A RECOMBINANT ADENOVIRUS EXPRESSING P27(KIP1) INDUCES CELL-CYCLE ARREST AND LASS OF CYCLIN-CDK ACTIVITY IN HUMAN BREAST-CANCER CELLS

In order to elucidate the biochemical mechanisms by which the universa l cyclin kinase inhibitor p27(Kip1) regulates cell cycle progression i n human breast cancer cells, a recombinant adenovirus expressing human p27 was constructed (Adp27). Upon infection of human breast cancer ce lls MDA-MB-231 and MCF-7 with Adp27, a high level of p27 expression wa s observed, and this resulted in a marked decrease in the proportion o f cells in S-phase, In multiple cell lines, comparison of the cytotoxi city of Adp27 with another adenovirus vector expressing the related un iversal cyclin kinase inhibitor WAF1/Cip1 (AdWAF1), showed Adp27 to be markedly more (up to 56-fold) toxic than AdWAF1, DNA histograms showe d Adp27 to cause a G(1)/S arrest at lower viral doses than AdWAF1, Ana lysis of cyclin dependent kinase activity following Adp27 infections s howed decreased Cdk2 and cyclin B1-Cdc2 activity at lower viral doses when compared with AdWAF1, Adp27 is therefore potentially useful for s tudies of growth regulation and for gene therapy when growth inhibitio n is desired.