Neuroblastoma (NB) is a pediatric malignancy developing in the sympathoadrenal lineage of the neural crest, characterized by clinical heterogeneity ranging from spontaneous regression to poor outcomes. Activating mutations in the receptor tyrosine kinase anaplastic lymphoma kinase (ALK) are frequently observed in both sporadic and familial NB, yet the functional role of ALK in tumor initiation is not fully understood. Using a patient-derived human induced pluripotent stem cell (iPSC) model of sympathoadrenal development, we show that upon sympathoadrenal lineage commitment, ALK R1275Q, the most common hotspot mutation found in familial NB, sustain a proliferative, immature Schwann cell precursor (SCP)-like cell state with elevated ALK signaling and increased susceptibility to MYCN-driven transformation. While ALK-mutant cells alone did not form tumors in vivo , they cooperated with MYCN to accelerate tumor initiation, suggesting that ALK R1275Q creates a permissive but insufficient state for transformation. These findings define an ALK-driven cell progenitor-like state that facilitates the initiation of NB during embryonal development.

Background High-risk neuroblastoma (HR-NB) is associated with therapy-resistant relapse, and novel therapeutic strategies are needed. GSPT1 is a GTPase involved in protein translation whose disruption may offer therapeutic potential in translation-dependent cancers. Methods GSPT1 expression was assessed in publicly available clinical data and tissue microarrays. GSPT1-degrading molecular glues were tested in MYCN-amplified NB organoids. Cell viability, cell death assays, western blotting, and proteomics were used to evaluate GSPT1 degraders. Effects on tumor growth and mouse survival were benchmarked against standard-of-care chemotherapy in a chemoresistant NB patient-derived xenograft (PDX) model. RNA sequencing and histopathological analysis were used to assess mechanisms of action in vivo. Results GSPT1 expression is associated with unfavorable outcomes in NB patients. Single-cell analysis revealed elevated GSPT1 expression in MYCN-amplified NB, whereas the E3 ligase CRBN (essential for protein degradation) was predominantly expressed in NB cells relative to non-malignant cells. GSPT1-specific degradation decreased cell viability and induced apoptosis in MYCN-amplified NB organoids and PDX models. GSPT1 degradation in vivo resulted in NB differentiation and suppression of MYCN and its related core regulatory gene networks. In vivo treatment further outperformed standard-of-care chemotherapy and increased survival in a highly chemoresistant NB PDX model. Conclusions Inhibition of the translational machinery by GSPT1-degrading molecular glues shows therapeutic potential in chemoresistant MYCN-amplified NB.

Neuroblastoma (NB) is an aggressive pediatric solid tumor which often develops chemoresistance. Ferroptosis is a potential vulnerability in NB, but its interplay with chemoresistance and standard-of-care chemotherapy is not known. Here, we report that key antioxidant pathways are enriched in refractory NB, and that ferroptosis can be induced in NB through various mechanisms of action (MOA) in vitro and in vivo. We observed that NB standard-of-care chemotherapy can interfere with certain ferroptosis-inducing mechanisms, particularly those targeting GPX4, and that the combination of ferroptosis-inducing drugs with current clinical therapy should be based on MOA. Our work also shows that a combination of chemotherapy and the thioredoxin reductase inhibitor Auranofin counteracted some of the anti-ferroptotic effects of chemotherapy and the combination outperformed chemotherapy alone, resulting in increased survival in a chemoresistant NB patient-derived xenograft model. The combination of Auranofin and chemotherapy decreased the population of immature mesenchymal-like NB cells in vivo and exerted its effect through ferritinophagy, lysosome accumulation and iron overload. Thus, upon careful selection of the MOA, the inclusion of ferroptosis-inducing agents within a clinically relevant treatment protocol is feasible and can outperform standard-of-care chemotherapy in high-risk NB.

