GX15-070 (Obatoclax), a Bcl-2 family proteins inhibitor engenders apoptosis and pro-survival autophagy and increases Chemosensitivity in neuroblastoma

Background

Neuroblastoma (NB) is a frequent pediatric tumor associated with poor prognosis. The disregulation of Bcl-2, an anti-apoptotic protein, is crucial for the tumoral development and chemoresistance. Autophagy is also implicated in tumor cell survival and chemoresistance. The aim of our study was to demonstrate therapeutic efficiency of GX 15–070, a pan-Bcl-2 family inhibitor, used alone and in combination with conventional drugs or with hydroxychloroquine (HCQ), an autophagy inhibitor.

Methods

Five neuroblastoma cell lines were tested for the cytotoxic activity of GX 15–070 alone or in combination with cisplatin, doxorubicin, HCQ or Z-VAD-FMK a broad-spectrum caspase inhibitor. Apoptosis and autophagy levels were studied by western-blot and FACS. Orthotopic injections were performed on NOD/LtSz-scid/IL-2Rgamma null mice that were treated with either GX 15–070 alone or in combination with HCQ.

Results

Synergistic cytotoxicity was observed for the drug combination in all of the 5 neuroblastoma cell lines tested, including MYCN amplified lines and in cancer stem cells. GX 15–070 significantly increased apoptosis and autophagy in neuroblastoma cells as evidenced by increased levels of the autophagy marker, LC3-II. Inhibition of autophagy by HCQ, further increased the cytotoxicity of this combinatorial treatment, suggesting that autophagy induced by these agent plays a cytoprotective role. In vivo, GX 15–070 combined with HCQ significantly decreased the growth of the tumor and the number of distant metastases.

Conclusions

Based on the synergistic effect of HCQ and GX 15–070 observed in this study, the combination of these two drugs may be utilized as a new therapeutic approach for neuroblastoma.

In vitro differentiated plasmacytoid dendritic cells as a tool to induce anti-leukemia activity of natural killer cells

Acute lymphoblastic leukemia (ALL) is believed to be resistant to NK cell-mediated killing. To overcome this resistance, we developed an innovative approach based on NK cell stimulation with Toll-like receptor (TLR)-activated plasmacytoid dendritic cells (pDC). The translation of this approach into the clinic requires the production of high numbers of human pDC. Herein, we show that in vitro differentiation of cord blood CD34+ progenitors in the presence of aryl hydrocarbon receptor antagonists gives rise to clinically relevant numbers of pDC, as about 108 pDC can be produced from a typical cord blood unit. Blocking the aryl hydrocarbon receptor (AHR) pathway significantly increased the yield of pDC. When compared to pDC isolated from peripheral blood, in vitro differentiated pDC (ivD-pDC) exhibited an increased capacity to induce NK cell-mediated killing of ALL. Although ivD-pDC produced lower amounts of IFN-α than peripheral blood pDC upon TLR activation, they produced more IFN-λ2, known to play a critical role in the induction of anti-tumoral NK cell functions. Both TLR-9 and TLR-7 ligands triggered pDC-induced NK cell activation, offering the possibility to use any clinical-grade TLR-7 or TLR-9 ligands in future clinical trials. Finally, adoptive transfer of ivD-pDC cultured in the presence of an AHR antagonist cured humanized mice with minimal ALL disease. Collectively, our results pave the way to clinical-grade production of sufficient numbers of human pDC for innate immunotherapy against ALL and other refractory malignancies.

Autophagy is associated with chemoresistance in neuroblastoma

Background

Neuroblastoma (NB) is a frequent pediatric tumor characterized by a poor prognosis where a majority of tumors progress despite intensive multimodality treatments. Autophagy, a self-degradative process in cells, could be induced by chemotherapy and be associated with chemoresistance. The aim of this study was to determine whether: 1) autophagy is present in NB, 2) chemotherapy modified its levels, and 3) its inhibition decreased chemoresistance.

Methods

Immunohistochemical stainings were performed on samples from 184 NB patients in order to verify the expression of LC3B, a specific marker for autophagy, and Beclin 1, a positive regulator of autophagy. In addition, we performed an in vitro study with six NB cell lines and six drugs (vincristine, doxorubicin, cisplatin temozolomide, LY294002 and syrolimus). Inhibition of autophagy was performed using ATG5 knockdown cells or hydroxychloroquine (HCQ). Cell survival was measured using the MTT cell proliferation assay. Autophagy was detected by monodansylcadaverine, confocal microscopy and Western blot. In vivo study with tumor xenografts in NSG mice was performed.

Results

Our results have indicated that autophagy was present at low levels in NB and was not a prognostic factor, while Beclin 1 was highly expressed in children with poor NB prognosis. However, autophagy levels increased after chemotherapy in vitro and in vivo. Tumor progression was significantly decreased in mice treated with a combination of HCQ and vincristine.

