Clinical strategies for the treatment of neuroblastoma

Nanocarrier-mediated targeting of tumor and tumor vascular cells improves uptake and penetration of drugs into neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in children, accounting for about 8% of childhood cancers. Despite aggressive treatment, patients suffering from high-risk NB have very poor 5-year overall survival rate, due to relapsed and/or treatment-resistant tumors. A further increase in therapeutic dose intensity is not feasible, because it will lead to prohibitive short-term and long-term toxicities. New approaches with targeted therapies may improve efficacy and decrease toxicity. The use of drug delivery systems allows site specific delivery of higher payload of active agents associated with lower systemic toxicity compared to the use of conventional (“free”) drugs. The possibility of imparting selectivity to the carriers to the cancer foci through the use of a targeting moiety (e.g., a peptide or an antibody) further enhances drug efficacy and safety. We have recently developed two strategies for increasing local concentration of anti-cancer agents, such as CpG-containing oligonucleotides, small interfering RNAs, and chemotherapeutics in NB. For doing that, we have used the monoclonal antibody anti-disialoganglioside (GD₂), able to specifically recognize the NB tumor and the peptides containing NGR and CPRECES motifs, that selectively bind to the aminopeptidase N-expressing endothelial and the aminopeptidase A-expressing perivascular tumor cells, respectively. The review will focus on the use of tumor- and tumor vasculature-targeted nanocarriers to improve tumor targeting, uptake, and penetration of drugs in preclinical models of human NB.

Synthesis and characterization of new copper thiosemicarbazone complexes with an ONNS quadridentate system: cell growth inhibition, S-phase cell cycle arrest and proapoptotic activities on cisplatin-resistant neuroblastoma cells

Two new copper thiosemicarbazone complexes with an ONNS quadridentate system were synthesized and evaluated for anticancer activity on cisplatin-resistant neuroblastoma cells. Among these two copper complexes, the substituted 8-hydroxyquinoline-2-carboxaldehyde-4,4-dimethyl-3-thiosemicarbazide (CuHQDMTS) exhibited stronger cell growth inhibition activity than the unsubstituted copper 8-hydroxyquinoline-2-carboxaldehyde thiosemicarbazide complex (CuHQTS). Both CuHQTS and CuHQDMTS showed dose-dependent cell growth inhibition, cell cycle arrest and apoptosis induction activities on the SK-N-DZ neuroblastoma cells. Increased expression of p53 protein molecules was detected in the SK-N-DZ cells treated with CuHQTS. The data obtained in this study suggest that CuHQDMTS and CuHQTS hold potential as new, effective drugs for treatment of refractory neuroblastoma in children.

Synthesis, Structure, and Anticancer Activity of Gallium(III) Complexes with Asymmetric Tridentate Ligands: Growth Inhibition and Apoptosis Induction of Cisplatin-Resistant Neuroblastoma Cells

Five gallium(III) complexes described as [Ga(III)(LX)2]ClO4, where (LX)- is the deprotonated form of a series of asymmetric ligands containing pyridine and 4,6-substituted phenol moieties, were synthesized and characterized by spectroscopic and spectrometric methods. Phenol substituents encompass the electron-withdrawing and electron-donating methoxy (1), nitro (2), chloro (3), bromo (4), and iodo (5) groups. Complexes 1 and 3 have had their molecular structure solved by X-ray crystallography and show distinct coordination modes. Complexes 1-5 were tested for growth-inhibition activity on cisplatin-resistant human neuroblastoma cells; those containing halogen substituents on the phenolate rings, i.e., 3-5, showed activity superior to that observed for cisplatin and induced apoptosis of neuroblastoma cells. Nitro-containing 2 suppressed proliferation of the neuroblastoma cells but induced apoptosis less effectively.

In vitro and In vivo Antitumor Activity of the Novel Derivatized Polyvinyl Alcohol-Based Polymer P10(4)

PURPOSE

The major limitation to successful chemotherapy of neuroblastoma is the toxicity of traditional antitumor drugs. Hence, less toxic and more effective drugs are to be found, and novel formulations of conventional compounds allowing a more favorable biodistribution should be sought for. In an attempt to pursue this task, we recently synthesized an amphiphilic polymer based on a polyvinyl alcohol backbone [P10(4)].

