AUTHOR=Ragab Nada , Viehweger Florian , Bauer Julia , Geyer Natalie , Yang Mingya , Seils Anna , Belharazem Djeda , Brembeck Felix H. , Schildhaus Hans-Ulrich , Marx Alexander , Hahn Heidi , Simon-Keller Katja TITLE=Canonical WNT/β-Catenin Signaling Plays a Subordinate Role in Rhabdomyosarcomas JOURNAL=Frontiers in Pediatrics VOLUME=6 YEAR=2018 URL=https://www.frontiersin.org/journals/pediatrics/articles/10.3389/fped.2018.00378 DOI=10.3389/fped.2018.00378 ISSN=2296-2360 ABSTRACT=

The development of skeletal muscle from immature precursors is partially driven by canonical WNT/β-catenin signaling. Rhabdomyosarcomas (RMS) are immature skeletal muscle-like, highly lethal cancers with a variably pronounced blockade of muscle differentiation. To investigate whether canonical β-catenin signaling in RMS is involved in differentiation and aggressiveness of RMS, we analyzed the effects of WNT3A and of a siRNA-mediated or pharmacologically induced β-catenin knock-down on proliferation, apoptosis and differentiation of embryonal and alveolar RMS cell lines. While the canonical WNT pathway was maintained in all cell lines as shown by WNT3A induced AXIN expression, more distal steps including transcriptional activation of its key target genes were consistently impaired. In addition, activation or inhibition of canonical WNT/β-catenin only moderately affected proliferation, apoptosis or myodifferentiation of the RMS tumor cells and a conditional knockout of β-catenin in RMS of Ptchdel/+ mice did not alter RMS incidence or multiplicity. Together our data indicates a subordinary role of the canonical WNT/β-catenin signaling for RMS proliferation, apoptosis or differentiation and thus aggressiveness of this malignant childhood tumor.