Withanolide E sensitizes renal carcinoma cells to TRAIL-induced apoptosis by increasing cFLIP degradation
C J Henrich1, A D Brooks2, K L Erickson3
11] Molecular Targets Laboratory, NCI-Frederick, Frederick, MD, USA [2] Basic Research Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD, USA.
Abstract:
Withanolide E, a steroidal lactone from Physalis peruviana, was found to be highly active for sensitizing renal carcinoma cells and a number of other human cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Withanolide E, the most potent and least toxic of five TRAIL-sensitizing withanolides identified, enhanced death receptor-mediated apoptotic signaling by a rapid decline in the levels of cFLIP proteins. Other mechanisms by which TRAIL sensitizers have been reported to work: generation of reactive oxygen species (ROS), changes in pro-and antiapoptotic protein expression, death receptor upregulation, activation of intrinsic (mitochondrial) apoptotic pathways, ER stress, and proteasomal inhibition proved to be irrelevant to withanolide E activity. Loss of cFLIP proteins was not due to changes in expression, but rather destabilization and/or aggregation, suggesting impairment of chaperone proteins leading to degradation. Indeed, withanolide E treatment altered the stability of a number of HSP90 client proteins, but with greater apparent specificity than the well-known HSP90 inhibitor geldanamycin. As cFLIP has been reported to be an HSP90 client, this provides a potentially novel mechanism for sensitizing cells to TRAIL. Sensitization of human renal carcinoma cells to TRAIL-induced apoptosis by withanolide E and its lack of toxicity were confirmed in animal studies. Owing to its novel activity, withanolide E is a promising reagent for the analysis of mechanisms of TRAIL resistance, for understanding HSP90 function, and for further therapeutic development. In marked contrast to bortezomib, among the best currently available TRAIL sensitizers, withanolide E's more specific mechanism of action suggests minimal toxic side effects.
Insights
Withanolide E, a natural compound, effectively sensitizes cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated cell death. It achieves this by destabilizing cFLIP proteins, offering a novel mechanism with potentially fewer side effects than current treatments.
Area of Science:
- Pharmacology
- Molecular Biology
- Oncology
Background:
- Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic, but its efficacy is often limited by cancer cell resistance.
- Identifying novel agents that can sensitize cancer cells to TRAIL-induced apoptosis is crucial for improving cancer treatment outcomes.
Purpose of the Study:
- To investigate the potential of Withanolide E, a steroidal lactone from Physalis peruviana, as a sensitizer of cancer cells to TRAIL-mediated apoptosis.
- To elucidate the molecular mechanisms underlying Withanolide E's TRAIL-sensitizing activity.
Main Methods:
- Screening of five withanolides for TRAIL-sensitizing activity in renal carcinoma and other human cancer cells.
- Analysis of cFLIP protein levels, reactive oxygen species (ROS) generation, apoptotic signaling pathways, and HSP90 client protein stability.
- In vivo studies using animal models to confirm efficacy and toxicity.
Main Results:
- Withanolide E demonstrated potent TRAIL-sensitizing activity with minimal toxicity, outperforming other tested withanolides.
- The primary mechanism involved rapid destabilization and/or aggregation of cFLIP proteins, leading to their degradation, rather than changes in expression.
- Withanolide E specifically altered the stability of HSP90 client proteins, suggesting a novel mechanism involving chaperone protein impairment.
- In vivo studies confirmed Withanolide E's ability to sensitize renal carcinoma cells to TRAIL-induced apoptosis without significant toxicity.
Conclusions:
- Withanolide E is a potent and specific TRAIL sensitizer with a novel mechanism of action involving cFLIP destabilization via HSP90 pathway modulation.
- Its low toxicity and specific mechanism suggest potential therapeutic applications and utility in studying TRAIL resistance and HSP90 function.
- Withanolide E represents a promising candidate for further therapeutic development in cancer treatment, potentially offering advantages over existing TRAIL sensitizers like bortezomib.