Conclusions

Taken together, autophagy is present in NB, induced by chemotherapy and associated with chemoresistance, which is significantly reduced by its inhibition. Therefore, targeting autophagy represents a very attractive approach to develop new therapeutic strategies in NB.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2906-9) contains supplementary material, which is available to authorized users.

Targeting apoptosis and autophagy by a novel bcl-2 inhibitor, GX15-070, in neuroblastoma

10048

Background: Neuroblastoma (NB) is a frequent pediatric tumor with poor prognosis. The disregulation of the anti-apoptotic protein Bcl-2 is crucial for the tumoral development and chemoresistance. Autophagy is also implicated in tumor cell survival and chemoresistance. The aim of our study was to demonstrate the in vitro and in vivo therapeutic efficiency of GX 15-070, a Bcl-2 inhibitor, used alone and in combination with conventional drugs used in the treatment of NB and hydroxychloroquine (HCQ), a known autophagy inhibitor. Methods: Using 6 NB cell lines, cell viability (MTT) assays were done at progressively increased concentrations of GX 15-070 alone or in combination with cisplatin or with Z-VAD-FMK, a broad-spectrum caspase inhibitor. Apoptosis was tested by evaluating the cleavage of caspase 3 by western blots (WB) and the Annexin V/7-AAD staining studied by FACS. To assess if autophagy was modified by GX 15-070, the cleavage of LC3 protein was tested by WB and cell survival were tested with combination of GX 15-070 and HCQ. To verify the anti-tumor activity in vivo of GX 15-070, orthotopic injections were made on NSG mice treated with GX 15-070 alone and in combination with HCQ. Results: It was observed a high sensitivity of the NB cells to GX 15-070 with increase of cell death and a potential synergistic of this molecule when it’s combined with cisplatin or HCQ. This cell death was due to apoptosis and may also be inhibited by Z-VAD-FMK. GX 15-070 alone or associated to cisplatin increased the autophagy. The in vivo study showed that GX 15-070 treatment used alone or in combination with HCQ significantly decreased the size of the tumor. Conclusions: Our results support the interest of GX 15-070 in the treatment of NB alone or in combination with classical drugs. Our studies also support that activation of apoptosis associated with inhibition of autophagy have a synergistic potential against tumoral progression and must have to be considered in further mechanistic studies for the optimization of more efficient combined therapies in the treatment of NB.

Abstract 3774: Regulation of the pro-invasive properties of neuroblastoma-stem cells by membrane type-1 matrix metalloproteinase

Neuroblastoma (NB) is an aggressive childhood cancer that represents the leading cause of cancer deaths in children. Despite aggressive therapy, more than half of the children with advanced NB usually die because of uncontrolled metastatic disease. In order to develop new therapeutic strategies to limit NB's metastatic potential, it is crucial to identify key molecular targets governing the invasive process. The study of Cancer stem cells (CSCs) may be of interest in this regard because after chemotherapy, CSCs persist in tumors and cause relapse and metastasis. We had recently demonstrated that CD133 allowed to detect CSCs in NB. Membrane type-1 matrix metalloproteinase (MT1-MMP) is important in the metastatic process and its expression was correlated with unfavourable outcome in NBs. Our preliminary data had indicated that MT1-MMP was highly expressed in CD133high NB.

The purpose of this study is to characterize the interaction between CD133 and MT1-MMP in NB and determinate the role of MT1-MMP in pro-invasive properties of CSCs. We constructed paraffin-embedded blocks of tissue microarrays (TMA) from 235 patients. In vitro experiments were performed on four established NB cell lines (SK-N-DZ, SK-N-FI and SK-N-SH and SJNB-10). We performed immunohistochemical studies on paraffin-embedded TMA sections with two antibodies (CD133, MT1-MMP). To verify correlation of expression of MT1-MMP and CD133, we realized western blot and immunofluorescence (IF) of both proteins in non treated versus treated NB cell lines. CD133high NB cells were isolated by flow cytometry. CD133high and CD133low NB cells were grown within a 3D collagen matrix and the cell migration assay was tested in collagen-coated transwells. All experiments were performed with or without an anti-MT1-MMP neutralizing antibody or GM6001, a broad-spectrum MMP inhibitor.

To assess the interaction between CD133 and MT1-MMP, lysates were subjected to immunoprecipitation (IP) using an anti-CD133 antibody, followed by immunodetection with an anti-MT1-MMP antibody. Finally, we determined which domain of MT1-MMP is involved in its interaction with CD133. Different dominant negative mutants of MT1-MMP (catalytically inactive E240A, cytoplasmic domain-deleted CΔ20 and non-phosphorylatable Y573F) were transfected into NB cells followed by an IP.