EXPERIMENTAL DESIGN

The cytotoxic activity of P10(4) was evaluated both in vitro on neuroblastoma and melanoma cell lines and in vivo in pseudometastatic neuroblastoma models. Apoptosis was assessed by morphology, cytofluorimetric analysis of DNA content, and DNA fragmentation assay. Caspases activation was investigated by kits specific for caspase-1, caspase-2, caspase-3, caspase-4, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, and caspase-13. Colony formation was evaluated by soft agar assay.

RESULTS

P10(4) exerted a potent cytotoxic activity on different neuroblastoma and melanoma cell lines through induction of both extrinsic and intrinsic caspase cascades and subsequent apoptosis. Moreover, the clonogenic potential of cells that survived P10(4) treatment was strongly reduced. Next, we tested the effects of P10(4) in nude mice injected with both a human and a murine neuroblastoma cell lines i.v. P10(4) significantly increased the life span and the long-term survival of treated mice over controls. No side effects were observed, even at doses higher than those used for therapeutic purposes.

CONCLUSIONS

Our data suggest that P10(4) holds promise as an anticancer compound and, because of its lack of interaction with DNA, is unlikely to give rise to drug resistance.

Surgical challenges associated with intensive treatment protocols for high-risk neuroblastoma

BACKGROUND

High-risk neuroblastoma (NB; age, >1 year; INSS stage 4) is associated with a poor outcome. At our institution, the current dose-intensive high-risk Children's Oncology Group protocol for advanced NB appears to have a higher surgical complication rate as compared with previous protocols.

METHODS

All stage 4 patients (n = 51) entered in high-risk protocols between 1995 and 2005 were analyzed. Patients in the current high-risk protocol, Children's Oncology Group A3973 (n = 22), were compared with those in the 2 previous protocols, CCG 3891 and POG 9341 (n = 29).

RESULTS

Patients were comparable in their mean age and tumor markers, including Shimada histology, MYCN amplification, 1p deletion, tumor origin, and extent of metastasis. However, transfusion requirement (86% vs 45%; P = .0019), postoperative infection rate (32% vs 3%; P = .02), and other postoperative issues including nutritional support (45% vs 3%; P = .0001) were significantly higher with the current protocol. No perioperative mortality was noted in either group, and the extent of resectability and margins were similar. Importantly, with the current protocol, the survival rate was higher (P = .0022) and the recurrence rate was significantly lower (P = .0003).

CONCLUSIONS

Despite higher surgical morbidity associated with the current high-risk protocol (2.59 vs 0.86 complications/person; P < .01), the recurrence rate is lower and interim survival rate is improved for patients with high-risk NB. Therefore, the higher surgical complication rates associated with the current high-risk protocol are acceptable.

Anti-neuroblastoma effect of ch14.18 antibody produced in CHO cells is mediated by NK-cells in mice

Successful treatment of stage 4 neuroblastoma remains a major challenge in pediatric oncology. In order to improve the outcome, passive immunotherapy using human-mouse chimeric monoclonal anti-disialoganglioside GD2 antibody ch14.18 has been evaluated in early phase clinical trials with promising results in progressing stage 4 neuroblastoma patients. In preparation of European phase III clinical trial (HR-NBL-1/ESIOP), the cell line used for production of ch14.18 was changed. Specifically, the plasmid encoding for ch14.18 antibody was recloned into CHO cells. Here, we report the in vitro and in vivo anti-neuroblastoma activity of antibody ch14.18 produced in CHO cells (ch14.18/CHO) compared to that of ch14.18 manufactured from SP2/0 (ch14.18/SP2/0) and NS0 cells (ch14.18/NS0). First, we demonstrate identical binding of ch14.18/CHO to the nominal antigen disialoganglioside GD2 in vitro compared to ch14.18/SP2/0 and ch14.18/NS0. Binding was GD2-specific, since all precursor- and metabolite-gangliosides of GD2 tested were not recognized by ch14.18/CHO. Second, the functional properties of ch14.18/CHO were determined in complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) reactions against GD2 positive neuroectodermal tumor cell lines in vitro. There was no difference in CDC mediated specific tumor cell lysis among the three different ch14.18 antibody preparations. Interestingly, ch14.18/CHO showed superior ADCC activity at low antibody concentrations. Third, the efficacy of ch14.18/CHO was evaluated in the NXS2 neuroblastoma model in vivo. Importantly, the ch14.18/CHO preparation was effective in suppression of experimental liver metastasis in this model. In vivo depletion of NK-cells completely abrogated this effect, suggesting that the mechanism involved in the ch14.18/CHO induced anti-neuroblastoma effect is mediated by NK-dependent ADCC.

