Feasibility of implementing molecular-guided therapy for the treatment of patients with relapsed or refractory neuroblastoma

A systematic analysis of the landscape of synthetic lethality-driven precision oncology

BACKGROUND

Synthetic lethality (SL) denotes a genetic interaction between two genes whose co-inactivation is detrimental to cells. Because more than 25 years have passed since SL was proposed as a promising way to selectively target cancer vulnerabilities, it is timely to comprehensively assess its impact so far and discuss its future.

METHODS

We systematically analyzed the literature and clinical trial data from the PubMed and Trialtrove databases to portray the preclinical and clinical landscape of SL oncology.

FINDINGS

We identified 235 preclinically validated SL pairs and found 1,207 pertinent clinical trials, and the number keeps increasing over time. About one-third of these SL clinical trials go beyond the typically studied DNA damage response (DDR) pathway, testifying to the recently broadening scope of SL applications in clinical oncology. We find that SL oncology trials have a greater success rate than non-SL-based trials. However, about 75% of the preclinically validated SL interactions have not yet been tested in clinical trials.

CONCLUSIONS

Dissecting the recent efforts harnessing SL to identify predictive biomarkers, novel therapeutic targets, and effective combination therapy, our systematic analysis reinforces the hope that SL may serve as a key driver of precision oncology going forward.

FUNDING

Funded by the Samsung Research Funding & Incubation Center of Samsung Electronics, the Institute of Information & Communications Technology Planning & Evaluation (IITP) grant funded by the Republic of Korea government (MSIT), the Kwanjeong Educational Foundation, the Intramural Research Program of the National Institutes of Health (NIH), National Cancer Institute (NCI), and Center for Cancer Research (CCR).

Arsenic Trioxide inhibits Activation of Hedgehog Pathway in Human Neuroblastoma Cell Line SK-N-BE(2) Independent of Itraconazole

BACKGROUND

Neuroblastoma (NB) remains associated with a low overall survival rate over the long term. Abnormal activation of the Hedgehog (HH) signaling pathway can activate the transcription of various downstream target genes that promote NB. Both arsenic trioxide (ATO) and itraconazole (ITRA) can inhibit tumor growth.

OBJECTIVE

To determine whether ATO combined with ITRA can be used to treat NB with HH pathway activation, we examined the effects of ATO and ITRA monotherapy or combined inhibition of the HH pathway in NB.

METHODS

Analysis of CCK8 and flow cytometry showed cell inhibition and cell cycle, respectively. Real-time PCR analysis was conducted to assess the mRNA expression of HH pathway.

RESULTS

We revealed that as concentrations of ATO and ITRA increased, the killing effects of both agents on SK-N-BE(2) cells became more apparent. During G2/M, the cell cycle was largely arrested by ATO alone and combined with ITRA, and in the G0/G1 phase by ITRA alone. In the HH pathway, ATO inhibited the transcription of the SHH, PTCH1, SMO and GLI2 genes, however, ITRA did not. Instead of showing synergistic effects in a combined mode, ITRA decreased ATO inhibitory effects.

CONCLUSION

We showed that ATO is an important inhibitor of HH pathway but ITRA can weaken the inhibitory effect of ATO. This study provides an experimental evidence for the clinical use of ATO and ITRA in the treatment of NB with HH pathway activation in cytology.

A pilot study of genomic-guided induction therapy followed by immunotherapy with difluoromethylornithine maintenance for high-risk neuroblastoma

BACKGROUND

Survival for patients with high-risk neuroblastoma (HRNB) remains poor despite aggressive multimodal therapies.

AIMS

To study the feasibility and safety of incorporating a genomic-based targeted agent to induction therapy for HRNB as well as the feasibility and safety of adding difluoromethylornithine (DFMO) to anti-GD2 immunotherapy.

