The efficacy of hyperthermia-based multimodal therapy is dependent on gatekeeper protein, BID.

OBJECTIVES: The combination of ferroptotic agent artesunate (ART) and apoptotic agent rhTRAIL (recombinant human tumor necrosis factor-related apoptosis-inducing ligand) has been shown to synergistically enhance apoptosis in various cancer cell lines via crosstalk between the endoplasmic reticulum (ER) stress response, the rhTRAIL-induced extrinsic cell death receptor pathway, and the intrinsic BID-Bax-mitochondrial-dependent-apoptosis pathway. This synergistic interaction has been demonstrated to be effective in multiple types of cancer cell lines, making artesunate combined with rhTRAIL a promising second-line therapy for colon cancer patients after cytoreductive surgery and chemotherapeutic treatments. To further enhance the second-line therapy's tumoricidal effect, a multimodal therapy was developed by combining artesunate, rhTRAIL, and hyperthermic conditions where samples were treated at 42 °C for 1 h. METHODS: The effects of this therapy were tested in human colon carcinoma HCT116 and pancreatic adenocarcinoma BxPC-3 cell models. The cytotoxic and synergistic effects were analyzed using fluorescence microscopy, cell survival assays, and protein analysis through Western blotting. RESULTS: Our findings demonstrated a significant enhancement of apoptosis when artesunate and rhTRAIL treatments were combined with heat exposure. The synergistic and apoptotic effect of the agents was effectively abrogated in BID-deficient and BID mutant-type cells as well as Bax-deficient cells, but not Bak-deficient cells. CONCLUSIONS: The results suggest that BID acts as a key gatekeeper molecule of apoptosis during hyperthermia-based multimodal treatment. These findings raise important questions about the underlying mechanisms of heat-induced apoptosis and its involvement in orchestrating various cellular stress pathways.