PI3K mediates protection against TRAIL-induced apoptosis in primary human melanocytes

Cell Death Differ. 2004 Oct;11(10):1084-91. doi: 10.1038/sj.cdd.4401475.

Abstract

Melanocytes are cells of the epidermis that synthesize melanin, which is responsible for skin pigmentation. Transformation of melanocytes leads to melanoma, a highly aggressive neoplasm, which displays resistance to apoptosis. In this report, we demonstrate that TNF-related apoptosis-inducing ligand (TRAIL), which was thought to kill only transformed cells, promotes very efficiently apoptosis of primary human melanocytes, leading to activation of caspases 8, 9 and 3, and the cleavage of vital proteins. Further, we show that stem cell factor (SCF), a physiologic melanocyte growth factor that activates both the phosphatidyl-inositol-3 kinase (PI3K) and the extracellular regulated kinase (ERK) pathways, strongly protects melanocytes from TRAIL and staurosporine killing. Interestingly, inhibition of PI3K or its downstream target AKT completely blocks the antiapoptotic effect of SCF, while inhibition of ERK has only a moderate effect. Our data indicate that protection evoked by SCF/PI3K/AKT cascade is not mediated by an increase in the intracellular level of FLIP. Further, only a sustained PI3K activity can protect melanocytes from apoptosis, thereby indicating that the PI3K/AKT pathway plays a pivotal role in melanocyte survival. The results gathered in this report bring new information on the molecular mechanisms involved in primary melanocyte apoptosis and survival that would help to better understand the process by which melanomas acquire their resistance to apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis Regulatory Proteins
  • Cells, Cultured
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Humans
  • Keratinocytes / drug effects
  • Keratinocytes / metabolism
  • Melanocytes / cytology
  • Melanocytes / drug effects*
  • Melanocytes / enzymology
  • Melanocytes / metabolism
  • Melanoma / pathology
  • Membrane Glycoproteins / pharmacology*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Signal Transduction / drug effects
  • Stem Cell Factor / pharmacology
  • TNF-Related Apoptosis-Inducing Ligand
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • Apoptosis Regulatory Proteins
  • Enzyme Inhibitors
  • Membrane Glycoproteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins
  • Stem Cell Factor
  • TNF-Related Apoptosis-Inducing Ligand
  • TNFSF10 protein, human
  • Tumor Necrosis Factor-alpha
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases