Rhabdomyosarcoma (RMS) is one of the most common soft tissue sarcomas in children and adolescents, in which PAX3-FOXO1 fusion gene positive patients have very poor prognosis. PAX3-FOXO1 has been identified as an independent prognostic predictor in RMS, with no currently available targeted therapeutic intervention. The novel tyrosine kinase inhibitor anlotinib exhibits a wide range of anticancer effects in multiple types of cancers; however, there have been no relevant studies regarding its application in RMS.

We investigated the effects of PAX3-FOXO1 on the therapeutic efficacy of anlotinib using the CCK-8 assay, flow cytometry, invasion assay, wound healing assay, western blotting, quantitative polymerase chain reaction(qPCR), and xenograft experiments. RNA-seq and co-immunoprecipitation assays were conducted to determine the specific mechanism by which anlotinib regulates PAX3-FOXO1 expression.

Anlotinib effectively inhibited RMS cell proliferation and promoted apoptosis and G2/M phase arrest while impeding tumor growth in vivo. Downregulation of PAX3-FOXO1 enhances the antitumor effects of anlotinib. Anlotinib upregulates protein kinase NEK2 and increases the degradation of PAX3-FOXO1 via the ubiquitin-proteasome pathway, leading to a reduction in PAX3-FOXO1 protein levels.

Anlotinib effectively inhibited the malignant progression of RMS and promoted degradation of the fusion protein PAX3-FOXO1. Anlotinib could be a targeted therapeutic approach to treat PAX3-FOXO1 fusion-positive RMS.