Antisense Targeting Protein Kinase C alpha and beta sub(1) Inhibits Gastric Carcinogenesis

Protein kinase C (PKC) family, which functions through serine/threonine kinase activity, is involved in signal transduction pathways necessary for cell proliferation, differentiation, and apoptosis. Its critical role in neoplastic transformation and tumor invasion renders PKC a potential target for anticancer therapy. In this study, we investigated the effect of targeting individual PKCs on gastric carcinogenesis. We established gastric cancer cell lines stably expressing antisense PKC alpha , PKC beta sub(1), and PKC beta sub(2) cDNA. These stable transfectants were characterized by cell morphology, cell growth, apoptosis, and tumorigenicity in vitro and in vivo. PKC alpha -AS and PKC beta sub(1)-AS transfectants showed a different morphology with flattened, long processes and decreased nuclear:cytoplasmic ratio compared with the control cells. Cell growth was markedly inhibited in PKC alpha -AS and PKC beta sub(1)-AS transfectants. PKC alpha -AS and PKC beta sub(1)-AS cells were more responsive to mitomycin C- or 5-fluorouracil- induced apoptosis. However, antisense targeting of PKC beta sub(2) did not have any significant effect on cell morphology, cell growth, or apoptosis. Furthermore, antisense inhibition of PKC alpha and PKC beta sub(1) markedly suppressed colony-forming efficiency in soft agar and in nude mice xenografts. Inhibition of PKC alpha or PKC beta sub(1) significantly suppressed transcriptional and DNA binding activity of activator protein in gastric cancer cells, suggesting that PKC alpha or PKC beta sub(1) exerts their effects on cell growth through regulation of activator protein activity. These data provide evidence that targeting PKC alpha and PKC beta sub(1) by antisense method is a promising therapy for gastric cancer.