title: Inhibiting effect of caffeine on spontaneous and urethan-induced lung tumors in strain A mice.
abstract: The i.p. injection of caffeine (8, 20, and 40 mg/kg) 3 times weekly for 8 weeks suppressed the development of spontaneous pulmonary adenomas in strain A mice. The same caffeine injection scheme suppressed urethan (0.25 and 1.0 mg/g)-induced lung tumor development when caffeine treatment started 1 week before urethan administration, but this suppression was not significant when caffeine treatment was initiated 1 week after urethan injection. The most pronounced suppression of lung tumor formation occurred when caffeine was given as only two injections 3 hr before and 3 hr after urethan administration. The incorporation of [3H]thymidine into lung tissue DNA of caffeine-treated mice was impaired at the time of urethan administration. Also, caffeine partially antagonized the effects of urethan on lung tissue, as measured by [3H]thymidine incorporation studies. One interpretation of these results is that caffeine-induced suppression of DNA synthesis interferes with pulmonary adenoma induction by decreasing the affinity of lung tissue DNA for urethan. The finding that chronic caffeine treatment produced continued suppression of [3H]thymidine incorporation into lung tissue DNA suggests that caffeine-induced inhibition of spontaneous pulmonary adenoma formation is due to a general suppression of lung DNA-synthetic activity.
mesh_terms: D000236:Adenoma / Q000139:chemically induced / Q000517:prevention & control; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D008175:Lung Neoplasms / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D051379:Mice; D008805:Mice, Inbred A; D009374:Neoplasms, Experimental / Q000517:prevention & control; D013936:Thymidine / Q000378:metabolism; D014520:Urethane / Q000037:antagonists & inhibitors*
chemical_list: D002110:Caffeine; D014520:Urethane; D004247:DNA; D013936:Thymidine