Metastatic melanoma is an aggressive skin disease for which there are no effective therapies. Emerging evidence indicates that melanomas can be sensitized to chemotherapy by increasing integrin function. Current integrin therapies work by targeting the extracellular domain, resulting in complete gains or losses of integrin function that lead to mechanism-based toxicities. An attractive alternative approach is to target proteins, such as vinculin, that associate with the integrin cytoplasmic domains and regulate its ligand-binding properties. Here, we report that a novel reagent, denoted vinculin-activating peptide or VAP, increases integrin activity from within the cell, as measured by elevated (i) numbers of active integrins, (ii) adhesion of cells to extracellular matrix ligands, (iii) numbers of cell–matrix adhesions, and (iv) downstream signaling. These effects are dependent on both integrins and a key regulatory residue A50 in the vinculin head domain. We 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 show that the increase in chemosensitivity results from increases in DNA damage–induced apoptosis in a p53-dependent manner. Collectively, these findings show that integrin function can be manipulated from within the cell and validate integrins as a new therapeutic target for the treatment of chemoresistant melanomas. Mol Cancer Res; 9(6); 1–12. ©2011 AACR.
Note: Supplementary data for this article are available at Molecular Cancer Research Online (http://mcr.aacrjournals.org/).
This article was presented, in part, as an oral presentation in the Tumor Biology Minisymposium at the 2010 AACR Annual Meeting in Washington, DC, and an abstract of this work was published in the 2010 Proceedings of the American Association for Cancer Research.
- Received January 1, 2011.
- Revision received March 8, 2011.
- Accepted March 23, 2011.
- ©2011 American Association for Cancer Research.