Senescence-like changes induced by hydroxyurea in human diploid fibroblasts

Hydroxyurea was found to inhibit the growth of human diploid fibroblasts, w hich resulted in senescence-like changes both in morphology and replicative potential similar to the replicative senescence. SA-beta-gal activity, a t ypical characteristic of the replicative senescence was also induced throug h a long-term treatment of the presenescent cells with 400-800 mu M of hydr oxyurea for about 3 weeks. In addition, we determined the levels of cyclin- dependent kinase inhibitors, p21(Waf1) and p16(INK4a), and the p53 tumor su ppressor in order to monitor its effect on cell cycle and stress responses. We observed a great induction of both p53 and p21(Waf1), but not of p16(IN K4a) in the premature senescent cells. UV-irradiation of the premature sene scent cells showed a decreased level of DNA fragmentation presumably ascrib ed to the reduced activation of stress-activated protein kinases, These res ults suggest that a chronic hydroxyurea treatment induces the cellular sene scence in association with the induction of p53 and p21(Waf1). (C) 2000 Els evier Science Inc. All rights reserved.