Abstract
Most melanoma cells are characterized by the V600E mutation in B-Raf kinase. This mutation leads to increased expression of interleukin (CXCL8), which plays a key role in cell growth and angiogenesis. Thus CXCL8 appears to be an interesting therapeutic target. Hence, we performed vaccination of mice with GST-CXCL8, which results in a reduced incidence of syngenic B16 melanoma cell xenograft tumors. We next addressed the molecular mechanisms responsible for aberrant CXCL8 expression in melanoma. The CXCL8 mRNA contains multiples AU-rich sequences (AREs) that modulate mRNA stability through the binding of tristetraprolin (TTP). Melanoma cell lines express very low TTP levels. We therefore hypothesized that the very low endogenous levels of TTP present in different melanoma cell lines might be responsible for the relative stability of CXCL8 mRNAs. We show that TTP is actively degraded by the proteasome and that extracellular-regulated kinase inhibition results in TTP accumulation. Conditional expression of TTP in A375 melanoma cells leads to CXCL8 mRNA destabilization via its 3' untranslated regions (3'-UTR), and TTP overexpression reduces its production. In contrast, downregulation of TTP by short hairpin RNA results in upregulation of CXCL8 mRNA. Maintaining high TTP levels in melanoma cells decreases cell proliferation and autophagy and induces apoptosis. Sorafenib, a therapeutic agent targeting Raf kinases, decreases CXCL8 expression in melanoma cells through reexpression of TTP. We conclude that loss of TTP represents a key event in the establishment of melanomas through constitutive expression of CXCL8, which constitutes a potent therapeutic target.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Animals
-
Antibodies / immunology
-
Antibodies / pharmacology
-
Antineoplastic Agents / pharmacology
-
Apoptosis / physiology
-
Autophagy / physiology
-
Benzamides / pharmacology
-
Benzenesulfonates / pharmacology
-
Cell Line, Tumor
-
Cell Proliferation / drug effects
-
Chemokine CXCL1 / immunology
-
Chemokine CXCL1 / pharmacology
-
Chemokine CXCL5 / immunology
-
Chemokine CXCL5 / pharmacology
-
Dichlororibofuranosylbenzimidazole / pharmacology
-
Down-Regulation / genetics*
-
Extracellular Signal-Regulated MAP Kinases / metabolism*
-
Female
-
Gene Expression / drug effects
-
Gene Expression / genetics
-
Genes, Reporter / genetics
-
Half-Life
-
Humans
-
Immunotherapy, Active / methods
-
Interleukin-8 / genetics
-
Interleukin-8 / immunology
-
Interleukin-8 / metabolism*
-
Interleukin-8 / pharmacology
-
Leupeptins / pharmacology
-
MAP Kinase Kinase Kinases / antagonists & inhibitors
-
MAP Kinase Kinase Kinases / metabolism
-
Melanoma / metabolism*
-
Melanoma / prevention & control
-
Membrane Proteins / genetics
-
Membrane Proteins / metabolism
-
Mice
-
Mice, Inbred BALB C
-
Microtubule-Associated Proteins / metabolism
-
Niacinamide / analogs & derivatives
-
Phenylurea Compounds
-
Phosphorylation / drug effects
-
Proteasome Endopeptidase Complex / metabolism
-
Proteasome Inhibitors
-
Proto-Oncogene Proteins / genetics
-
Proto-Oncogene Proteins / metabolism
-
Pyridines / pharmacology
-
RNA Stability / drug effects
-
RNA Stability / physiology*
-
RNA, Messenger / genetics
-
RNA, Messenger / metabolism
-
RNA, Small Interfering / genetics
-
Receptors, Interleukin-8B / metabolism
-
Sorafenib
-
Transfection
-
Tristetraprolin / genetics
-
Tristetraprolin / metabolism*
-
Tumor Cells, Cultured
-
Vaccination
Substances
-
2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide
-
Antibodies
-
Antineoplastic Agents
-
BNIP3 protein, human
-
Benzamides
-
Benzenesulfonates
-
Chemokine CXCL1
-
Chemokine CXCL5
-
Cxcl1 protein, mouse
-
Cxcl5 protein, mouse
-
Interleukin-8
-
Leupeptins
-
MAP1LC3A protein, human
-
Membrane Proteins
-
Microtubule-Associated Proteins
-
Phenylurea Compounds
-
Proteasome Inhibitors
-
Proto-Oncogene Proteins
-
Pyridines
-
RNA, Messenger
-
RNA, Small Interfering
-
Receptors, Interleukin-8B
-
Tristetraprolin
-
ZFP36 protein, human
-
Niacinamide
-
Dichlororibofuranosylbenzimidazole
-
Sorafenib
-
Extracellular Signal-Regulated MAP Kinases
-
MAP Kinase Kinase Kinases
-
Proteasome Endopeptidase Complex
-
benzyloxycarbonylleucyl-leucyl-leucine aldehyde