Integrin signaling links protein kinase Cepsilon to the protein kinase B/Akt survival pathway in recurrent prostate cancer cells

Oncogene. 2004 Nov 11;23(53):8659-72. doi: 10.1038/sj.onc.1207900.

Abstract

Failure of hormone therapy often involves an outgrowth of protein kinase Cepsilon (PKCepsilon)-positive cells in recurrent prostate cancer. Our previous investigations have uncovered evidence of a complex signaling network operating downstream of this oncogenic protein kinase to actively advance the survival and proliferation of prostate cancer cells. In this study, we present evidence of a functional interplay among integrin receptors, PKCepsilon, and protein kinase B (PKB/Akt) in recurrent CWR-R1 prostate cancer cells. Flow cytometry and confocal microscopy provided evidence that PKCepsilon signaling promoted the assembly of matrix adhesions containing an abundance of colocalized actin filaments and beta1 integrins that exhibited an exposed activation epitope on the surface of live CWR-R1 cells. Reciprocal coimmunoprecipitations provided evidence of signaling complexes containing PKCepsilon, beta1 integrins, Src, and PKB/Akt in CWR-R1 cell cultures. An investigation into the functional significance of these interactions, and of their positive influence on beta1 integrins, demonstrated that PKCepsilon and several key components of the PKB/Akt signaling pathway remain constitutively phosphorylated/activated in adherent but not suspension cultures of PTEN-positive CWR-R1 cells. Gene transfer, antisense and pharmacological experiments provided additional support for the hypothesis that a mutually reinforcing signaling loop sustains the activation of beta1 integrins, PKCepsilon, and PKB/Akt in adherent prostate cancer cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Adhesion
  • Cell Line, Tumor
  • Cell Survival
  • Cytoskeletal Proteins / metabolism
  • Extracellular Matrix / metabolism
  • Fibronectins / metabolism
  • Humans
  • Integrins / chemistry
  • Integrins / metabolism*
  • Male
  • Phosphorylation
  • Prostatic Neoplasms / enzymology
  • Prostatic Neoplasms / metabolism*
  • Prostatic Neoplasms / pathology*
  • Protein Kinase C / metabolism*
  • Protein Kinase C-epsilon
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Signal Transduction*
  • Trans-Activators / metabolism
  • Transcription, Genetic
  • Transplantation, Heterologous
  • beta Catenin
  • src-Family Kinases / metabolism

Substances

  • CTNNB1 protein, human
  • Cytoskeletal Proteins
  • Fibronectins
  • Integrins
  • Proto-Oncogene Proteins
  • Trans-Activators
  • beta Catenin
  • integrin-linked kinase
  • src-Family Kinases
  • AKT1 protein, human
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • PRKCE protein, human
  • Protein Kinase C
  • Protein Kinase C-epsilon