Antisense Expression of Protein Kinase Cα Inhibits the Growth and Tumorigenicity of Human Glioblastoma Cells

Abstract

TO INVESTIGATE THE role of protein kinase C (PKC) in the growth of astrocytic brain tumors, human glioblastoma cell line U-87 was stably transfected with the antisense complementary deoxyribonucleic acid encoding PKCα. The effect of selectively down-regulating the α isoform on other PKC isoforms, as well as serum-dependent proliferation and in vivo tumorigenicity, was determined. U-87 cells expressed high levels of PKCα and lesser amounts of the γ, η, and ζ isoforms, and a similar PKC isoform pattern was observed in two other human glioblastoma cell lines. Expression of the antisense PKCα complementary deoxyribonucleic acid resulted in no detectable PKCα by immunoblotting and a 95% reduction in total Ca²⁺/phospholipid-dependent PKC activity. U-87 cells expressing antisense PKCα exhibited an increase in doubling time in vitro, less serum-dependent growth, and reduced sensitivity to a selective PKC inhibitor, Ro 31-8220. The transplantation of U-87 cells expressing antisense PKCα into nude mice resulted in no tumor formation. These observations suggest that the inhibition of PKCα may be an important chemotherapeutic target for arresting the growth of glioblastomas.