Expression of insulin-like growth factor pathway proteins in rhabdomyosarcoma: IGF-2 expression is associated with translocation-negative tumors

Myogenic IGFBP5 levels in rhabdomyosarcoma are nourished by mesenchymal stromal cells and regulate growth arrest and apoptosis

BACKGROUND

Mesenchymal stromal cells belong to a diverse collection of cells in different states that are poorly characterized in soft-tissue sarcomas. In this study, we explored tumor growth-regulatory signaling between differentially educated non-malignant mesenchymal stromal cells and malignant cells in pediatric rhabdomyosarcoma (RMS).

METHODS

Xenograft experiments demonstrated that non-malignant stromal cells influence tumor behavior. Gene expression analysis identified deregulated genes, which were further studied using cell culture assays and patient data. Clinicopathological correlations were made in a discovery cohort (N = 147) and a validation cohort (N = 101).

RESULTS

The results revealed transiently suppressive paracrine effects of orthotopic stromal cells derived from skeletal muscle. These effects were lost when the stromal cells were exposed to RMS cells, either short-term in vitro, or long-term in hindlimb muscle in vivo. High resolution microarray-based Clariom D gene expression analysis identified insulin-like growth factor binding protein 5 (IGFBP5) as the top upregulated gene in RMS cells exposed to naïve stromal cells, and effects on growth arrest, caspase 3/7 activation, and myogenic cell identity were demonstrated in functional assays. Furthermore, IGFBP5 associated with the caspase 3 substrate growth arrest specific protein 2 (GAS2), lower disease stage and favorable survival in patient cohorts.

CONCLUSIONS

This study uses functional modeling and omics approaches to identify IGFBP5 as a candidate mediator of anti-tumor growth mechanisms originating from tumor-neighboring mesenchymal stromal cells. Tumors of mesenchymal origin, such as RMS, are known for their heterogeneity, and this could potentially pose a limitation to the study. However, a clinical relevance is emphasized by consistent findings across patient cohorts. These insights pave the way for novel therapeutic strategies modulating activities of stromal cell subsets at primary and metastatic sites in RMS.

Receptor tyrosine kinase gene expression profiling of orbital rhabdomyosarcoma unveils MET as a potential biomarker and therapeutic target

Receptor tyrosine kinases (RTKs) serve as molecular targets for the development of novel personalized therapies in many malignancies. In the present study, expression pattern of receptor tyrosine kinases and its clinical significance in orbital RMS has been explored. Eighteen patients with histopathologically confirmed orbital RMS formed part of this study. Comprehensive q-PCR gene expression profiles of 19 RTKs were generated in the cases and controls. The patients were followed up for 59.53 ± 20.93 years. Clustering and statistical analysis tools were applied to identify the significant combination of RTKs associated with orbital rhabdomyosarcoma patients. mRNA overexpression of RTKs which included MET, AXL, EGFR was seen in 60-80% of cases; EGFR3, IGFR2, FGFR1, RET, PDGFR1, VEGFR2, PDGFR2 in 30-60% of cases; and EGFR4, FGFR3,VEGFR3 and ROS,IGFR1, EGFR1, FGFR2, VEGFR1 in 10-30% of cases. Immunoexpression of MET was seen in 89% of cases. A significant association was seen between MET mRNA and its protein expression. In all the cases MET gene expression was associated with worst overall survival (P = 0.03).There was a significant correlation of MET mRNA expression with RET, ROS, AXL, FGFR1, FGFR3, PDGFR1, IGFR1, VEGFR2, and EGFR3 genes. Association between MET gene and collective expression of RTKs was further evaluated by semi-supervised gene cluster analysis and Principal component analysis, which showed well-separated tumor clusters. MET gene overexpression could be a useful biomarker for identifying high risk orbital rhabdomyosarcoma patients. Well-separated tumor clusters confirmed the association between MET gene and collective expression of RTK genes. Therefore, the therapeutic potential of multi-kinase inhibitors targeting MET and the 9 other significant RTKs needs to be explored.