There is a correlation between MT1-MMP and CD133 expressions in tumors of patients and in cell lines. Cells selected after chemotherapy express both CD133 and MT1-MMP. CD133high cells presented higher migration and invasion properties than CD133low which were MT1-MMP dependent. IF and IP showed a colocalization and interaction between CD133 and MT1-MMP. The cytoplasmic domain of MT1-MMP seems to be responsible for the interaction with CD133.

These results contribute to a better understanding CSCs properties in NB and may be of great interest to improve new therapeutic strategies.

Citation Format: Assila Belounis, Carine Nyalendo, Sonia Cournoyer, Sarah Hadj-Mimoune, Alexandre Benoit, Elliot Lasalle, Jonathan Girard, Mona Beaunoyer, Pierre Teira, Hervé Sartelet. Regulation of the pro-invasive properties of neuroblastoma-stem cells by membrane type-1 matrix metalloproteinase. [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 3774. doi:10.1158/1538-7445.AM2013-3774

Preclinical study of a PARP inhibitor in neuroblastoma

9570

Background: Neuroblastoma (NB) is the most common extracranial solid tumor of childhood. In spite of many therapeutic improvements, only 60% survive long term despite aggressive combinations of multi-agent chemotherapy. In previous studies, we have demonstrated that tumor initiating cells (TIC) expressing CD133 (CD133high) in NB are more resistant to chemotherapy. Moreover, these cells express higher levels of PARP-1, a central protein involved in DNA repair. PARP-1 expression is significantly lower in NB usually showing spontaneous regression than in standard NB, suggesting an implication of PARP-1 in NB progression. The objective of this study is to determine the efficacy in vitro of AG-014699 (AG), a PARP- inhibitor, used in monotherapy or in combination to cisplatine (CP) and doxorubicine (DR), classical chemotherapeutic agents used in NB treatment, on NB cell survival. Methods: Six NB cell lines (parental or CD133high purified by flow cytometry (FACS)) were treated with AG alone or in association to CP or DR. PARP-1 ELISA protein assay was used to determine the optimal drug concentration needed to inhibit the protein. Cell survival was measured by MTT test. Western Blots were done to evaluate any apoptotic or autophagic pathway modulations. Quantification of DNA damage in treated cell was done by immunofluorescence of H2A-X protein. Results: We showed that a 4µM concentration of AG is sufficient for PARP-1 inhibition. One third of celllines presented a sensitivity to AG when used in monotherapy with an IC50 lower than 5µM. However, AG demonstrated synergistic effects when associated to DR, decreasing the IC50 by half, although none is observed when combined to CP. Sentitivity of the TIC did not appear to be more important than the bulk cells. With increasing concentration of AG, our WB showed no increase in cleaved Caspase-3 suggesting no modulation of the apoptotic pathway. However, autophagy seemed to be upregulated confirmed by an increase in cleaved LC3 II protein. Double strand breaks increased 2.5 folds when 4µM AG is added to the IC50 of DR. Conclusions: AG used in combination at potentially therapeutic doses shows promising results in NB. These results will allow for the improvement of NB treatments by introducing a new therapeutic strategy.

Preclinical study of a Bcl-2 inhibitor in neuroblastoma

9563

Background: Neurblastoma (NB) is the most common and deadly extracranial solid tumor of childhood. This malignant tumor exhibits a broad spectrum of clinical features, including spontaneous regression or maturation without any treatment or progression to metastisis leading to death. However, in spite of many therapeutic improvements, only 60% survive long term. In fact, 40% of patients with high-risk NB still relapse and eventually die of the disease despite aggressive combinations of multi-agent chemotherapy. In those cases, new therapeutic strategies must be developed. Studies have shown that BCl-2, a central anti-apoptotic protein, is over-expressed in NB. Although Bcl-2 is not a significant prognostic factor in NB, its increased expression would contribute to chemotherapy resistance. BCl-2 is also shown to be involved in the modulation of autophagy by inhibiting Beclin-1. Therefore, BCl-2 protein represents an attractive target for new therapeutic strategies in NB.The objective of this study is to determine the efficacy in vitro of Obatoclax (OB), a BCl-2 inhibitor, used in monotherapy or in combination to cisplatine (CP), a classical chemotherapeutic agent used in NB treatment, on NB cell survival. Methods: Six NB cell lines (SK-N-DZ, SK-N-FI, SK-N-SH, N91, NB8 and NB10) were treated with OB alone or in association to CP. Cell survival was measured by MTT test. Autophagy was measured by MDC test. Western Blots (WB) were done to evaluate the modulation of apoptotic and autophagic pathways in treated cells. Results: OB used in monotherapy shows promising results on NB cell lines with an average IC50 of 0.12µM. Also, OB demonstrates synergistic effects when associated to CP. The IC50 of CP treated cells varied from 3.183µM to 6.837µM but dropped from 0.003µM to 0.008µM when combined with 0.5µM of OB. Moreover, our WB show an increase in cleaved Caspase-3 and PARP-1 expression, suggesting an upregulation of apoptosis in treated cells. Autophagy is also upregulated confirmed by an increase in autophagic vacuoles and cleaved LC3 II protein. Conclusions: OB used in monotherapy or in combination at potentially therapeutic doses shows promising results in NB. These results will allow for the improvement of NB treatments by introducing a new therapeutic strategy.

