A biobank of pediatric patient-derived-xenograft models in cancer precision medicine trial MAPPYACTS for relapsed and refractory tumors

Pediatric patients with recurrent and refractory cancers are in most need for new treatments. This study developed patient-derived-xenograft (PDX) models within the European MAPPYACTS cancer precision medicine trial (NCT02613962). To date, 131 PDX models were established following heterotopical and/or orthotopical implantation in immunocompromised mice: 76 sarcomas, 25 other solid tumors, 12 central nervous system tumors, 15 acute leukemias, and 3 lymphomas. PDX establishment rate was 43%. Histology, whole exome and RNA sequencing revealed a high concordance with the primary patient's tumor profile, human leukocyte-antigen characteristics and specific metabolic pathway signatures. A detailed patient molecular characterization, including specific mutations prioritized in the clinical molecular tumor boards are provided. Ninety models were shared with the IMI2 ITCC Pediatric Preclinical Proof-of-concept Platform (IMI2 ITCC-P4) for further exploitation. This PDX biobank of unique recurrent childhood cancers provides an essential support for basic and translational research and treatments development in advanced pediatric malignancies.

Histone deacetylase inhibitor panobinostat induces antitumor activity in epithelioid sarcoma and rhabdoid tumor by growth factor receptor modulation

Background

Epithelioid sarcomas and rhabdoid tumors are rare, aggressive malignancies with poor prognosis. Both are characterized by INI1 alterations and deregulation of growth factor receptors albeit their interaction has not been elucidated.

Methods

In this study, we investigated the activity of a panel of epigenetic modulators and receptor tyrosine kinase inhibitors in vitro on respective cell lines as well as on primary patient-derived epithelioid sarcoma cells, and in vivo on xenografted mice. Focusing on histone deacetylase (HDAC) inhibitors, we studied the mechanism of action of this class of agents, its effect on growth factor receptor regulation, and changes in epithelial-to-mesenchymal transition by using cell- and RT-qPCR-based assays.

Results

Pan-HDAC inhibitor panobinostat exhibited potent anti-proliferative activity at low nanomolar concentrations in A204 rhabdoid tumor, and VAESBJ/GRU1 epithelioid sarcoma cell lines, strongly induced apoptosis, and resulted in significant tumor growth inhibition in VAESBJ xenografts. It differentially regulated EGFR, FGFR1 and FGFR2, leading to downregulation of EGFR in epithelioid sarcoma and to mesenchymal-to-epithelial transition whereas in rhabdoid tumor cells, EGFR was strongly upregulated and reinforced the mesenchymal phenotype. All three cell lines were rendered more susceptible towards combination with EGFF inhibitor erlotinib, further enhancing apoptosis.

Conclusions

HDAC inhibitors exhibit significant anticancer activity due to their multifaceted actions on cytotoxicity, differentiation and drug sensitization. Our data suggest that the tailored, tissue-specific combination of HDAC inhibitors with therapeutics which target cellular salvage mechanisms might increase their therapeutic relevance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08579-w.

ALK mutation dynamics and clonal evolution in a neuroblastoma model exhibiting two ALK mutations

The ALK gene is a major oncogene of neuroblastoma cases exhibiting ALK activating mutations. Here, we characterized two neuroblastoma cell lines established from a stage 4 patient at diagnosis either from the primary tumor (PT) or from the bone marrow (BM). Both cell lines exhibited similar genomic profiles. All cells in the BM-derived cell line exhibited an ALK F1174L mutation, whereas this mutation was present in only 5% of the cells in the earliest passages of the PT-derived cell line. The BM-derived cell line presented with a higher proliferation rate in vitro and injections in Nude mice resulted in tumor formation only for the BM-derived cell line. Next, we observed that the F1174L mutation frequency in the PT-derived cell line increased with successive passages. Further Whole Exome Sequencing revealed a second ALK mutation, L1196M, in this cell line. Digital droplet PCR documented that the allele fractions of both mutations changed upon passages, and that the F1174L mutation reached 50% in late passages, indicating clonal evolution. In vitro treatment of the PT-derived cell line exhibiting the F1174L and L1196M mutations with the alectinib inhibitor resulted in an enrichment of the L1196M mutation. Using xenografts, we documented a better efficacy of alectinib compared to crizotinib on tumor growth and an enrichment of the L1196M mutation at the end of both treatments. Finally, single-cell RNA-seq analysis was consistent with both mutations resulting in ALK activation. Altogether, this study provides novel insights into ALK mutation dynamics in a neuroblastoma model harbouring two ALK mutations.