Relapse and treatment resistance are common in children with high-risk neuroblastoma, and novel therapies are needed. Conventional drug discovery is slow, expensive, often fails in practice, and consequently falls short in addressing pediatric and rare conditions. In such instances, drug repurposing is a promising strategy. Here, we used two independent in silico prediction tools including machine learning to identify approved drugs for repurposing against neuroblastoma. The combination of statins and phenothiazines showed strong synergistic effects in human neuroblastoma organoids, decreased tumor growth, and prolonged survival in MYCN-amplified neuroblastoma patient-derived xenografts. The drug combination altered cholesterol metabolism through two different mechanisms and induced a phenotypic change toward an adrenergic state in vitro, which was associated with enhanced chemosensitivity. Integration of the drug combination into standard-of-care chemotherapy regressed tumors and prolonged survival in chemoresistant patient-derived xenografts. Thus, a combination of safe and approved medications added to standard-of-care chemotherapy outperforms chemotherapy alone in chemoresistant neuroblastoma.

Abstract: Relapse and treatment resistance are common in children with high-risk neuroblastoma, and novel therapies are needed. Conventional drug discovery is slow, expensive, often fails in practice, and consequently falls short in addressing pediatric and rare conditions. In such instances, drug repurposing is a promising strategy. Here, we used two independent in silico prediction tools including machine learning to identify approved drugs for repurposing against neuroblastoma. The combination of statins and phenothiazines showed strong synergistic effects in human neuroblastoma organoids, decreased tumor growth and prolonged survival in MYCN-amplified neuroblastoma patient-derived xenografts. The drug combination altered cholesterol metabolism through a dual-hit mechanism and induced a phenotypic switch towards an adrenergic cell state accompanied by increased sensitivity to chemotherapy. Integration of the drug combination into standard-of-care chemotherapy regressed tumors and prolonged survival in chemoresistant patient-derived xenografts. Thus, a combination of safe and approved medications added to standard-of-care chemotherapy outperforms chemotherapy alone in chemoresistant neuroblastoma. ### Competing Interest Statement DBe has received research funding from Healx, ENEA, and aPODD Foundation for this project. CS is shareholder of Oncoheroes Biosciences Inc. DM, DO, IR, AL, JB, ED, DBr, and NT are (or have been) employed at Healx. All other authors report no conflict of interest.

Despite the advent of advanced molecular prognostic tools, it is still difficult to predict the course of disease for cancer patients at the individual level. This lack of predictability is also reflected in many experimental cancer model systems, begging the question of whether certain biological aspects of cancer (eg. growth, evolution etc.) can ever be anticipated or if there remains an inherent unpredictability to cancer, similar to other complex biological systems. We demonstrate by a combination of agent-based mathematical modelling, analysis of patient-derived xenograft model systems from multiple cancer types, and in-vitro culture that certain conditions increase stochasticity of the clonal landscape of cancer growth. Our findings indicate that under those conditions, the cancer genome may behave as a complex dynamic system, making its long-term evolution inherently unpredictable.

Amplification of the MYCN proto-oncogene serves as a key marker of aggressive disease and poor treatment outcomes in certain pediatric tumors originating from the nervous system, including neuroblastoma and medulloblastoma. However, the complex nature of the challenging MYCN protein underscores the urgent need for additional targets and therapies to tackle neuroblastoma and medulloblastoma. In this study, with a primary focus on neuroblastoma and the aim of also benefiting children with medulloblastoma, we identified FLIX5, a small compound that exhibits broad cytotoxicity against both neuroblastoma and medulloblastoma cells, primarily by triggering apoptosis. Furthermore, FLIX5 enhances the cholesterol dependency of neuroblastoma cells under conditions where mitochondrial function is impaired. FLIX5 as well shows a synergistic effect when combined with vincristine, a conventional anticancer drug, against neuroblastoma cells and organoids. Through proteome integral solubility alteration, computational molecular docking predictions, and cellular thermal shift assays for target identification and validation, FLIX5 reveals EPLIN (Epithelial Protein Lost In Neoplasm) as a previously unexplored drug target. EPLIN is involved in several cellular processes, including cholesterol uptake and mitochondrial function. The discovery of FLIX5 targeting EPLIN presents new opportunities for treating malignant pediatric tumors, with the potential to target chemoresistant dormant cancer cells and broaden its therapeutic applications to other tumor types.

