title: 8-Cl-adenosine is an active metabolite of 8-Cl-cAMP responsible for its in vitro antiproliferative effects on CHO mutants hypersensitive to cytostatic drugs.
abstract: 8-Cl-cAMP has been undergoing clinical trials as a potential chemotherapy agent, but there is much discussion in the literature as to whether the active agent is 8-Cl-cAMP itself, or its major metabolite, 8-Cl-adenosine. 8-Cl-cAMP is susceptible to the action of serum enzymes such as phosphodiesterases, and its metabolism when administered to cancer patients raises questions as to the mechanism of action of 8-Cl-cAMP. The stability of 8-Cl-cAMP when incubated with serum, and the effects of both 8-Cl-cAMP and 8-Cl-adenosine on the proliferation of variant lines of CHO cells hypersensitive to 8-Cl-cAMP were investigated. A solid-phase extraction (SPE) purification protocol and the HPLC method previously developed were used to determine 8-Cl-cAMP and 8-Cl-adenosine. Heat treatment of serum inactivated the enzymes in the culture medium responsible for activating 8-Cl-cAMP. Under these conditions 8-Cl-cAMP remained stable and there were no traces of its metabolite, 8-Cl-adenosine. Cell culture experiments showed that 8-Cl-cAMP only affected cell growth in medium that contained untreated serum. In contrast, 8-Cl-adenosine was shown to be growth inhibitory in medium containing either heat-treated or untreated serum. HPLC analysis of the culture medium from the cell culture experiments supported the hypothesis that 8-Cl-cAMP was only effective in inhibiting cell growth after metabolism to 8-Cl-adenosine. Thus further studies of this drug and its mechanism of action should focus on 8-Cl-adenosine.
authors.affiliation: School of Biological and Molecular Sciences, Oxford Brookes University, UK.
authors.forename: S K
authors.initials: SK
authors.lastname: Robbins
authors.forename: S
authors.initials: S
authors.lastname: Houlbrook
authors.forename: J D
authors.initials: JD
authors.lastname: Priddle
authors.forename: A L
authors.initials: AL
authors.lastname: Harris
mesh_terms: D015762:2-Chloroadenosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D000241:Adenosine / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D016466:CHO Cells; D002455:Cell Division / Q000187:drug effects*; D017606:Chlorine Compounds / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D013696:Temperature
chemical_list: D000970:Antineoplastic Agents; D017606:Chlorine Compounds; D015762:2-Chloroadenosine; D015124:8-Bromo Cyclic Adenosine Monophosphate; C044258:8-chloro-cyclic adenosine monophosphate; D000241:Adenosine; C075440:8-chloroadenosine