Neuroblastoma patient-derived orthotopic xenografts reflect the microenvironmental hallmarks of aggressive patient tumours

Differences in treatment outcome between translational platforms in developing therapies for gastrointestinal cancers

The variability in translational models profoundly impacts the outcomes and predictive value of preclinical studies for gastrointestinal (GI) cancer treatments. Preclinical models, including 2D cell cultures, 3D organoids, patient-derived xenografts (PDXs), and animal models, provide distinct advantages and limitations in replicating the complex tumor microenvironment (TME) of human cancers. Each model's unique biological and structural differences contribute to discrepancies in treatment responses, challenging the direct translation of experimental results to clinical settings. While 2D cell cultures are cost-effective and suitable for high-throughput screening, they lack the 3D architecture and cellular interactions of the in vivo TME. Organoids offer a more comprehensive 3D structure that better mirrors tumor heterogeneity, yet they still face limitations in fully mimicking in vivo conditions, such as vascularization and immune cell interactions. PDXs, although more representative of human cancers due to their genetic fidelity and TME preservation, are costly and resource-intensive, with human stromal and immune components gradually replaced by murine counterparts over time. This review assesses the strengths and limitations of each model, highlighting recent advancements in translational platforms that incorporate complex TME features. Understanding the influence of model selection on treatment efficacy predictions is essential for enhancing the reliability of preclinical findings and advancing personalized therapeutic strategies for GI cancers.

Preclinical Models of Neuroblastoma-Current Status and Perspectives

Preclinical in vitro and in vivo models remain indispensable tools in cancer research. These classic models, including two- and three-dimensional cell culture techniques and animal models, are crucial for basic and translational studies. However, each model has its own limitations and typically does not fully recapitulate the course of the human disease. Therefore, there is an urgent need for the development of novel, advanced systems that can allow for efficient evaluation of the mechanisms underlying cancer development and progression, more accurately reflect the disease pathophysiology and complexity, and effectively inform therapeutic decisions for patients. Preclinical models are especially important for rare cancers, such as neuroblastoma, where the availability of patient-derived specimens that could be used for potential therapy evaluation and screening is limited. Neuroblastoma modeling is further complicated by the disease heterogeneity. In this review, we present the current status of preclinical models for neuroblastoma research, discuss their development and characteristics emphasizing strengths and limitations, and describe the necessity of the development of novel, more advanced and clinically relevant approaches.

Monocyte and Macrophage in Neuroblastoma: Blocking Their Pro-Tumoral Functions and Strengthening Their Crosstalk with Natural Killer Cells

Over the past decade, immunotherapy has represented an enormous step forward in the fight against cancer. Immunotherapeutic approaches have increasingly become a fundamental part of the combined therapies currently adopted in the treatment of patients with high-risk (HR) neuroblastoma (NB). An increasing number of studies focus on the understanding of the immune landscape in NB and, since this tumor expresses low or null levels of MHC class I, on the development of new strategies aimed at enhancing innate immunity, especially Natural Killer (NK) cells and macrophages. There is growing evidence that, within the NB tumor microenvironment (TME), tumor-associated macrophages (TAMs), which mainly present an M2-like phenotype, have a crucial role in mediating NB development and immune evasion, and they have been correlated to poor clinical outcomes. Importantly, TAM can also impair the antibody-dependent cellular cytotoxicity (ADCC) mediated by NK cells upon the administration of anti-GD2 monoclonal antibodies (mAbs), the current standard immunotherapy for HR-NB patients. This review deals with the main mechanisms regulating the crosstalk among NB cells and TAMs or other cellular components of the TME, which support tumor development and induce drug resistance. Furthermore, we will address the most recent strategies aimed at limiting the number of pro-tumoral macrophages within the TME, reprogramming the TAMs functional state, thus enhancing NK cell functions. We also prospectively discuss new or unexplored aspects of human macrophage heterogeneity.

Patient-derived models: Advanced tools for precision medicine in neuroblastoma

Neuroblastoma is a childhood cancer derived from the sympathetic nervous system. High-risk neuroblastoma patients have a poor overall survival and account for ~15% of childhood cancer deaths. There is thus a need for clinically relevant and authentic models of neuroblastoma that closely resemble the human disease to further interrogate underlying mechanisms and to develop novel therapeutic strategies. Here we review recent developments in patient-derived neuroblastoma xenograft models and in vitro cultures. These models can be used to decipher mechanisms of metastasis and treatment resistance, for drug screening, and preclinical drug testing. Patient-derived neuroblastoma models may also provide useful information about clonal evolution, phenotypic plasticity, and cell states in relation to neuroblastoma progression. We summarize current opportunities for, but also barriers to, future model development and application. Integration of patient-derived models with patient data holds promise for the development of precision medicine treatment strategies for children with high-risk neuroblastoma.