METHODS

Twenty newly diagnosed HRNB patients were treated on this multicenter pilot trial. Molecular tumor boards selected one of six targeted agents based on tumor-normal whole exome sequencing and tumor RNA-sequencing results. Treatment followed standard upfront HRNB chemotherapy with the addition of the selected targeted agent to cycles 3-6 of induction. Following consolidation, DFMO (750 mg/m² twice daily) was added to maintenance with dinutuximab and isotretinoin, followed by continuation of DFMO alone for 2 years. DNA methylation analysis was performed retrospectively and compared to RNA expression.

RESULTS

Of the 20 subjects enrolled, 19 started targeted therapy during cycle 3 and 1 started during cycle 5. Eighty-five percent of subjects met feasibility criteria (receiving 75% of targeted agent doses). Addition of targeted agents did not result in toxicities requiring dose reduction of chemotherapy or permanent discontinuation of targeted agent. Following standard consolidation, 15 subjects continued onto immunotherapy with DFMO. This combination was well-tolerated and resulted in no unexpected adverse events related to DFMO.

CONCLUSION

This study demonstrates the safety and feasibility of adding targeted agents to standard induction therapy and adding DFMO to immunotherapy for HRNB. This treatment regimen has been expanded to a Phase II trial to evaluate efficacy.

The landscape of receptor-mediated precision cancer combination therapy via a single-cell perspective

Mining a large cohort of single-cell transcriptomics data, here we employ combinatorial optimization techniques to chart the landscape of optimal combination therapies in cancer. We assume that each individual therapy can target any one of 1269 genes encoding cell surface receptors, which may be targets of CAR-T, conjugated antibodies or coated nanoparticle therapies. We find that in most cancer types, personalized combinations composed of at most four targets are then sufficient for killing at least 80% of tumor cells while sparing at least 90% of nontumor cells in the tumor microenvironment. However, as more stringent and selective killing is required, the number of targets needed rises rapidly. Emerging individual targets include PTPRZ1 for brain and head and neck cancers and EGFR in multiple tumor types. In sum, this study provides a computational estimate of the identity and number of targets needed in combination to target cancers selectively and precisely.

Clinical Utility of Precision Medicine in Pediatric Oncology: A Systematic Review

PURPOSE

Precision medicine uses advanced molecular techniques to guide the use of targeted therapeutic drugs and is an emerging paradigm in pediatric oncology. Clinical evidence related to the efficacy of many novel targeted drugs, however, is currently very limited given the rarity of pediatric cancer and the lack of published evidence for the use of these drugs in children. This systematic review aimed to evaluate the existing evidence for the feasibility and clinical efficacy of precision medicine in pediatric oncology.

METHODS

A systematic review was conducted using the PubMed, Medline, and Embase databases. Clinical trials and observational studies, which used molecular assays such as whole-exome sequencing to identify molecular targets that guided the allocation of targeted cancer drugs and reported clinical outcomes, were included in this review.

RESULTS

Twenty-one clinical trials and observational studies were identified, collectively enrolling 1,408 pediatric patients across nine countries. Therapeutic targets were found in 647 patients (46.0%); however, only 175 of these patients (27.0%) received a targeted drug. Objective responses were recorded for 73 (41.7%) of these 175 patients, only 5.2% of the total sample. Inconsistent outcome reporting and limited comparison with conventional treatment hindered evaluation of the clinical utility of precision medicine.

CONCLUSION

Precision medicine can feasibly identify molecular targets in a clinical setting. However, the inaccessibility of targeted drugs is a significant barrier, restricting the exploration of its therapeutic potential in pediatric oncology. Future clinical trials should endeavor to link the molecular testing results with access to targeted drugs and standardize outcome reporting to advance understanding of the benefits of this novel paradigm in improving patient outcomes.

