ABSTRACT
Ewing sarcoma is the second most common bone cancer in children, and while patients who present with metastatic disease at the time of diagnosis have a dismal prognosis. Ewing sarcoma tumors are driven by the fusion gene EWS/Fli1, and while these tumors are genetically homogenous, the transcriptional heterogeneity can lead to a variety of cellular processes including metastasis. In this study, we demonstrate that in Ewing sarcoma cells, the canonical Wnt/ß-Catenin signaling pathway is heterogeneously activated in vitro and in vivo, correlating with hypoxia and EWS/Fli1 activity. Ewing sarcoma cells predominantly express ß-Catenin on the cell membrane bound to CDH11, which can respond to exogenous Wnt ligands leading to the immediate activation of Wnt/ß-Catenin signaling within a tumor. Knockdown of CDH11 leads to delayed and decreased response to exogenous Wnt ligand stimulation, and ultimately decreased metastatic propensity. Our findings strongly indicate that CDH11 is a key component of regulating Wnt//ß-Catenin signaling heterogeneity within Ewing sarcoma tumors, and is a promising molecular target to alter Wnt//ß-Catenin signaling in Ewing sarcoma patients.
Subject(s)
Cadherins , Sarcoma, Ewing , Wnt Signaling Pathway , beta Catenin , Sarcoma, Ewing/metabolism , Sarcoma, Ewing/pathology , Sarcoma, Ewing/genetics , Humans , Cadherins/metabolism , Cadherins/genetics , Cell Line, Tumor , beta Catenin/metabolism , Animals , Bone Neoplasms/metabolism , Bone Neoplasms/pathology , Bone Neoplasms/genetics , Mice , Oncogene Proteins, Fusion/metabolism , Oncogene Proteins, Fusion/genetics , Proto-Oncogene Protein c-fli-1/metabolism , Proto-Oncogene Protein c-fli-1/genetics , RNA-Binding Protein EWS/metabolism , RNA-Binding Protein EWS/geneticsABSTRACT
Ewing sarcoma is the second most common bone cancer in children, accounting for 2% of pediatric cancer diagnoses. Patients who present with metastatic disease at the time of diagnosis have a dismal prognosis, compared to the >70% 5-year survival of those with localized disease. Here, we utilized single cell RNA-sequencing to characterize the transcriptional landscape of primary Ewing sarcoma tumors and surrounding tumor microenvironment (TME). Copy-number analysis identified subclonal evolution within patients prior to treatment. Primary tumor samples demonstrate a heterogenous transcriptional landscape with several conserved gene expression programs, including those composed of genes related to proliferation and EWS targets. Single cell RNA-sequencing and immunofluorescence of circulating tumor cells at the time of diagnosis identified TSPAN8 as a novel therapeutic target.
