BRAFV600E mutation, TIMP-1 upregulation, and NF-κB activation: closing the loop on the papillary thyroid cancer trilogy

Endocr Relat Cancer. 2011 Nov 14;18(6):669-85. doi: 10.1530/ERC-11-0076. Print 2011 Dec.

Abstract

BRAF(V600E) is the most common mutation found in papillary thyroid carcinoma (PTC). Tissue inhibitor of metalloproteinases (TIMP-1) and nuclear factor (NF)-κB have been shown to play an important role in thyroid cancer. In particular, TIMP-1 binds its receptor CD63 on cell surface membrane and activates Akt signaling pathway, which is eventually responsible for its anti-apoptotic activity. The aim of our study was to evaluate whether interplay among these three factors exists and exerts a functional role in PTCs. To this purpose, 56 PTC specimens were analyzed for BRAF(V600E) mutation, TIMP-1 expression, and NF-κB activation. We found that BRAF(V600E) mutation occurs selectively in PTC nodules and is associated with hyperactivation of NF-κB and upregulation of both TIMP-1 and its receptor CD63. To assess the functional relationship among these factors, we first silenced BRAF gene in BCPAP cells, harboring BRAF(V600E) mutation. We found that silencing causes a marked decrease in TIMP-1 expression and NF-κB binding activity, as well as decreased invasiveness. After treatment with specific inhibitors of MAPK pathway, we found that only sorafenib was able to increase IκB-α and reduce both TIMP-1 expression and Akt phosphorylation in BCPAP cells, indicating that BRAF(V600E) activates NF-κB and this pathway is MEK-independent. Taken together, our findings demonstrate that BRAF(V600E) causes upregulation of TIMP-1 via NF-κB. TIMP-1 binds then its surface receptor CD63, leading eventually to Akt activation, which in turn confers antiapoptotic behavior and promotion of cell invasion. The recognition of this functional trilogy provides insight on how BRAF(V600E) determines cancer initiation, progression, and invasiveness in PTC, also identifying new therapeutic targets for the treatment of highly aggressive forms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acid Substitution / physiology
  • Carcinoma
  • Carcinoma, Papillary
  • Cell Transformation, Neoplastic / genetics*
  • Cell Transformation, Neoplastic / pathology
  • Disease Progression
  • Female
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Neoplastic
  • Gene Regulatory Networks / physiology
  • Glutamic Acid / genetics
  • Humans
  • Male
  • Middle Aged
  • Mutation, Missense / physiology
  • NF-kappa B / metabolism*
  • Neoplasm Invasiveness
  • Proto-Oncogene Proteins B-raf / genetics*
  • Proto-Oncogene Proteins B-raf / physiology
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • Thyroid Cancer, Papillary
  • Thyroid Neoplasms / genetics*
  • Thyroid Neoplasms / metabolism*
  • Thyroid Neoplasms / pathology
  • Tissue Inhibitor of Metalloproteinase-1 / genetics*
  • Tissue Inhibitor of Metalloproteinase-1 / metabolism
  • Tumor Cells, Cultured
  • Up-Regulation / genetics
  • Valine / genetics

Substances

  • NF-kappa B
  • TIMP1 protein, human
  • Tissue Inhibitor of Metalloproteinase-1
  • Glutamic Acid
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Valine