Macrophage infiltration promotes regrowth in MYCN-amplified neuroblastoma after chemotherapy

Despite aggressive treatment, the 5-year event-free survival rate for children with high-risk neuroblastoma is <50%. While most high-risk neuroblastoma patients initially respond to treatment, often with complete clinical remission, many eventually relapse with therapy-resistant tumors. Novel therapeutic alternatives that prevent the recurrence of therapy-resistant tumors are urgently needed. To understand the adaptation of neuroblastoma under therapy, we analyzed the transcriptomic landscape in 46 clinical tumor samples collected before (PRE) or after (POST) treatment from 22 neuroblastoma patients. RNA sequencing revealed that many of the top-upregulated biological processes in POST MYCN amplified (MNA⁺) tumors compared to PRE MNA⁺ tumors were immune-related, and there was a significant increase in numerous genes associated with macrophages. The infiltration of macrophages was corroborated by immunohistochemistry and spatial digital protein profiling. Moreover, POST MNA⁺ tumor cells were more immunogenic compared to PRE MNA⁺ tumor cells. To find support for the macrophage-induced outgrowth of certain subpopulations of immunogenic tumor cells following treatment, we examined the genetic landscape in multiple clinical PRE and POST tumor samples from nine neuroblastoma patients revealing a significant correlation between an increased amount of copy number aberrations (CNA) and macrophage infiltration in POST MNA⁺ tumor samples. Using an in vivo neuroblastoma patient-derived xenograft (PDX) chemotherapy model, we further show that inhibition of macrophage recruitment with anti-CSF1R treatment prevents the regrowth of MNA⁺ tumors following chemotherapy. Taken together, our work supports a therapeutic strategy for fighting the relapse of MNA⁺ neuroblastoma by targeting the immune microenvironment.

Research Progress, Challenges, and Breakthroughs of Organoids as Disease Models

Traditional cell lines and xenograft models have been widely recognized and used in research. As a new research model, organoids have made significant progress and development in the past 10 years. Compared with traditional models, organoids have more advantages and have been applied in cancer research, genetic diseases, infectious diseases, and regenerative medicine. This review presented the advantages and disadvantages of organoids in physiological development, pathological mechanism, drug screening, and organ transplantation. Further, this review summarized the current situation of vascularization, immune microenvironment, and hydrogel, which are the main influencing factors of organoids, and pointed out the future directions of development.

A New Player in Neuroblastoma: YAP and Its Role in the Neuroblastoma Microenvironment

Neuroblastoma is the most common extra-cranial pediatric solid tumor that accounts for more than 15% of childhood cancer-related deaths. High risk neuroblastomas that recur during or after intense multimodal therapy have a <5% chance at a second sustained remission or cure. The solid tumor microenvironment (TME) has been increasingly recognized to play a critical role in cancer progression and resistance to therapy, including in neuroblastoma. The Yes-Associated Protein (YAP) in the Hippo pathway can regulate cancer proliferation, tumor initiation, and therapy response in many cancer types and as such, its role in the TME has gained interest. In this review, we focus on YAP and its role in neuroblastoma and further describe its demonstrated and potential effects on the neuroblastoma TME. We also discuss the therapeutic strategies for inhibiting YAP in neuroblastoma.

The Promise of Patient-Derived Preclinical Models to Accelerate the Implementation of Personalised Medicine for Children with Neuroblastoma

Patient-derived preclinical models are now a core component of cancer research and have the ability to drastically improve the predictive power of preclinical therapeutic studies. However, their development and maintenance can be challenging, time consuming, and expensive. For neuroblastoma, a developmental malignancy of the neural crest, it is possible to establish patient-derived models as xenografts in mice and zebrafish, and as spheroids and organoids in vitro. These varied approaches have contributed to comprehensive packages of preclinical evidence in support of new therapeutics for neuroblastoma. We discuss here the ethical and technical considerations for the creation of patient-derived models of neuroblastoma and how their use can be optimized for the study of tumour evolution and preclinical therapies. We also discuss how neuroblastoma patient-derived models might become avatars for personalised medicine for children with this devastating disease.

