Rhabdomyosarcoma xenotransplants in zebrafish embryos

Rhabdomyosarcomas (RMS) are the most common pediatric soft tissue sarcomas. High-risk and metastatic disease continues to be associated with very poor prognosis. RMS model systems that faithfully recapitulate the human disease and provide rapid, cost-efficient estimates of anti-tumor efficacy of candidate drugs are needed to facilitate drug development and personalized medicine approaches. Here, we present a new zebrafish-based xenotransplant model allowing for rapid and easily accessible drug screening using low numbers of viable tumor cells and relatively small amounts of water-soluble chemicals. Under optimized temperature conditions, embryonal RMS-xenografts were established in zebrafish embryos at 3 hours post fertilization (hpf). In proof-of-principle experiments, chemotherapy drugs with established clinical anti-RMS efficacy (vincristine, dactinomycin) and the MEK inhibitor trametinib were shown to significantly reduce the cross-sectional area of the tumors by 120 hpf. RMS xenograft models in zebrafish embryos henceforth could serve as a valuable addition to cell culture and mammalian models of RMS and represent a rapid and cost-effective solution for pre-clinical candidate drug testing.