In-Vitro and In-Vivo Establishment and Characterization of Bioluminescent Orthotopic Chemotherapy-Resistant Human Osteosarcoma Models in NSG Mice

Osteosarcoma, the most common bone malignancy with a peak incidence at adolescence, had no survival improvement since decades. Persistent problems are chemo-resistance and metastatic spread. We developed in-vitro osteosarcoma models resistant to chemotherapy and in-vivo bioluminescent orthotopic cell-derived-xenografts (CDX). Continuous increasing drug concentration cultures in-vitro resulted in five methotrexate (MTX)-resistant and one doxorubicin (DOXO)-resistant cell lines. Resistance persisted after drug removal except for MG-63. Different resistance mechanisms were identified, affecting drug transport and action mechanisms specific to methotrexate (RFC/SCL19A1 decrease, DHFR up-regulation) for MTX-resistant lines, or a multi-drug phenomenon (PgP up-regulation) for HOS-R/DOXO. Differential analysis of copy number abnormalities (aCGH) and gene expression (RNAseq) revealed changes of several chromosomic regions translated at transcriptomic level depending on drug and cell line, as well as different pathways implicated in invasive and metastatic potential (e.g., Fas, Metalloproteinases) and immunity (enrichment in HLA cluster genes in 6p21.3) in HOS-R/DOXO. Resistant-CDX models (HOS-R/MTX, HOS-R/DOXO and Saos-2-B-R/MTX) injected intratibially into NSG mice behaved as their parental counterpart at primary tumor site; however, they exhibited a slower growth rate and lower metastatic spread, although they retained resistance and CGH main characteristics without drug pressure. These models represent valuable tools to explore resistance mechanisms and new therapies in osteosarcoma.

Establishment and characterization of in vivo orthotopic bioluminescent xenograft models from human osteosarcoma cell lines in Swiss nude and NSG mice

Osteosarcoma is one of the most common primary bone tumors in childhood and adolescence. Metastases occurrence at diagnosis or during disease evolution is the main therapeutic challenge. New drug evaluation to improve patient survival requires the development of various preclinical models mimicking at best the complexity of the disease and its metastatic potential. We describe here the development and characteristics of two orthotopic bioluminescent (Luc/mKate2) cell‐derived xenograft (CDX) models, Saos‐2‐B‐Luc/mKate2‐CDX and HOS‐Luc/mKate2‐CDX, in different immune (nude and NSG mouse strains) and bone (intratibial and paratibial with periosteum activation) contexts. IVIS SpectrumCT system allowed both longitudinal computed tomography (CT) and bioluminescence real‐time follow‐up of primary tumor growth and metastatic spread, which was confirmed by histology. The murine immune context influenced tumor engraftment, primary tumor growth, and metastatic spread to lungs, bone, and spleen (an unusual localization in humans). Engraftment in NSG mice was found superior to that found in nude mice and intratibial bone environment more favorable to engraftment compared to paratibial injection. The genetic background of the two CDX models also led to distinct primary tumor behavior observed on CT scan. Saos‐2‐B‐Luc/mKate2‐CDX showed osteocondensed, HOS‐Luc/mKate2‐CDX osteolytic morphology. Bioluminescence defined a faster growth of the primary tumor and metastases in Saos‐2‐B‐Luc/mKate2‐CDX than in HOS‐Luc/mKate2‐CDX. The early detection of primary tumor growth and metastatic spread by bioluminescence allows an improved exploration of osteosarcoma disease at tumor progression, and metastatic spread, as well as the evaluations of anticancer treatments. Our orthotopic models with metastatic spread bring complementary information to other types of existing osteosarcoma models.

