UCLA

Aberrant cellular signaling networks lie at the heart of cancer pathogenesis. Whether stimulated by a dominant oncogene or activated receptor tyrosine kinase, these signals affect biological processes such as proliferation and apoptosis. In the Ewing sarcoma family of tumors (EFST), a group of pediatric bone and soft tissue malignancies, EWS/FLI1 transcriptional modulation and insulin-like growth factor 1 (IGF1) signaling are the two main forces that drive tumorigenesis. In order to obtain a comprehensive view of signaling, we applied a mass spectrometry-based phosphoproteomic approach to quantify global changes in phosphorylation after IGF1 stimulation, IGF1 receptor inhibition, and EWS/FLI1 knock down. Our analyses identified hundreds unique phosphopeptides enriched in processes such as regulation of cell cycle and cytoskeleton organization. In particular, examination of tyrosine phosphopeptides downstream of IGF1 identified potential roles for Src family kinases and members of the Eph family of receptor tyrosine kinases in ESFT pathogenesis. Additionally, phosphotyrosine profiling revealed a large up regulation of Stat3 phosphorylation upon EWS/FLI1 knock down. Further investigation revealed this activation occurs through a paracrine mechanism. Overall, phosphoproteomic profiling has uncovered novel regulators and mechanisms for ESFT signaling, allowing for the development of new therapeutic strategies.