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Modulation of mitogen-activated protein kinases and phosphorylation of Bcl-2 by vinblastine represent persistent

M Fan1, L Du, A A Stone

  • 1Department of Biochemistry, University of Arkansas for Medical Sciences, Little Rock 72205, USA.

Cancer Research
|December 5, 2000
PubMed

Insights

Microtubule inhibitors trigger cell death pathways. However, these signaling events, including Bcl-2 phosphorylation and JNK activation, normally occur during the G2-M phase, not just in response to drug-induced damage.

Area of Science:

  • Cell Biology
  • Molecular Oncology
  • Signal Transduction

Background:

  • Microtubule inhibitors are key cancer chemotherapy agents inducing G2-M arrest and apoptosis.
  • These drugs commonly activate signaling pathways like Raf-1/Bcl-2 phosphorylation and c-Jun NH2-terminal kinase (JNK).
  • Existing research suggests these pathways are activated by microtubule damage to promote apoptosis, but some studies indicate Bcl-2 phosphorylation occurs in non-apoptotic G2-M cells.

Purpose of the Study:

  • To investigate whether signaling pathways modulated by microtubule inhibitors are a response to microtubule damage or reflect normal mitotic events.
  • To determine if Bcl-2 phosphorylation and JNK activation occur in untreated cells during the G2-M phase.

Main Methods:

  • Synchronization of KB-3 cells to the G2-M phase.
  • Treatment with vinblastine (a microtubule inhibitor).
  • Analysis of signaling pathway modulation, including Bcl-2 phosphorylation, JNK, extracellular response kinase, and p38 activity.

Main Results:

  • Bcl-2 phosphorylation and JNK activation were observed as discrete, transient events during the G2-M phase in untreated synchronized cells.
  • Extracellular response kinase and p38 inactivation also occurred transiently at G2-M in untreated cells.
  • These signaling modulations were not solely a response to vinblastine-induced microtubule damage.

Conclusions:

  • Modulation of key signaling pathways (Bcl-2 phosphorylation, JNK, ERK, p38) is a normal occurrence during the G2-M phase.
  • The extent, duration, and irreversibility of these signals, rather than their mere presence, differentiate pre-apoptotic cells from those destined to divide.
  • Findings offer new insights into the interplay between mitotic and apoptotic signaling and the mechanism of antimitotic drugs.

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