Genomic and Transcriptomic Analysis of Relapsed and Refractory Childhood Solid Tumors Reveals a Diverse Molecular Landscape and Mechanisms of Immune Evasion

Children with treatment-refractory or relapsed (R/R) tumors face poor prognoses. As the genomic underpinnings driving R/R disease are not well defined, we describe here the genomic and transcriptomic landscapes of R/R solid tumors from 202 patients enrolled in Beat Childhood Cancer Consortium clinical trials. Tumor mutational burden (TMB) was elevated relative to untreated tumors at diagnosis, with one-third of tumors classified as having a pediatric high TMB. Prior chemotherapy exposure influenced the mutational landscape of these R/R tumors, with more than 40% of tumors demonstrating mutational signatures associated with platinum or temozolomide chemotherapy and two tumors showing treatment-associated hypermutation. Immunogenomic profiling found a heterogenous pattern of neoantigen and MHC class I expression and a general absence of immune infiltration. Transcriptional analysis and functional gene set enrichment analysis identified cross-pathology clusters associated with development, immune signaling, and cellular signaling pathways. While the landscapes of these R/R tumors reflected those of their corresponding untreated tumors at diagnosis, important exceptions were observed suggestive of tumor evolution, treatment resistance mechanisms, and mutagenic etiologies of treatment.

Excellent Early Outcomes of Combined Chemotherapy With Arsenic Trioxide for Stage 4/M Neuroblastoma in Children: A Multicenter Nonrandomized Controlled Trial

This nonrandomized, multicenter cohort, open-label clinical trial evaluated the efficacy and safety of combined chemotherapy with arsenic trioxide (ATO) in children with stage 4/M neuroblastoma (NB). We enrolled patients who were newly diagnosed with NB and assessed as stage 4/M and received either traditional chemotherapy or ATO combined with chemotherapy according to their own wishes. Twenty-two patients were enrolled in the trial group (ATO combined with chemotherapy), and 13 patients were enrolled in the control group (traditional chemotherapy). Objective response rate (ORR) at 4 weeks after completing induction chemotherapy was defined as the main outcome, and adverse events were monitored and graded in the meantime. Data cutoff date was December 31, 2019. Finally, we found that patients who received ATO combined with chemotherapy had a significantly higher response rate than those who were treated with traditional chemotherapy (ORR: 86.36% vs. 46.16%, p=0.020). Reversible cardiotoxicity was just observed in three patients who were treated with ATO, and no other differential adverse events were observed between the two groups. ATO combined with chemotherapy can significantly improve end-induction response in high-risk NB, and our novel regimen is well tolerated in pediatric patients. These results highlight the superiority of chemotherapy with ATO, which creates new opportunity for prolonging survival. In addition, this treatment protocol minimizes therapeutic costs compared with anti-GD2 therapy, MIBG, and proton therapy and can decrease the burden to families and society. However, we also need to evaluate more cases to consolidate our conclusion.

Neuroblastoma patient-derived cultures are enriched for a mesenchymal gene signature and reflect individual drug response

Ex vivo evaluation of personalized models can facilitate individualized treatment selection for patients, and advance the discovery of novel therapeutic options. However, for embryonal malignancies, representative primary cultures have been difficult to establish. We developed patient‐derived cell cultures (PDCs) from chemo‐naïve and post–treatment neuroblastoma tumors in a consistent and efficient manner, and characterized their in vitro growth dynamics, histomorphology, gene expression, and functional chemo‐response. From 34 neuroblastoma tumors, 22 engrafted in vitro to generate 31 individual PDC lines, with higher engraftment seen with metastatic tumors. PDCs displayed characteristic immunohistochemical staining patterns of PHOX2B, TH, and GD2 synthase. Concordance of MYCN amplification, 1p and 11q deletion between PDCs and patient tumors was 83.3%, 72.7%, and 80.0% respectively. PDCs displayed a predominantly mesenchymal‐type gene expression signature and showed upregulation of pro‐angiogenic factors that were similarly enriched in culture medium and paired patient serum samples. When tested with standard‐of‐care cytotoxics at human C_max‐equivalent concentrations, MYCN‐amplified and non‐MYCN‐amplified PDCs showed a differential response to cyclophosphamide and topotecan, which mirrored the corresponding patients’ responses, and correlated with gene signatures of chemosensitivity. In this translational proof‐of‐concept study, early‐phase neuroblastoma PDCs enriched for the mesenchymal cell subpopulation recapitulated the individual molecular and phenotypic profile of patient tumors, and highlighted their potential as a platform for individualized ex vivo drug‐response testing.

