Aqueous-soluble components of sporoderm-removed Ganoderma lucidum spore powder promote ferroptosis in oral squamous cell carcinoma.

Objective: Ferroptosis is a novel cell death process which displays a promising role in cancer treatment. However, clinically available drugs targeting ferroptosis are rarely used, and yet there are no studies reporting on inducing ferroptosis via Chinese herbal extracts. Here we explored the tumor inhibition effects of Ganoderma lucidum (G. lucidum) on oral squamous cell carcinoma (OSCC). Specifically, we aimed to clarify the biological mechanism of components in the dietary, aqueous-soluble sporoderm-removed G. lucidum spore powder (A-GSP). Methods: Preliminary transcriptome analysis revealed the significant enrichment of the ferroptosis pathway. Cellular Fe2+, glutathione (GSH), malondialdehyde (MDA), reactive oxygen species (ROS) and lipid peroxide levels were measured to identify ferroptosis occurrence. Western blotting was used to measure ferroptosis-related proteins. Changes in mitochondria morphology and function were observed with transmission electron microscopy (TEM) and ATP detection assays. Ferroptosis inhibitor ferrostatin-1 was then used to verify the anti-tumor effects of A-GSP. Finally, nude mice xenograft models of oral cancer confirmed that A-GSP inhibited tumor growth. Results: A-GSP promoted ferroptosis in oral cancer cells by inducing Fe2+ influx, GSH depletion, as well as lipid peroxide and ROS accumulation. Ferroptosis-related proteins exhibited corresponding changes, particularly Acyl-coA synthetase long chain family member 4 (ACSL4) increase and glutathione peroxidase 4 (GPX4) decrease. A-GSP considerably lowered mitochondrial volume and ridge number, while significantly decreasing ATP production. Ferrostatin-1 reversed all of these A-GSP-induced changes. In vivo, A-GSP exerted a ferroptosis-mediated tumor-suppressing effect without observable adverse reactions. Conclusions: Our findings demonstrate the therapeutic potential of A-GSP for treating patients with OSCC by targeting ferroptosis.