Splice-switching of the insulin receptor pre-mRNA alleviates tumorigenic hallmarks in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is an aggressive pediatric tumor with a poor prognosis for metastasis and recurrent disease. Large-scale sequencing endeavors demonstrate that Rhabdomyosarcomas have a dearth of precisely targetable driver mutations. However, IGF-2 signaling is known to be grossly altered in RMS. The insulin receptor (IR) exists in two alternatively spliced isoforms, IR-A and IR-B. The IGF-2 signaling molecule binds both its innate IGF-1 receptor as well as the insulin receptor variant A (IR-A) with high affinity. Mitogenic and proliferative signaling via the canonical IGF-2 pathway is, therefore, augmented by IR-A. This study shows that RMS patients express increased IR-A levels compared to control tissues that predominantly express the IR-B isoform. We also found that Hif-1α is significantly increased in RMS tumors, portraying their hypoxic phenotype. Concordantly, the alternative splicing of IR adapts to produce more IR-A in response to hypoxic stress. Upon examining the pre-mRNA structure of the gene, we identified a potential hypoxia-responsive element, which is also the binding site for the RNA-binding protein CUG-BP1 (CELF1). We designed Splice Switching Oligonucleotides (SSO) against this binding site to decrease IR-A levels in RMS cell lines and, consequently, rescue the IR-B expression levels. SSO treatment resulted in a significant reduction in cell proliferation, migration, and angiogenesis. Our data shows promising insight into how impeding the IGF-2 pathway by reducing IR-A expression mitigates tumor growth. It is evident that Rhabdomyosarcomas use IR alternative splicing as yet another survival strategy that can be exploited as a therapeutic intervention in conjunction with already established anti-IGF-1 receptor therapies.

Unraveling the IGF System Interactome in Sarcomas Exploits Novel Therapeutic Options

Aberrant bioactivity of the insulin-like growth factor (IGF) system results in the development and progression of several pathologic conditions including cancer. Preclinical studies have shown promising anti-cancer therapeutic potentials for anti-IGF targeted therapies. However, a clear but limited clinical benefit was observed only in a minority of patients with sarcomas. The molecular complexity of the IGF system, which comprises multiple regulators and interactions with other cancer-related pathways, poses a major limitation in the use of anti-IGF agents and supports the need of combinatorial therapeutic strategies to better tackle this axis. In this review, we will initially highlight multiple mechanisms underlying IGF dysregulation in cancer and then focus on the impact of the IGF system and its complexity in sarcoma development and progression as well as response to anti-IGF therapies. We will also discuss the role of Ephrin receptors, Hippo pathway, BET proteins and CXCR4 signaling, as mediators of sarcoma malignancy and relevant interactors with the IGF system in tumor cells. A deeper understanding of these molecular interactions might provide the rationale for novel and more effective therapeutic combinations to treat sarcomas.

Signaling pathways in Rhabdomyosarcoma invasion and metastasis

Rhabdomyosarcoma (RMS) is an aggressive childhood mesenchymal tumor with two major molecular and histopathologic subtypes: fusion-positive (FP)RMS, characterized by the PAX3-FOXO1 fusion protein and largely of alveolar histology, and fusion-negative (FN)RMS, the majority of which exhibit embryonal tumor histology. Metastatic disease continues to be associated with poor overall survival despite intensive treatment strategies. Studies on RMS biology have provided some insight into autocrine as well as paracrine signaling pathways that contribute to invasion and metastatic propensity. Such pathways include those driven by the PAX3-FOXO1 fusion oncoprotein in FPRMS and signaling pathways such as IGF/RAS/MEK/ERK, PI3K/AKT/mTOR, cMET, FGFR4, and PDGFR in both FP and FNRMS. In addition, specific cytoskeletal proteins, G protein coupled receptors, Hedgehog, Notch, Wnt, Hippo, and p53 pathways play a role, as do specific microRNA. Paracrine factors, including secreted proteins and RMS-derived exosomes that carry cargo of protein and miRNA, have also recently emerged as potentially important players in RMS biology. This review summarizes the known factors contributing to RMS invasion and metastasis and their implications on identifying targets for treatment and a better understanding of metastatic RMS.

Pharmacologic Inhibition of Ezrin-Radixin-Moesin Phosphorylation is a Novel Therapeutic Strategy in Rhabdomyosarcoma

Intermediate and high-risk rhabdomyosarcoma (RMS) patients have poor prognosis with available treatment options, highlighting a clear unmet need for identification of novel therapeutic strategies. Ezrin-radixin-moesin (ERM) family members are membrane-cytoskeleton linker proteins with well-defined roles in tumor metastasis, growth, and survival. ERM protein activity is regulated by dynamic changes in the phosphorylation at a conserved threonine residue in their C-terminal actin-binding domain. Interestingly, ERM family member, ezrin, has elevated expression in the RMS tissue. Despite this, the translational scope of targeting ERM family proteins in these tumors through pharmacological inhibition has never been considered. This study investigates the inhibition of ERM phosphorylation using a small molecule pharmacophore NSC668394 as a potential strategy against RMS. Upon in vitro treatment with NSC668394, RMS cells exhibit a dose-dependent decrease in cell viability and proliferation, with induction of caspase-3 cleavage and apoptosis. siRNA-mediated knockdown of individual ERM protein expression revealed that each regulates RMS survival to a different degree. In vivo administration of NSC668394 in RMS xenografts causes significant decrease in tumor growth, with no adverse effect on body weight. Collectively, this study highlights the importance of the active conformation of ERM proteins in RMS progression and survival and supports pharmacologic inhibition of these proteins as a novel therapeutic approach.