Novel Therapies for Relapsed and Refractory Neuroblastoma

While recent increases in our understanding of the biology of neuroblastoma have allowed for more precise risk stratification and improved outcomes for many patients, children with high-risk neuroblastoma continue to suffer from frequent disease relapse, and despite recent advances in our understanding of neuroblastoma pathogenesis, the outcomes for children with relapsed neuroblastoma remain poor. These children with relapsed neuroblastoma, therefore, continue to need novel treatment strategies based on a better understanding of neuroblastoma biology to improve outcomes. The discovery of new tumor targets and the development of novel antibody- and cell-mediated immunotherapy agents have led to a large number of clinical trials for children with relapsed neuroblastoma, and additional clinical trials using molecular and genetic tumor profiling to target tumor-specific aberrations are ongoing. Combinations of these new therapeutic modalities with current treatment regimens will likely be needed to improve the outcomes of children with relapsed and refractory neuroblastoma.

Genomics of adult and pediatric solid tumors

Different types of cancers exhibit disparate spectra of genomic alterations (germline and/or somatic). These alterations can include single nucleotide variants (SNVs), copy number alterations (CNAs) or structural changes (e.g. gene fusions and chromosomal rearrangements). Identification of those genomic alterations has provided the opportune element to derive new strategies for molecular-based precision medicine of adult and pediatric cancers including risk assessment, non-invasive detection, molecular diagnosis and personalized therapy. Moreover, it is now becoming clear that the spectra of genomic-based alterations and mechanisms in pediatric malignancies are different from those predominantly occurring in adult cancer. Adult cancers on average exhibit substantially higher mutational burdens compared with the vast majority of childhood tumors. Accumulating evidence also suggests that the type of genomic alterations frequently encountered in adult cancers is different from those observed in pediatric malignancies. In this review, we discuss the state of knowledge on adult and pediatric cancer genomes (or "mutatomes"), specifically focusing on solid tumors. We present an overview of mutational signatures and processes in cancer as well as comprehensively compare and contrast the diverse spectra of genomic alterations (somatic and familial) among major adult and pediatric solid tumors. The review also discusses the role of genomics in molecular-based precision medicine of adult and pediatric solid malignancies as well as comprehending resistance mechanisms to various targeted therapies. In addition, we present a perspective that discusses upon emerging concepts in cancer genomics including intratumoral heterogeneity, the precancer (premalignant) genome as well as the interface between the host immune response and tumor genome - immunogenomics - as they relate to adult and pediatric tumors.

Autophagy inhibition improves the cytotoxic effects of receptor tyrosine kinase inhibitors

Background

A growing field of evidence suggests the involvement of oncogenic receptor tyrosine kinases (RTKs) in cell transformation. Deregulated activity of RTKs in tumors can determine disease progression and therapeutic responses in several types of cancer, including neuroblastoma (NB). Therefore, RTKs targeting is a worthwhile challenge for the oncologists. Nevertheless, acquired resistance to RTK inhibitors (RTKi) remains a serious problem. Autophagy activation is among the possible obstacles for good efficacy of the therapy with RTKi.

Methods

Under different treatment conditions we measured autophagic flux using immunoblot and immunofluorescence assays. Death induction was validated by trypan blue exclusion assay and FACS analysis (calcein-AM/propidium iodide). The NB cell lines SH-SY5Y and Kelly were used for the in vitro study.

Results

In order to define whether autophagy might be a limiting factor for the efficacy of RTKi in NB cells, we firstly checked its activation following the treatment with several RTKi. Next, we investigated the possibility to increase their therapeutic efficiency by combining RTKi with autophagy blocking agents in vitro. We exploited the effectiveness of three RTKi either alone or in combination with autophagy inhibitors (Chloroquine-CQ and Spautin-1). We demonstrated that autophagy induction was drug-dependent, and that its inhibition increased the anti-tumor activity of a single RTKi unevenly. We observed that the combined use of blocking agents which impair late autophagy events, such as CQ, and RTKi can be more effective with respect to the use of RTKi alone.

