VGLL2-NCOA2 leverages developmental programs for pediatric sarcomagenesis

Clinical sequencing efforts are rapidly identifying sarcoma gene fusions that lack functional validation. An example is the new fusion of transcriptional coactivators, VGLL2-NCOA2, found in infantile rhabdomyosarcoma. To delineate VGLL2-NCOA2 tumorigenic mechanisms and identify therapeutic vulnerabilities, we implemented a cross-species comparative oncology approach with zebrafish, mouse allograft, and patient samples. We found that VGLL2-NCOA2 is sufficient to generate mesenchymal tumors that display features of immature skeletal muscle and recapitulate the human disease. A subset of VGLL2-NCOA2 zebrafish tumors transcriptionally cluster with embryonic somitogenesis and identify VGLL2-NCOA2 developmental targets, including a RAS family GTPase, arf6/ARF6. In VGLL2-NCOA2 zebrafish, mouse allograft, and patient tumors, arf6/ARF6 is highly expressed and is absent from mature skeletal muscle. Moreover, ARF6 is overexpressed in adult and pediatric sarcoma subtypes. Our data indicate that VGLL2-NCOA2 is an oncogene which leverages developmental programs for tumorigenesis, and that the reactivation or persistence of arf6/ARF6 could represent a therapeutic opportunity. Overall design: Examination of RNA-seq transcriptional profiles from zebrafish tumors derived from mosaic human VGLL2-NCOA2 expression, and a comparison to mature zebrafish skeletal muscle and CIC-DUX4 generated zebrafish tumors. Examination of C2C12 mouse myoblasts stably transfected with human VGLL2-NCOA2, and allografted to generate tumor models. These are compared to allografts of C2C12-empty controls.