In vitro and in vivo antitumor activity of liposomal Fenretinide targeted to human neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood. In advanced disease stages, prognosis is poor and treatments have limited efficacy, thus novel strategies are warranted. The synthetic retinoid Fenretinide (HPR) induces apoptosis in NB and melanoma cell lines. We reported an in vitro potentiation of HPR effects on melanoma cells when the drug is incorporated into GD2-targeted immunoliposomes (anti-GD2-SIL-HPR). We investigated the antitumor activity of anti-GD2-SIL-HPR against NB cells, both in vitro and in vivo. Anti-GD2-SIL showed specific, competitive binding to and uptake by, various NB cell lines. In in vitro cytotoxicity studies, NB cells, incubated with 30 microM HPR entrapped in anti-GD2-immunoliposomes, showed a significant reduction in cellular growth compared to free HPR, HPR entrapped in Ab-free liposomes or anti-GD2 empty liposomes. In an in vivo NB metastatic model, we demonstrated that anti-GD2-SIL-HPR completely inhibited the development of macroscopic and microscopic metastases in comparison to controls. Similar, but significantly less potent, antitumor effect was observed also in mice treated with anti-GD2 immunoliposomes without HPR (anti-GD2-SIL-blank) or anti-GD2 MAb alone (p = 0.0297 and p = 0.0294, respectively, vs. anti-GD2-SIL-HPR). Moreover, our results clearly demonstrated that although anti-GD2 MAb had a strong antitumor effect in this in vivo NB model, 100% curability was obtained only after treatment with anti-GD2-SIL-HPR (p < 0.0001). Anti-GD2 liposomal HPR should receive clinical evaluation as adjuvant therapy of neuroblastoma.

Inhibition of neuroblastoma-induced angiogenesis by fenretinide

Retinoids are a class of natural or synthetic compounds that participate in the control of cell proliferation, differentiation and fetal development. The synthetic retinoid fenretinide (HPR) inhibits carcinogenesis in various animal models. Retinoids have also been suggested to be effective inhibitors of angiogenesis. The effects of HPR on certain endothelial cell functions were investigated in vitro, and its effects on angiogenesis was studied in vivo, by using the chorioallantoic membrane (CAM) assay. HPR inhibited vascular endothelial growth factor- (VEGF-) and fibroblast growth factor-2- (FGF-2)-induced endothelial cell proliferation without affecting endothelial motility; moreover, HPR inhibited growth factor-induced angiogenesis in the CAM assay. Furthermore, a significant antiangiogenic potential of HPR has also been observed in neuroblastoma (NB) biopsy-induced angiogenesis in vivo. We previously demonstrated that supernatants derived from NB cell lines stimulated endothelial cell proliferation. In the present study, we found that this effect was abolished when NB cells were incubated in the presence of HPR. VEGF- and FGF-2-specific ELISA assays, performed on both NB cells derived from conditioned medium and cellular extracts, indicated no consistent effect of HPR on the level of these angiogenic cytokines. Moreover, RT-PCR analysis of VEGF and FGF-2 gene expression confirmed the above lack of effect. HPR was also able to significantly repress the spontaneous growth of endothelial cells, requiring at least 48-72 hr of treatment with HPR, followed by a progressive accumulation of cells in G(1) at subsequent time points. Finally, immunohistochemistry experiments performed in the CAM assay demonstrated that endothelial staining of both VEGF receptor 2 and FGF-2 receptor-2 was reduced after implantation of HPR-loaded sponges, as compared to control CAMs. These data suggest that HPR exerts its antiangiogenic activity through both a direct effect on endothelial cell proliferative activity and an inhibitory effect on the responsivity of the endothelial cells to the proliferative stimuli mediated by angiogenic growth factors.

