLI1 in the Ewing sarcoma cell line TC71. Gene expression analyses were performed to study the effect of RNA interference on the genetic signature of EWS-FLI1 and to identify genes that could contribute to tumourigenesis.

RESULTS

EWS-FLI1 inhibition induced apoptosis, reduced cell migratory and tumourigenic capacities, and caused reduction in tumour growth. IGF-1 was downregulated and the IGF-1/IGF-1R signalling pathway was impaired. PBK/TOPK (T-LAK cell-originated protein kinase) expression was decreased because of EWS-FLI1 inhibition. We showed that TOPK is a new target gene of EWS-FLI1. TOPK inhibition prompted a decrease in the proliferation rate and a dramatic change in the cell's ability to grow in coalescence.

CONCLUSION

This is the first report of TOPK activity in Ewing sarcoma and suggests a significant role of this MAPKK-like protein kinase in the Ewing sarcoma biology.

The insulin-like growth factor-I receptor as an oncogene

The insulin-like growth factor-I receptor (IGF-IR) mediates the biological actions of both IGF-I and IGF-II. The IGF-IR is expressed in most transformed cells, where it displays potent antiapoptotic, cell-survival, and transforming activities. IGF-IR expression is a fundamental prerequisite for the acquisition of a malignant phenotype, as suggested by the finding that IGF-IR-null cells (derived from IGF-IR knock-out embryos) are unable to undergo transformation when exposed to cellular or viral oncogenes. This review article will focus on the underlying molecular mechanisms that are responsible for the normal, physiological control of IGF-IR gene expression, as well as the cellular pathways that underlie its aberrant expression in cancer. Examples from the clinics will be presented, including a description of how the IGF system is involved in breast, prostate, pediatric, and gynecological cancers. Finally, current attempts to target the IGF-IR as a therapeutic approach will be described.

The insulin-like growth factor system and sarcomas

Sarcomas are a diverse group of malignant mesenchymal tumours arising from bone and soft tissues. The identification of critical cellular signalling pathways in sarcomas is an important issue for the development of new targeted therapies. This review highlights the experimental and clinical evidence supporting the role of the insulin-like growth factor (IGF) signalling system in the cellular transformation and progression of several types of sarcoma, including rhabdomyosarcoma, synovial sarcoma, leiomyosarcoma, Ewing's sarcoma and osteosarcoma. Preclinical data suggest that the IGF system could be a promising target for therapy in these sarcomas. Currently, therapies interrupting IGF signalling have been or are being developed. In recent phase 1 clinical studies with humanized monoclonal antibodies directed against IGF receptor type 1 (IGF-1R), objective tumour responses were observed in several patients with Ewing's sarcoma, encouraging further clinical testing in Ewing's sarcoma and other sarcoma (sub)types. Moreover, the occasional occurrence of paraneoplastic hypoglycaemia as a result of the secretion of incompletely processed forms of pro-IGF-II by sarcomas is discussed.

Pediatric developmental therapies: interesting new drugs now in early-stage clinical trials

The current high cure rates for children diagnosed with cancer can be attributed in part to emphasis on large cooperative group clinical trials. The significant improvement in pediatric cancer survival over the past few decades is the result of optimized chemotherapy drug dosing, timing, and intensity; however, further alterations in traditional chemotherapy agents are unlikely to produce substantially better outcomes. Furthermore, there remains a subset of patients who have a very poor prognosis due to tumor type or stage at presentation, or who have a dismal prognosis with relapse or recurrence. As such, innovative approaches to therapy and new drugs are clearly needed for introduction into the current pediatric oncology arsenal. A variety of biologically targeted therapies that have shown promise in preclinical studies and early-phase adult clinical trials are now being explored in pediatric clinical trials. These novel agents hold the promise for continuing to drive forward improvements in patient survival, with potentially less toxicity than exists with traditional chemotherapy drugs.

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.