Conclusions

In the present report, we assessed the conditions under which autophagy is activated during the use of different RTKi currently in the pre-clinical evaluation for NB. We summarized the achievements of combined RTK/autophagy inhibitors treatment as a promising approach to enhance the efficacy of RTKi in impairing tumor cells viability.

Molecular Guided Therapy Provides Sustained Clinical Response in Refractory Choroid Plexus Carcinoma

Choroid plexus carcinomas (CPCs) are rare, aggressive pediatric brain tumors with no established curative therapy for relapsed disease, and poor survival rates. TP53 Mutation or dysfunction correlates with poor or no survival outcome in CPCs. Here, we report the case of a 4 month-old female who presented with disseminated CPC. After initial response to tumor resection and adjuvant-chemotherapy, the tumor recurred and metastasized with no response to aggressive relapse therapy suggesting genetic predisposition. This patient was then enrolled to a Molecular Guided Therapy Clinical Trial. Genomic profiling of patient tumor and normal sample identified a TP53 germline mutation with loss of heterozygosity, somatic mutations including IDH2, and aberrant activation of biological pathways. The mutations were not targetable for therapy. However, targeting the altered biological pathways (mTOR, PDGFRB, FGF2, HDAC) guided identification of possibly beneficial treatment with a combination of sirolimus, thalidomide, sunitinib, and vorinostat. This therapy led to 92% reduction in tumor size with no serious adverse events, excellent quality of life and long term survival.

Decorin gene upregulation mediated by an adeno-associated virus vector increases intratumoral uptake of nab-paclitaxel in neuroblastoma via inhibition of stabilin-1

The availability of effective medication for the treatment of refractory or recurrent neuroblastoma remains limited. This study sought to investigate the effects of increased decorin (DCN) expression on the intratumoral uptake of nab-paclitaxel as a potential novel approach to NB. Correlation between the clinical characteristics of neuroblastoma and the expression of DCN, secreted protein acidic and rich in cysteine (SPARC) and stabilin-1 was evaluated. The anticancer effect of recombinant adeno-associated virus-DCN (rAAV-DCN) was assessed in vivo and in vitro. And the effect of rAAV-DCN on the intratumoral uptake of paclitaxel was also studied in neuroblastoma-grafted nude mice. Overall, 12.5%, 17.7%, and 71.9% of the tumors stained positive for DCN, SPARC and stabilin-1 respectively and correlated to age, stage and N-MYC status in 96 children and adolescents with neuroblastoma. Transfected neuroblastoma cells stably expressed DCN, with in vivo and in vitro studies demonstrating rAAV-DCN sensitized the anticancer effect of nab-paclitaxel. Systemic rAAV-DCN in neuroblastoma-grafted nude mice inhibited stabilin-1, up-regulated SPARC, and increased the intratumoral uptake of paclitaxel. Macrophage depletion or anti-stabilin-1 monoclonal antibody increased the intratumoral uptake of nab-paclitaxel and its anticancer effects to a degree comparable to that achieved by systemic rAAV-DCN. The systemic administration of rAAV-DCN up-regulates DCN in neuroblastoma and accelerates the intratumoral uptake of nab-paclitaxel by inhibiting stabilin-1 mediated SPARC degradation.

Suberoylanilide hydroxamic acid sensitizes neuroblastoma to paclitaxel by inhibiting thioredoxin-related protein 14-mediated autophagy