In vivo activity in a catalytic antibody-prodrug system: Antibody catalyzed etoposide prodrug activation for selective chemotherapy

Effective chemotherapy remains a key issue for successful cancer treatment in general and neuroblastoma in particular. Here we report a chemotherapeutic strategy based on catalytic antibody-mediated prodrug activation. To study this approach in an animal model of neuroblastoma, we have synthesized prodrugs of etoposide, a drug widely used to treat this cancer in humans. The prodrug incorporates a trigger portion designed to be released by sequential retro-aldol/retro-Michael reactions catalyzed by aldolase antibody 38C2. This unique prodrug was greater than 10(2)-fold less toxic than etoposide itself in in vitro assays against the NXS2 neuroblastoma cell line. Drug activity was restored after activation by antibody 38C2. Proof of principle for local antibody-catalyzed prodrug activation in vivo was established in a syngeneic model of murine neuroblastoma. Mice with established 100-mm3 s.c. tumors who received one intratumoral injection of antibody 38C2 followed by systemic i.p. injections with the etoposide prodrug showed a 75% reduction in s.c. tumor growth. In contrast, injection of either antibody or prodrug alone had no antitumor effect. Systemic injections of etoposide at the maximum tolerated dose were significantly less effective than the intratumoral antibody 38C2 and systemic etoposide prodrug combination. Significantly, mice treated with the prodrug at 30-fold the maximum tolerated dose of etoposide showed no signs of prodrug toxicity, indicating that the prodrug is not activated by endogenous enzymes. These results suggest that this strategy may provide a new and potentially nonimmunogenic approach for targeted cancer chemotherapy.

Delivery of c-myb antisense oligodeoxynucleotides to human neuroblastoma cells via disialoganglioside GD(2)-targeted immunoliposomes: antitumor effects

BACKGROUND

Advanced-stage neuroblastoma resists conventional treatment; hence, novel therapeutic approaches are required. We evaluated the use of c-myb antisense oligodeoxynucleotides (asODNs) delivered to cells via targeted immunoliposomes to inhibit c-Myb protein expression and neuroblastoma cell proliferation in vitro.

METHODS

Phosphorothioate asODNs and control sequences were encapsulated in cationic lipid, and the resulting particles were coated with neutral lipids to produce coated cationic liposomes (CCLs). Monoclonal antibodies directed against the disialoganglioside GD(2) were covalently coupled to the CCLs. (3)H-labeled liposomes were used to measure cellular binding, and cellular uptake of asODNs was evaluated by dot-blot analysis. Growth inhibition was quantified by counting trypan blue dye-stained cells. Expression of c-Myb protein was examined by western blot analysis.

RESULTS

Our methods produced GD(2)-targeted liposomes that stably entrapped 80%-90% of added c-myb asODNs. These liposomes showed concentration-dependent binding to GD(2)-positive neuroblastoma cells that could be blocked by soluble anti-GD(2) monoclonal antibodies. GD(2)-targeted liposomes increased the uptake of asODNs by neuroblastoma cells by a factor of fourfold to 10-fold over that obtained with free asODNs. Neuroblastoma cell proliferation was inhibited to a greater extent by GD(2)-targeted liposomes containing c-myb asODNs than by nontargeted liposomes or free asODNs. GD(2)-targeted liposomes containing c-myb asODNs specifically reduced expression of c-Myb protein by neuroblastoma cells. Enhanced liposome binding and asODN uptake, as well as the antiproliferative effect, were not evident in GD(2)-negative cells.

