Activators of vinculin enhance cell adhesion and sensitize melanomas to chemotherapy

Metastatic melanoma is among the most aggressive forms of cancer for which there are no effective therapies. Emerging evidence indicates that melanomas can be sensitized to chemotherapy by increasing the function of integrin transmembrane adhesion receptors. Current integrin therapies work by targeting the extracellular domain, resulting in complete gains or losses of integrin function that lead to toxicity.An attractive alternative approach is to target proteins from inside the cell, such as vinculin, that associate with the integrin cytoplasmic domains and regulate its ligand binding properties. The work presented in this thesis describes a novel reagent, denoted vinculin activating peptide or VAP, which increases integrin activity from within the cell as measured by elevated: (1) numbers of active integrins, (2) adhesion of cells to extracellular matrix ligands, (3) numbers of cell-matrix adhesions, and (4) downstream signaling. The effects of VAP are dependent on both integrins and a key regulatory residue A50 in the vinculin head domain. I further show that VAP dramatically increases the sensitivity of melanomas to chemotherapy in clonal growth assays and in vivo mouse models of melanoma. Finally, we demonstrate that the increase in chemosensitivity results from increases in DNA damage-induced apoptosis by a mechanism that requires both p53 and β1 integrin. Collectively these findings demonstrate that integrin function can be manipulated from within the cell and validate integrins as a new therapeutic target for the treatment of chemoresistant melanomas.