DIFFERENTIATION OF HL-60 LEUKEMIA BY TYPE-I REGULATORY SUBUNIT ANTISENSE OLIGODEOXYNUCLEOTIDE OF CAMP-DEPENDENT PROTEIN-KINASE

A marked decrease in the type I cAMP-dependent protein kinase regulatory subunit (RI-alpha) and an increase in the type II protein kinase regulatory subunit (RII-beta) correlate with growth inhibition and differentiation induced in a variety of types of human cancer cells, in vitro and in vivo, by site-selective cAMP analogs. To directly determine whether RI-alpha is a growth-inducing protein essential for neoplastic cell growth, human HL-60 promyelocytic leukemia cells were exposed to 21-mer RI-alpha antisense oligodeoxynucleotide, and the effects on cell replication and differentiation were examined. The RI-alpha antisense oligomer brought about growth inhibition and monocytic differentiation, bypassing the effects of an exogenous cAMP analog. These effects of RI-alpha antisense oligodeoxynucleotide correlated with a decrease in RI-alpha receptor and an increase in RII-beta receptor level. The growth inhibition and differentiation were abolished, however, when these cells were exposed simultaneously to both RI-alpha and RII-beta antisense oligodeoxynucleotides. The RII-beta antisense oligodeoxynucleotide alone has been previously shown to specifically block the differentiation inducible by cAMP analogs. These results provide direct evidence that RI-alpha cAMP receptor plays a critical role in neoplastic cell growth and that cAMP receptor isoforms display specific roles in cAMP regulation of cell growth and differentiation.