Raf kinase inhibitor RKIP inhibits MDA-9/syntenin-mediated metastasis in melanoma

Cancer Res. 2012 Dec 1;72(23):6217-26. doi: 10.1158/0008-5472.CAN-12-0402. Epub 2012 Oct 11.

Abstract

Melanoma differentiation associated gene-9 (MDA-9), also known as syntenin, functions as a positive regulator of melanoma progression and metastasis. In contrast, the Raf kinase inhibitor, RKIP, a negative modulator of RAF-stimulated MEKK activation, is strongly downregulated in metastatic melanoma cells. In this study, we explored a hypothesized inverse relationship between MDA-9 and RKIP in melanoma. Tumor array and cell line analyses confirmed an inverse relationship between expression of MDA-9 and RKIP during melanoma progression. We found that MDA-9 transcriptionally downregulated RKIP in support of a suggested cross-talk between these two proteins. Furthermore, MDA-9 and RKIP physically interacted in a manner that correlated with a suppression of FAK and c-Src phosphorylation, crucial steps necessary for MDA-9 to promote FAK/c-Src complex formation and initiate signaling cascades that drive the MDA-9-mediated metastatic phenotype. Finally, ectopic RKIP expression in melanoma cells overrode MDA-9-mediated signaling, inhibiting cell invasion, anchorage-independent growth, and in vivo dissemination of tumor cells. Taken together, these findings establish RKIP as an inhibitor of MDA-9-dependent melanoma metastasis, with potential implications for targeting this process therapeutically.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Differentiation / physiology
  • Cell Line, Tumor
  • Chick Embryo
  • Down-Regulation
  • Focal Adhesion Kinase 1 / metabolism
  • Humans
  • Immunohistochemistry
  • Melanoma / genetics
  • Melanoma / metabolism*
  • Melanoma / pathology*
  • NF-kappa B / metabolism
  • Neoplasm Invasiveness
  • Phosphatidylethanolamine Binding Protein / biosynthesis
  • Phosphatidylethanolamine Binding Protein / genetics
  • Phosphatidylethanolamine Binding Protein / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Signal Transduction
  • Syntenins / antagonists & inhibitors*
  • Syntenins / biosynthesis
  • Syntenins / metabolism
  • raf Kinases / antagonists & inhibitors*
  • raf Kinases / genetics
  • raf Kinases / metabolism

Substances

  • NF-kappa B
  • PEBP1 protein, human
  • Phosphatidylethanolamine Binding Protein
  • RNA, Messenger
  • SDCBP protein, human
  • Syntenins
  • Focal Adhesion Kinase 1
  • PTK2 protein, human
  • raf Kinases