Overexpression of protein kinase C epsilon is oncogenic in rat colonic epithelial cells.
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.
Perletti
G P
GP
Istituto di Farmacologia, Università degli studi di Milano, Italy.
Folini
M
M
Lin
H C
HC
Mischak
H
H
Piccinini
F
F
Tashjian
A H
AH
D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D003106:Colon / Q000201:enzymology*; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D004847:Epithelial Cells; D004848:Epithelium / Q000201:enzymology / Q000473:pathology; D015870:Gene Expression; D011905:Genes, ras; D007527:Isoenzymes / Q000096:biosynthesis; D051379:Mice; D008819:Mice, Nude; D011493:Protein Kinase C / Q000096:biosynthesis*; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014183:Transplantation, Heterologous
D007527:Isoenzymes; D011994:Recombinant Proteins; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate