Antisense targeting protein kinase Cα and β1 inhibits gastric carcinogenesis

Abstract

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 PKCα, PKCβ 1, and PKCβ 2 cDNA. These stable transfectants were characterized by cell morphology, cell growth, apoptosis, and tumorigenicity in vitro and in vivo. PKCα-AS and PKCβ 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 PKCα-AS and PKCβ 1-AS transfectants. PKCα-AS and PKCβ 1-AS cells were more responsive to mitomycin C- or 5-fluorouracil-induced apoptosis. However, antisense targeting of PKCβ 2 did not have any significant effect on cell morphology, cell growth, or apoptosis. Furthermore, antisense inhibition of PKCα and PKCβ 1 markedly suppressed colony-forming efficiency in soft agar and in nude mice xenografts. Inhibition of PKCα or PKCβ 1 significantly suppressed transcriptional and DNA binding activity of activator protein in gastric cancer cells, suggesting that PKCα or PKCβ 1 exerts their effects on cell growth through regulation of activator protein activity. These data provide evidence that targeting PKCα and PKCβ 1 by antisense method is a promising therapy for gastric cancer.