BACKGROUND:Neuroblastoma (NB) is a childhood cancer with a high relapse rate despite intensive treatment. TRPA1 is a pain-sensing ion channel with downstream impacts on proliferative and pro-apoptotic pathways. Here, we evaluated TRPA1 expression in NB and performed pharmacological inhibition in preclinical models to assess its potential as a therapeutic target in NB. METHODS:TRPA1 protein levels were assessed in NB patient tumors on tissue microarrays. Bulk and single-cell gene expression data were retrieved from publicly available databases. The effects of three TRPA1 inhibitors (AP-18, A967079, and Bay 390) on NB cell viability and cell death were evaluated using NB patient-derived xenograft (PDX)-derived organoids. In vivo testing was performed in a MYCN-amplified NB PDX model. Drug combination testing was performed using combination or sequential treatments and evaluated using drug synergy scores. RESULTS:TRPA1 is widely expressed in NB patient tumors and preclinical patient-derived NB models. Pharmacological TRPA1 inhibition decreased NB cell viability and increased cell death. In vivo TRPA1 inhibition alone did not significantly affect NB tumor growth. Pretreatment with TRPA1 inhibition prior to chemotherapy resulted in synergistic effects in vitro. CONCLUSIONS:TRPA1 is expressed in NB tumors, and pharmacological TRPA1 inhibition can be effective in vitro and synergistic when used as pretreatment to chemotherapy. However, the tested inhibitors did not show in vivo efficacy, at least as monotherapy.

Neuroblastoma (NB) is one of the most lethal childhood cancers due to its propensity to become treatment resistant. By spatial mapping of subclone geographies before and after chemotherapy across 89 tumor regions from 12 NBs, we find that densely packed territories of closely related subclones present at diagnosis are replaced under effective treatment by islands of distantly related survivor subclones, originating from a different most recent ancestor compared to lineages dominating before treatment. Conversely, in tumors that progressed under treatment, ancestors of subclones dominating later in disease are present already at diagnosis. Chemotherapy treated xenografts and cell culture models replicate these two contrasting scenarios and show branching evolution to be a constant feature of proliferating NB cells. Phylogenies based on whole genome sequencing of 505 individual NB cells indicate that a rich repertoire of parallel subclones emerges already with the first oncogenic mutations and lays the foundation for clonal replacement under treatment. Neuroblastoma (NB) is a frequent childhood cancer that often becomes resistant to therapy. Here, the authors perform spatiotemporal genomic profiling of NBs before and after chemotherapy and find an evolutionary process characteristic of NBs growing resistant after first responding to treatment.

