ARTICLE ABSTRACTWe showed previously that daily gavage of Angelica gigas Nakai (AGN) root ethanolic extract starting 8 weeks of age inhibited growth of prostate epithelium and neuroendocrine carcinomas (NE-Ca) in the transgenic adenocarcinoma of mouse prostate (TRAMP) model. Because decursin (D) and its isomer decursinol angelate (DA) are major pyranocoumarins in AGN extract, we tested the hypothesis that D/DA represented active/prodrug compounds against TRAMP carcinogenesis. Three groups of male C57BL/6 TRAMP mice were gavage treated daily with excipient vehicle, AGN (5 mg per mouse), or equimolar D/DA (3 mg per mouse) from 8 weeks to 16 or 28 weeks of age. Measurement of plasma and NE-Ca D, DA, and their common metabolite decursinol indicated similar retention from AGN versus D/DA dosing. The growth of TRAMP dorsolateral prostate (DLP) in AGN- and D/DA-treated mice was inhibited by 66% and 61% at 16 weeks and by 67% and 72% at 28 weeks, respectively. Survival of mice bearing NE-Ca to 28 weeks was improved by AGN, but not by D/DA. Nevertheless, AGN- and D/DA-treated mice had lower NE-Ca burden. Immunohistochemical and mRNA analyses of DLP showed that AGN and D/DA exerted similar inhibition of TRAMP epithelial lesion progression and key cell-cycle genes. Profiling of NE-Ca mRNA showed a greater scope of modulating angiogenesis, epithelial–mesenchymal transition, invasion–metastasis, and inflammation genes by AGN than D/DA. The data therefore support D/DA as probable active/prodrug compounds against TRAMP epithelial lesions, and they cooperate with non-pyranocoumarin compounds to fully express AGN efficacy against NE-Ca. Cancer Prev Res; 8(9); 835–44. ©2015 AACR.