Paclitaxel is not as effective for neuroblastoma as most of the front‐line chemotherapeutics due to drug resistance. This study explored the regulatory mechanism of paclitaxel‐associated autophagy and potential solutions to paclitaxel resistance in neuroblastoma. The formation of autophagic vesicles was detected by scanning transmission electron microscopy and flow cytometry. The autophagy‐associated proteins were assessed by western blot. Autophagy was induced and the autophagy‐associated proteins LC3‐I, LC3‐II, Beclin 1, and thioredoxin‐related protein 14 (TRP14), were found to be upregulated in neuroblastoma cells that were exposed to paclitaxel. The inhibition of Beclin 1 or TRP14 by siRNA increased the sensitivity of the tumor cells to paclitaxel. In addition, Beclin 1‐mediated autophagy was regulated by TRP14. Furthermore, the TRP14 inhibitor suberoylanilide hydroxamic acid (SAHA) downregulated paclitaxel‐induced autophagy and enhanced the anticancer effects of paclitaxel in normal control cancer cells but not in cells with upregulated Beclin 1 and TRP14 expression. Our findings showed that paclitaxel‐induced autophagy in neuroblastoma cells was regulated by TRP14 and that SAHA could sensitize neuroblastoma cells to paclitaxel by specifically inhibiting TRP14.

Neuroblastoma in children: Update on clinicopathologic and genetic prognostic factors

Neuroblastoma is the most common extracranial solid tumor in childhood accounting for 8-10% of all childhood malignancies. The tumor is characterized by a spectrum of histopathologic features and a heterogeneous clinical phenotype. Modern multimodality therapy results in variable clinical response ranging from cure in localized tumors to limited response in aggressive metastatic disease. Accurate clinical staging and risk assessment based on clinical, surgical, biologic and pathologic criteria are of pivotal importance in assigning prognosis and planning effective treatment approaches. Numerous studies have analyzed the presence of several clinicopathologic and biologic factors in association with the patient's prognosis and outcome. Although patient's age, tumor stage, histopathologic classification, and MYCN amplification are the most commonly validated prognostic markers, several new gene mutations have been identified in sporadic and familial neuroblastoma cases that show association with an adverse outcome. Novel molecular studies have also added data on chromosomal segmental aberrations in MYCN nonamplified tumors. In this review, we provide an updated summary of the clinical, serologic and genetic prognostic indicators in neuroblastoma including classic factors that have consistently played a role in risk stratification of patients as well as newly discovered biomarkers that may show a potential significance in patients' management.

Overview and recent advances in the treatment of neuroblastoma

INTRODUCTION

Children with neuroblastoma have widely divergent outcomes, ranging from cure in >90% of patients with low risk disease to <50% for those with high risk disease. Recent research has shed light on the biology of neuroblastoma, allowing for more accurate risk stratification and treatment reduction in many cases, although newer treatment strategies for children with high-risk and relapsed neuroblastoma are needed to improve outcomes. Areas covered: Neuroblastoma epidemiology, diagnosis, risk stratification, and recent advances in treatment of both newly diagnosed and relapsed neuroblastoma. Expert commentary: The identification of newer tumor targets and of novel cell-mediated immunotherapy agents may lead to novel therapeutic approaches, and clinical trials for regimens designed to target individual genetic aberrations in tumors are underway. A combination of therapeutic modalities will likely be required to improve survival and cure rates for patients with high-risk neuroblastoma.

BLM germline and somatic PKMYT1 and AHCY mutations: Genetic variations beyond MYCN and prognosis in neuroblastoma

