The spectraplakin Dystonin antagonizes YAP activity and suppresses tumourigenesis

Aberrant expression of the Spectraplakin Dystonin (DST) has been observed in various cancers, including those of the breast. However, little is known about its role in carcinogenesis. In this report, we demonstrate that Dystonin is a candidate tumour suppressor in breast cancer and provide an underlying molecular mechanism. We show that in MCF10A cells, Dystonin is necessary to restrain cell growth, anchorage-independent growth, self-renewal properties and resistance to doxorubicin. Strikingly, while Dystonin maintains focal adhesion integrity, promotes cell spreading and cell-substratum adhesion, it prevents Zyxin accumulation, stabilizes LATS and restricts YAP activation. Moreover, treating DST-depleted MCF10A cells with the YAP inhibitor Verteporfin prevents their growth. In vivo, the Drosophila Dystonin Short stop also restricts tissue growth by limiting Yorkie activity. As the two Dystonin isoforms BPAG1eA and BPAG1e are necessary to inhibit the acquisition of transformed features and are both downregulated in breast tumour samples and in MCF10A cells with conditional induction of the Src proto-oncogene, they could function as the predominant Dystonin tumour suppressor variants in breast epithelial cells. Thus, their loss could deem as promising prognostic biomarkers for breast cancer. The authors acknowledge the support of the Bloomington Drosophila Stock Centre, the National Institute of Genetics (NIG-Fly) the services of the Animal, Imaging and Cytometry and Genomics facilities at Instituto Gulbenkian de Ciência, and of the i3S Scientific Platforms, including the Cell Culture and Genotyping (CCGen) and the Genomics (GenCore) platforms, as well as the Bioimaging and the Advanced Light Microscopy platforms. We are also grateful to M. J. Amorim and N. Tapon for reagents and to A. Monteiro for fly food preparation. We specially thank K. Struhl for providing the TAM-inducible ER-Src and PBabe cell lines and Rafeeq Mir, Eurico Morais-de-Sá, Archana Pawar and Carla Oliveira for comments on the manuscript. This work was supported by funds from Fundação para a Ciência e Tecnologia (FCT), co-financed by Fundo Europeu de Desenvolvimento Regional (FEDER) through Programa Operacional Competitividade e Internacionalização (POCI) (POCI-01-0145-FEDER-016390) and the Laço Grant in breast cancer 2015 to F.J. The i3S Bioimaging and Advanced Light Microscopy scientific platforms are both member of the national infrastructure PPBI-Portuguese Platform of BioImaging, supported by POCI-01-0145-FEDER-022122. P.J. was the recipient of fellowships from FCT (PD/ BD/52439/2013). F.J. was the recipient of IF/01031/2012.