CONCLUSIONS

Encapsulation of asODNs into immunoliposomes appears to enhance their toxicity toward targeted cells while shielding nontargeted cells from antisense effects and may be efficacious for the delivery of drugs with broad therapeutic applications to tumor cells.

Tumor-targeted IL-2 amplifies T cell-mediated immune response induced by gene therapy with single-chain IL-12

Induction, maintenance, and amplification of tumor-protective immunity after cytokine gene therapy is essential for the clinical success of immunotherapeutic approaches. We investigated whether this could be achieved by single-chain IL-12 (scIL-12) gene therapy followed by tumor-targeted IL-2 using a fusion protein containing a tumor-specific recombinant anti-ganglioside GD(2) antibody and IL-2 (ch14.18-IL-2) in a poorly immunogenic murine neuroblastoma model. Herein, we demonstrate the absence of liver and bone marrow metastases after a lethal challenge with NXS2 wild-type cells only in mice (five of six animals) vaccinated with scIL-12-producing NXS2 cells and given a booster injection of low-dose ch14.18-IL-2 fusion protein. This tumor-protective immunity was effective 3 months after initial vaccination, in contrast to control animals treated with a nonspecific fusion protein or an equivalent mixture of antibody and IL-2. Only vaccinated mice receiving the tumor-specific ch14.18-IL-2 fusion protein revealed a reactivation of CD8(+) T cells and subsequent MHC class I-restricted tumor target cell lysis in vitro. The sequential increase in the usage of TCR chains Vbeta11 and -13 in mouse CD8(+) T cells after vaccination and amplification with ch14.18-IL-2 suggests that the initial polyclonal CD8(+) T cell response is effectively boosted by targeted IL-2. In conclusion, we demonstrate that a successful boost of a partially protective memory T cell immune response that is induced by scIL-12 gene therapy could be generated by tumor-specific targeting of IL-2 with a ch14.18-IL-2 fusion protein. This approach could increase success rates of clinical cancer vaccine trials.

Immunocytokines: a promising approach to cancer immunotherapy

Recombinant antibody-cytokine fusion proteins are immunocytokines that achieve high cytokine concentrations in the tumor microenvironment and thereby effectively stimulate cellular immune responses against malignancies. The activation and expansion of immune effector cells, such as CD8+ T lymphocytes, by interleukin-2 immunocytokines resulted in the eradication of established pulmonary and hepatic metastases of murine melanoma and colorectal carcinoma in syngeneic mouse models. These immunocytokines were equally effective in eliminating established bone marrow and liver metastases of murine neuroblastoma by activating natural killer cells. The effective eradication of metastases by immunocytokines resulted in significant prolongation in life span of mice over that of controls receiving equivalent mixtures of antibody and interleukin-2, which failed to reduce the growth of disseminated metastases. Proof of concept was established, indicating that immunocytokine-induced activation and expansion of immune effector cells in the tumor microenvironment can effectively eradicate established tumor metastases. This promising new approach to cancer immunotherapy may lead to clinical applications that improve treatment of cancer patients with minimal residual disease in an adjuvant setting.

Targeted interleukin-2 therapy for spontaneous neuroblastoma metastases to bone marrow

BACKGROUND

Advanced (stage 4) cases of neuroblastoma, a childhood cancer of the nervous system, are associated with high relapse rates, even after intensive chemotherapy, radiotherapy, and autologous bone marrow transplantation. Therefore, the use of monoclonal antibodies directed against the neuroblastoma tumor marker disialoganglioside GD2 (GD2), in combination with recombinant human interleukin 2 (rhIL-2), is under clinical investigation. We hypothesize that targeted cytokine immunotherapy with a recombinant anti-GD2 antibody-interleukin 2 fusion protein (ch14.18-IL-2) is superior to a combination of ch14.18 and rhIL-2. Our purpose was as follows: 1) to develop a syngeneic model for murine neuroblastoma that expresses GD2 and features both experimental and spontaneous metastases to bone marrow and liver, and 2) to assess anti-GD2-targeted IL-2 therapy in this mode.

