Ingenol esters induce apoptosis in Jurkat cells through an AP-1 and NF-kappaB independent pathway.
BACKGROUND
Ingenol derivatives have received constant and multidisciplinary attention on account of their pleiotropic pattern of biological activity. This includes activation of protein kinase C (PKC), tumour-promotion, anticancer, and anti-HIV properties, and the possibility of dissecting co-cancerogenic and clinically useful activities has been demonstrated. Certain ingenol esters show powerful anticancer activity, and a structure-activity relationship model to discriminate between their apoptotic and non-apoptotic properties has been developed.


RESULTS
The polyhydroxylated southern region of ingenol was selectively modified, using the anticancer and PKC activator ingenol 3,20-dibenzoate (IDB) as a lead compound. The evaluation of IDB analogues in apoptosis assays showed strict structure-activity relationships, benzoylation of the 20-hydroxyl being required to trigger apoptosis through a pathway involving caspase-3 and occurring at the specific cell cycle checkpoint that controls the S-M phase transition. Conversely, a study on the activation of the PKC-dependent transcription factors AP-1 and NF-kappaB by IDB analogues showed significant molecular flexibility, including tolerance to changes at the 3- and 20-hydroxyls. IDB-induced apoptosis was independent of activation of PKC, since it was not affected by treatment with the non-isoform-selective PKC inhibitor GF 109230X0.


CONCLUSIONS
Remarkable deviations from the tumour-promotion pharmacophore were observed for both the apoptotic and the PKC-activating properties of IDB analogues, showing that ingenol is a viable template to selectively target crucial pathways involved in tumour promotion and development. Since the apoptotic and the PKC-activating properties of ingenoids are mediated by different pathways and governed by distinct structure-activity relationships, it is possible to dissect them by suitable chemical modification. In this context, the esterification pattern of the 5- and 20-hydroxyls is critical.
Blanco-Molina
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Departamento de Biología Celular, Fisiología e Immunología, Universidad de Córdoba, Spain. bc1blmom@uco.es
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D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D004247:DNA / Q000032:analysis / Q000378:metabolism; D053938:DNA Fragmentation; D004224:Diterpenes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D024202:Electrophoretic Mobility Shift Assay; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D019169:Jurkat Cells; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013329:Structure-Activity Relationship; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D061945:Caspase Inhibitors; D004224:Diterpenes; D004952:Esters; D016328:NF-kappa B; D018808:Transcription Factor AP-1; C011875:ingenol dibenzoate; D004247:DNA; D008156:Luciferases; D011493:Protein Kinase C; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C008125:ingenol