title: Targeted inhibition of T-cell factor activity promotes syndecan-2 expression and sensitization to doxorubicin in osteosarcoma cells and bone tumors in mice.
abstract: Alterations of Wnt signaling appear to be involved in the pathogenesis of osteosarcoma, presenting mutations of adenomatous polyposis coli (APC) and epigenetic downregulation of Wnt inhibitory factor 1. However, the precise role of Wnt effectors in the bone cancer progression remains unclear. We previously showed that Wnt/β-catenin/T-cell factor (TCF) activation are responsible for the repression of syndecan-2, a key modulator of apoptosis and chemosensitivity in osteosarcoma cells, suggesting a role of Wnt signaling in chemoresistance. In this study, we investigated the functional relationship between syndecan-2, Wnt/β-catenin/TCF signaling and chemosensitivity in these cells. To this goal, we selected resistant osteosarcoma cells from sensitive human cell lines using repeated exposures to doxorubicin. In doxorubicin-responsive but not in doxorubicin-resistant-derived cells syndecan-2 expression was upregulated by doxorubicin treatment. Moreover, syndecan-2 overexpression restored the sensitivity to doxorubicin in resistant-derived cells. We found that syndecan-2 induction by doxorubicin is forkhead box protein O3A (Foxo3a)-dependent. Foxo3a overexpression resulted in increased syndecan-2 expression in sensitive and resistant-derived cells. Doxorubicin modulated Foxo3a binding on syndecan-2 gene promoter and induced Foxo-dependent inhibition of Wnt/TCF activity. Conversely, β-catenin/TCF activation impaired syndecan-2 induction by doxorubicin, indicating that Wnt signaling is competing with the action of the cytotoxic drug. However, β-catenin was also found to be required for Foxo3a activity. Consistently, Dickkopf 1 (DKK1) and secreted frizzled-related protein 1 (sFRP-1) altered doxorubicin action in sensitive cells, whereas inhibition of TCF activity strongly decreased cell viability and increased sensitivity to doxorubicin in sensitive and resistant cells. TCF inhibition also increased the effect of doxorubicin treatment in an orthotopic bone tumor model in mice. Altogether, these data provide evidence that the repression of syndecan-2 by Wnt/β-catenin/TCF signaling contributes to the resistance of osteosarcoma cells to doxorubicin and suggest that TCF inhibition may represent a novel therapeutic strategy in osteosarcoma.
authors.affiliation: Laboratory of Osteoblast Biology and Pathology, INSERM U606, Paris, France. dominique.modrowski@inserm.fr
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Dieudonné
authors.forename: Allison
authors.initials: A
authors.lastname: Marion
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Marie
authors.forename: Dominique
authors.initials: D
authors.lastname: Modrowski
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001859:Bone Neoplasms / Q000188:drug therapy / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000494:pharmacology / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism; D018390:Gene Targeting; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D012516:Osteosarcoma / Q000188:drug therapy* / Q000473:pathology*; D053669:Syndecan-2 / Q000378:metabolism*; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D060449:Wnt Signaling Pathway / Q000187:drug effects; D000099274:Frizzled-Related Proteins
chemical_list: D004317:Doxorubicin; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053669:Syndecan-2; D051820:TCF Transcription Factors; D000099274:Frizzled-Related Proteins; C501126:DKK1 protein, human; C499517:FOXO3 protein, human