METHODS

A hybrid neuroblastoma cell line was used to generate the GD2-positive NXS2 cell line. Bone marrow and liver metastases were quantified by reverse transcription-polymerase chain reaction for tyrosine hydroxylase and by organ weight or counts of macroscopic tumor foci, respectively. All P values reported are two-sided.

RESULTS

Injection of NXS2 cells resulted in disseminated bone marrow and liver metastases exhibiting stable, but heterogeneous expression of GD2. Treatment with fusion protein (10 microg/day for 6 days) effectively suppressed growth of both experimental and spontaneous metastases to bone marrow and liver (P<.001). In contrast, a mixture of rhIL-2 and ch14.18 at equivalent dose levels was inefficient. Only mice treated with ch14.18-IL-2 showed a twofold prolongation in life span (P<.001).

CONCLUSION

Targeted IL-2 therapy with a ch14.18-IL-2 fusion protein elicits an effective antitumor response. Our data suggest that a study of ch14.18-IL-2 as an adjuvant treatment in patients with minimal residual disease may be of value.

Positive selection and transplantation of peripheral CD34+ progenitor cells: feasibility and purging efficacy in pediatric patients with neuroblastoma

Peripheral stem cells were mobilized and collected in 20 children with stage 4 neuroblastoma. A total of 37 leukaphereses were performed in the 20 patients. The mean number of collected cells was 5.6 +/- 2.4 x 10(8)/kg (range 1.9-10.5), and the number of collected CD34+ progenitors was 6.1 +/- 6.3 x 10(6)/kg (range 0.75-21.7). CD34-positive selection was performed using the CellPro method. Of the adsorbed cells, 42 +/- 20% (range 4.3-76.6) stained positively for CD34, and the number of positively selected CD34+ cells was 2.0 +/- 1.9 x 10(6)/kg (range 0.09-7.1). The mean recovery of CD34+ cells was 36 +/- 20% (range 6-67). For detection of contaminating neuroblastoma cells before and after CD34-positive selection, a murine antidisialoganglioside GD2 antibody (14.G2a) was used, followed by the alkaline phosphatase antialkaline phosphatase (APAAP) method. Before the positive selection, various numbers of contaminating neuroblastoma cells were found in the leukaphereses of 7 patients. After positive selection, neuroblastoma cells were still detectable in all 7 patients, with a mean log depletion of tumor cells of 1.41 +/- 0.45 (range 0.69-2.13). In 1 patient, contaminating neuroblastoma cells were found only after CD34-positive selection. In 15 of the 20 patients, high-dose chemotherapy was performed, and positively selected CD34+ cells were reinfused in 12 patients. In 10 of these, the mean time to reach > 0.5 x 10(9)/L granulocytes was 12.3 +/- 1.7 days (range 10-16). One patient died at day 7 due to sepsis, and in 1 patient the backup was given at day 15. Because of the low number of collected CD34+ cells, 3 patients were grafted with a combination of unmanipulated PBSC and CD34+ progenitors. In summary, we have shown that positive selection of peripheral CD34+ progenitors is feasible in pediatric patients. However, strategies to improve the recovery of the CD34+ cells and the purging efficacy of this method (i.e., higher enrichment of CD34+ cells, combination of positive and negative selection methods) should be evaluated further.

[Apheresis tolerance and acceptability in the child weighing 30 kg or less, with the exception of infants]

Over the ten past years, we performed 336 apheresis among 51 children who were 19 months to 15 years old (10 to 30 kg body weight). 3 types of apheresis were carried out. 14 red blood cell exchange, 293 plasma exchanges and 29 peripheral blood stem cell collections (CSP). 5 different types of continuous or discontinuous flow machines have been used. Technical adaptations depending on patient blood volume, hematocrit, type of machine used and apheresis performed permitted us to obtain a very good tolerance and acceptability. According us, the apheresis should be used each time this treatment is needed in the child, because of the very low frequency of side effects.