Abstract 3812: Target identification in rhabdomyosarcomas induced in mouse skeletal muscle.

Abstract

Abstract Soft-tissue sarcomas are a group of cancers arising in non-hematopoietic, mesodermal tissues. Rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children and adolescents, represents a biologically heterogeneous category of mesodermal, non-hematopoietic malignancies, which exhibit evidence of skeletal muscle differentiation. This study builds on the premise that ex-vivo induction of sarcomas by cell-specific activation of sarcoma-relevant pathways can be used to model biologically distinct sarcoma categories in mice and identify novel downstream targets. Up to 35% of human RMS tumors carry Ras mutations, and we have demonstrated Ras/ Raf/ Mek/ Erk pathway activation in approximately 50% of human RMS tumors surveyed. We showed that Kras-expressing; p16p19null muscle satellite cells gave rise to mouse pleomorphic RMS, whereas Kras-expressing; p16p19null non-myogenic progenitors typically induced pleomorphic non-myogenic sarcomas (NMS). Transcriptional profiling demonstrated that myogenic and non-myogenic Kras; p16p19null sarcomas recapitulate gene expression signatures of human RMS and share a cluster of concordantly upregulated genes (many associated with Ras pathway activation) with human RMS. We used a customized RT² Profiler™ PCR Array (SA Biosciences) to confirm that 105 out of these 141 candidate genes were indeed upregulated in Kras;16p19null sarcomas compared to mouse skeletal muscle. The functional contributions of individual candidate genes to sarcoma proliferation were evaluated using a customized shRNA-based proliferation screen in cell lines established from Kras; p16p19null sarcoma explants. These comprehensive experiments identified a small group of high-priority candidates that contributed significantly to the growth of Kras; p16p19null NMS (n=11 genes) and RMS (n=10 genes) (q<0.05). The effects of shRNA mediated silencing of selected candidate genes in human sarcoma cells were verified using human sarcoma cell lines. We conclude that these genes have potential broad importance in sarcoma biology and anti-sarcoma therapy. Future studies will help to illuminate their roles in promoting RMS growth and may suggest new approaches for therapeutic intervention. Citation Format: Simone Hettmer, Anna Schinzel, William C. Hahn, Amy Wagers. Target identification in rhabdomyosarcomas induced in mouse skeletal muscle. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3812. doi:10.1158/1538-7445.AM2013-3812