The comparative effects of 5'-methylthioadenosine and some of its analogs on cells containing, and deficient in, 5'-methylthioadenosine phosphorylase.
The antiproliferative effects of 5'-methylthioadenosine and the 5'-methylthioadenosine analogs, 5'-isobutylthioadenosine, 5'-deoxyadenosine and 5'-methylthiotubercidin were examined using two mouse cell lines, one 5'-methylthioadenosine phosphorylase-deficient the other containing 5'-methylthioadenosine phosphorylase. All of the compounds were found to be growth inhibitory to both cell lines, demonstrating that these compounds need not be degraded to exert their inhibitory effects. A correlation was observed between the potency of the growth inhibitory effect and the ability of the cells to degrade these compounds. 5'-Methylthioadenosine, 5'-deoxyadenosine and 5'-isobutylthioadenosine, all of which are substrates for the 5'-methylthioadenosine phosphorylase in vitro, were more growth inhibitory to the 5'-methylthioadenosine phosphorylase-deficient cells than to the 5'-methylthioadenosine phosphorylase-containing cells, whereas, the 7-deaza analog, 5'-methylthiotubercidin, a nondegradable inhibitor of the 5'-methylthioadenosine phosphorylase, was a more potent inhibitor of the 5'-methylthioadenosine phosphorylase-containing cell line. Due to the inhibition by 5'-methylthiotubercidin on 5'-methylthioadenosine phosphorylase in vitro the disposition of cellularly-synthesized 5'-methylthioadenosine was explored using both cell types. 5'-Methylthiotubercidin inhibited the accumulation of exogenous 5'-methylthioadenosine from 5'-methylthioadenosine phosphorylase-deficient cells with no effect on intracellular 5'-methylthioadenosine. In contrast, 5'-methylthiotubercidin caused a large accumulation of extracellular 5'-methylthioadenosine with a concomitant smaller increase intracellularly in 5'-methylthioadenosine phosphorylase-containing cells. That cellularly-synthesized 5'-methylthioadenosine as well as the cellular excretion of this nucleoside are altered in response to treatment with 5'-methylthiotubercidin suggests two possible sites at which 5'-methylthiotubercidin may exert its effect.
D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003839:Deoxyadenosines; D007939:Leukemia L1210 / Q000378:metabolism; D051379:Mice; D008806:Mice, Inbred AKR; D010430:Pentosyltransferases / Q000378:metabolism*; D011683:Purine-Nucleoside Phosphorylase / Q000172:deficiency / Q000378:metabolism*; D013872:Thionucleosides / Q000378:metabolism / Q000494:pharmacology*
D003839:Deoxyadenosines; D013872:Thionucleosides; C008500:5'-methylthioadenosine; D010430:Pentosyltransferases; D011683:Purine-Nucleoside Phosphorylase; C021784:5'-methylthioadenosine phosphorylase; D000241:Adenosine