Bioactive diterpenoid metabolism and cytotoxic activities of genetically transformed Euphorbia lathyris roots

Authors: Ricigliano, Vincent; SICA, VINCENT - University Of North Carolina Greensboro; KNOWELS, SONYA - University Of North Carolina Greensboro; DIETTE, NICOLE - University Of Colorado; HOWARTH, DIANELLA - St John'S University; OBERLIES, NICHOLAS - University Of North Carolina Greensboro

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2020
Publication Date: 9/25/2020
Publication URL: https://handle.nal.usda.gov/10113/7130875
Citation: Ricigliano, V.A., Sica, V.P., Knowels, S.L., Diette, N., Howarth, D.G., Oberlies, N.K. 2020. Bioactive diterpenoid metabolism and cytotoxic activities of genetically transformed Euphorbia lathyris roots. Phytochemistry. 179:1-9. https://doi.org/10.1016/j.phytochem.2020.112504.
DOI: https://doi.org/10.1016/j.phytochem.2020.112504

Interpretive Summary: Plant natural products possess vast structural and chemical diversity that cannot be matched by synthetic molecules. They are evolutionarily optimized as drug-like chemicals and remain the best sources of drugs and drug prototypes. Plants in the genus Euphorbia produce a wide variety of pharmacologically active diterpenoids with anticancer, multidrug resistance reversal, and antiviral properties. Similar to other high value phytochemicals, Euphorbia diterpenoids accumulate at low concentrations in field-grown plants and chemical synthesis produces similarly low yields. One alternative strategy for gaining greater access to these compounds is to employ biotechnological and metabolic engineering tools. We established genetically transformed root tissue cultures of Euphorbia lathryis, which exhibited rapid growth rates, high metabolite production, and suitability for adaptation to large-scale systems. Metabolomic analyses of root culture biomass identified a variety of bioactive diterpenoids including ingenol, a FDA approved chemotherapeutic agent. We also demonstrated the potential of the root culture platform for natural product drug discovery applications by measuring its anticancer activities using a panel of human carcinoma cell lines derived from prostate, cervix, breast, and lung.

Technical Abstract: lants in the genus Euphorbia produce a wide variety of pharmacologically active diterpenoids with anticancer, multidrug resistance reversal, and antiviral properties. Some are the primary industrial source of ingenol mebutate, which is approved for treatment of the precancerous skin condition actinic keratosis. Similar to other high value phytochemicals, Euphorbia diterpenoids accumulate at low concentrations in planta and chemical synthesis produces similarly low yields. We established genetically transformed hairy root cultures of Euphorbia lathryis as a strategy to gain greater access to diterpenoids from this genus. Hairy roots generated via stem explant infection with Agrobacterium rhizogenes strain 15834 recapitulated the metabolite profiles of field-grown plant roots and aerial tissues. Several putative diterpenoids were present in hairy roots including ingenol and closely related structures, indicating that root cultures are a promising approach to Euphorbia-specific diterpenoid production. Treatment with methyl jasmonate led to a significant, transient increase in mRNA levels of early diterpenoid biosynthetic enzymes (farnesyl pyrophosphate synthase, geranylgeranyl pyrophosphate synthase, and casbene synthase), suggesting that elicitation could prove useful in future pathway characterization and metabolic engineering efforts. We also demonstrate the potential of Euphorbia root cultures for natural product drug discovery applications by measuring their anticancer activities using a panel of human carcinoma cell lines derived from prostate, cervix, breast, and lung.