Invadopodia are actin-based proteolytic structures which facilitate cancer cell invasion and metastasis. While it was previously believed that invadopodia are not required for tumor cell growth, based on studies in monolayer cell culture, more recently we have noted a role for invadopodia proteins in growth in more physiological 3-dimensional (3D) extracellular matrix contexts. From previous work in our lab, the Tks adaptor proteins with 5 (Tks5) and 4 (Tks4) SH3 domains, respectively, were identified as Src kinase substrates and both are essential molecules for functional invadopodia formation in mouse and human cancer cells.
Here, we assess the roles of the Tks adaptors in melanoma tumor growth and invasion both in vivo and in vitro. To address the mechanism as to how the Tks adaptors control tumor growth and invasion, in vitro 3D growth assays in collagen I were performed. Knockdown of either Tks4 or Tks5 in C8161.9 or A375 melanoma cells decreased 3D growth in collagen I, a process that also appeared to be dependent upon metalloproteinase (MMP) activity. Interestingly, knockdown of either Tks4 or Tks5 in A375 melanoma cells decreased cell-surface expression of MT1-MMP, a key protease involved in tumor growth and metastasis. In vivo tumor growth and metastasis assays in mice using human and mouse melanoma cells depleted of Tks4 or Tks5 by shRNA revealed roles for the Tks adaptors in both the size and the number of lung metastases. Finally, analysis of a human melanoma tissue array with a Tks5 antibody, and RNAseq data, indicates that Tks5 expression is increased in lymph node and other metastases in comparison to nevi and primary sites.
These data suggest that the Tks adaptors control melanoma tumor growth and invasion by regulating invadopodia formation and perhaps also cell surface expression of MT1-MMP, and thus contribute to melanoma progression.
Citation Format: Shinji Iizuka, Christine M. Gould, Matthew D. Buschman, Diaz Begoña, Christopher Abdullah, Sara Courtneidge. Tks adaptor proteins and invadopodia formation in the growth and metastasis of melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3155. doi:10.1158/1538-7445.AM2014-3155