Apoptosis, growth arrest and suppression of invasiveness by CRE-decoy oligonucleotide in ovarian cancer cells: Protein kinase A downregulation and cytoplasmic export of CRE-binding proteins

The CRE (cyclic AMP response element)-transcription factor complex plays a critical role in response to hormonal signals for cell proliferation, diffe rentiation, and apoptosis. We have reported previously that the CRE-transcr iption factor decoy oligonucleotide specifically slows tumor cell prolifera tion and inhibits CRE- and Ap-1-directed transcription in vivo (Park et al. , 1999 [12]). We have investigated the effect of inhibiting CRE-directed tr anscription on ovarian cancer cell growth. Here, we report that CRE-decoy o ligonucleotide treatment results in the inhibition of cell growth and a mar ked reduction in the expression of the regulatory and catalytic subunits of protein kinase A and the type I and type II protein kinase A holoenzymes. Growth inhibition was accompanied by changes in cell morphology, appearance of apoptotic nuclei, and DNA fragmentation. In addition, MMP-9 (matrix met halloproteinase-9) activity was markedly reduced in CRE-decoy treated cells . Indirect immunofluorescence revealed that CRE-decoy oligonucleotide treat ment promoted export of the CRE-binding protein, CREB, from the nucleus to the cytoplasm, while importing the catalytic subunit of protein kinase A fr om the cytoplasm to the nucleus. The results indicate that the decoy oligon ucleotide, by binding specifically to CRE-transcription factors, interferes with CRE-directed transcription in vivo. These results show a critical rol e for CRE-directed transcription in ovarian cancer cell growth. Thus, the C RE-decoy oligonucleotide may provide a powerful means to combat ovarian can cer.