Dual inhibition using cabozantinib overcomes HGF/MET signaling mediated resistance to pan-VEGFR inhibition in orthotopic and metastatic neuroblastoma tumors

MET is expressed on neuroblastoma cells and may trigger tumor growth, neoangiogenesis and metastasis. MET upregulation further represents an escape mechanism to various anticancer treatments including VEGF signaling inhibitors. We developed in vitro a resistance model to pan-VEGFR inhibition and explored the simultaneous inhibition of VEGFR and MET in neuroblastoma models in vitro and in vivo using cabozantinib, an inhibitor of the tyrosine kinases including VEGFR2, MET, AXL and RET. Resistance in IGR-N91-Luc neuroblastoma cells under continuous in vitro exposure pressure to VEGFR1-3 inhibition using axitinib was associated with HGF and p-ERK overexpression. Cabozantinib exhibited anti-proliferative effects in neuroblastoma cells and reduced cell migration in vitro as measured by phase-contrast with IncuCyte system. In vivo, an enhanced number of animals with IGR-N91-Luc metastases was noted following axitinib treatment as compared to control animals. Orally administered cabozantinib per gavage at 30 and 60 mg/kg/day significantly inhibited tumor growth of orthotopic adrenal IGR-N91-Luc and metastatic IMR-32-Luc xenografts. Antitumor activity was associated with decreased vascularization, inhibition of p-SRC and induction of apoptotic cell death. Activation of the HGF-mediated MET pathway is involved in escape to selective VEGFR inhibition in neuroblastoma suggesting combined inhibition of MET and VEGFR signaling to reduce secondary resistance and enhanced invasiveness.

Iron Overload Exacerbates Busulfan-Melphalan Toxicity Through a Pharmacodynamic Interaction in Mice

PURPOSE

Busulfan-melphalan high-dose chemotherapy followed by autologous stem cell transplantation is an essential consolidation treatment of high-risk neuroblastoma in children. Main treatment limitation is hepatic veno-occlusive disease, the most severe and frequent extra-hematological toxicity. This life threatening toxicity has been related to a drug interaction between busulfan and melphalan which might be increased by prior disturbance of iron homeostasis, i.e. an increased plasma ferritin level.

METHODS

We performed an experimental study of busulfan and melphalan pharmacodynamic and pharmacokinetics in iron overloaded mice.

RESULTS

Iron excess dramatically increased the toxicity of melphalan or busulfan melphalan combination in mice but it did not modify the clearance of either busulfan or melphalan. We show that prior busulfan treatment impairs the clearance of melphalan. This clearance alteration was exacerbated in iron overloaded mice demonstrating a pharmacokinetic interaction. Additionally, iron overload increased melphalan toxicity without altering its pharmacokinetics, suggesting a pharmacodynamic interaction between iron and melphalan. Based on iron homeostasis disturbance, we postulated that prior induction of ferritin, through Nrf2 activation after oxidative stress, may be associated with the alteration of melphalan metabolism.

CONCLUSION

Iron overload increases melphalan and busulfan-melphalan toxicity through a pharmacodynamic interaction and reveals a pharmacokinetic drug interaction between busulfan and melphalan.

Polo-like Kinase Inhibitor Volasertib Exhibits Antitumor Activity and Synergy with Vincristine in Pediatric Malignancies

BACKGROUND

Polo-like kinase 1 (PLK1) controls the main cell-cycle checkpoints, suggesting utility of its inhibition for cancer treatment, including of highly proliferative pediatric cancer. This preclinical study explored the selective PLK1 inhibitor volasertib (BI 6727) alone and combined with chemotherapy in pediatric malignancies.

MATERIALS AND METHODS

Inhibition of proliferation was explored in vitro using dimethylthiazol carboxymethoxyphenyl sulfophenyl tetrazolium (MTS) assay. Mice bearing human xenografts were treated with weekly intravenous injections of volasertib.

RESULTS

Volasertib inhibited proliferation in all 40 cell lines tested, with a mean half-maximal growth inhibitory concentration of 313 nmol/l (range: 4-5000 nmol/l). Volasertib was highly active against RMS-1 alveolar rhabdomyosarcoma xenografts, resulting in 100% tumor regression. Activity was associated with complete and prolonged G2/M arrest and subsequent apoptotic cell death. Volasertib showed synergistic activity with vincristine but antagonistic effects with etoposide.