Picropodophyllin (PPP) is a potent rhabdomyosarcoma growth inhibitor both in vitro and in vivo

Background

Insulin-like growth factors and insulin are important factors promoting cancer growth and metastasis. The molecules act through IGF1 (IGF1R) and insulin (InsR) receptors. Rhambodmyosarcomas (RMS) overproduce IGF2 – a potent ligand for IGF1R and, at the same time, highly express IGF1 receptor. The purpose of the study was to evaluate possible application of picropodophyllin (PPP) – a potent IGF1R inhibitor.

Methods

In our study we used a number of in vitro assays showing influence of IGF1R blockage on RMS cell lines (both ARMS and ERMS) proliferation, migration, adhesion, cell cycling and signal transduction pathways. Additionally, we tested possible concomitant application of PPP with commonly used chemotherapeutics (vincristine, actinomycin-D and cisplatin). Moreover, we performed an in vivo study where PPP was injected intraperitoneally into RMS tumor bearing SCID mice.

Results

We observed that PPP strongly inhibits RMS proliferation, chemotaxis and adhesion. What is more, application of the IGF1R inhibitor attenuates MAPK phosphorylation and cause cell cycle arrest in G2/M phase. PPP increases sensitivity of RMS cell lines to chemotherapy, specifically to vincristine and cisplatin. In our in vivo studies we noted that mice treated with PPP grew smaller tumors and displayed significantly decreased seeding into bone marrow.

Conclusions

The cyclolignan PPP effectively inhibits RMS tumor proliferation and metastasis in vitro and in an animal model.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3495-y) contains supplementary material, which is available to authorized users.

Investigation of IGF2, IGFBP2 and p63 proteins in rhabdomyosarcoma tumors

Many efforts have been made to address involvement of the insulin-like growth-factor (IGF) pathway in rhabdomyosarcoma (RMS) pathogenesis, but the actual role of IGF in RMS is still controversial.

OBJECTIVE

To investigate the implications of IGF2, IGFBP2 and p63 in RMS, and further explored their potential interaction.

DESIGN

A total of 114 specimens of RMS along with clinic-pathologic characteristics were collected from the year of 2003 to 2013. Protein abundance was detected by immunohistochemical staining, potential relationships between protein levels and clinic-pathological parameters were applied using correlation analysis.

RESULTS

The results showed positive correlation between IGFBP2 and p63 (r=0.271, p=0.003), suggesting that the interaction of IGFBP2 and p63 might account for the pathogenesis of RMS. In the subtype analysis, positive correlation was still found in embryonal rhabdomyosarcoma (ERMS, r=0.214, p=0.034) and alveolar rhabdomyosarcoma (ARMS, r=0.498, p=0.048). By focusing on the interaction of IGF pathway and p63, our results reveal additional signs to elucidate difference of pathogenesis and severity between ERMS and ARMS.

CONCLUSIONS

The present study provides novel evidence to elucidate RMS pathogenesis and may be beneficial to clinical diagnosis and therapy for RMS.

Does it make sense to target one tumor cell chemotactic factor or its receptor when several chemotactic axes are involved in metastasis of the same cancer?

The major problem with cancer progression and anti-cancer therapy is the inherent ability of cancer cells to migrate and establish distant metastases. This ability to metastasize correlates with the presence in a growing tumor of cells with a more malignant phenotype, which express certain cancer stem cell markers. The propensity of malignant cells to migrate and their resistance to radio-chemotherapy somewhat mimics the properties of normal developmentally early stem cells that migrate during organogenesis in the developing embryo. In the past, several factors, including cell migration-promoting cytokines, chemokines, growth factors, bioactive lipids, extracellular nucleotides, and even H(+) ions, were found to influence the metastasis of cancer cells. This plethora of pro-migratory factors demonstrates the existence of significant redundancy in the chemoattractants for cancer cells. In spite of this obvious fact, significant research effort has been dedicated to demonstrating the crucial involvement of particular pro-metastatic factor-receptor axes and the development of new drugs targeting one receptor or one chemoattractant. Based on our own experience working with a model of metastatic rhabdomyosarcoma as well as the work of others, in this review we conclude that targeting a single receptor-ligand pro-metastatic axis will not effectively prevent metastasis and that we should seek other more effective therapeutic options.

