Effects of enhancing p21 waf1 on proliferation and expression of G1cyclins andCDKs in human breast cancer cells

The cyclin-dependent kinase inhibitor p21( waf1/cip1/sdil) is an important negative regulator in control of cell cycle. Its functions of inhibiting cancer cell growth and its effects on expression of G1 phase cyclins and related CDKs are a worthy topic for study. The plasmid expressing p2l with high level was transformed to human breast cancer cells, and the expression of p2l in cells was enhanced, then the cell growth rate, anchorage-independent growth and tu-morigenecity were tested, at the same time the expression levels of cyclinD1, CDK4, cyclinE and CDK2 were analyzed by Northern blot. The results showed that since the expression of p21 was enhanced in the cell, the rate of cell growth and anchorage-independent growth was inhibited, tumorigenecity was suppressed, the level of expression of cyclinE and CDK2 decreased while that of cyclinDl and CDK4 was not affected. It is suggested that the enhanced expression of p21 markedly inhibits the proliferation and lessens the tumorigenecity of breast cancer cells, and that p2l expression is not related to that of cyclinDl and CDK4, but affects the expression of cyclinE and CDK2 .