Podophyllotoxin Disrupts the XIAP and Caspase-9 Complex in a Concentration-Dependent Manner: Scientific Reports Study Validated with a Quantitative Split-Luciferase Assay, Published November 11
Scientific Reports published a study by Katrin Ebrahimi, Farangis Ataei and Saman Hosseinkhani on November 11, 2026, examining how the plant-derived lignan podophyllotoxin acts on the apoptosis pathway. Podophyllotoxin has potent anticancer properties, and the study hypothesized that it mimics Smac activity by interacting with the BIR domains of inhibitor of apoptosis proteins.
The team developed and validated a highly sensitive, cell-free split-luciferase complementation assay designed to quantify the real-time interaction dynamics between the BIR2 to BIR3 domains of XIAP and its key targets, caspase-3 and caspase-9. The results demonstrate that the interaction with caspase-9 is significantly more robust and stable than the interaction with caspase-3, highlighting a preferential binding mechanism at the initiator caspase level.
Using this platform, the team investigated the effects of podophyllotoxin in modulating the interaction. Consistent with in silico docking predictions, podophyllotoxin disrupted the XIAP and caspase-9 complex in a concentration-dependent manner, leading to a marked reduction in luminescence and a subsequent restoration of caspase-9 enzymatic activity. Podophyllotoxin showed a minor inhibitory effect on the XIAP and caspase-3 interaction, while its impact on the caspase-9 axis was markedly more pronounced.
Carboplatin, a DNA-crosslinking agent, exhibited no significant impact on these protein-protein interactions, confirming the specificity of the observed podophyllotoxin effects. The authors state that the findings establish a sensitive, real-time platform for monitoring the XIAP and caspase axis and provide compelling evidence that podophyllotoxin acts as a targeted modulator of the apoptotic pathway, warranting its further development as a pharmacological agent. This report follows the abstract of the paper.
Source: Scientific
Published by GSM · USA (original Chinese edition)
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