FN1 and melanoma: However, on fibronectin-coated substrates, B16 melanoma cells formed focal adhesions enriched with GFP-integrin-β3 (Fig. 4C), whereas paxillin-rich clusters formed on galectin-8 did not contain GFP-integrin-β3 (Fig. 4C), and were associated with short actin filaments, rather than with the ends of stress fibers.