Identification of the triterpenoid, pristimerin, as an inhibitor of CCND2 transactivation. (A) Rank-ordered dot plot of the Spectrum library of 2000 drugs and natural compounds (x-axis) showing their specific effects on CCND2 promoter transactivation relative to NIH3T3 viability (as ratio of luciferase and MTT assays on vertical axis, normalized to vehicle controls with no effect). The activity of pristimerin, the top-ranked hit, and of glucocorticoids is indicated. Lopac and Prestwick drug libraries were previously screened³  but are not shown. (B) Histogram showing the effects of pristimerin on luciferase expression when transcribed from the CCND2 promoter or from a control RSV promoter. The activities of the various reporter cell lines are normalized to vehicle-treated controls. Pristimerin suppresses CCND2 transactivation both in the presence (P = .005) and absence (P = .04) of the MAF transactivator but does not suppress luciferase when expressed from a control RSV promoter. Error bars represent the sum of relative error in separate viability and luciferase measurements, determined from the standard deviation of triplicate assays. (C) Time course of pristimerin-induced suppression of CCND2 promoter expressed luciferase in NIH3T3; the luciferase protein has an estimated half-life of 3 hours. (D) Chemical structure of pristimerin.