Targeted Chemotherapy in Bone and Soft-Tissue Sarcoma

Historically surgical intervention has been the mainstay of therapy for bone and soft-tissue sarcomas, augmented with adjuvant radiation for local control. Although cytotoxic chemotherapy revolutionized the treatment of many sarcomas, classic treatment regimens are fraught with side effects while outcomes have plateaued. However, since the approval of imatinib in 2002, research into targeted chemotherapy has increased exponentially. With targeted therapies comes the potential for decreased side effects and more potent, personalized treatment options. This article reviews the evolution of medical knowledge regarding sarcoma, the basic science of sarcomatogenesis, and the major targets and pathways now being studied.

Insulin-like Growth Factor 2 Gene Expression Molecularly Differentiates Pleuropulmonary Blastoma and Embryonal Rhabdomyosarcoma

The sarcomatous element in pleuropulmonary blastoma (PPB) is often histologically indistinguishable from embryonal rhabdomyosarcoma (ERMS). A diagnosis of PPB is often made after definitive surgical resection based on pathologic features, most notably the presence of hamartomatous pulmonary elements. Samples from seven PPB patients were obtained from the rhabdomyosarcomatous portion of the tumor by macrodissection. Representative ERMS tumor tissue was selected from 21 ERMS patient samples. Formalin-fixed paraffin-embedded tissue scrolls from each sample were analyzed using the Affymetrix Human Exon arrays. All PPB patients and 7 of 21 ERMS patients were 3 years old and younger. Twenty transcripts (10 annotated, 10 noncoding RNAs) were significantly differentially expressed in ERMS when compared with PPB samples. Insulin-like growth factor 2 (IGF2) was uniformly overexpressed in ERMS (19/21>400) but was expressed at low levels in PPB (P<0.001). Two ERMS cases that had low level IGF2 expression were 3 years and younger of age. No other differences between the 2 approached this degree of significance, despite a common rhabdomyogenic phenotype in the sarcomatous areas of PPB. PPB, unlike most ERMS, appears not to be driven by autocrine IGF2 signaling.

5‑Azacytidine inhibits human rhabdomyosarcoma cell growth by downregulating insulin‑like growth factor 2 expression and reactivating the H19 gene product miR‑675, which negatively affects insulin‑like growth factors and insulin signaling

Insulin-like growth factor 2 (IGF2) and 1 (IGF1) and insulin (INS) promote proliferation of rhabdomyosarcoma (RMS) cells by interacting with the insulin-like growth factor 1 receptor (IGF1R) and the insulin receptor (INSR). Loss of imprinting (LOI) by DNA hypermethylation at the differentially methylated region (DMR) for the IGF2‑H19 locus is commonly observed in RMS cells and results in an increase in the expression of proliferation-promoting IGF2 and downregulation of proliferation-inhibiting non-coding H19 miRNAs. One of these miRNAs, miR‑675, has been reported in murine cells to be a negative regulator of IGF1R expression. To better address the role of IGF2 and 1, as well as INS signaling in the pathogenesis of RMS and the involvement of LOI at the IGF2‑H19 locus, we employed the DNA demethylating agent 5‑azacytidine (AzaC). We observed that AzaC‑mediated demethylation of the DMR at the IGF2‑H19 locus resulted in downregulation of IGF2 and an increase in the expression of H19. This epigenetic change resulted in a decrease in RMS proliferation due to downregulation of IGF2 and, IGF1R expression in an miR‑675‑dependent manner. Interestingly, we observed that miR‑675 not only inhibited the expression of IGF1R in a similar manner in human and murine cells, but we also observed its negative effect on the expression of the INSR. These results confirm the crucial role of LOI at the IGF2‑H19 DMR in the pathogenesis of RMS and are relevant to the development of new treatment strategies.

Adoptive cell therapy for sarcoma

Current therapy for sarcomas, though effective in treating local disease, is often ineffective for patients with recurrent or metastatic disease. To improve outcomes, novel approaches are needed and cell therapy has the potential to meet this need since it does not rely on the cytotoxic mechanisms of conventional therapies. The recent successes of T-cell therapies for hematological malignancies have led to renewed interest in exploring cell therapies for solid tumors such as sarcomas. In this review, we will discuss current cell therapies for sarcoma with special emphasis on genetic approaches to improve the effector function of adoptively transferred cells.

