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Cancer Res. 2016 Sep 1;76(17):5040-53. doi: 10.1158/0008-5472.CAN-15-3422. Epub 2016 Jun 30.

Activation of Wnt/β-Catenin in Ewing Sarcoma Cells Antagonizes EWS/ETS Function and Promotes Phenotypic Transition to More Metastatic Cell States.

Author information

1
Translational Oncology Program, The University of Michigan, Ann Arbor, Michigan. Department of Pathology, The University of Michigan, Ann Arbor, Michigan.
2
Department of Computational Medicine & Bioinformatics, The University of Michigan, Ann Arbor, Michigan.
3
Translational Oncology Program, The University of Michigan, Ann Arbor, Michigan. Department of Pediatrics, and Communicable Diseases, The University of Michigan, Ann Arbor, Michigan.
4
Department of Pathology, The University of Michigan, Ann Arbor, Michigan.
5
Department of Cancer Research and Biostatistics, Seattle, Washington.
6
Department of Pathology, The University of Michigan, Ann Arbor, Michigan. Department of Internal Medicine, The University of Michigan, Ann Arbor, Michigan. Department of Human Genetics, The University of Michigan, Ann Arbor, Michigan.
7
Department of Internal Medicine, The University of Michigan, Ann Arbor, Michigan.
8
Translational Oncology Program, The University of Michigan, Ann Arbor, Michigan. Department of Pediatrics, and Communicable Diseases, The University of Michigan, Ann Arbor, Michigan. Department of Pathology, The University of Michigan, Ann Arbor, Michigan. elawlor@med.umich.edu.

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/β-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 β-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/β-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/β-catenin-activated tumor cells. Consistent with this, Wnt/β-catenin-activated cells displayed a phenotype that was reminiscent of Ewing sarcoma cells with partial EWS/ETS loss of function. Specifically, activation of Wnt/β-catenin induced alterations to the actin cytoskeleton, acquisition of a migratory phenotype, and upregulation of EWS/ETS-repressed genes. Notably, activation of Wnt/β-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/β-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.

PMID:
27364557
PMCID:
PMC5010452
DOI:
10.1158/0008-5472.CAN-15-3422
[Indexed for MEDLINE]
Free PMC Article

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