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Identification of Transcription Factor Regulators using Medium-Throughput Screening of Arrayed Libraries and a Dual-Luciferase-Based Reporter
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ERK and PI3K negatively regulate STAT-transcriptional activities in human melanoma cells: implications towards

Mikhail Krasilnikov1, Vladimir N Ivanov, Jinali Dong

  • 1Institute of Carcinogenesis, NN Blochin Cancer Research Center, Moscow, Russia.

Oncogene
|June 25, 2003
PubMed

Insights

Melanoma cells with high MAPK and PI3K-AKT activity show inhibited JAK-STAT signaling. Inhibiting these pathways sensitizes melanoma cells to apoptosis through distinct mechanisms.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Signaling

Background:

  • Signal transducers and activators of transcription (STAT) proteins regulate gene expression in response to extracellular signals.
  • Protein kinases, including MAPKs and PI3K-AKT, play crucial roles in modulating STAT activity and cellular responses like apoptosis.
  • Melanoma cell lines exhibit varying basal levels of MAPK and PI3K-AKT activity, influencing their signaling profiles and sensitivity to treatments.

Purpose of the Study:

  • To investigate the interplay between MAPK, PI3K-AKT, and JAK-STAT signaling pathways in melanoma.
  • To determine how these signaling pathways affect STAT activity and apoptosis sensitization in different melanoma cell lines.
  • To explore the therapeutic potential of inhibiting MEK-ERK and PI3K pathways in melanoma.

Main Methods:

  • Utilized two melanoma cell lines (LU1205 and FEMX) with distinct MAPK and PI3K-AKT activities.
  • Administered pharmacological inhibitors: PD98059 (MEK-ERK inhibitor) and LY294002 (PI3K inhibitor).
  • Assessed changes in STAT activity (GAS-Luc reporter assay), tyrosine phosphorylation of JAK/STAT proteins, and apoptosis induction.

Main Results:

  • Inhibitors PD and LY increased STAT activity in LU1205 cells (high basal MAPK/PI3K-AKT) but not FEMX cells.
  • PD and LY treatments increased tyrosine phosphorylation of STAT3/5 and JAK2 in LU1205 cells, indicating inhibition of JAK-STAT signaling by active MAPK/PI3K.
  • PD treatment sensitized both cell lines to apoptosis via distinct death cascades (TNFalpha for FEMX, TRAIL for LU1205); combined LY and PD synergistically increased apoptosis.

Conclusions:

  • Constitutively active MAPK and PI3K-AKT signaling pathways downregulate JAK-STAT signaling in melanoma.
  • These kinases also affect additional targets, sensitizing melanoma cells to apoptosis through distinct death receptor pathways.
  • Combined inhibition of PI3K and MAPK pathways offers a synergistic approach to enhance melanoma apoptosis.

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