Oligonucleotide sequence-specific inhibition of gene expression, tumor growth inhibition, and modulation of cAMP signaling by an RNA-DNA hybrid antisense targeted to protein kinase A RI alpha subunit

The primary mediator of cAMP action in mammalian cells is cAMP-dependent pr otein kinase (PKA), There are two types of PKA, type I (PKA-I) and type II (PKA-II), which share a common catalytic subunit but contain distinct regul atory subunits, RI and RII, respectively. Evidence suggests that increased expression of RIalpha/PKA-I correlates with neoplastic cell growth. Here, w e show that sequence-specific oligonucleotide inhibition of RIalpha express ion results in inhibition of growth and modulation of cAMP signaling in can cer cells. The antisense promoted growth inhibition in a time-dependent, co ncentration-dependent, and sequence-dependent manner in human cancer cells in monolayer culture, and it inhibited colony formation in soft agar and tu mor growth in nude mice. Among the cancer cells are LS-174T, HCT-15, and Co le-205 colon carcinoma cells; A-549 lung carcinoma cells; LNCaP prostate ad enocarcinoma cells; Molt-4 leukemia cells; and Jurkat T lymphoma cells, Nor thern blot and immunoprecipitation analyses revealed that the growth inhibi tory effect of the antisense correlated with a decrease in RIalpha expressi on at both the mRNA and protein levels. Pulse-chase experiments revealed th at the antisense-directed inhibition of RIalpha expression resulted in comp ensatory changes in expression of the isoforms of R and C subunits and cAMP signaling in a cell type-specific manner, These results demonstrate that c AMP is ubiquitous in the regulation of cell growth and that the antisense o ligonucleotide, which inhibits the synthesis of the RIalpha subunit of PKA, can be targeted to a single gene for treatment of cancer in a variety of c ell types.