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Smac mimetic sensitizes renal cell carcinoma cells to interferon-α-induced apoptosis
Michael Reiter1, Ines Eckhardt2, Axel Haferkamp3
1Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstr. 3a, 60528 Frankfurt, Germany; Department of Urology, University Hospital Frankfurt, 60590 Frankfurt, Germany.
Abstract:
The prognosis of metastatic or relapsed renal cell carcinoma (RCC) is still very poor, highlighting the need for new treatment strategies. Here, we identify a cooperative antitumor activity of interferon-α (IFNα) together with the Smac mimetic BV6 that antagonizes antiapoptotic IAP proteins. BV6 and IFNα act together to reduce cell viability and to induce apoptosis in various RCC cell lines. Molecular studies revealed that BV6/IFNα co-treatment triggers apoptosis independently of autocrine/paracrine Tumor Necrosis Factor (TNF)α signaling, since the TNFα-blocking antibody Enbrel fails to rescue cell death. Importantly, knockdown of Receptor-Interacting Protein (RIP)1 significantly decreases BV6/IFNα-mediated apoptosis, whereas the RIP1 kinase inhibitor necrostatin-1 (Nec-1) provides no protection. This demonstrates that RIP1 protein is critically required for BV6/IFNα-induced apoptosis, while RIP1 kinase activity is dispensable, pointing to a scaffold function of RIP1. Consistently, BV6 and IFNα cooperate to trigger the interaction of RIP1, Fas-Associated Death Domain protein (FADD) and caspase-8 to form a cytosolic cell death complex that drives caspase activation. Addition of the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) significantly protects RCC cells against BV6/IFNα-induced apoptosis, demonstrating that caspase activity is required for apoptosis. In conclusion, the combination approach of IFNα and BV6 represents a promising strategy for cooperative induction of apoptosis in RCC cells, which warrants further investigation.
Insights
Interferon-alfa (IFNα) and Smac mimetic BV6 show cooperative antitumor activity against renal cell carcinoma (RCC). This combination induces apoptosis by forming a cell death complex involving RIP1, FADD, and caspase-8, offering a promising new strategy for RCC treatment.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Metastatic or relapsed renal cell carcinoma (RCC) has a poor prognosis, necessitating novel therapeutic strategies.
- Antiapoptotic IAP proteins contribute to treatment resistance in cancer.
- Interferon-alfa (IFNα) and Smac mimetics are potential therapeutic agents.
Purpose of the Study:
- To investigate the cooperative antitumor activity of interferon-α (IFNα) and the Smac mimetic BV6 in renal cell carcinoma (RCC).
- To elucidate the molecular mechanisms underlying the combined therapeutic effect of IFNα and BV6 on RCC cells.
Main Methods:
- Treatment of various RCC cell lines with BV6 and IFNα, individually and in combination.
- Assessment of cell viability and apoptosis induction.
- Molecular analyses including knockdown of Receptor-Interacting Protein (RIP)1, use of RIP1 kinase inhibitor necrostatin-1 (Nec-1), TNFα-blocking antibody (Enbrel), and caspase inhibitor (zVAD.fmk).
- Investigation of RIP1, FADD, and caspase-8 complex formation.
Main Results:
- BV6 and IFNα synergistically reduce RCC cell viability and induce apoptosis.
- The combination therapy triggers apoptosis independently of TNFα signaling.
- Receptor-Interacting Protein (RIP)1 is essential for BV6/IFNα-mediated apoptosis, functioning as a scaffold rather than through its kinase activity.
- BV6 and IFNα promote the formation of a RIP1-FADD-caspase-8 death complex, leading to caspase activation and apoptosis.
Conclusions:
- The combination of IFNα and BV6 demonstrates a promising cooperative strategy for inducing apoptosis in RCC cells.
- This approach targets key components of the apoptotic pathway, highlighting its potential as a novel therapeutic option for RCC.
- Further investigation is warranted to explore the clinical applicability of this combination therapy.
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