Neuroblastoma Invasion Strategies Are Regulated by the Extracellular Matrix

Neuroblastoma is a paediatric malignancy of the developing sympathetic nervous system. About half of the patients have metastatic disease at the time of diagnosis and a survival rate of less than 50%. Our understanding of the cellular processes promoting neuroblastoma metastases will be facilitated by the development of appropriate experimental models. In this study, we aimed to explore the invasion of neuroblastoma cells and organoids from patient-derived xenografts (PDXs) grown embedded in 3D extracellular matrix (ECM) hydrogels by time-lapse microscopy and quantitative image analysis. We found that the ECM composition influenced the growth, viability and local invasion of organoids. The ECM compositions induced distinct cell behaviours, with Matrigel being the preferred substratum for local organoid invasion. Organoid invasion was cell line- and PDX-dependent. We identified six distinct phenotypes in PDX-derived organoids. In contrast, NB cell lines were more phenotypically restricted in their invasion strategies, as organoids isolated from cell line-derived xenografts displayed a broader range of phenotypes compared to clonal cell line clusters. The addition of FBS and bFGF induced more aggressive cell behaviour and a broader range of phenotypes. In contrast, the repression of the prognostic neuroblastoma marker, MYCN, resulted in less aggressive cell behaviour. The combination of PDX organoids, real-time imaging and the novel 3D culture assays developed herein will enable rapid progress in elucidating the molecular mechanisms that control neuroblastoma invasion.

An in vivo model allowing continuous observation of human vascular formation in the same animal over time

Angiogenesis contributes to numerous pathological conditions. Understanding the molecular mechanisms of angiogenesis will offer new therapeutic opportunities. Several experimental in vivo models that better represent the pathological conditions have been generated for this purpose in mice, but it is difficult to translate results from mouse to human blood vessels. To understand human vascular biology and translate findings into human research, we need human blood vessel models to replicate human vascular physiology. Here, we show that human tumor tissue transplantation into a cranial window enables engraftment of human blood vessels in mice. An in vivo imaging technique using two-photon microscopy allows continuous observation of human blood vessels until at least 49 days after tumor transplantation. These human blood vessels make connections with mouse blood vessels as shown by the finding that lectin injected into the mouse tail vein reaches the human blood vessels. Finally, this model revealed that formation and/or maintenance of human blood vessels depends on VEGFR2 signaling. This approach represents a useful tool to study molecular mechanisms of human blood vessel formation and to test effects of drugs that target human blood vessels in vivo to show proof of concept in a preclinical model.

The noradrenergic profile of plasma metanephrine in neuroblastoma patients is reproduced in xenograft mice models and arise from PNMT downregulation

Metanephrines (MNs; normetanephrine (NMN), metanephrine (MN) and methoxytyramine (MT)) detected in urine or plasma represent the best biomarker for neuroblastoma (NB) diagnosis, however the metabolism of both catecholamine (CAT) and MNs remains enigmatic in NB. Using patient-derived xenograft (PDX) models derived from primary NB cells, we observed that the plasma levels of MNs in NB-PDX-bearing mice were comparable as in patients. Interestingly, murine plasma displayed an elevated fraction of glucuronidated forms of MNs relative to human plasma where sulfonated forms prevail. In tumors, the concentration ranges of MNs and CAT and the expression levels of the main genes involved in catecholamine metabolism were similar between NB-PDX and human NB tissues. Likewise, plasma and intratumoral profiles of individual MNs, with increased levels of MT and NMN relative to MN, were also conserved in mouse models as in patients. We further demonstrated the downregulation of the Phenylethanolamine N-Methyltransferase gene in NB biopsies and in NB-PDX explaining this biochemical phenotype, and giving a rational to the low levels of epinephrine and MN measured in NB affected patients. Thus, our subcutaneous murine NB-PDX models not only reproduce the phenotype of primary NB tumors, but also the metabolism of catecholamine as observed in patients. This may potentially open new avenues in preclinical studies for the follow up of novel therapeutic options for NB through the quantification of plasma MNs.

Mouse models of high-risk neuroblastoma

Informative and realistic mouse models of high-risk neuroblastoma are central to understanding mechanisms of tumour initiation, progression, and metastasis. They also play vital roles in validating tumour drivers and drug targets, as platforms for assessment of new therapies and in the generation of drug sensitivity data that can inform treatment decisions for individual patients. This review will describe genetically engineered mouse models of specific subsets of high-risk neuroblastoma, the development of patient-derived xenograft models that more broadly represent the diversity and heterogeneity of the disease, and models of primary and metastatic disease. We discuss the research applications, advantages, and limitations of each model type, the importance of model repositories and data standards for supporting reproducible, high-quality research, and potential future directions for neuroblastoma mouse models.

