TGFB1 and melanoma: Temporary contact with platelets is sufficient to induce invasive behavior in CTCs through TGF-β1.74 Blockage of TGF-β1 receptor I (TβR1) kinase activity through the use of SD-208, a small molecule inhibitor, was shown to prevent the development of TGF-β induced bone metastases in a melanoma mouse model.100 Thus, blocking platelet-CTC signaling is a potentially viable targeted therapy to prevent the formation of additional metastases.