Oncogenic B-RAF negatively regulates the tumor suppressor LKB1 to promote melanoma cell proliferation

Mol Cell. 2009 Jan 30;33(2):237-47. doi: 10.1016/j.molcel.2008.12.026.

Abstract

The LKB1-AMPK signaling pathway serves as a critical cellular sensor coupling energy homeostasis to cell growth, proliferation, and survival. However, how tumor cells suppress this signaling pathway to gain growth advantage under conditions of energy stress is largely unknown. Here, we show that AMPK activation is suppressed in melanoma cells with the B-RAF V600E mutation and that downregulation of B-RAF signaling activates AMPK. We find that in these cells LKB1 is phosphorylated by ERK and Rsk, two kinases downstream of B-RAF, and that this phosphorylation compromises the ability of LKB1 to bind and activate AMPK. Furthermore, expression of a phosphorylation-deficient mutant of LKB1 allows activation of AMPK and inhibits melanoma cell proliferation and anchorage-independent cell growth. Our findings provide a molecular linkage between the LKB1-AMPK and the RAF-MEK-ERK pathways and suggest that suppression of LKB1 function by B-RAF V600E plays an important role in B-RAF V600E-driven tumorigenesis.

Publication types

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

MeSH terms

  • AMP-Activated Protein Kinases / metabolism
  • Animals
  • COS Cells
  • Cell Proliferation
  • Cells, Cultured
  • Chlorocebus aethiops
  • Gene Expression Regulation, Neoplastic
  • Genes, Tumor Suppressor*
  • HeLa Cells
  • Humans
  • Melanoma / enzymology*
  • Melanoma / genetics
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism*
  • Signal Transduction

Substances

  • STK11 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins B-raf
  • AMP-Activated Protein Kinases