ANTISENSE EXPRESSION OF PROTEIN-KINASE C-ALPHA INHIBITS THE GROWTH AND TUMORIGENICITY OF HUMAN GLIOBLASTOMA CELLS

TO INVESTIGATE THE role of protein kinase C (PKC) in the growth of ast rocytic brain tumors, human glioblastoma cell line U-87 was stably tra nsfected with the antisense complementary deoxyribonucleic acid encodi ng PKC alpha. The effect of selectively down-regulating the alpha isof orm on other PKC isoforms, as well as serum-dependent proliferation an d in vivo tumorigenicity, was determined. U-87 cells expressed high le vels of PKC alpha and lesser amounts of the gamma, epsilon, and zeta i soforms, and a similar PKC isoform pattern was observed in two other h uman glioblastoma cell lines. Expression of the antisense PKC alpha co mplementary deoxyribonucleic acid resulted in no detectable PKC alpha by immunoblotting and a 95% reduction in total Ca2+/phospholipid-depen dent PKC activity. U-87 cells expressing antisense PKC alpha exhibited an increase in doubling time in vitro, less serum-dependent growth, a nd reduced sensitivity to a selective PKC inhibitor, Ro 31-8220. The t ransplantation of U-87 cells expressing antisense PKC alpha into nude mice resulted in no tumor formation. These observations suggest that t he inhibition of PKC alpha may be an important chemotherapeutic target for arresting the growth of glioblastomas.