CRE-Transcription factor decoy oligonucleotide inhibition of MCF-7 breast cancer cells: Cross-talk with p53 signaling pathway

The CRE, 5'-TGACGTCA-3', has been described as the consensus sequence for t he cis-element that directs cAMP-regulated gene expression Many transcripti on factors bind to this element and regulate the expression of a wide varie ty of cellular and viral genes. We have shown that CRE-transcription factor decoy oligonucleotide restrains the growth of cancer cells in vitro and in vivo [Park, Y. G., Nesterova, M., Agrawal, S., and Cho-Chung, Y. S. (1999) J. Biol. Chem. 274, 1573-1580]. The growth inhibition was accompanied by c hanges in cell morphology and apoptosis. To elucidate the molecular mechani sm (s) of the growth inhibition by the CRE-decoy oligonucleotide, we invest igated the p53 signaling pathway. Herein, we report that CRE-decoy oligonuc leotide treatment results in an increase in the p53 protein level in MCF-7 human breast cancer cells that express wild-type p53. The p21WAF1/Cip1 prot ein levels were also increased in the CRE-decoy oligonucleotide treated cel ls accompanying a reduction in Cdk2- and cyclin E-dependent kinase activity and pRb phosphorylation. Pulse-chase experiments reveal that the p53 upreg ulation was due to increased stability of the protein. The decoy oligonucle otide treatment also enhanced the p53 promotor-directed transcription in vi vo along with the increase in p53-CBP (CREB-binding protein) complex format ion. Thus, the stabilization and activation of p53 may have contributed to the growth inhibition induced by CRE-transcription factor decoy oligonucleo tide in MCF-7 breast cancer cells. This decoy oligonucleotide approach offe rs great promise as a tool for defining cellular regulatory processes and t reating cancer and other diseases.