Abstract Background Neuroblastoma (NB) is a heterogeneous pediatric solid tumor of the sympathetic nervous system that accounts for 15% of pediatric childhood deaths. High-risk NB is often chemoresistant, with <50% survival. Additionally, its low mutational load and immunosuppressive tumor microenvironment (i-TME) have hindered the success of immunotherapy. NB has a strong dependency on iron metabolism, making induction of ferroptosis, an iron-mediated immunogenic cell death, a potential treatment for chemoresistant NB. Ferroptosis also has the potential to enhace immune cell therapy. Natural killer (NK) cells have emerged as a promising immunotherapeutic tool for pediatric tumors, as they don’t depend on specific mutations, but new strategies are needed to overcome the i-TME. Comnination with immunogenic ferroptosis induction could be a solution. Here we explore the combination of ferroptosis induction, standard-of-care chemotherapy and NK cell therapy, to identify novel therapeutic combinations to tackle high-risk NB. Results Using NB patient-derived models, we analyzed multiple ferroptosis-inducing compounds with different mechanisms of action. Auranofin (thioredoxin reductase inhibitor) and RSL3 (inhibitor of glutathione peroxidase 4, GPX4) were identified as promising agents against chemoresistant NB. Both agents increased survival, reduced tumor growth, and decreased the population of chemoresistant immature mesenchymal-like cells in vivo. Upon combination with chemotherapy, the distinct mechanisms of ferroptosis induction led to differential interactions with COJEC, the standard-of-care 5-drug cocktail used to treat NB patients. Auranofin exhibited an additive effect, while RSL3 showed an antagonistic interaction due to upregulation of GPX4 and other ferroptosis inhibitors by COJEC, primarily driven by etoposide. The combination Auranofin-COJEC decreased tumor growth and increased survival in a chemoresistant NB patient-derived xenograft (PDX) model through ferritinophagy, lysosome accumulation, and iron overload. Upon RNA analysis of PDX tumors treated with Auranofin and RSL3, we observed that RSL3 enhanced the expression of pathways associated with inflammation, while Auranofin had the opposite effect. Treatment with ferroptosis-inducing agents in vitro led to the release of damage-associated molecular patterns (DAMPs) and, when combined in a sequential manner with NK cell therapy, an additive effect was observed. Conclusions The use of ferroptosis-inducing agents, based on their mechanisms of action, in combination with chemotherapy and immunotherapy, is a feasible and promising strategy that outperforms standard-of-care chemotherapy in chemoresistant NB. Future work should identify which ferroptosis-inducing mechanisms are best to combine with chemotherapy and immunotherapy, and which patients can benefit from each combination based on tumor characteristics. The availability of multiple ferrotosis-inducing mechanism opens the door to personalized treatment protocols. Citation Format: Adriana Mañas, Alexandra Seger, Aleksandra Adamska, Kyriaki Smyrilli, Lucía Sánchez, Antonio Pérez-Martínez, Daniel Bexell. Targeted ferroptosis induction enhances chemotherapy and natural killer cell immunotherapy in neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pediatric Cancer Research; 2024 Sep 5-8; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl):Abstract nr A078.

Supplementary Table 3. siRNA oligos used for transfections.

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.

Supplementary Table 2. Nucleotide sequences of primers used for qPCR reactions.

Figure legends corresponding to Supplementary Figures 1-4.

Supplementary Table 1. Antibodies used for western blotting.

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.

CD169+ resident macrophages in lymph nodes of breast cancer patients are for unknown reasons associated with a beneficial prognosis. This contrasts CD169+ macrophages present in primary breast tumors (CD169+ TAMs), that correlate with a worse prognosis. We recently showed that these CD169+ TAMs were associated with tertiary lymphoid structures (TLSs) and Tregs in breast cancer. Here, we show that CD169+ TAMs can be monocyte-derived and express a unique mediator profile characterized by type I IFNs, CXCL10, PGE2 and inhibitory co-receptor expression pattern. The CD169+ monocyte-derived macrophages (CD169+ Mo-M) possessed an immunosuppressive function in vitro inhibiting NK, T and B cell proliferation, but enhanced antibody and IL6 secretion in activated B cells. Our findings indicate that CD169+ Mo-M in the primary breast tumor microenvironment are linked to both immunosuppression and TLS functions, with implications for future targeted Mo-M therapy.

Supplementary Table S3. Related to Figure 3. Gene ontology for genes with higher expression in patient tumors vs. PDOXs. Supplementary Table S4. Related to Figure 3. List of the gene clusters defined across PDOXs #1-5 obtained from serial orthotopic passaging. Supplementary Table S5. Related to Figure 3. List of enriched Gene Ontology terms by cluster defined in PDOXs #1-5.

Supplementary Figure 1. Knockdown of IGF2R does not affect HIF2A transcription.

Supplementary Figure 3. Knockdown or chemical inhibition of Akt does not affect HIF2A expression.