MYC-driven pediatric tumors, such as high-risk neuroblastoma (NB) and group 3 medulloblastoma (G3MB), represent some of the most aggressive and therapy-resistant cancers. To date, only one direct MYC inhibitor has passed a phase I trial, yet its safety and therapeutic potential in pediatric oncology remain unclear. Our findings show that mitochondrial stress-inducing drugs, including common antibiotics, can indirectly suppress MYC proteins and trigger MYC-dependent cell death in multidrug-resistant NB via mitochondrial integrated stress response (mitoISR). This project aims to leverage the identified mitochondrial synthetic lethality as a selective therapeutic approach for tumors dependent on high levels of MYC proteins. Using NB as proof of concept, we will apply our novel cumate-inducible MYC/MYCN models for the first-in-field uncompromised screening for MYC-synthetic lethal drugs in a custom FDA-approved drug library, rationally enriched with ribosomal antibiotics and mitochondrial stressors. Hits will be validated in MYC-driven NB, G3MB, and Burkitt lymphoma cell lines and characterized for mitochondrial selectivity, including luciferase assays in cell-free translation and mitoISR reporter systems. The efficiency of key candidates will be further tested in spheroid cultures and in vivo using a zebrafish model of MYCN-driven NB. To facilitate repurposing for pediatric tumors, potent MYC-synthetic lethal drugs will be prioritized based on known safety profiles, and their therapeutic potential will be assessed in highly relevant preclinical models accessed via multicentric international collaboration: (i) in vitro, in a panel of primary patient-derived cell lines from relapsed/refractory tumors, (ii) in vivo, in zebrafish xenograft and patient-derived xenograft models. This translational research project is designed to deliver robust data that could pave the way for clinical trials of well-tolerated drugs repurposed to treat resistant MYC-driven pediatric tumors.

The integrated stress response (ISR) is a key pathway that relays stress signals from damaged or dysfunctional mitochondria. Depending on its extent, the mitochondrially activated ISR (mitoISR) restores mitochondrial homeostasis or triggers apoptosis. As shown by our group and others, mitoISR-inducing drugs efficiently overcome therapy resistance in aggressive cancers that overexpress MYC transcription factors. Yet, molecular determinants that underlie the vulnerability of MYC-driven tumors to the inhibition of mitochondrial gene expression machinery remain poorly understood. Building on our data that reveals a previously unrecognized link between mitoISR and degradation of MYC proteins, this project will dissect mitoISR activities genetically and pharmacologically to elucidate their role in regulating the “undruggable” MYC proteins. We will develop novel inducible MYC/MYCN expression models, avoiding mitochondrial off-target effects of previous systems, to provide unique insights into mitoISR/ISR as potential synthetic lethality targets for therapy of MYC-driven tumors.

Neuroblastoma (NB) remains a highly lethal pediatric solid tumor accounting for 15% of cancer-related deaths in children. NB shows extensive heterogeneity that dictates its clinical course, ranging from spontaneous regression to treatment-resistant metastatic disease. Several biomarkers, including genetic aberrations, have significantly improved NB risk assessment and treatment assignment. Yet, up to 10% of NB patients diagnosed with low- and intermediate-risk tumors eventually die from progressive disease and survival of high-risk NB patients has plateaued at 60%. NB arises mainly in the adrenal glands and sympathetic ganglia and is thought to originate in the neural crest cell-derived sympathoadrenal lineage. Recent single-cell transcriptomics studies of normal sympathoadrenal development have discovered unprecedented differentiation trajectories and cell state clusters relevant to NB heterogeneity. We have shown in NB cell lines that key cluster-specific genes might be highly informative of the different NB origins and aggressiveness. Expanding on these results and our preliminary data, we propose an internationally collaborative project that will comprehensively investigate selected genes defining the distinct cell phenotypes in the normal sympathoadrenal development to evaluate their potential utility as new therapeutic targets and/or markers refining prognosis in NB. We will utilize NB transcriptomics, tissue sections and patient-derived cell lines to reveal potential correlations between the cell cluster-specific gene expression and clinicopathological features. Promising candidates will be functionally and pharmacologically characterized in NB cells and validated in single-cell transcriptomics datasets and a unique, large cohort of NB tissue samples. This project aims to pinpoint clinically relevant genes/proteins that might reflect developmental origins of NB and that could help to improve risk classification systems or predict novel therapies for NB.

This project is aimed at finding new molecular targets for the treatment of giant cell tumor of bone (GCTB) using low-molecular weight inhibitors of receptor tyrosine kinases and other signaling molecules. GCTB is rare, but an aggressive osteolytic tumor that typically originates in the epimetaphyseal region of a long bones. GCTB is clinically defined as a benign bone tumor, but is characterized by locally aggressive growth and usually leads to an extensive bone lesion. Phosphorylation profile of receptor tyrosine kinases and other signaling molecules in native tumor tissue samples as well as in subsequently derived cell lines should be included in this study. Expression and phosphorylation of selected signaling molecules should be retrospectively analysed in a set of parafine blocks. Inhibition of activated signaling pathways on cellular processes (i.e. proliferation and cell death) should be studied in vitro and the anti-tumor activity of inhibitors should be validated in vivo using xenografted tumors. The obtained data should bring new information concerning receptor tyrosine kinases and the downstream signaling pathways as therapeutic targets in GCTB.