Rhabdoid tumors (RT) are among the most aggressive tumors in early childhood. Overall survival remains poor, and treatment only effectively occurs at the cost of high toxicity and late adverse effects. It has been reported that the neurokinin-1 receptor/ substance P complex plays an important role in cancer and proved to be a promising target. However, its role in RT has not yet been described. This study aims to determine whether the neurokinin-1 receptor is expressed in RT and whether neurokinin-1 receptor (NK1R) antagonists can serve as a novel therapeutic approach in treating RTs. By in silico analysis using the cBio Cancer Genomics Portal we found that RTs highly express neurokinin-1 receptor. We confirmed these results by RT-PCR in both tumor cell lines and in human tissue samples of various affected organs. We demonstrated a growth inhibitory and apoptotic effect of aprepitant in viability assays and flow cytometry. Furthermore, this effect proved to remain when used in combination with the cytostatic cisplatin. Western blot analysis showed an upregulation of apoptotic signaling pathways in rhabdoid tumors when treated with aprepitant. Overall, our findings suggest that NK1R may be a promising target for the treatment of RT in combination with other anti-cancer therapies and can be targeted with the NK1R antagonist aprepitant.

Background: As the variable clinical outcome of patients with hepatoblastoma (HB) cannot be explained by genetics alone, the identification of drugs with the potential to effectively reverse epigenetic alterations is a promising approach to overcome poor therapy response. The gene ubiquitin like with PHD and ring finger domains 1 (UHRF1) represents an encouraging epigenetic target due to its regulatory function in both DNA methylation and histone modifications and its clinical relevance in HB. Methods: Patient-derived xenograft in vitro and in vivo models were used to study drug response. The mechanistic basis of CM-272 treatment was elucidated using RNA sequencing and western blot experiments. Results: We validated in comprehensive data sets that UHRF1 is highly expressed in HB and associated with poor outcomes. The simultaneous pharmacological targeting of UHRF1-dependent DNA methylation and histone H3 methylation by the dual inhibitor CM-272 identified a selective impact on HB patient-derived xenograft cell viability while leaving healthy fibroblasts unaffected. RNA sequencing revealed downregulation of the IGF2-activated survival pathway as the main mode of action of CM-272 treatment, subsequently leading to loss of proliferation, hindered colony formation capability, reduced spheroid growth, decreased migration potential, and ultimately, induction of apoptosis in HB cells. Importantly, drug response depended on the level of IGF2 expression, and combination assays showed a strong synergistic effect of CM-272 with cisplatin. Preclinical testing of CM-272 in a transplanted patient-derived xenograft model proved its efficacy but also uncovered side effects presumably caused by its strong antitumor effect in IGF2-driven tumors. Conclusions: The inhibition of UHRF1-associated epigenetic traces, such as IGF2-mediated survival, is an attractive approach to treat high-risk HB, especially when combined with the standard-of-care therapeutic cisplatin.

Hepatoblastoma (HB) is the main paediatric liver cancer, but it is a very rare disease. Despite significant improvements in the treatment of children diagnosed with HB, limited treatment options exist for patients with advanced tumours. Besides, survivors generally have long-term adverse effects derived from treatment such as ototoxicity, cardiotoxicity, delayed growth, and secondary tumours. Accordingly, there is an urgent need to define new and efficient therapeutic strategies for patients with HB. Computational methods to predict drug sensitivity from a tumour’s transcriptome have been successfully applied for some common adult malignancies, but specific efforts in paediatric cancers are lacking because of paucity of data. In this study, we computationally screened the efficacy of drugs in HB patients with the aggressive C2 subtype and poor clinical outcome starting from their transcriptome. Our method utilized publicly available collections of pan-cancer transcriptional profiles and drug responses across 36 tumour types and 495 compounds. The drugs predicted to be most effective were experimentally validated using patient-derived xenograft (PDX) models of HB grown in vitro and in vivo. We thus identified two CDK9 inhibitors, alvocidib and dinaciclib as potent HB growth inhibitors for the high-risk C2 molecular subtype. We also found that in a cohort of 46 patients with HB, high CDK9 tumour expression was significantly associated with poor prognosis. Our work proves the usefulness of computational methods trained on pan-cancer datasets to reposition drugs in rare paediatric cancers such as HB, and to help clinicians in choosing the best treatment options for their patients. Export

