A Canadian paediatric brain tumour consortium (CPBTC) phase II molecularly targeted study of imatinib in recurrent and refractory paediatric central nervous system tumours

PURPOSE: To evaluate the safety, efficacy and pharmacokinetics of imatinib in children with recurrent or refractory central nervous system (CNS) tumours expressing KIT and/or PDGFRA. METHODS: Nineteen patients aged 2-18 years, with recurrent or refractory CNS tumours expressing either of the target receptors KIT and/or PDGFRA (by immunohistochemistry) were eligible. Participants received imatinib orally at a dose of 440 mg/m(2)/day and toxicities and tumour responses were monitored. Serial blood and cerebrospinal fluid samples for pharmacokinetics were obtained in a subset of consenting patients. Frozen tumour samples were analysed retrospectively for KIT and PDGFRA gene amplification in a subset of patients for whom samples were available. RESULTS: Common toxicities were lymphopaenia, neutropaenia, leucopaenia, elevated serum transaminases and vomiting. No intratumoural haemorrhages were observed. Although there were no objective responses to imatinib, four patients had long-term stable disease (SD) (38-104 weeks). Our results suggest a possible relationship between KIT expression and maintenance of SD with imatinib treatment; KIT immunopositivity was seen in only 58% (11/19) of study participants overall, but in 100% of patients with SD at 38 weeks. All patient tumours showed PDGFRA expression. Pharmacokinetic data showed a high interpatient variability, but corresponded with previously reported values. CONCLUSIONS: Imatinib at 440 mg/m(2)/day is relatively safe in children with recurrent CNS tumours, but induced no objective responses. Demonstration of SD in previously progressing patients (KIT-expressing) suggests cytostatic activity of imatinib.info:eu-repo/semantics/publishedVersio

Selective targeting of neuroblastoma tumour-initiating cells by compounds identified in stem cell-based small molecule screens

Neuroblastoma (NB) is the most deadly extra-cranial solid tumour in children necessitating an urgent need for effective and less toxic treatments. One reason for the lack of efficacious treatments may be the inability of existing drugs to target the tumour-initiating or cancer stem cell population responsible for sustaining tumour growth, metastases and relapse. Here, we describe a strategy to identify compounds that selectively target patient-derived cancer stem cell-like tumour-initiating cells (TICs) while sparing normal paediatric stem cells (skin-derived precursors, SKPs) and characterize two therapeutic candidates. DECA-14 and rapamycin were identified as NB TIC-selective agents. Both compounds induced TIC death at nanomolar concentrations in vitro, significantly reduced NB xenograft tumour weight in vivo, and dramatically decreased self-renewal or tumour-initiation capacity in treated tumours. These results demonstrate that differential drug sensitivities between TICs and normal paediatric stem cells can be exploited to identify novel, patient-specific and potentially less toxic therapies

Tissue Microenvironment Modulates CXCR4 Expression and Tumor Metastasis in Neuroblastoma

Neuroblastoma (NB) is derived from intrinsic migratory neural crest cells and has a high potential for distant metastasis. Growing evidence has implicated chemokine receptors, especially CXCR4, which normally control immune and inflammatory cell migration, as having important roles in tumor progression. In this study, we investigated the expression of CXCR4 in eight different NB cell lines and found that CXCR4 expression is dynamically regulated in NB and can be modulated by different tissue stromata. In addition, we demonstrate that IL-5 and IFN-γ are released from stromal cells and act as differential mediators for CXCR4 expression. We also overexpressed CXCR4 in two NB cell lines, NUB-7 and SK-N-BE(2), and studied the role of CXCR4 in NB metastasis both in vitro and in vivo. In vitro transwell invasion assay showed that CXCR4 overexpression promoted NB cell migration preferentially toward a bone marrow stromal cell-conditioned medium. Using an in vivo xenograft model, CXCR4-overexpressing cells showed an increased incidence of metastasis, most notably bone marrow metastasis. Our studies reveal critical roles for CXCR4 in NB metastasis and provide insights into the regulatory mechanism of chemokine receptors in NB and the importance of the tissue microenvironment in modulating tumor cell behavior