Orthotopic Implantation Achieves Better Engraftment and Faster Growth Than Subcutaneous Implantation in Breast Cancer Patient-Derived Xenografts

Patient-Derived Xenograft (PDX) is now accepted as a murine model that better mimics human cancer when compared to a conventional cancer cell-line inoculation model. Some claim the advantage of orthotopic site implantation of patient tumor (OS) over ectopic implantation into the subcutaneous space (SQ); however, there has been no study that describes a head-to-head comparison of oncological differences between these two models to date. We hypothesize that OS tumors re-transplant and grow better than SQ tumors and are therefore a better model to evaluate tumor aggressiveness. Breast cancer PDXs were generated using the tumors derived from 11 patients into NOD scid gamma (NSG) mice. We used six ER(+)HER2(-) tumors and five triple negative (TN) tumors for a total of 11 tumors. Five PDX lines grew for an overall engraftment rate of 45%. We present our OS implantation method in detail. The re-transplantation rate of TN tumors in each transplant site was significantly higher in OS when compared to SQ tumors (70.1% vs. 32.1%, p < 0.01). OS tumors grow significantly faster than SQ tumors. Similarly, OS tumors demonstrated significantly more mitotic figures and Ki-67 positive cells than SQ tumors. The tumor re-transplantation rate significantly increased by the second and third generations with the OS method. The time from implantation to development of a palpable tumor dramatically decreased after the first passage. PDX of ER(+) tumors demonstrated significantly lower engraftment rates and slower tumor growth than TN tumors, which remarkably improved by the first passage. Orthotopically implanted PDX tumors showed better re-transplantation rates, greater tumor size, and more significant growth compared to the subcutaneously implanted model.

Accelerating development of high-risk neuroblastoma patient-derived xenograft models for preclinical testing and personalised therapy

Background

Predictive preclinical models play an important role in the assessment of new treatment strategies and as avatar models for personalised medicine; however, reliable and timely model generation is challenging. We investigated the feasibility of establishing patient-derived xenograft (PDX) models of high-risk neuroblastoma from a range of tumour-bearing patient materials and assessed approaches to improve engraftment efficiency.

Methods

PDX model development was attempted in NSG mice by using tumour materials from 12 patients, including primary and metastatic solid tumour samples, bone marrow, pleural fluid and residual cells from cytogenetic analysis. Subcutaneous, intramuscular and orthotopic engraftment were directly compared for three patients.

Results

PDX models were established for 44% (4/9) of patients at diagnosis and 100% (5/5) at relapse. In one case, attempted engraftment from pleural fluid resulted in an EBV-associated atypical lymphoid proliferation. Xenogeneic graft versus host disease was observed with attempted engraftment from lymph node and bone marrow tumour samples but could be prevented by T-cell depletion. Orthotopic engraftment was more efficient than subcutaneous or intramuscular engraftment.

Conclusions

High-risk neuroblastoma PDX models can be reliably established from diverse sample types. Orthotopic implantation allows more rapid model development, increasing the likelihood of developing an avatar model within a clinically useful timeframe.

Developing preclinical models of neuroblastoma: driving therapeutic testing

Despite advances in cancer therapeutics, particularly in the area of immuno-oncology, successful treatment of neuroblastoma (NB) remains a challenge. NB is the most common cancer in infants under 1 year of age, and accounts for approximately 10% of all pediatric cancers. Currently, children with high-risk NB exhibit a survival rate of 40–50%. The heterogeneous nature of NB makes development of effective therapeutic strategies challenging. Many preclinical models attempt to mimic the tumor phenotype and tumor microenvironment. In vivo mouse models, in the form of genetic, syngeneic, and xenograft mice, are advantageous as they replicated the complex tumor-stroma interactions and represent the gold standard for preclinical therapeutic testing. Traditional in vitro models, while high throughput, exhibit many limitations. The emergence of new tissue engineered models has the potential to bridge the gap between in vitro and in vivo models for therapeutic testing. Therapeutics continue to evolve from traditional cytotoxic chemotherapies to biologically targeted therapies. These therapeutics act on both the tumor cells and other cells within the tumor microenvironment, making development of preclinical models that accurately reflect tumor heterogeneity more important than ever. In this review, we will discuss current in vitro and in vivo preclinical testing models, and their potential applications to therapeutic development.

