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.