INHIBITION OF PROTEIN-KINASE C-ALPHA EXPRESSION IN HUMAN A549 CELLS BY ANTISENSE OLIGONUCLEOTIDES INHIBITS INDUCTION OF INTERCELLULAR-ADHESION MOLECULE-1 (ICAM-1) MESSENGER-RNA BY PHORBOL ESTERS

We have identified 20-mer phosphorothioate oligodeoxynucleotides which potently (IC50 values of 100-200 nM) and specifically inhibit protein kinase C (PKC)-(alpha mRNA and protein expression in human lung carci noma (A549) cells. These oligonucleotides target multiple, diverse sit es on PKC-alpha mRNA including the AUG translation codon and 3'-untran slated sequences. 2'-O-Methyl phosphorothioate analogs of these oligon ucleotides were without effect on PKC-alpha( )mRNA levels, suggesting that the reduction in targeted PKC-alpha mRNA is through RNase H-media ted cleavage. One oligonucleotide, however, was effective at inhibitin g PKC-alpha protein levels as a 2'-O-methyl phosphorothioate at concen trations 2-3-fold greater than its phosphorothioate/deoxy homolog. The se results suggest that the ability to serve as an RNase H substrate, although not required for all oligonucleotides, certainly increases th eir potency. These oligonucleotides have been used to examine the role played by PKC-alpha in mediating the phorbol ester-induced changes in mRNA levels of the cell adhesion molecule ICAM-1. In A549 cells, ICAM -1 mRNA is increased 10-20-fold by treatment of cells with the phorbol ester phorbol 12-myristate 13-acetate. When PKC-alpha protein levels are depleted by oligonucleotide treatment of A549 cells, the increase in ICAM-1 expression in response to phorbol 12-myristate 13-acetate is greatly reduced, demonstrating that PKC-alpha plays a major role in t his process.