8-Cl-adenosine induces growth arrest without differentiation of primary mouse epidermal keratinocytes

[摘要] In some cell systems, the antiproliferative effects of 8-Cl-cAMP, a site-selective cAMP analog specific for the type I cAMP-dependent protein kinase, are mediated by its metabolite, 8-Cl-adenosine. These effects were once thought to be specific to transformed cells. We investigated the ability of 8-Cl-adenosine to regulate growth and differentiation in primary cultures of mouse epidermal keratinocytes. A 24 h exposure of keratinocytes to 8-Cl-adenosine inhibited [H-3]thymidine incorporation in a dose-dependent manner with an apparent IC50 of 7.5 muM, and these effects were completely reversible. To determine the ability of 8-Cl-adenosine to induce differentiation of primary keratinocytes, we measured keratin-1 expression and transglutaminase activity, markers of early and later stages of keratinocyte differentiation, respectively. Interestingly, exposure of keratinocytes to 25 muM 8-Cl-adenosine for 24 h had no effect on keratin-1 expression or transglutaminase activity. The 8-Cl-adenosine-induced growth arrest of keratinocytes required uptake of the compound and was accompanied by an increase in protein expression of the cyclin-dependent protein kinase inhibitor p21(WAF1/Cip1). These results demonstrate that 8-Cl-adenosine inhibits growth in a nontransformed/nonimmortalized cell system, possibly through an elevation in p21(WAF1/Cip1) protein levels, without inducing differentiation.

[发布日期] 2001-12-01

[关键词] cell cycle;keratin-1;p21(WAF1/Cip1);transglutaminase