Investigating the Contribution of Collagen to the Tumor Biomechanical Phenotype with Noninvasive Magnetic Resonance Elastography

Increased stiffness in the extracellular matrix (ECM) contributes to tumor progression and metastasis. Therefore, stromal modulating therapies and accompanying biomarkers are being developed to target ECM stiffness. Magnetic resonance (MR) elastography can noninvasively and quantitatively map the viscoelastic properties of tumors in vivo and thus has clear clinical applications. Herein, we used MR elastography, coupled with computational histopathology, to interrogate the contribution of collagen to the tumor biomechanical phenotype and to evaluate its sensitivity to collagenase-induced stromal modulation. Elasticity (G d) and viscosity (G l) were significantly greater for orthotopic BT-474 (G d = 5.9 ± 0.2 kPa, G l = 4.7 ± 0.2 kPa, n = 7) and luc-MDA-MB-231-LM2-4 (G d = 7.9 ± 0.4 kPa, G l = 6.0 ± 0.2 kPa, n = 6) breast cancer xenografts, and luc-PANC1 (G d = 6.9 ± 0.3 kPa, G l = 6.2 ± 0.2 kPa, n = 7) pancreatic cancer xenografts, compared with tumors associated with the nervous system, including GTML/Trp53KI/KI medulloblastoma (G d = 3.5 ± 0.2 kPa, G l = 2.3 ± 0.2 kPa, n = 7), orthotopic luc-D-212-MG (G d = 3.5 ± 0.2 kPa, G l = 2.3 ± 0.2 kPa, n = 7), luc-RG2 (G d = 3.5 ± 0.2 kPa, G l = 2.3 ± 0.2 kPa, n = 5), and luc-U-87-MG (G d = 3.5 ± 0.2 kPa, G l = 2.3 ± 0.2 kPa, n = 8) glioblastoma xenografts, intracranially propagated luc-MDA-MB-231-LM2-4 (G d = 3.7 ± 0.2 kPa, G l = 2.2 ± 0.1 kPa, n = 7) breast cancer xenografts, and Th-MYCN neuroblastomas (G d = 3.5 ± 0.2 kPa, G l = 2.3 ± 0.2 kPa, n = 5). Positive correlations between both elasticity (r = 0.72, P < 0.0001) and viscosity (r = 0.78, P < 0.0001) were determined with collagen fraction, but not with cellular or vascular density. Treatment with collagenase significantly reduced G d (P = 0.002) and G l (P = 0.0006) in orthotopic breast tumors. Texture analysis of extracted images of picrosirius red staining revealed significant negative correlations of entropy with G d (r = -0.69, P < 0.0001) and G l (r = -0.76, P < 0.0001), and positive correlations of fractal dimension with G d (r = 0.75, P < 0.0001) and G l (r = 0.78, P < 0.0001). MR elastography can thus provide sensitive imaging biomarkers of tumor collagen deposition and its therapeutic modulation. SIGNIFICANCE: MR elastography enables noninvasive detection of tumor stiffness and will aid in the development of ECM-targeting therapies.

Evidence of Tumour Microenvironment and Stromal Cellular Components in Retinoblastoma

BACKGROUND

The tumour microenvironment (TME) consisting of tumour cells and multiple stromal cell types regulate tumour growth, invasion and metastasis. While the concept of TME and presence of stromal cellular components is widely established in cancers, its significance in the paediatric intraocular malignancy, retinoblastoma (RB), remains unknown.

METHODS

The study qualitatively identified the presence of multiple stromal cellular subtypes in RB TME by immunohistochemistry.

RESULTS

Results of the study identified the presence of stromal cell types such as endothelial cells, tumour-associated macrophages, fibroblasts, cancer-associated fibroblasts, retinal astrocytes and glia in RB TME. The extent of stromal marker positivity, however, did not correlate with histopathological features of RB.

CONCLUSIONS

The findings of the study convincingly suggest the presence of a stromal component in RB tumours. The interactions between stromal cells and tumour cells might be of profound importance in RB progression.

The Avatar Acceptability Study: Survivor, Parent and Community Willingness to Use Patient-Derived Xenografts to Personalize Cancer Care

BACKGROUND

Using patient-derived xenografts (PDXs) to assess chemosensitivity to anti-cancer agents in real-time may improve cancer care by enabling individualized clinical decision-making. However, it is unknown whether this new approach will be met with acceptance by patients, family and community.

METHODS

We used a cross-sectional structured survey to investigate PDX acceptability with 1550 individuals across Australia and New Zealand (648 survivors of adult and childhood cancer, versus 650 community comparisons; and 48 parents of childhood cancer survivors versus 204 community parents). We identified factors influencing willingness-to-use PDXs, willingness-to-pay, maximum acceptable wait-time, and maximum acceptable number of mice used per patient.

FINDINGS

PDXs were highly acceptable: >80% of those affected by cancer felt the potential advantages of PDXs outweighed the disadvantages (community participants: 68%). Survivors' and survivors' parents' most highly endorsed advantage was 'increased chance of survival'. 'Harm to animals' was the least endorsed disadvantage for all groups. Cancer survivors were more willing to use PDXs than community comparisons [p < ·001]. Survivors and survivors' parents were willing to pay more [p < ·001; p = ∙004 respectively], wait longer for results [p = ·03; p = ∙01], and use more mice [p = ·01; p < ∙001] than community comparisons. Male survivors found PDXs more acceptable [p = ·01] and were willing to pay more [p < ·001] than female survivors. Survivors with higher incomes found PDXs more acceptable [p = ·002] and were willing to pay more [p < ·001] than survivors with lower incomes. Mothers found PDXs more acceptable [p = ·04] but were less willing to wait [p = ·02] than fathers.

INTERPRETATION

We found significant attitudinal support for PDX-guided cancer care. Willingness-to-pay and maximum acceptable number of mice align well with likely future usage. Maximum acceptable wait-times were lower than is currently achievable, highlighting an important area for future patient education until technology has caught up.

Patient-Derived Xenograft Models Reveal Intratumor Heterogeneity and Temporal Stability in Neuroblastoma

Patient-derived xenografts (PDX) and the Avatar, a single PDX mirroring an individual patient, are emerging tools in preclinical cancer research. However, the consequences of intratumor heterogeneity for PDX modeling of biomarkers, target identification, and treatment decisions remain underexplored. In this study, we undertook serial passaging and comprehensive molecular analysis of neuroblastoma orthotopic PDXs, which revealed strong intrinsic genetic, transcriptional, and phenotypic stability for more than 2 years. The PDXs showed preserved neuroblastoma-associated gene signatures that correlated with poor clinical outcome in a large cohort of patients with neuroblastoma. Furthermore, we captured spatial intratumor heterogeneity using ten PDXs from a single high-risk patient tumor. We observed diverse growth rates, transcriptional, proteomic, and phosphoproteomic profiles. PDX-derived transcriptional profiles were associated with diverse clinical characteristics in patients with high-risk neuroblastoma. These data suggest that high-risk neuroblastoma contains elements of both temporal stability and spatial intratumor heterogeneity, the latter of which complicates clinical translation of personalized PDX-Avatar studies into preclinical cancer research.Significance: These findings underpin the complexity of PDX modeling as a means to advance translational applications against neuroblastoma. Cancer Res; 78(20); 5958-69. ©2018 AACR.

Patient-derived tumor xenografts of lung squamous cell carcinoma alter long non-coding RNA profile but not responsiveness to cisplatin

Lung squamous cell carcinoma (LSCC), the second most common type of lung cancer, has received limited attention. Patient-derived tumor xenografts (PDTXs) are useful preclinical models to reproduce the diverse heterogeneity of cancer, but it is important to identify potential variations during their establishment. A total of 18 PDTXs were established from 37 the surgical specimens and 16 were serially passaged to third generation. Second- and third-generation xenografts had a faster growth rate in mice. The tumor implantation success rate was associated with poorer differentiation, larger tumor volume and higher expression of Ki-67. The xenografts largely retained histological and key immunophenotypic features (including p53, p63, cytokeratin5/6, and E-cadherin). However, increased Ki-67 expression was identified in partial xenografts. Long non-coding RNA (lncRNA) and mRNA expression in third-generation xenografts differed from that of matched primary tumors. Gene Ontology and pathway analysis showed that mRNAs involved in cell cycle, and metabolism regulation were generally upregulated in xenografts, while those associated with immune responses were typically downregulated. Furthermore, the responses of xenografts to cisplatin were consistent with clinical outcome. In the present study, PDTXs of SCC were successfully established, and closely resembled their original tumor regarding their immunophenotype and response to cisplatin. Overall, PDTXS of LSCC altered the lncRNA profile and increased the proliferative activity of cancer cells, whilst retaining responsiveness to cisplatin.