Investigation of IGF2, Hedgehog and fusion gene expression profiles in pediatric sarcomas

The childhood sarcomas are malignant tumors with high mortality rates. They are divided into two genetic categories: a category without distinct pattern karyotypic changes and the other category showing unique translocations that originate gene rearrangements. This category includes rhabdomyosarcoma (RMS), Ewing's sarcoma (ES) and synovial sarcoma (SS). Diverse studies have related development genes, such as; IGF2, IHH, PTCH1 and GLI1 and sarcomatogenesis.

OBJECTIVE

To characterize the RMS, ES and SS rearrangements, we quantify the expression of IGF2 IHH, PTCH1 and GLI1 genes and correlate molecular data with clinical parameters of patients.

DESIGN

We analyzed 29 RMS, 10 SS and 60 ES tumor samples by RT-PCR (polymerase chain reaction-reverse transcription) and qPCR (quantitative PCR).

RESULTS

Among the samples of ARMS, 50% had rearrangements of PAX3/7-FOXO1, 60% of ES samples were EWS-FLI1 positive and 90% of SS samples were positive for SS18-SSX1/2. In relation to the control reference samples (QPCR Human Reference Total RNA-Stratagene, Human Skeletal Muscle Total RNA-Ambion, Universal RNA Human Normal Tissues-Ambion), RMS samples showed a high IGF2 gene expression (p<0.0001). Moreover, ES samples showed a low IGF2 gene expression (p<0.0001) and high IHH (p<0.0001), PTCH1 (p=0.0173) and GLI1 (p=0.0113) gene expressions.

CONCLUSIONS

The molecular characterization of IGF and Hedgehog pathway in these pediatric sarcomas may collaborate to enable a better understanding of the biological behavior of these neoplasms.

Investigation of PAX3/7-FKHR fusion genes and IGF2 gene expression in rhabdomyosarcoma tumors

The purpose of our study was to investigate the prevalence of the PAX3/7-FKHR fusion genes and quantify the IGF2 gene expression in rhabdomyosarcoma (RMS) samples. Soft tissue sarcomas account 5% of childhood cancers and 50% of them are RMS. Morphological evaluation of pediatric RMS has defined two histological subtypes, embryonal (ERMS) and alveolar (ARMS). Chromosomal analyses have demonstrated two translocations associated with ARMS, resulting in the PAX3/7-FKHR rearrangements. Reverse transcriptase-polymerase chain reaction (RT-PCR) is extremely useful in the diagnosis of ARMS positive for these rearrangements. Additionally, several studies have shown a significant involvement of IGF pathway in the pathogenesis of RMS. The presence of PAX3/7-FKHR gene fusions was studied in 25 RMS samples from patients attending the IOP-GRAACC/UNIFESP and three RMS cell lines by RT-PCR. IGF2 gene expression was quantified by qPCR and related with clinic pathological parameters. Of the 25 samples, nine (36%) were ARMS and 16 (64%) were ERMS. PAX3/7-FKHR gene fusions expression was detected in 56% of ARMS tumor samples. IGF2 overexpression was observed in 80% of samples and could indicate an important role of this pathway in RMS biology.

RasGRF1 regulates proliferation and metastatic behavior of human alveolar rhabdomyosarcomas

The involvement of the Ras superfamily of GTPases in the pathogenesis of rhabdomysarcoma (RMS) is not well understood. While mutant H-Ras leads to embryonal RMS (ERMS) formation in experimental animals and in Costello syndrome patients, no data exists on the potential role of Ras GTPases in the pathogenesis of alveolar RMS (ARMS). To address this issue better, we focused on the role of the GTP exchange factor RasGRF1 in this process. We observed that, in comparison to normal skeletal muscle cells, RasGRF1 mRNA is upregulated in the majority of human ARMS cell lines and subsequently confirmed its high expression in patient samples. By employing confocal microscopy analysis, we observed RasGRF1 accumulation in cell filopodia, which suggests its involvement in ARMS cell migration. Furthermore, we observed that RasGRF1 becomes phosphorylated in ARMS after stimulation by several pro-metastatic factors, such as SDF-1 and HGF/SF, as well as after exposure to growth-promoting Igf-2 and insulin. More importantly, activation of RasGRF1 expression correlated with activation of p42/44 MAPK and AKT. When the expression of RasGRF1 was down-regulated in ARMS cells by an shRNA strategy, these RasGRF1-kd RMS cells did not respond to stimulation by SDF-1, HGF/SF, Igf-2 or insulin by phosphorylation of p42/44 MAPK and AKT and lost their chemotactic responsiveness; however, their adhesion was not affected. We also observed that RasGRF1-kd ARMS cells proliferated at a very low rate in vitro, and, more importantly, after inoculation into immunodeficient SCID/beige inbred mice they formed significantly smaller tumors. We conclude that RasGRF1 plays an important role in ARMS pathogenesis and is a new potential therapeutic target to inhibit ARMS growth.