Pediatr Blood Cancer Treatment With Topotecan Plus Cyclophosphamide in Children With First Relapse of Neuroblastoma

INTRODUCTION Over the past decade the survival for children with high-risk neuroblastoma has improved. However, approximately half of highrisk patients either progress during initial therapy or recur following autologous stem cell transplant Topoisomerase I inhibitors, including the camptothecin derivatives topotecan and irinotecan At the Hospital for Sick Children between 1999 and 2009, in the absence of an open phase II clinical trial, our standard of care regimen for children with first recurrence or refractory neuroblastoma (hereafter termed "first relapse") was TOPO/CTX administered for up to 2 years. As per COG P9642, the chemotherapy was delivered over 5 days consecutively every 3 weeks in an outpatient setting, thus avoiding the need for hospitalizations other than for Background: Reports of responses and toxicities of salvage therapies for relapsed neuroblastoma are rare and often confounded by effects of additional treatments. Our objective was to describe the outcomes and toxicities for a topotecan and cyclophosphamide (TOPO/CTX) regimen for first relapse or progression of high-risk neuroblastoma. Methods: We retrospectively reviewed charts of relapsed or refractory neuroblastoma patients treated between 1999 and 2009 with our standard-of-care outpatient TOPO/CTX (0.75 and 250 mg/

Tumor Dynamics in Response to Antiangiogenic Therapy with Oral Metronomic Topotecan and Pazopanib in Neuroblastoma Xenografts

Metronomic chemotherapy, combined with targeted antiangiogenic drugs, has demonstrated significant anticancer efficacy in various studies. Though, tumors do acquire resistance. Here, we have investigated the effect of prolonged therapy with oral metronomic topotecan and pazopanib on tumor behavior in a neuroblastoma mouse xenograft model. SK-N-BE(2) xenograft-bearing mice were treated with either of the following regimens (daily, orally): vehicle (control), 150 mg/kg pazopanib, 1.0 mg/kg topotecan, and combination of topotecan and pazopanib. Planned durations of treatment for each regimen were 28, 56, and 80 days or until the end point, after which animals were sacrificed. We found that only combination-treated animals survived until 80 days. Combination halted tumor growth for up to 50 days, after which gradual growth was observed. Unlike single agents, all three durations of combination significantly lowered microvessel densities compared to the control. However, the tumors treated with the combination for 56 and 80 days had higher pericyte coverage compared to control and those treated for 28 days. the proliferative and mitotic indices of combination-treated tumors were higher after 28 days of treatment and comparable after 56 days and 80 days of treatment compared to control. Immunohistochemistry, Western blot, and real-time polymerase chain reaction revealed that combination treatment increased the hypoxia and angiogenic expression. Immunohistochemistry for Glut-1 and hexokinase II expression revealed a metabolic switch toward elevated glycolysis in the combination-treated tumors. We conclude that prolonged combination therapy with metronomic topotecan and pazopanib demonstrates sustained antiangiogenic activity but also incurs resistance potentially mediated by elevated glycolysis.Queen Elizabeth II/Dr Dina Gordon Malkin Scholarship in Science and TechnologyJames Fund for Neuroblastoma ResearchHosp Sick Children, Div Hematol & Oncol, Dept Pediat, Toronto, ON M5G 1X8, CanadaUniv Toronto, Inst Med Sci, Toronto, ON, CanadaHosp Sick Children, Dept Pediat Lab Med, Toronto, ON M5G 1X8, CanadaUniversidade Federal de São Paulo, Oncol Sect, Dept Pediat, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Morphol & Genet, Div Genet, São Paulo, BrazilUniversidade Federal de São Paulo, Oncol Sect, Dept Pediat, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Morphol & Genet, Div Genet, São Paulo, BrazilWeb of Scienc