Genotype analysis of tumor-initiating cells expressing CD133 in neuroblastoma

Neuroblastoma (NB) is the most common and lethal extracranial solid tumor of childhood. Despite aggressive therapy, more than half of the children with advanced NB will die of uncontrolled metastatic disease. After chemotherapy, tumor-initiating cells (TICs) could persist, cause relapses and metastasis. The aim of this study is to demonstrate the tumor-initiating properties of CD133high NB cells and to identify new specific genetic abnormalities. Isolation of the CD133high cell population from NB cell lines was followed by neurosphere formation, soft agar assays, and orthotopic injections in NOD/SCID/IL2Rγc-null mice. A differential genotyping analysis was performed with Affymetrix SNP 6.0 arrays on CD133low and CD133high populations and the frequency of the abnormalities of 36 NB tumors was determined. Our results show that CD133high NB cells possess tumor-initiating properties, as CD133high cells formed significantly more neurospheres and produced significantly more colonies in soft agar than CD133low. Injection of 500 CD133high cells was sufficient to generate primary tumors and frequent metastases in mice. Differential genotyping analysis demonstrated two common regions with gains (16p13.3 and 19p13.3) including the gene EFNA2 in the CD133high population, and two with loss of heterozygosity (16q12.1 and 21q21.3) in the CD133low population. The gain of EFNA2 correlated with increased expression of the corresponding protein. These abnormalities were found in NB samples and some were significantly correlated with CD133 expression. Our results show that CD133high NB cells have TICs properties and present different genotyping characteristics compared to CD133low cells. Our findings reveal insights into new therapeutic targets in NB TICs.

Abstract 2477: Autophagy is correlated with chemoresistance in neuroblastoma

Neuroblastoma (NB) is a frequent pediatric tumor. After combined treatments of chemotherapy, bone marrow transplantation, surgery and/or radiotherapy, metastatic NBs still have a poor prognosis. Therefore, finding new therapeutic strategies to increase the survival rate of patients with NB is essential. Autophagy is a self-degradative process induced primarily by starvation and, with the intermediate of lysosomes, damaged macromolecules and cell organelles are degraded. This degradation insures cell survival by adapting to stress conditions. In addition, recent studies proposed that autophagy may contribute to cancer resistance to chemotherapy and radiotherapy. However, in some circumstances, autophagy can induce non-apoptotic programmed cell death. The aim of this study is to determine how autophagy is regulated and whether it is associated with chemoresistance in NB. Firstly, tissue Microarray blocks containing 184 patients NB were used for an immunohistochemistry study in order to identify the expression of LC3, a cytosolic protein required for autophagic vacuole (autophagosome) formation, and beclin 1, a positive regulator of autophagy. Secondly, in vitro and in vivo (NOD/SCID/IL2Rαc-null mice) studies were performed to determine the level of autophagy in NB cells following chemotherapy. Finally, autophagy was inhibited in NB cells with shRNA targeting Atg5 (an essential protein for autophagy) or with hydroxychloroquine (HCQ), a pharmacological inhibitor of autophagy. NB cells were further treated with conventional drugs used in NB treatments to evaluate if they retain their ability to resist to chemotherapy. Cell survival was measured using MTT cell proliferation assay. Autophagy was detected by labelling the autophagic vacuoles with monodansylcadaverine (MDC) and by Western blot analysis of LC3 cleavage and Atg5 expression. Our study demonstrated that autophagy is present at low levels in a majority of NB. LC3 expression was not correlated with any clinical pathological data. On the other hand, Beclin1 expression in NB was higher in children older than one year of age who have a poor prognosis. Also, it had a higher level in primitive tumors than in metastases. In our in vitro and in vivo studies, autophagy, which was detected by cleavage of LC3 and by MDC test, was correlated with increasing concentrations of therapeutic agents. Interestingly, inhibition of autophagy with either Atg5 shRNA or HCQ strongly increased the sensitivity of NB cells to chemotherapy.Overall, these results suggest that autophagy contributes to NB cells resistance to chemotherapy. Therefore, inhibition of autophagy in combination with current treatments may be of great interest in order to improve therapeutic strategies of NB.

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 2477. doi:1538-7445.AM2012-2477