FAQ: Explain how fenbendazole induces pyroptosis in cancer cells.
Fenbendazole effectively switches the cancer cell's fate from a non-inflammatory death (apoptosis) to a highly inflammatory death (pyroptosis).
Based on the provided sources, fenbendazole (FBZ) induces pyroptosis—a highly inflammatory form of programmed cell death characterized by cell swelling, membrane pore formation, and the release of pro-inflammatory cytokines—in cancer cells through two distinct molecular pathways, depending on the type of cancer.
Here is how fenbendazole triggers pyroptosis in these different contexts:
1. The HK2/Caspase-3/GSDME Pathway (Observed in Breast Cancer) In breast cancer models, fenbendazole links metabolic disruption directly to pyroptotic cell death by targeting the tumor’s energy metabolism.
Inhibition of Glycolysis (HK2 Downregulation): FBZ interacts with the p53 signaling pathway to significantly suppress the expression of hexokinase 2 (HK2), a critical enzyme required for aerobic glycolysis (the Warburg effect).
Activation of the BAX/Caspase-3 Cascade: The inhibition of HK2 acts as a trigger that upregulates the pro-apoptotic protein BAX, which subsequently activates the executioner enzyme caspase-3.
Cleavage of GSDME: While caspase-3 is traditionally associated with silent apoptosis, in cells expressing the protein Gasdermin E (GSDME), activated caspase-3 cleaves GSDME into its active N-terminal fragment (GSDME-NT).
Pore Formation and Cell Lysis: The GSDME-NT fragments oligomerize and insert themselves into the cancer cell’s plasma membrane, forming pores. This rapidly causes the cancer cells to swell, form large balloon-like membrane blisters, and burst, releasing their intracellular contents, including lactate dehydrogenase (LDH) and highly inflammatory cytokines like IL-1β and IL-18 into the tumor microenvironment.
2. The NF-κB/NLRP3/GSDMD Pathway (Observed in Glioblastoma) In human glioblastoma cells, fenbendazole (along with other benzimidazoles like mebendazole and flubendazole) utilizes a different gasdermin protein and inflammasome pathway to execute pyroptosis.
NF-κB Nuclear Translocation: FBZ treatment promotes the translocation of the NF-κB transcription factor from the cytosol to the nucleus.
Inflammasome Activation: The activation of NF-κB drives the expression and assembly of the NLRP3 inflammasome.
Caspase-1 Activation and GSDMD Cleavage: The NLRP3 inflammasome recruits and activates caspase-1. Activated caspase-1 then cleaves a different gasdermin protein, Gasdermin D (GSDMD), to generate an active N-terminal fragment (GSDMD-N).
Pore Formation and Cytokine Release: Similar to GSDME, the newly formed GSDMD-N fragments insert into the plasma membrane to create pores. This ruptures the glioblastoma cells and triggers the massive release of LDH, IL-1β, and IL-18.
In both mechanisms, fenbendazole effectively shifts the cancer cell’s fate from non-inflammatory death (apoptosis) to highly inflammatory death (pyroptosis), which not only kills the cancer cell but also alters the tumor microenvironment by releasing immune-stimulating signals.