Dendriplexes in alveolar rhabdomyosarcoma therapy

Alveolar rhabdomyosarcoma (ARMS) is an aggressive pediatric soft tissue sarcoma most commonly driven by the PAX3-FOXO1 fusion oncogene and associated with poor outcomes despite intensive multimodal therapy. Targeted molecular strategies capable of complementing standard treatment remain limited. Here, we evaluated partially glycosylated fourth-generation poly(propylene imine) dendrimers (PPI-G4) as delivery systems for PAX3-FOXO1-specific siRNA. All tested glycodendrimers formed stable dendriplexes; however, dendrimers with the lowest degree of surface modification, PPI-M3-20 and PPI-Lac-27, showed the highest transfection efficiency and biological activity. In vitro, dendriplexes significantly reduced RH30 cell viability and impaired cell migration. In vivo, intratumoral administration resulted in significant tumor growth inhibition without observable short-term toxicity, and dendriplex-derived fluorescence was cleared from circulation within one week. Among the tested formulations, siRNA_2-PPI-M3-20 showed the strongest antitumor response and suppressed PAX3-FOXO1 expression together with associated downstream transcriptional programs in tumor tissue. Importantly, tumor mass was also significantly reduced in the PPI-M3-20 vector control group, indicating that the glycodendrimer carrier retained measurable antitumor activity in vivo at the applied dose. Overall, these findings support the potential of an intratumorally administered, low-dose, dual-action nanotherapeutic strategy for the local modulation of fusion-positive ARMS tumors. While additional studies are needed to assess systemic delivery, efficacy in metastatic disease models, and long-term safety, PAX3-FOXO1-targeted siRNA delivery using biologically active PPI glycodendrimers represents a promising adjuvant approach warranting further investigation.