CONCLUSION

These findings support the further exploration of volasertib for pediatric malignancies, particularly alveolar rhabdomyosarcoma, and its combination with mitotic spindle poison.

Papillary glioneuronal tumors: histological and molecular characteristics and diagnostic value of SLC44A1-PRKCA fusion

INTRODUCTION

Papillary Glioneuronal Tumor (PGNT) is a grade I tumor which was classified as a separate entity in the World Health Organization Classification of the Central Nervous System 2007 in the group of mixed glioneuronal tumors. This tumor is rare and subclassifying PGNT represents a challenge. Recently, a fusion between SLC44A1 and PRKCA which encodes a protein kinase C involved in MAPK signaling pathway has been described in two studies (five cases). The current study aimed at raising the cytogenetic, histological and molecular profiles of PGNT and to determine if SLC44A1-PRKCA fusion represented a specific diagnostic marker to distinguish it from other glioneuronal tumors.

RESULTS

We report on four pediatric cases of PGNT, along with clinico-radiologic and immunohistological features for which SLC44A1-PRKCA fusion assessment by fluorescence in situ hybridization, BRAF V600E and FGFR1 mutation by immunohistochemistry and direct DNA sequencing and KIAA1549-BRAF fusion by RT-PCR were performed. MAPK signaling pathway activation was investigated using phospho-ERK immunohistochemistry and western blot. We analyzed fifteen cases of tumors with challenging histological or clinical differential diagnoses showing respectively a papillary architecture or periventricular location (PGNT mimics). fluorescence in situ hybridization analysis revealed a constant SLC44A1-PRKCA fusion signal in all PGNTs. None of PGNT mimics showed the SLC44A1-PRKCA fusion signal pattern. All PGNTs were negative for BRAF V600E and FGFR1 mutation, and KIAA1549-BRAF fusion. Phospho-ERK analysis provides arguments for the activation of the MAPK signaling pathway in these tumors.

CONCLUSIONS

Here we confirmed and extended the molecular data on PGNT. These results suggest that PGNT belong to low grade glioma with MAPK signaling pathway deregulation. SLC44A1-PRKCA fusion seems to be a specific characteristic of PGNT with a high diagnostic value and detectable by FISH.

Regorafenib: Antitumor Activity upon Mono and Combination Therapy in Preclinical Pediatric Malignancy Models

The multikinase inhibitor regorafenib (BAY 73-4506) exerts both anti-angiogenic and anti-tumorigenic activity in adult solid malignancies mainly advanced colorectal cancer and gastrointestinal stromal tumors. We intended to explore preclinically the potential of regorafenib against solid pediatric malignancies alone and in combination with anticancer agents to guide the pediatric development plan. In vitro effects on cell proliferation were screened against 33 solid tumor cell lines of the Innovative Therapies for Children with Cancer (ITCC) panel covering five pediatric solid malignancies. Regorafenib inhibited cell proliferation with a mean half maximal growth inhibition of 12.5 μmol/L (range 0.7 μmol/L to 28 μmol/L). In vivo, regorafenib was evaluated alone at 10 or 30 mg/kg/d or in combination with radiation, irinotecan or the mitogen-activated protein kinase kinase (MEK) inhibitor refametinib against various tumor types, including patient-derived brain tumor models with an amplified platelet-derived growth factor receptor A (PDGFRA) gene. Regorafenib alone significantly inhibited tumor growth in all xenografts derived from nervous system and connective tissue tumors. Enhanced effects were observed when regorafenib was combined with irradiation and irinotecan against PDGFRA amplified IGRG93 glioma and IGRM57 medulloblastoma respectively, resulting in 100% tumor regressions. Antitumor activity was associated with decreased tumor vascularization, inhibition of PDGFR signaling, and induction of apoptotic cell death. Our work demonstrates that regorafenib exhibits significant antitumor activity in a wide spectrum of preclinical pediatric models through inhibition of angiogenesis and induction of apoptosis. Furthermore, radio- and chemosensitizing effects were observed with DNA damaging agents in PDGFR amplified tumors.