IGF-1 receptor inhibitors in clinical trials--early lessons

The insulin-like growth factor pathway plays a major role in cancer cell proliferation, survival and resistance to anti-cancer therapies in many human malignancies, including breast cancer. As a key signaling component of IGF system, the IGF-1 receptor is the target of several investigational agents in clinical and pre-clinical development. This review will focus on the rationale for targeting the IGF-1 receptor and other components of the IGF-1 system. In addition, we will examine the role of IGF-1 signaling in resistance to clinically important breast cancer therapies, including cytotoxic chemotherapy, hormonal therapy and erbB targeted agents. We will also review the completed and ongoing clinical investigations with IGF-1 receptors inhibitors to date and the utility of these early data in designing future breast cancer studies with IGF-1 signaling inhibition strategies.

Early drug development of inhibitors of the insulin-like growth factor-I receptor pathway: lessons from the first clinical trials

The insulin-like growth factor-I receptor (IGF-IR) was first cloned in 1986. Since then, intense work has defined classic phosphorelays activated via the IGF-IR, which regulate cell proliferation, apoptosis, motility, and fate. The understanding of the roles of hormones in cancer and the growth hormone-IGF-IGF-binding protein axis specifically has yield to a second wave of development: the design of specific inhibitors that interrupt the signaling associated with this axis. The ability to manipulate these pathways holds not only significant therapeutic implications but also increase the chance of deeper insight about the role of the axis in carcinogenesis and metastasis. Nowadays, >25 molecules with the same goal are at different stages of development. Here, we review the clinical and preclinical experience with the two most-investigated strategies, tyrosine kinase inhibitors and monoclonal antibodies, and the advantages and disadvantages of each strategy, as well as other alternatives and possible drug combinations. We also review the biomarkers explored in the first clinical trials, the strategies that have been explored thus far, and the clinical trials that are going to explore their role in cancer treatment.

Targeting insulin-like growth factor 1 receptor in sarcomas

PURPOSE OF REVIEW

The present review examines the rationale for targeting insulin-like growth factor-I receptor in sarcoma therapy and highlights some key issues that need to be addressed as clinical trials targeting insulin-like growth factor-I receptor proceed.

RECENT FINDINGS

Preclinical evidence supports proof of principle for targeting insulin-like growth factor-I receptor signaling in sarcomas. The insulin-like growth factor system is activated by or associated with most of the fusion oncoproteins that genetically characterize a group of sarcomas, but alterations in this pathway appear as a common feature. Correlation of cancer risk with insulin-like growth factor-I receptor signaling expression and polymorphisms has also been described. Blockade of insulin-like growth factor-I receptor functions results in an inhibition of tumor growth and metastasis, both when the targeted drugs were used as single agents and in combined therapies. Antibodies against insulin-like growth factor-I receptor and small kinase inhibitors represent, at this point, the most probable clinical options.

SUMMARY

Sarcomas are good candidates for the design of a clinical study targeting insulin-like growth factor-I receptor. An attention to schedule with chemotherapy agents and new drugs, measurement of relevant indicators of response and better molecular understanding of the metabolic functions of insulin-like growth factor-I receptor and its functional relationship with insulin receptor are necessary to proceed safely with the design of anti-insulin-like growth factor strategies.

Targeting the type 1 insulin-like growth factor receptor as a treatment for cancer

BACKGROUND

The type 1 insulin-like growth factor receptor (IGF1R) plays a critical role in transformation, invasion and apoptosis protection, and is an attractive cancer treatment target.

OBJECTIVE

To review IGF1R antibodies and kinase inhibitors that are in preclinical and clinical development, and to discuss questions that will influence the success of this approach in clinical practice.

METHODS

This review is drawn from published literature, meeting abstracts and online resources.

RESULTS/CONCLUSION

IGF1R blockade is generally well tolerated although it can induce hyperglycaemia. Single-agent activity has been documented in Ewing's sarcoma but not thus far in common solid tumours. Key issues include identification of factors that influence sensitivity to IGF1R blockade, and how most effectively to combine IGF1R inhibitors with other treatments.