Advances in pediatric rhabdomyosarcoma characterization and disease model development

Rhabdomyosarcoma (RMS), a form of soft tissue sarcoma, is one of the most common pediatric malignancies. A complex disease with at least three different subtypes, it is characterized by perturbations in a number of signaling pathways and genetic abnormalities. Extensive clinical studies have helped classify these tumors into high and low risk groups to facilitate different treatment regimens. Research into the etiology of the disease has helped uncover numerous potential therapeutic intervention points which can be tested on various animal models of RMS; both genetically modified models and tumor xenograft models. Taken together, there has been a marked increase in the survival rate of RMS patients but the highly invasive, metastatic forms of the disease continue to baffle researchers. This review aims to highlight and summarize some of the most important developments in characterization and in vivo model generation for RMS research, in the last few decades.

Downregulation of microRNAs miR-1, -206 and -29 stabilizes PAX3 and CCND2 expression in rhabdomyosarcoma

Elevated levels of PAX3 and cell proliferation genes are characteristic features of rhabdomyosarcoma (RMS). We hypothesize that the increased levels of these genes are stabilized due to downregulation of specific miRNAs. In this study, we show that downregulation of miR-1, -206 and -29 stabilizes the expression of PAX3 and CCND2 in both embryonal (ERMS) and alveolar (ARMS) RMS types. Ectopic expression of miR-1 and 206 in JR1, an ERMS cell line, show significant downregulation of PAX3 protein expression, whereas overexpression of these miRNAs in Rh30, an ARMS cell line, did not show any effect in PAX3 protein levels. In ARMS, PAX3 forms a fusion transcript with FOXO1 and the resultant loss of PAX3 3'UTR in the fusion transcript indicate an oncogenic mechanism to evade miRNA-mediated regulation of PAX3. Further, we show that miR-1, -206 and -29 can regulate the expression of CCND2, a cell cycle gene. In addition to CCND2, miR-29 also targets E2F7, another cell cycle regulator. Cell function analysis shows that overexpression of miR-29 downregulates the expression of these cell cycle genes, induces partial G1 arrest leading to decreased cell proliferation. Taken together our data suggest that the RMS state is stabilized by the deregulation of multiple miRNAs and their target genes, supporting a tumor suppressor role for these miRNA.

Update on rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a malignant childhood tumor of mesenchymal origin that currently has a greater than 70% overall 5-year survival. Multimodality treatment is determined by risk stratification according to pretreatment stage, postoperative group, histology, and site of the primary tumor. Pretreatment staging is dependent on primary tumor site, size, regional lymph node status, and presence of metastases. Unique to RMS is the concept of postoperative clinical grouping that assesses the completeness of disease resection and takes into account lymph node evaluation. At all tumor sites, the clinical grouping, and therefore completeness of resection, is an independent predictor of outcome. Overall, the prognosis for RMS is dependent on primary tumor site, patient age, completeness of resection, extent of disease, including the presence and number of metastatic sites and histology and biology of the tumor cells. Therefore, the surgeon plays a vital role in RMS by contributing to risk stratification for treatment, local control of the primary tumor, and outcome. The current state-of-the-art treatment is determined by treatment protocols developed by the Soft Tissue Sarcoma Committee of the children's Oncology Group.

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.