Abstract 4537: Geranyloxy-ifosfamide: A pre-activated ifosfamide analogue showing an increased therapeutic index

Ifosfamide (IFO) is an alkylating agent used in routine clinical practices for treatment of cancer for many years. As a prodrug it requires cytochrome P450 bio-activation (Giraud et al. Expert Opin.Drug Metab. Toxicol. 2010, 6, 919-938) oxidising the position C-4 leading to the formation of the 4-HO-IFO (10%) which releases of the active compound (isophosphoramide mustard) responsible for the DNA cross links. However, during high dose protocols, this bio-activation leads to the release of two toxic metabolites: i) acrolein, an urotoxic compound, concomitantly generated with the active isophosphoramide mustard and, ii) chloroacetaldehyde, a neurotoxic and nephrotoxic compound, arising from the oxidation of the side chains (Kerbusch et al. Clin Pharmacokinet. 2001, 40, 41-62) responsible for limiting side-effects.

To circumvent these toxic side-effects, we have designed several pre-activated compounds by covalent binding of several O- and S-alkyl moieties on the carbon C-4 to avoid cytochrome bio-activation favoring the release of the 4-HO-IFO, control this release by the physico-chemical properties of the engrafted moiety and limit the chloroacetaldehyde release. Among these designed compounds, some showed a self assembling property leading to nano-assemblies formulation. Moreover, the in vitro evaluation of these compounds in absence of cytochrome has revealed that one of them: the geranyloxy-ifosfamide showed a greater activity under nano-assemblies (600nM) compared to the bulk form (15μM) on rhabdomyosarcoma. This interesting finding has led us to deepen our investigation of this compound to understand and explain the meaning of this increased activity. We present here the latest results obtained for this compound from additional in vitro evaluation on a wide panel of cancer cell line, internalization studies within the cell. Moreover, transmission electron microscopy imaging of this formulation allows the determination of the shape of these nano-assemblies. Previous studies regarding the release kinetic profile of 4-HO-IFO of this compound in vitro in mice plasma at 37°C showed an interesting release profile which was increased when tested as nano-assemblies compared to the bulk form. To validate this finding, a pharmacokinetic study has also been investigated compared to IFO, showing a higher release of 4-HO-IFO compound suggesting that this compound might have an increased therapeutic index. Also, in vivo studies are being carried out at different dose to evaluate the efficacy of this compound (as bulk and nano-assemblies) on rhabdomyosarcoma xenografted mice compared to IFO. These results increase acknowledge of this compound which could become a promising candidate for both oral and IV administration in a wide panel of tumors.

Citation Format: Charles Skarbek, Didier Desmaele, Alain Deroussent, Lea Lesueur, Estelle Daudigeos-Dubus, Ludivine Le Dret, Michael Rivard, Thierry Martens, Gilles Vassal, Patrick Couvreur, Angelo PACI. Geranyloxy-ifosfamide: A pre-activated ifosfamide analogue showing an increased therapeutic index. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4537. doi:10.1158/1538-7445.AM2015-4537

Establishment and characterization of new orthotopic and metastatic neuroblastoma models

BACKGROUND/AIM

Treatment of metastatic neuroblastoma remains a challenge in pediatric oncology. Relevant preclinical models may improve exploration of oncogenesis and new therapies. We developed new orthotopic and metastatic models derived from stage 4 neuroblastoma.

MATERIAL AND METHODS

Orthotopic and systemic models were established in BalbC Rag2(-/-)gammaC(-/-) mice following adrenal and intravenous injection of luciferase-transfected IMR-32 and IGR-N91 cells, respectively.

RESULTS

All four models exhibited 100% tumor take rate. Metastatic spread of orthotopic IMR-32-Luc cells was observed mainly to the lung, liver and bone; that of IGR-N91-Luc cells to liver, spleen and adrenals. Interestingly, systemic IMR-32-Luc cells metastasized rather to the lung, liver and bone, and IGR-N91-Luc to liver, lung, spleen and adrenals. Feasibility of non-invasive, real-time antitumor response evaluation was validated in the systemic models.

CONCLUSION

These neuroblastoma models with distinct patterns of metastatic spread represent relevant tools for exploring local and metastatic tumor cell tropism, mechanisms of spread and evaluating new cancer therapeutics.