Using PDX for Preclinical Cancer Drug Discovery: The Evolving Field

The ability to create patient derived xenografts (PDXs) has evolved considerably from the breakthrough of the development of immune compromised mice. How researchers in drug discovery have utilized PDX of certain cancer types has also changed from traditionally selecting a few models to profile a drug, to opting to assess inter-tumor response heterogeneity by screening across a broad range of tumor models, and subsequently to enable clinical stratification strategies. As with all models and methodologies, imperfections with this approach are apparent, and our understanding of the fidelity of these models continues to expand. To date though, they are still viewed as one of the most faithful modeling systems in oncology. Currently, there are many efforts ongoing to increase the utility and translatability of PDXs, including introducing a human immune component to enable immunotherapy studies.

Intratumoral Delivery of Interferonγ-Secreting Mesenchymal Stromal Cells Repolarizes Tumor-Associated Macrophages and Suppresses Neuroblastoma Proliferation In Vivo

Neuroblastoma, the most common extracranial solid tumor in childhood, remains a therapeutic challenge. However, one promising patient treatment strategy is the delivery of anti-tumor therapeutic agents via mesenchymal stromal cell (MSC) therapy. MSCs have been safely used to treat genetic bone diseases such as osteogenesis imperfecta, cardiovascular diseases, autoimmune diseases, and cancer. The pro-inflammatory cytokine interferon-gamma (IFNγ) has been shown to decrease tumor proliferation by altering the tumor microenvironment (TME). Despite this, clinical trials of systemic IFNγ therapy have failed due to the high blood concentration required and associated systemic toxicities. Here, we developed an intra-adrenal model of neuroblastoma, characterized by liver and lung metastases. We then engineered MSCs to deliver IFNγ directly to the TME. In vitro, these MSCs polarized murine macrophages to the M1 phenotype. In vivo, we attained a therapeutically active TME concentration of IFNγ without increased systemic concentration or toxicity. The TME-specific IFNγ reduced tumor growth rate and increased survival in two models of T cell deficient athymic nude mice. Absence of this benefit in NOD SCID gamma (NSG) immunodeficient mouse model indicates a mechanism dependent on the innate immune system. IL-17 and IL-23p19, both uniquely M1 polarization markers, transiently increased in the tumor interstitial fluid. Finally, the MSC vehicle did not promote tumor growth. These findings reveal that MSCs can deliver effective cytokine therapy directly to the tumor while avoiding systemic toxicity. This method transiently induces inflammatory M1 macrophage polarization, which reduces tumor burden in our novel neuroblastoma murine model. Stem Cells 2018;36:915-924.

Investigation of major genetic alterations in neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood. This malignancy shows a wide spectrum of clinical outcome and its prognosis is conditioned by manifold biological and genetic factors. We investigated the tumor genetic profile and clinical data of 29 patients with NB by multiplex ligation-dependent probe amplification (MLPA) to assess therapeutic risk. In 18 of these tumors, MYCN status was assessed by fluorescence in situ hybridization (FISH). Copy number variation was also determined for confirming MLPA findings in two 6p loci. We found 2p, 7q and 17q gains, and 1p and 11q losses as the most frequent chromosome alterations in this cohort. FISH confirmed all cases of MYCN amplification detected by MLPA. In view of unexpected 6p imbalance, copy number variation of two 6p loci was assessed for validating MLPA findings. Based on clinical data and genetic profiles, patients were stratified in pretreatment risk groups according to international consensus. MLPA proved to be effective for detecting multiple genetic alterations in all chromosome regions as requested by the International Neuroblastoma Risk Group (INRG) for therapeutic stratification. Moreover, this technique proved to be cost effective, reliable, only requiring standard PCR equipment, and attractive for routine analysis. However, the observed 6p imbalances made PKHD1 and DCDC2 inadequate for control loci. This must be considered when designing commercial MLPA kits for NB. Finally, four patients showed a normal MLPA profile, suggesting that NB might have a more complex genetic pattern than the one assessed by presently available MLPA kits.

