The RASSF8 candidate tumor suppressor inhibits cell growth and regulates the Wnt and NF-kappa B signaling pathways

Research output: Contribution to journalArticle

Authors

  • Thomas Dunwell
  • D Matallanas
  • W Cooper
  • L Hesson
  • A Recino
  • A Ward
  • T Pavlova
  • E Zabarovsky
  • AD Chalmers
  • W Kolch
  • FE Lock

Colleges, School and Institutes

Abstract

The Ras-assocation domain family (RASSF) of tumor suppressor proteins until recently contained six proteins named RASSF1-6. Recently, four novel family members, RASSF7-10, have been identified by homology searches for RA-domain-containing proteins. These additional RASSF members are divergent and structurally distinct from RASSF1-6, containing an N-terminal RA domain and lacking the Sav/RASSF/Hpo (SARAH) domain. Here, we show that RASSF8 is ubiquitously expressed throughout the murine embryo and in normal human adult tissues. Functionally, RNAi-mediated knockdown of RASSF8 in non-small-cell lung cancer (NSCLC) cell lines, increased anchorage-independent growth in soft agar and enhanced tumor growth in severe combined immunodeficiency (SCID) mice. Furthermore, EdU staining of RASSF8-depleted cells showed growth suppression in a manner dependent on contact inhibition. We show that endogenous RASSF8 is not only found in the nucleus, but is also membrane associated at sites of cell-cell adhesion, co-localizing with the adherens junction (AJ) component beta-catenin and binding to E-cadherin. Following RASSF8 depletion in two different lung cancer cell lines using alternative small interfering RNA (siRNA) sequences, we show that AJs are destabilized and E-cadherin is lost from the cell membrane. The AJ components beta-catenin and p65 are also lost from sites of cell-cell contact and are relocalized to the nucleus with a concomitant increase in beta-catenin-dependent and nuclear factor-kappa B (NF-kappa B)-dependent signaling following RASSF8 depletion. RASSF8 may also be required to maintain actin -cytoskeletal organization since immunofluorescence analysis shows a striking disorganization of the actincytoskeleton following RASSF8 depletion. Accordingly, scratch wound healing studies show increased cellular migration in RASSF8-deficient cells. These results implicate RASSF8 as a tumor suppressor gene that is essential for maintaining AJs function in epithelial cells and have a role in epithelial cell migration. Oncogene (2010) 29, 4307-4316; doi: 10.1038/onc.2010.192; published online 31 May 2010

Details

Original languageEnglish
Pages (from-to)4307-4316
Number of pages10
JournalOncogene
Volume29
Issue number30
Publication statusPublished - 1 Jul 2010

Keywords

  • lung cancer, adherens junctions, RASSF8