the phosphodiesterase inhibitors theophylline , caffeine , and 3-isobutyl-1-methylxanthine ( ibx ) at concentrations of 10 ( -3 ) m , maintained continuously , were all found to inhibit the expression of 3-methylcholanthrene-induced malignant transformation when added 7 days after removal of carcinogen .
C0039771
theophylline
C0000096
3-isobutyl-1-methylxanthine