The role of Tks adaptor proteins in invadopodia formation, growth and metastasis of melanoma

// Shinji Iizuka 1,2 , Christopher Abdullah 1,2,3 , Matthew D. Buschman 1,4 , Begona Diaz 1,5 and Sara A. Courtneidge 1,2,6 1 Sanford|Burnham|Prebys Medical Discovery Institute, La Jolla, CA, USA 2 Department of Cell, Developmental & Cancer Biology, Oregon Health & Science University, Portland, OR, USA 3 Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA, USA 4 Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, USA 5 Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA 6 Department of Biomedical Engineering and Knight Cancer Institute, Oregon Health & Science University, Portland, OR, USA Correspondence to: Sara A. Courtneidge, email: // Keywords : invadopodia, Tks5, Tks4, MT1-MMP, melanoma Received : August 11, 2016 Accepted : October 22, 2016 Published : October 27, 2016 Abstract Metastatic cancer cells are characterized by their ability to degrade and invade through extracellular matrix. We previously showed that the Tks adaptor proteins, Tks4 and Tks5, are required for invadopodia formation and/or function in Src-transformed fibroblasts and a number of human cancer cell types. In this study, we investigated the role of Tks adaptor proteins in melanoma cell invasion and metastasis. Knockdown of either Tks4 or Tks5 in both mouse and human melanoma cell lines resulted in a decreased ability to form invadopodia and degrade extracellular matrix. In addition, Tks-knockdown melanoma cells had decreased proliferation in a 3-dimensional type l collagen matrix, but not in 2-dimensional culture conditions. We also investigated the role of Tks proteins in melanoma progression in vivo using xenografts and experimental metastasis assays. Consistent with our in vitro results, reduction of Tks proteins markedly reduced subcutaneous melanoma growth as well as metastatic growth in the lung. We explored the clinical relevance of Tks protein expression in human melanoma specimens using a tissue microarray. Compared to non-malignant nevi, both Tks proteins were highly expressed in melanoma tissues. Moreover, metastatic melanoma cases showed higher expression of Tks5 than primary melanoma cases. Taken together, these findings suggest the importance of Tks adaptor proteins in melanoma growth and metastasis in vivo , likely via functional invadopodia formation.