Overexpression of protein kinase C epsilon is oncogenic in rat colonic epithelial cells

Oncogene. 1996 Feb 15;12(4):847-54.


We have analysed the expression of five protein kinase C [PKC] isoforms in an in vitro model using nontumorigenic rat colonic epithelial cells FRC/TEX CL D [D/WT] and in the related tumorigenic Ha-ras-transformed FRC/TEX CL D/H-ras line [D/ras]. The PKC subspecies alpha, delta, epsilon and xi were expressed at the protein level in both D/WT and D/ras cells, while beta PKC was undetectable in both lines. The levels of expression of the delta and xi isoforms were similar in D/WT and D/ras cells. Alpha PKC expression was decreased and epsilon PKC was increased in D/ras cells compared to the D/WT line. To assess whether overexpression of epsilon PKC was linked to the transformed phenotype, we have generated from D/WT cells two clones (D/epsilon-5 and D/epsilon-9) which stably overexpress epsilon PKC about fivefold. Overexpression of epsilon PKC caused marked morphological changes in both transfected clones, which were accompanied by increased saturation densities and anchorage-independent colony formation in semisolid agar. These growth effects were attenuated or reversed by chronic incubation with phorbol 12-myristate 13-acetate. Furthermore, D/epsilon-5 and D/epsilon-9 cells formed tumors in athymic nude mice with 100% incidence while the parental D/WT or vector alone (D/MV12) controls produced no tumors. We conclude that epsilon PKC can act as an oncoprotein when modestly overproduced in nontumorigenic D/WT colonic cells, and that this isoform of PKC may be linked to ras-modulated signal transduction leading to neoplastic transformation in colonic epithelium.

Publication types

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

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Adhesion
  • Cell Division / drug effects
  • Cell Line
  • Cell Transformation, Neoplastic*
  • Colon / enzymology*
  • Colonic Neoplasms / genetics*
  • Colonic Neoplasms / pathology
  • Epithelial Cells
  • Epithelium / enzymology
  • Epithelium / pathology
  • Gene Expression
  • Genes, ras*
  • Isoenzymes / biosynthesis
  • Mice
  • Mice, Nude
  • Protein Kinase C / biosynthesis*
  • Rats
  • Recombinant Proteins / biosynthesis
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transfection
  • Transplantation, Heterologous


  • Isoenzymes
  • Recombinant Proteins
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate