Curcumin-induced antiproliferative and proapoptotic effects in melanoma cells are associated with suppression of IkappaB kinase and nuclear factor kappaB activity and are independent of the B-Raf/mitogen-activated/extracellular signal-regulated protein kinase pathway and the Akt pathway

Cancer. 2005 Aug 15;104(4):879-90. doi: 10.1002/cncr.21216.

Abstract

Background: Nuclear factor-kappaB (NF-kappaB) plays a central role in cell survival and proliferation in human melanoma; therefore, the authors explored the possibility of exploiting NF-kappaB for melanoma treatment by using curcumin, an agent with known, potent, NF-kappaB-inhibitory activity and little toxicity in humans.

Methods: Three melanoma cell lines (C32, G-361, and WM 266-4), all of which had B-raf mutations, were treated with curcumin, and the authors assessed its effects on viability ((3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide assay) and apoptosis (flow-cytometric analysis of annexin V/propidium iodide-stained cells). Curcumin-treated cells also were examined for NF-kappaB binding activity (electrophoretic mobility shift assay) and for the activity of its upstream regulator, IkappaB kinase (IKK) (immune complex kinase assay). In addition, relevant signaling, as reflected by B-Raf kinase activity (kinase cascade assay), and steady-state levels of activated, downstream effectors, as reflected by mitogen-activated signal-regulated protein kinase (MEK), extracellular signal-regulated protein kinase (ERK), and Akt phosphorylation levels (immunoblots), were assessed.

Results: Curcumin treatment decreased cell viability of all 3 cell lines in a dose-dependent manner (50% inhibitory concentration = 6.1-7.7 microM) and induced apoptosis. NF-kappaB and IKK were active constitutively in all melanoma cell lines examined, and curcumin, under apoptosis-inducing conditions, down-regulated NF-kappaB and IKK activities. However, curcumin did not inhibit the activities of B-Raf, MEK, or ERK, and Akt phosphorylation was enhanced. Furthermore, in the presence of curcumin, the Akt inhibitor 1L-6-hydroxymethyl-chiro-inositol 2-[(R)-2-O-methyl-3-O-octadecylcarbonate] no longer suppressed Akt phosphorylation.

Conclusions: Curcumin has potent antiproliferative and proapoptotic effects in melanoma cells. These effects were associated with the suppression of NF-kappaB and IKK activities but were independent of the B-Raf/MEK/ERK and Akt pathways.

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects
  • Blotting, Western
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Curcumin / pharmacology*
  • Dose-Response Relationship, Drug
  • Electrophoretic Mobility Shift Assay
  • Extracellular Signal-Regulated MAP Kinases / drug effects
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Flow Cytometry
  • Humans
  • I-kappa B Kinase
  • Interleukin-8 / metabolism
  • Melanoma / drug therapy*
  • Melanoma / metabolism
  • NF-kappa B / drug effects*
  • NF-kappa B / metabolism
  • Protein-Serine-Threonine Kinases / drug effects*
  • Protein-Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / drug effects
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins B-raf / drug effects
  • Proto-Oncogene Proteins B-raf / metabolism
  • Proto-Oncogene Proteins c-akt
  • Signal Transduction / drug effects*
  • Signal Transduction / physiology

Substances

  • Antineoplastic Agents
  • Interleukin-8
  • NF-kappa B
  • Proto-Oncogene Proteins
  • AKT1 protein, human
  • BRAF protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins c-akt
  • CHUK protein, human
  • I-kappa B Kinase
  • IKBKB protein, human
  • IKBKE protein, human
  • Extracellular Signal-Regulated MAP Kinases
  • Curcumin