Radiotherapy (RT) is important for local control at primary and metastatic sites in pediatric rhabdomyosarcoma (RMS) even though loco-regional recurrence is frequently observed. Therefore, radio-sensitizers with high toxicity to cancer and low to normal tissues are urgently needed. The alveolar (A)RMS and the embryonal (E)RMS variant, despite genetic differences, are sustained by common molecular networks. Identifying and targeting the crucial nodes of the molecular network supporting RMSs radio-resistance could radio-sensitize RMSs. With this project we want to identify pathways regulating intrinsic and promoting acquired radio-resistance in RMS and select and validate in vitro pharmacological compounds targeting identified pathways. To this purpose, shRNA-based strategy will be used to identify genes sustaining intrinsic radio-resistance. Pathways involved in acquiring radio-resistant phenotype will be identified using transcriptomics, mass cytometry and phosphoproteomics. Then, pharmacological compounds selected versus candidate targets previously identified and prioritized will be screened. These will be validated, in vitro, for their ability to counteract intrinsic and acquired radio-resistance. The validated pathways will be studied in patients¿ samples to evaluate their relevance as clinical correlate to inform future treatments. Expected results are to unveil molecular mechanisms responsible for radio-resistance and to identify pharmacological strategies to counteract intrinsic and acquired radio-resistance. Data collected from this project will contribute to identify the mechanisms responsible of radio-resistance and could have a significant impact in planning new RT-based therapeutic strategies able to reduce the toxicity and improve the efficacy of RT.
One of the main reasons for the failure of radiotherapy in RMS is the intrinsic radio-resistance of the cells that finally determine local recurrence and dissemination. Radiosensitizers are compounds that, when combined with radiation, achieve greater tumor inactivation than would have been expected from the additive effect of each modality. Furthermore, radiosensitizing could trigger the ability of radiotherapy to induce anti-cancer immune response as well as to permit the use of immunotherapy also in cold tumors like RMS. No radiosensitizers have been yet identified for RMA. The aim of this proposal is to identify molecular profiling predicting radio-resistance in patients affected by RMS in order to predict the response to the treatment and identify new cancer-specific radiosensitizing strategies. This project will contribute to the understanding of the mechanisms mediating sensitivity and resistance to RT and could have a significant impact by guiding their successful clinical development in RMS.