Alpha v integrin antagonists induce the disassembly of focal contacts in melanoma cells

In recent years, several antagonists of alpha(nu)beta(3), have been used to develop therapeutic approaches to the treatment of melanoma neoplasia. We studied the effects of anti-alpha(nu)-integrin-blocking antibodies on attac hed M21 melanoma cells, the cellular distribution of alpha(nu)-integrin and the molecular organization of focal structures. Anti-alpha(nu)-integrin-bl ocking antibodies 17E6 and LM609, and an anti-alpha(nu)beta(3)-integrin ant agonist peptide cRGD 85189 induced detachment of M21 melanoma cells culture d for 24 hours on various substrates. cRGD was the most effective antagonis t, reducing the number of adherent cells by 80%, while 17E6 reduced adhesio n by only 30%. Light- and electron microscopy revealed attached cells with a flat shape and well-formed actin cytoskeleton. After treatment, cells bec ame rounded and detached from the culture dish. alpha(nu)-Integrins and foc al-contact proteins were observed at adhesion sites in focal structures by immunocytochemistry. After treatment, however, cell rounding was accompanie d by disorganization of the actin filaments and redistribution of alpha(nu) -integrins and most of the focal proteins studied, except vinculin and tens in. Our results indicate that treatment of M21 melanoma cells with alpha(nu )-integrin antagonists disrupts the actin cytoskeleton, redistributes alpha (nu)-integrin and induces molecular disassembly of focal contacts.