Resistance to conventional chemotherapy remains a huge challenge in the clinical management of hepatoblastoma, the most common liver tumor in childhood. By integrating the gene expression data of hepatoblastoma patients into the perturbation prediction tool Connectivity Map, we identified the clinical widely used anthelmintic mebendazole as a drug to circumvent chemoresistance in permanent and patient-derived xenograft cell lines that are resistant to cisplatin, the therapeutic backbone of hepatoblastoma treatment. Viability assays clearly indicated a potent reduction of tumor cell growth upon mebendazole treatment in a dose-dependent manner. The combination of mebendazole and cisplatin revealed a strong synergistic effect, which was comparable to the one seen with cisplatin and doxorubicin, the current treatment for high-risk hepatoblastoma patients. Moreover, mebendazole treatment resulted in reduced colony and tumor spheroid formation capabilities, cell cycle arrest, and induction of apoptosis of hepatoblastoma cells. Mechanistically, mebendazole causes blockage of microtubule formation and transcriptional downregulation of genes encoding the unwindosome, which are highly expressed in chemoresistant tumors. Most importantly, mebendazole significantly reduced tumor growth in a subcutaneous xenograft transplantation mouse model without side effects. In conclusion, our results strongly support the clinical use of mebendazole in the treatment of chemoresistant hepatoblastoma and highlight the potential theranostic value of unwindosome-associated genes.

Background/Objectives: Hepatoblastoma, the most common malignant liver tumor in pediatric patients, is characterized by a remarkably low mutation rate, thereby impeding targeted therapies. Current treatment regimens rely on conventional cytotoxic agents that often cause severe adverse effects, necessitating the search for novel, less toxic therapeutic approaches. Methods: In this study, we explored the anti-tumor potential of heat shock protein 90 (HSP90) inhibitors using a unique collection of hepatoblastoma in vitro models. Results: Among the five tested inhibitors, we identified ganetespib as the most effective, significantly suppressing tumor cell growth while sparing healthy, non-tumor cells. Ganetespib treatment at low nanomolar concentrations markedly reduced cell proliferation, impaired long-term survival, and inhibited three-dimensional spheroid growth, ultimately leading to the induction of apoptosis. Mechanistically, ganetespib downregulated the expression of the HSP90 client protein cyclin-dependent kinase 1, a key cell cycle regulator controlling G2/M phase transition, which is heavily upregulated in hepatoblastoma. This disruption consequently resulted in cell cycle arrest, further contributing to its anti-tumor effects. Conclusions: HSP90 inhibition by ganetespib demonstrates significant potential as a novel therapeutic strategy for hepatoblastoma, offering a potential alternative to current cytotoxic treatments with fewer adverse effects.

Hepatoblastoma (HB), the most common pediatric liver cancer, exhibits marked variability in therapeutic response despite minimal genetic heterogeneity, implicating epigenetic regulation as a key driver of tumor behavior. Among these, polycomb repressor complexes (PRC) remain poorly explored as therapeutic targets. Integrative analysis of samples from patients with HB and public datasets identified BMI1, a core component of PRC1, as significantly upregulated, with high expression strongly associated with aggressive disease and poor survival. Functional screening of epigenetic inhibitors across 15 HB cell lines revealed BMI1 inhibition as the most effective therapeutic strategy, with strong concordance between in vitro predictions and in vivo responses in patient-derived xenograft (PDX) models. The BMI1 inhibitor PTC596 demonstrated the highest potency, consistently suppressing tumor growth across models. Mechanistically, PTC596 induced BMI1 degradation, reduced histone H2A ubiquitination, impaired microtubule dynamics, and restored intrinsic apoptosis by shifting the BCL2–BAX balance, leading to caspase-3/7 activation. Transcriptomic profiling confirmed apoptosis as the most significantly enriched pathway. In vivo, PTC596 markedly reduced tumor burden and proliferation while inducing pro-apoptotic signaling, without detectable toxicity. Together, these findings establish BMI1 as a critical oncogenic dependency in HB, demonstrate the value of robust preclinical tumor modeling for therapeutic validation, and identify PTC596 as a promising, mechanism-based treatment strategy.