Activation of Wnt/?-Catenin in Ewing Sarcoma Cells Antagonizes EWS/ETS Function and Promotes Phenotypic Transition to More Metastatic Cell States.
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ABSTRACT: Ewing sarcomas are characterized by the presence of EWS/ETS fusion genes in the absence of other recurrent genetic alterations and mechanisms of tumor heterogeneity that contribute to disease progression remain unclear. Mutations in the Wnt/?-catenin pathway are rare in Ewing sarcoma but the Wnt pathway modulator LGR5 is often highly expressed, suggesting a potential role for the axis in tumor pathogenesis. We evaluated ?-catenin and LGR5 expression in Ewing sarcoma cell lines and tumors and noted marked intra- and inter-tumor heterogeneity. Tumors with evidence of active Wnt/?-catenin signaling were associated with increased incidence of tumor relapse and worse overall survival. Paradoxically, RNA sequencing revealed a marked antagonism of EWS/ETS transcriptional activity in Wnt/?-catenin-activated tumor cells. Consistent with this, Wnt/?-catenin-activated cells displayed a phenotype that was reminiscent of Ewing sarcoma cells with partial EWS/ETS loss of function. Specifically, activation of Wnt/?-catenin induced alterations to the actin cytoskeleton, acquisition of a migratory phenotype, and upregulation of EWS/ETS-repressed genes. Notably, activation of Wnt/?-catenin signaling led to marked induction of tenascin C (TNC), an established promoter of cancer metastasis, and an EWS/ETS-repressed target gene. Loss of TNC function in Ewing sarcoma cells profoundly inhibited their migratory and metastatic potential. Our studies reveal that heterogeneous activation of Wnt/?-catenin signaling in subpopulations of tumor cells contributes to phenotypic heterogeneity and disease progression in Ewing sarcoma. Significantly, this is mediated, at least in part, by inhibition of EWS/ETS fusion protein function that results in derepression of metastasis-associated gene programs. Cancer Res; 76(17); 5040-53. ©2016 AACR.
SUBMITTER: Pedersen EA
PROVIDER: S-EPMC5010452 | biostudies-literature | 2016 Sep
REPOSITORIES: biostudies-literature
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