Abstract 5671: Enhanced activity of pre-activated oxazaphosphorine prodrugs designed for drug delivery strategy: influence of the length of the engrafted group

Oxazaphosphorines are alkylating antineoplasic agents used in the treatment of cancer and have demonstrated activity against various tumor types, such as soft tissue sarcomas or lymphomas. Oxazaphosphorines are non-toxic prodrugs that require cytochrome P450 (CYP) bioactivation. In the case of Ifosfamide (IFO), the bioactivation produces the 4-OH-IFO, which after ring opening liberates the active nitrogen mustard displaying DNA cross-links. Associated toxicities of IFO are due to 1) acrolein, an urotoxic metabolite concomitantly generated with the nitrogen mustard and 2) chloroacetaldehyde, a neuro and nephrotoxic metabolite obtained by oxidation of the side chains (Kerbusch et al., 2001).

To circumvent these toxicities, we have designed pre-activated oxazaphosphorines through electrochemical oxidation and binding of various moieties such as O-alkyl groups and S-alkyl groups. IFO is activated by oxidation of position 4 with labile moieties leading to pre-activated cytotoxic entities. We observed physical-chemical characteristics leading to nano-assemblies depending on the length of the linked moieties, which could bring tissue specificity for drug delivery purposes. Some of these pre-activated prodrugs may be constitutive of drug delivery systems, such as nanoparticules, aiming to address alkylating moieties to their target.

We present here the use of different length moieties, from C1 (methoxy) to C30 (Squalenoyl, SQ) with intermediate length of C5 (Pentoxy) and C10 (Geranioxy and DimethylOctanoxy). These compounds are pre-activated formulation of IFO with C4-oxidation allowing to by-pass the CYP activation with direct release of 4-OH-IFO and then the alkylating mustard. Some of them, SQ-(O)-IFO, SQ-(S)-IFO and Geranioxy-IFO are able to self-assembly leading to nanoparticules. The length and nature of the engrafted moieties allow the study of the parameters that lead the kinetics of liberation of the activated compound.

The nanoparticules have been fully characterized with a mean diameter of 182 nm for SQ-(O)-IFO and SQ-(S)-IFO and 130 nm for Geranioxy-IFO. The cytotoxic activity of SQ-(O)-IFO and SQ-(S)-IFO has been studied in vitro on a panel of 15 human and murine cancer lines (RMS-1, RD, TC71, A673, SK-N-MC, UW 479, Lan-5, SAOS-2, IGR-OV1, MCF-7(MDR), A549, M109, KB 3.1, B16F10, MiaPaCa-2). The cytotoxic activity of Pentoxy-IFO, Geranioxy-IFO and DimethylOctanoxy-IFO has been studied in vitro on a panel of 2 human cancer lines (A673 and RMS-1). All IFO derivatives present high in vitro activity while IFO has no activity on these cells. This proves the pre-activated property of these new compounds and the lack of CYP activation requirements. Their therapeutic activity is currently studied in vivo on human Ewing sarcoma TC71 and human Lung cancer A549 xenografts in mice after i.v. administration. These compounds are now patented.

Citation Format: Charles Skarbek, Hubert Chapuis, Léa Lesueur, Michael Rivard, Thierry Martens, Didier Desmaele, Estelle Daudigeos-Dubus, Jean-Rémi Bertrand, Alain Deroussent, Gilles Vassal, Patrick Couvreur, Angelo Paci. Enhanced activity of pre-activated oxazaphosphorine prodrugs designed for drug delivery strategy: influence of the length of the engrafted group. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5671. doi:10.1158/1538-7445.AM2013-5671

Abstract 5702: NanoOxaza, pre-activated oxazaphosphorines prodrugs designed for drug delivery strategy with wide anticancer activity

