Raf kinase inhibitory protein suppresses a metastasis signalling cascade involving LIN28 and let-7

Surabhi Dangi-Garimella, Jieun Yun, Eva M. Eves, Martin Newman, Stefan J. Erkeland, Scott M. Hammond, Andy J. Minn, Marsha Rich Rosner

Research output: Contribution to journalArticleAcademicpeer-review

329 Citations (Scopus)


Raf kinase inhibitory protein (RKIP) negatively regulates the MAP kinase (MAPK), G protein-coupled receptor kinase-2, and NF-κB signalling cascades. RKIP has been implicated as a metastasis suppressor for prostate cancer, but the mechanism is not known. Here, we show that RKIP inhibits invasion by metastatic breast cancer cells and represses breast tumour cell intravasation and bone metastasis in an orthotopic murine model. The mechanism involves inhibition of MAPK, leading to decreased transcription of LIN28 by Myc. Suppression of LIN28 enables enhanced let-7 processing in breast cancer cells. Elevated let-7 expression inhibits HMGA2, a chromatin remodelling protein that activates pro-invasive and pro-metastatic genes, including Snail. LIN28 depletion and let-7 expression suppress bone metastasis, and LIN28 restores bone metastasis in mice bearing RKIP-expressing breast tumour cells. These results indicate that RKIP suppresses invasion and metastasis in part through a signalling cascade involving MAPK, Myc, LIN28, let-7, and downstream let-7 targets. RKIP regulation of two pluripotent stem cell genes, Myc and LIN28, highlights the importance of RKIP as a key metastasis suppressor and potential therapeutic agent.

Original languageEnglish
Pages (from-to)347-358
Number of pages12
JournalEMBO Journal
Issue number4
Early online date15 Jan 2009
Publication statusPublished - 18 Feb 2009

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Copyright © 2009 European Molecular Biology Organization.


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