Induction of a regenerative microenvironment in skeletal muscle is sufficient to induce embryonal rhabdomyosarcoma in p53-deficient mice

We have previously reported that mice with muscular dystrophy, including mdx mice, develop embryonal rhabdomyosarcoma (eRMS) with a low incidence after 1 year of age and that almost all such tumours contain cancer-associated p53 mutations. To further demonstrate the relevance of p53 inactivation, we created p53-deficient mdx mice. Here we demonstrate that loss of one or both p53 (Trp53) alleles accelerates eRMS incidence in the mdx background, such that almost all Trp53(-/-) mdx animals develop eRMS by 5 months of age. To ascertain whether increased tumour incidence was due to the regenerative microenvironment found in dystrophic skeletal muscles, we induced muscle regeneration in Trp53(+/+) and Trp53(-/-) animals using cardiotoxin (Ctx). Wild-type (Trp53(+/+) ) animals treated with Ctx, either once every 7 days or once every 14 days from 1 month of age onwards, developed no eRMS; however, all similarly Ctx-treated Trp53(-/-) animals developed eRMS by 5 months of age at the site of injection. Most of these tumours displayed markers of human eRMS, including over-expression of Igf2 and phosphorylated Akt. These data demonstrate that the presence of a regenerative microenvironment in skeletal muscle, coupled with Trp53 deficiency, is sufficient to robustly induce eRMS in young mice. These studies further suggest that consideration should be given to the potential of the muscle microenvironment to support tumourigenesis in regenerative therapies for myopathies.

High IGFBP2 expression correlates with tumor severity in pediatric rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common childhood sarcoma and is identified as either the embryonal or alveolar (ARMS) subtype. In approximately 75% of cases, ARMSs are characterized by specific chromosomal translocations that involve PAX and FKHR genes. ARMS gene expression signatures vary, depending on the presence or absence of the translocations. Insulin-like growth factor-binding protein 2 (IGFBP2) is strongly overexpressed in translocation-negative RMS. Because IGFBP2 is associated with tumorigenesis, we investigated its functional role in RMS. An analysis of IGFBP2 distribution in RMS cell lines revealed a strong accumulation in the Golgi complex, in which morphological characteristics appeared peculiarly modified. After silencing IGFBP2 expression, our microarray analysis revealed mostly cell cycle and actin cytoskeleton gene modulations. In parallel, IGFBP2-silenced cells showed reduced cell cycle and rates of invasion and decreased seeding in the lungs after tail vein injections in immunodeficient mice. An analysis of IGFBP2 mRNA and protein localization in human tumors showed abnormal protein accumulation in the Golgi complex, mostly in PAX/FKHR-negative RMS. Moreover, an analysis of patients with RMS revealed the presence of conspicuous circulating levels of IGFBP2 proteins in children with highly aggressive RMS tumors. Taken together, our data provide evidence that IGFBP2 contributes to tumor progression and that it could be used as a marker to better classify clinical and biological risks in RMS.

Immunohistochemical expression and cluster analysis of mesenchymal and neural stem cell-associated proteins in pediatric soft tissue sarcomas

Pediatric undifferentiated soft tissue sarcomas (USTSs) are a group of malignancies composed predominantly of primitive round cell sarcomas, the histogenesis of which is uncertain. Thus, diagnosis and therapy remain a challenge. The aims of the current study were to determine whether differential expression of stem cell-associated proteins could be used to aid in determining the histogenesis of pediatric USTSs and to determine whether pediatric USTSs expressed a unique panel of stem cell-associated proteins to aid diagnosis. Tumors included 28 Ewing sarcoma/primitive neuroectodermal tumors (ESs), 22 embryonal rhabdomyosarcomas (ERMSs), 8 alveolar rhabdomyosarcomas (ARMSs), 5 synovial sarcomas (SSs), 5 malignant peripheral nerve sheath tumors (MPNSTs), and 13 USTSs. Stem cell antibodies included 3 mesenchymal stem cell markers (CD44, CD105, and CD166) and 5 neural stem cell markers (CD15, CD29, CD56, CD133, and nestin). Sections were scored followed by statistical analysis, clustering analysis, and visualizations using Partek Genomic Suite Software. The Euclidean clustering divided the tumors into 2 major groups. ESs and USTSs formed the majority of the 1st group, whereas ERMSs, ARMSs, MPNSTs, and SSs formed the 2nd group. Reduced expression of CD56 was strongly associated with the ES/USTS cluster (P < 0.0001). ESs and USTSs were further separated by CD166 staining, wherein increased expression was associated with ES (P < 0.0001). The 2nd group included the majority of other sarcomas, with no consistent separation between subtypes. The current study demonstrates the usefulness of applying stem cell markers to pediatric sarcomas and indicates that USTSs and ESs are closely related and may share a common histogenesis.

