Control of Tumor Cell – Bone Metastasis By Regulation of F-Actin Dynamics

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This project aims at revealing a key pathway, which is currently too little understood: the contribution of F-actin dynamics and proteins that govern this to metastasis, particularly bone metastasis. Indeed, highly active F-actin dynamics has been designated a hallmark for aggressive, metastasizing cancer cells. We hypothesized that SWAP-70 as a unique type of F-actin binding and bundling protein is a prime candidate to be involved in metastasis and, as we now showed, indeed supports tumor cell metastasis. Our aim is to analyze and understand this role on as many relevant levels as possible: from metastasis in animals to cellular, molecular and biophysical aspects. The first funding period has yielded very interesting insights into both, the in vivo role of SWAP-70 in metastasis and into the molecular and cellular functions of SWAP-70 related to metastasis. It became clear that metastasis by SWAP-70 deficient tumor cells is much reduced and that SWAP-70 contributes a number of F-actin related cellular and molecular properties to tumor cells important for metastasis. We will now perform investigations in further developed animal models and deepened in vitro studies of mechanistic aspects of SWAP-70’s contribution to F-actin dynamics related to metastasis. Our two overall aims are (1) Determine the role of SWAP-70 in tumor cell bone metastasis in vivo, and (2) Define SWAP-70 dependent, F-actin related features of bone metastatic tumor cells in vitro.To reveal structure-function features of SWAP-70 related to metastasis we will use specific mutants of the protein in vivo and in cell culture assays, i.e. in complementation experiments. Metastasis to the bone, also to the lung, CTC formation and properties, and tumor cell exosome properties and effects will be analyzed in animal models. In vitro we will molecularly characterize SWAP-70 dependent features of exosomes and their biological effects, will perform a selection of migration, adhesion, spheroid formation and colony formation assays, will determine F-actin dynamics and biophysical cell features such as cell deformability and stiffness depending on SWAP-70. This combination of in vivo and in vitro experiments will allow us to define the SWAP-70/F-actin dependent mechanism in metastasis and in mid term enable the development of new therapeutic avenues.