The oxazaphosphorines belong to the alkylating drug class with a wide spectrum of antineoplasic activity. Ifosfamide (IFO) demonstrated activity against various tumour types, from soft tissue sarcomas to lymphomas both in adult and paediatric patients. Oxazaphosphorines are metabolised by cytochromes, leading to ring opening and subsequent production of active nitrogen mustards, which display DNA cross-links. Associated toxicities of IFO are due to 1) acrolein, a urotoxic metabolite concomitantly generated with the release of the alkylating mustard and 2) chloroacetaldehyde, a metabolite derived from oxidation of side chains of the molecule via the action of cytochrome P450 (CYP) known to be responsible for neurotoxicity and nephrotoxicity (Kerbusch et al., 2001). To circumvent the oxidative related-toxicities, we have designed pre-activated oxazaphosphorines. (Paci et al., 2001) through electrochemical oxidation and engraftment of various moieties such as O-alkyl groups (fatty acids, alcohols, polyols, or sugars) and S-alkyl (thionyl) groups. Actually, IFO is activated by substitution at position 4 with labile moieties leading to the release of the cytotoxic entity without enzyme activity. These moieties can bring tissue specificity or physico-chemical characteristics leading to nanoassemblies for drug delivery purposes. Some of these pre-activated prodrugs may be constitutive of drug delivery systems, such as nanoparticles, aiming to address alkylating moieties to their target. We present here the use of squalene conjugation as squalene-based drug delivery systems have been favourably used for drug delivery (Couvreur et al. 2006). The designed compounds, SQ-IFO and SQ-thioIFO, have then two interesting properties. First, they are pre-activated formulations of IFO with C4-oxidation allowing to by-pass the CYP activation with the direct release of the alkylating mustard. The second property is the described capacity of squalenic derivatives for self-assembly in aqueous medium leading to nanoparticles. The SQ-IFO and SQ-thioIFO nanoparticles have been fully characterized with a mean diameter of 182 nm when prepared at 1mg/mL in 5% Dextrose. The cytotoxic activity of these nanoassemblies has been studied in vitro on a panel of 9 human and murine cancer lines (A549, MCF-7, B16F10, M109, MiaPaCa-2, KB 3.1, SK-N-MC, UW 479, IGR-OV1). Squalenoyl IFO derivatives present high activity in vitro while IFO has no activity on these cells even it is used in clinical practices to treat these cancers. This proves the pre-activated property of these new compounds and the lack of CYP activation needs. Their therapeutic activity is currently studied in vivo on human Ewing sarcoma xenografts in mice after i.v. administration. These new formulations of IFO could constitute promising candidates for both oral and IV administration in a wide panel of tumours.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5702. doi:1538-7445.AM2012-5702

The selective VEGFR1-3 inhibitor axitinib (AG-013736) shows antitumor activity in human neuroblastoma xenografts

Tumor angiogenesis in childhood neuroblastoma is an important prognostic factor suggesting a potential role for antiangiogenic agents in the treatment of high-risk disease. Within the KidsCancerKinome project, we evaluated the new oral selective pan-VEGFR tyrosine kinase inhibitor axitinib (AG-013736) against neuroblastoma cell lines and the subcutaneous and orthotopic xenograft model IGR-N91 derived from a primary bone marrow metastasis. Axitinib reduced cell proliferation in a dose-dependent manner with IC(50) doses between 274 and >10,000 nmol/l. Oral treatment with 30 mg/kg BID for 2 weeks in advanced tumors yielded significant tumor growth delay, with a median time to reach five times initial tumor volume of 11.4 days compared to controls (p = 0.0006) and resulted in significant reduction in bioluminescence. Simultaneous inhibition of VEGFR downstream effector mTOR using rapamycin 20 mg/kg q2d×5 did not statistically enhance tumor growth delay compared to single agent activities. Axitinib downregulated VEGFR-2 phosphorylation resulting in significantly decreased microvessel density (MVD) and overall surface fraction of tumor vessels (OSFV) in all xenografts as measured by CD34 immunohistochemical staining (mean MVD ± SD and OSFV at 14 days 21.27 ± 10.03 in treated tumors vs. 48.79 ± 17.27 in controls and 0.56% vs. 1.29%; p = 0.0006, respectively). We further explored the effects of axitinib on circulating mature endothelial cells (CECs) and endothelial progenitor cells (CEPs) measured by flow cytometry. While only transient modification was observed for CECs, CEP counts were significantly reduced during and up to 14 days after end of treatment. Axitinib has potent antiangiogenic properties that may warrant further evaluation in neuroblastoma.

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

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