Laryngeal embryonal rhabdomyosarcoma in an adult - a case presentation in the eyes of geneticists and clinicians

1. Abstract

Targeting the insulin-like growth factor pathway in rhabdomyosarcomas: rationale and future perspectives

Rhabdomyosarcomas (RMS) are a heterogeneous group of tumors that share features of skeletal myogenesis and represent the most common pediatric soft tissue sarcoma. Even though significant advances have been achieved in RMS treatment, prognosis remains very poor for many patients. Several elements of the Insulin-like Growth Factor (IGF) pathway are involved in sarcomas, including RMS. The IGF2 ligand is highly expressed in most, if not all, RMS, and frequent overexpression of the receptor IGF1R is also found. This is confirmed here through mining expression profiling data of a large series of RMS samples. IGF signaling is implicated in the genesis, growth, proliferation, and metastasis of RMS. Blockade of this pathway is therefore a potential therapeutic strategy for the treatment of RMS. In this paper we examine the biological rationale for targeting the IGF pathway in RMS as well as the current associated preclinical and clinical experience.

Myogenesis and rhabdomyosarcoma the Jekyll and Hyde of skeletal muscle

Rhabdomyosarcoma, a neoplasm composed of skeletal myoblast-like cells, represents the most common soft tissue sarcoma in children. The application of intensive chemotherapeutics and refined surgical and radiation therapy approaches have improved survival for children with localized disease over the past 3 decades; however, these approaches have not improved the dismal outcome for children with metastatic and recurrent rhabdomyosarcoma. Elegant studies have defined the molecular mechanisms driving skeletal muscle lineage commitment and differentiation, and the machinery that couples differentiation with irreversible cell proliferation arrest. Further, detailed molecular analyses indicate that rhabdomyosarcoma cells have lost the capacity to fully differentiate when challenged to do so in experimental models. We review the intersection of normal skeletal muscle developmental biology and the molecular genetic defects in rhabdomyosarcoma with the underlying premise that understanding how the differentiation process has gone awry will lead to new treatment strategies aimed at promoting myogenic differentiation and concomitant cell cycle arrest.

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.

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.

Mice lacking dystrophin or alpha sarcoglycan spontaneously develop embryonal rhabdomyosarcoma with cancer-associated p53 mutations and alternatively spliced or mutant Mdm2 transcripts

Altered expression of proteins in the dystrophin-associated glycoprotein complex results in muscular dystrophy and has more recently been implicated in a number of forms of cancer. Here we show that loss of either of two members of this complex, dystrophin in mdx mice or alpha sarcoglycan in Sgca(-/-) mice, results in the spontaneous development of muscle-derived embryonal rhabdomyosarcoma (RMS) after 1 year of age. Many mdx and Sgca(-/-) tumors showed increased expression of insulin-like growth factor 2, retinoblastoma protein, and phosphorylated Akt and decreased expression of phosphatase and tensin homolog gene, much as is found in a human RMS. Further, all mdx and Sgca(-/-) RMS analyzed had increased expression of p53 and murine double minute (mdm)2 protein and contained missense p53 mutations previously identified in human cancers. The mdx RMS also contained missense mutations in Mdm2 or alternatively spliced Mdm2 transcripts that lacked an exon encoding a portion of the p53-binding domain. No Pax3:Fkhr or Pax7:Fkhr translocation mRNA products were evident in any tumor. Expression of natively glycosylated alpha dystroglycan and alpha sarcoglycan was reduced in mdx RMS, whereas dystrophin expression was absent in almost all human RMS, both for embryonal and alveolar RMS subtypes. These studies show that absence of members of the dystrophin-associated glycoprotein complex constitutes a permissive environment for spontaneous development of embryonal RMS associated with mutation of p53 and mutation or altered splicing of Mdm2.

Molecular and cellular biology of rhabdomyosarcoma

Rhabdomyosarcoma is a group of soft-tissue sarcomas that share features of skeletal myogenesis, but show extensive heterogeneity in histology, age and site of onset, and prognosis. This review matches recent molecular data with biological features of rhabdomyosarcoma. Alterations in molecular pathways, animal models, cell of origin and potential new therapeutic targets are discussed.

Pediatric genitourinary tumors

PURPOSE OF REVIEW

We will review the 2007/2008 literature on pediatric genitourinary tumors.

RECENT FINDINGS

Newly identified constitutional epigenetic defects in Wilms tumor genes extend the understanding of Wilms tumor risk in children lacking syndromic features, and add to the complexity of the pathogenesis of these tumor suppressor genes. Pediatric renal cell carcinoma has distinct molecular characteristics and clinical associations from the adult counterpart. The pathway from PAX3-FKHR translocation to the development of rhabdomyosarcoma tumors has been further elucidated.

SUMMARY

Therapeutic strategies continue to be driven by developments in molecular diagnostics in pediatric genitourinary tumors.