8-Cl-adenosine induces growth arrest without differentiation of primary mouse epidermal keratinocytes.
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 [3H]thymidine incorporation in a dose-dependent manner with an apparent IC(50) of 7.5 microM, 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 microM 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 non-transformed/non-immortalized cell system, possibly through an elevation in p21(WAF1/Cip1) protein levels, without inducing differentiation.
Dransfield
D T
DT
Department of Medicine, Institute of Molecular Medicine and Genetics Program in Cell Signaling, Medical College of Georgia, Augusta, 30912, USA.
Griner
R D
RD
Ray
S
S
Keskintepe
M
M
Bollag
W B
WB
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015415:Biomarkers; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D000078404:Epidermal Cells; D016193:G1 Phase / Q000187:drug effects; D015603:Keratinocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D007633:Keratins / Q000096:biosynthesis; D051379:Mice; D008813:Mice, Inbred ICR; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D011503:Transglutaminases / Q000378:metabolism
D000970:Antineoplastic Agents; D015415:Biomarkers; D015124:8-Bromo Cyclic Adenosine Monophosphate; D007633:Keratins; C044258:8-chloro-cyclic adenosine monophosphate; D011503:Transglutaminases