Bone tumors in adolescents and young adults

OPINION STATEMENT

Bone tumors, particularly osteosarcomas and members of the Ewing Sarcoma Family of Tumors (ESFT), are typical malignancies of adolescents and young adults. Current diagnostic and therapeutic guidelines for patients of all ages were developed in this specific age group. The aim of bone sarcoma therapy should be to cure the patient from both the primary tumor and all (micro-)metastatic deposits while maintaining as much (extremity) function and causing as few treatment-specific late effects as possible. Bone sarcoma therapy requires close multidisciplinary cooperation. Usually, it consists of induction chemotherapy, followed by local therapy of the primary tumor (and, if present, primary metastases) and further, adjuvant chemotherapy. Local treatment for osteosarcoma should be surgery whenever feasible. Surgery is also gaining importance in ESFT, which was long considered a domain of radiotherapy. Modern reconstructive techniques continue to expand the indications for limb salvage, particularly for patients who have not yet reached skeletal maturity. Treatment within the framework of prospective, multi-institutional trials should be considered standard of care not only for children, but also for affected adolescents and (young) adults. Such trials are essential in guaranteeing that all patients have access to appropriate care and that progress from biological studies can be translated into prognostic improvements without undue delay. The rarity of bone sarcomas increasingly requires trials to be multinational.

Candidate genes involved in enhanced growth of human prostate cancer under high fat feeding identified by microarray analysis

BACKGROUND

Several studies have suggested that a high fat diet (HFD) may be a risk factor of prostate cancer (PCa). As a first step to delineate the molecular mechanisms underlying the enhanced progression of PCa under HFD, we investigated the differential gene expressions of a human PCa xenograft under HFD and a low fat diet (LFD).

METHODS

LNCaP cells were subcutaneously injected in 20 nude mice, which were equally divided into two groups, the HFD group and LFD group. Oligonucleotide microarray analyses were performed using mice xenografts from HFD and LFD, and the results of candidate genes with a significant differential expression were validated by quantitative RT-PCR experiments. As for insulin-like growth factor I receptor (IGF-IR), protein expression levels were further examined by immunohistochemistry in xenograft tissues and in 78 radical prostatectomy specimens.

RESULTS

Tumor volume and serum PSA levels were significantly higher in the HFD group than in the LFD group (P<0.001 and P=0.006, respectively). We found 64 up-regulated genes (0.19%) and 14 down-regulated genes (0.04%) with more than twofold differences in the HFD xenograft. IGF-IR, TNFRSF, and LPL showed striking differences in the quantitative RT-PCR experiment. Immunostaining further revealed marked enhanced IGF-IR expression in the HFD xenograft. In human PCa, the lowest IGF-IR immunoreactivity group tended to have the lowest body mass index in both normal and PCa epithelium.

CONCLUSION

HFD induced remarkable up- and down-regulation of mRNA of a substantial number of genes. Furthermore, the IGF-I system may be involved in the HFD-associated enhanced progression of PCa.

Mechanisms of disease: signaling of the insulin-like growth factor 1 receptor pathway--therapeutic perspectives in cancer

The insulin-like growth factor 1 (IGF1) signaling pathway is implicated in the development of cancer. High levels of circulating IGF1 and certain genetic polymorphisms of IGF1 and IGFBP3 are associated with an increased risk of several common cancers. The IGF1 receptor (IGF1R) has been shown to be expressed in a wide range of tumors, and IGF1R signaling is crucial for tumor transformation and the survival of malignant cells. Several monoclonal antibodies and small-molecule inhibitors have been tested in preclinical studies and early-phase clinical studies. IGF1R signaling interferes with numerous growth factors and receptors such as VEGF and EGFR. In the experimental system, IGF1R signaling has been found to correlate with resistance to therapies based on the inhibition of EGFR and HER2. This Review highlights the most relevant studies in this exciting area of research, focusing in particular on the role of IGF1R in resistance to other receptor-targeted therapies for cancer.

Modifying IGF1 activity: an approach to treat endocrine disorders, atherosclerosis and cancer

Insulin-like growth factor 1 (IGF1) is a polypeptide hormone that has a high degree of structural similarity to human proinsulin. Owing to its ubiquitous nature and its role in promoting cell growth, strategies to inhibit IGF1 actions are being pursued as potential adjunctive measures for treating diseases such as short stature, atherosclerosis and diabetes. In addition, most tumour cell types possess IGF1 receptors and conditions in the tumour microenvironment, such as hypoxia, can lead to enhanced responsiveness to IGF1. Therefore, inhibiting IGF1 action has been proposed as a specific mechanism for potentiating the effects of existing anticancer therapies or for directly inhibiting tumour cell growth.