Patient-derived xenografts as preclinical neuroblastoma models

The prognosis for children with high-risk neuroblastoma is often poor and survivors can suffer from severe side effects. Predictive preclinical models and novel therapeutic strategies for high-risk disease are therefore a clinical imperative. However, conventional cancer cell line-derived xenografts can deviate substantially from patient tumors in terms of their molecular and phenotypic features. Patient-derived xenografts (PDXs) recapitulate many biologically and clinically relevant features of human cancers. Importantly, PDXs can closely parallel clinical features and outcome and serve as excellent models for biomarker and preclinical drug development. Here, we review progress in and applications of neuroblastoma PDX models. Neuroblastoma orthotopic PDXs share the molecular characteristics, neuroblastoma markers, invasive properties and tumor stroma of aggressive patient tumors and retain spontaneous metastatic capacity to distant organs including bone marrow. The recent identification of genomic changes in relapsed neuroblastomas opens up opportunities to target treatment-resistant tumors in well-characterized neuroblastoma PDXs. We highlight and discuss the features and various sources of neuroblastoma PDXs, methodological considerations when establishing neuroblastoma PDXs, in vitro 3D models, current limitations of PDX models and their application to preclinical drug testing.

Neuroblastoma patient-derived xenograft cells cultured in stem-cell promoting medium retain tumorigenic and metastatic capacities but differentiate in serum

Cultured cancer cells serve as important models for preclinical testing of anti-cancer compounds. However, the optimal conditions for retaining original tumor features during in vitro culturing of cancer cells have not been investigated in detail. Here we show that serum-free conditions are critical for maintaining an immature phenotype of neuroblastoma cells isolated from orthotopic patient-derived xenografts (PDXs). PDX cells could be grown either as spheres or adherent on laminin in serum-free conditions with retained patient-specific genomic aberrations as well as tumorigenic and metastatic capabilities. However, addition of serum led to morphological changes, neuronal differentiation and reduced cell proliferation. The epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) were central for PDX cell proliferation and MYCN expression, and also hindered the serum-induced differentiation. Although serum induced a robust expression of neurotrophin receptors, stimulation with their cognate ligands did not induce further sympathetic differentiation, which likely reflects a block in PDX cell differentiation capacity coupled to their tumor genotype. Finally, PDX cells cultured as spheres or adherent on laminin responded similarly to various cytotoxic drugs, suggesting that both conditions are suitable in vitro screening models for neuroblastoma-targeting compounds.

Advances in emerging drugs for the treatment of neuroblastoma

INTRODUCTION

Neuroblastoma is the most common solid extracranial tumor of childhood. Outcome for children with high-risk neuroblastoma remains suboptimal. More than half of children diagnosed with high-risk neuroblastoma either do not respond to conventional therapies or relapse after treatment with dismal prognosis. Areas covered: This paper presents a short review of the state of the art in the current treatment of high-risk neuroblastoma. An updated review of new targeted therapies in this group of patients is also presented. Expert opinion: In order to improve prognosis for high-risk patients there is an urgent need to better understand spatial and temporal heterogeneity and obtain new predictive preclinical models in neuroblastoma. Combination strategies with conventional chemotherapy and/or other targeted therapies may overcome current ALK inhibitors resistance. Improvement of international and transatlantic cooperation to speed clinical trials accrual is needed.

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.

Therapeutic targeting of hypoxia and hypoxia-inducible factors in cancer

Insufficient tissue oxygenation, or hypoxia, contributes to tumor aggressiveness and has a profound impact on clinical outcomes in cancer patients. At decreased oxygen tensions, hypoxia-inducible factors (HIFs) 1 and 2 are stabilized and mediate a hypoxic response, primarily by acting as transcription factors. HIFs exert differential effects on tumor growth and affect important cancer hallmarks including cell proliferation, apoptosis, differentiation, vascularization/angiogenesis, genetic instability, tumor metabolism, tumor immune responses, and invasion and metastasis. As a consequence, HIFs mediate resistance to chemo- and radiotherapy and are associated with poor prognosis in cancer patients. Intriguingly, perivascular tumor cells can also express HIF-2α, thereby forming a "pseudohypoxic" phenotype that further contributes to tumor aggressiveness. Therefore, therapeutic targeting of HIFs in cancer has the potential to improve treatment efficacy. Different strategies to target hypoxic cancer cells and/or HIFs include hypoxia-activated prodrugs and inhibition of HIF dimerization, mRNA or protein expression, DNA binding capacity, and transcriptional activity. Here we review the functions of HIFs in the progression and treatment of malignant solid tumors. We also highlight how HIFs may be targeted to improve the management of patients with therapy-resistant and metastatic cancer.