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Novel pathway in Bcr-Abl signal transduction involves Akt-independent, PLC-gamma1-driven activation of

B Markova1, C Albers, F Breitenbuecher

  • 1Department of Medicine (Cancer Research), West German Cancer Center, University Hospital, Essen, Germany.

Oncogene
|November 3, 2009
PubMed

Insights

A novel phospholipase C-gamma1 (PLC-gamma1) pathway drives cancer cell survival in chronic myeloid leukemia. Inhibiting PLC-gamma1 alongside Bcr-Abl treatment induces leukemia cell death, offering a new therapeutic target.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • The phosphoinositide 3-kinase (PI3K)/Akt pathway is critical for chronic myeloid leukemia (CML) cell survival and proliferation.
  • Mammalian target of rapamycin (mTOR) and S6-kinase are key downstream effectors in this pathway.

Purpose of the Study:

  • To comprehensively analyze the molecular events activating mTOR/S6-kinase signaling in CML.
  • To identify and characterize novel mechanisms of mTOR/p70S6-kinase activation beyond the classical Akt-dependent pathway.

Main Methods:

  • Analysis of signaling pathways in Bcr-Abl-positive CML cells treated with imatinib.
  • Pharmacological inhibition and siRNA knockdown of phospholipase C-gamma1 (PLC-gamma1).
  • Investigation of calcium signaling, CaMK, and PKCs involvement.

Main Results:

  • Short-term imatinib treatment reduced p70S6-K and S6 phosphorylation without Akt inactivation, suggesting an alternative activation route.
  • Bcr-Abl-expressing cells showed significant PLC-gamma1 activation, which was suppressed by imatinib.
  • PLC-gamma1 inhibition, along with calcium signaling modulators, blocked p70S6-K/S6 phosphorylation, inhibited proliferation, and induced apoptosis.
  • Combined PLC-gamma1 and Bcr-Abl inhibition resulted in near-complete leukemia cell death.
  • The pivotal role of PLC-gamma1 was confirmed in a mouse model of leukemogenesis.

Conclusions:

  • A previously unrecognized PLC-gamma1-controlled pathway activates mTOR/p70S6-kinase in parallel to Akt.
  • This novel pathway is essential for CML cell survival and proliferation.
  • Targeting PLC-gamma1 represents a promising therapeutic strategy for CML, particularly in combination with Bcr-Abl inhibition.

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