Neuroblastoma (NB) is the most common extra cranial solid tumor of childhood and often lethal in childhood. Clinical and biologic characteristics that are independently prognostic of outcome in NB are currently used for risk stratification to optimally the therapy. It includes age at diagnosis, International Neuroblastoma Staging System tumor histopathology and MYCN amplification. However, even in patients with theoretically good prognosis, such as localized tumor and non-amplified MYCN, either disease progress or recurrence may occur. Potential genetic determinants of this unfavorable behavior are not yet fully clarified. The presence of elevated expression of AHCY, PKMYT1, and BLM has accompanied poor prognosis MYCN-amplified neuroblastoma patients. Considering the potential implication of these genes on the clinical management of NB, we hypothesize that the identification of genetic variations may have significant impact during development of the recurrent or progressive disease. Using targeted DNA sequencing, we analyzed the mutation profiles of the genes PKMYT1, AHCY, and BLM in tumor samples of five patients with MYCN amplified and 15 MYCN non-amplified NB. In our study, BLM germline variants were detected in two patients with MYCN-non-amplified neuroblastoma. Our data allow us to hypothesize that, regardless of MYCN status, these mutations partially abolish BLM protein activity by impairing its ATPase and helicase activities. BLM mutations are also clinically relevant because BLM plays an important role in DNA damage repair and the maintenance of genomic integrity. We also found a novel variant in our cohort, PKMYT1 mutation localized in the C-terminal domain with effect unknown on NB. We hypothesize that this variant may affect the catalytic activity of PKMYT1 in NB, specifically when CDK1 is complexed to cyclins. The prognostic value of this mutation must be further investigated. Another mutation identified was a nonsynonymous variant in AHCY. This variant may be related to the slow progression of the disease, even in more aggressive cases. It affects the maintenance of the catalytic capacity of AHCY, leading to the consequent functional effects observed in the NB patients studied. In conclusion, our hypothesis may provide that mutations in BLM, AHCY and PKMYT1 genes found in children with MYCN-amplified or MYCN-non amplified neuroblastomas, may be associated with the prognosis of the disease.

Patient-derived xenografts for childhood solid tumors: a valuable tool to test new drugs and personalize treatments

The use of preclinical models is essential in translational cancer research and especially important in pediatric cancer given the low incidence of each particular type of cancer. Cell line cultures have led to significant advances in cancer biology. However, cell lines have adapted to growth in artificial culture conditions, thereby undergoing genetic and phenotypic changes which may hinder the translational application. Tumor grafts developed in mice from patient tumor tissues, generally known as patient-derived xenografts (PDXs), are interesting alternative approaches to reproducing the biology of the original tumor. This review is focused on highlighting the interest of PDX models in pediatric cancer research and supporting strategies of personalized medicine. This review provides: (1) a description of the background of PDX in cancer, (2) the particular case of PDX in pediatric cancer, (3) how PDX can improve personalized medicine strategies, (4) new methods to increase engraftment, and, finally, (5) concluding remarks.

mda-7/IL-24 Induces Cell Death in Neuroblastoma through a Novel Mechanism Involving AIF and ATM

Advanced stages of neuroblastoma, the most common extracranial malignant solid tumor of the central nervous system in infants and children, are refractive to therapy. Ectopic expression of melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) promotes broad-spectrum antitumor activity in vitro, in vivo in preclinical animal models, and in a phase I clinical trial in patients with advanced cancers without harming normal cells. mda-7/IL-24 exerts cancer-specific toxicity (apoptosis or toxic autophagy) by promoting endoplasmic reticulum stress and modulating multiple signal transduction pathways regulating cancer cell growth, invasion, metastasis, survival, and angiogenesis. To enhance cancer-selective expression and targeted anticancer activity of mda-7/IL-24, we created a tropism-modified cancer terminator virus (Ad.5/3-CTV), which selectively replicates in cancer cells producing robust expression of mda-7/IL-24 We now show that Ad.5/3-CTV induces profound neuroblastoma antiproliferative activity and apoptosis in a caspase-3/9-independent manner, both in vitro and in vivo in a tumor xenograft model. Ad.5/3-CTV promotes these effects through a unique pathway involving apoptosis-inducing factor (AIF) translocation into the nucleus. Inhibiting AIF rescued neuroblastoma cells from Ad.5/3-CTV-induced cell death, whereas pan-caspase inhibition failed to promote survival. Ad.5/3-CTV infection of neuroblastoma cells increased ATM phosphorylation instigating nuclear translocation and increased γ-H2AX, triggering nuclear translocation and intensified expression of AIF. These results were validated further using two ATM small-molecule inhibitors that attenuated PARP cleavage by inhibiting γ-H2AX, which in turn inhibited AIF changes in Ad.5/3-CTV-infected neuroblastoma cells. Taken together, we elucidate a novel pathway for mda-7/IL-24-induced caspase-independent apoptosis in neuroblastoma cells mediated through modulation of AIF, ATM, and γ-H2AX. Cancer Res; 76(12); 3572-82. ©2016 AACR.