The cardiac glycoside periplocymarin sensitizes gastric cancer to ferroptosis via the ATP1A1-Src-YAP/TAZ-TFRC axis.

[BACKGROUND] Targeting ferroptosis vulnerabilities in tumors has become an increasingly promising therapeutic strategy. While the regulatory effects of natural products on ferroptosis are progressively being elucidated, the role of cardiac glycosides in modulating ferroptosis remains poorly understood.

[PURPOSE] This study aims to investigate the ferroptosis-sensitizing effects of periplocymarin (PPM), a cardiac glycoside derived from the traditional plant Periploca sepium, and to elucidate the underlying molecular mechanisms.

[METHODS] The effects of PPM on ferroptosis regulation were comprehensively assessed through functional assays, followed by sequencing analysis to identify associated signaling pathways. Subsequent mechanistic validation experiments were conducted to confirm the upstream and downstream regulatory components involved in this ferroptosis-modulating axis.

[RESULTS] PPM induced slow and mild apoptosis in gastric cancer cells through the inhibition of glycolysis. However, when combined with ferroptosis inducers, it promoted rapid and robust ferroptosis. In vivo, PPM sensitized gastric cancer xenografts to cisplatin-induced ferroptosis with no observable cardiotoxicity or renal impairment. Mechanistically, PPM targeted the α1 subunit of the Na+/K+-ATPase (ATP1A1), leading to the activation of Src, which subsequently induced tyrosine phosphorylation of YAP/TAZ in a Hippo-independent manner, promoting their nuclear translocation. The YAP/TAZ-TEAD transcriptional complex directly bound to the TFRC promoter region between nucleotides 401-409 upstream of the transcription start site, thereby activating TFRC transcription. This resulted in increased iron influx, elevated lipid peroxidation, and heightened sensitivity to ferroptosis. Notably, ATP1A1 was essential for ferroptosis resistance, as its knockdown mimicked the sensitizing effect of PPM on ferroptosis. Moreover, the oncogenic Src-YAP/TAZ-TFRC axis may have represented a ferroptosis vulnerability and a potential biomarker in ferroptosis therapy for cancer. Importantly, other cardiac glycosides targeting Na+/K+-ATPase, such as digitoxin and bufalin, also enhanced ferroptosis sensitivity in gastric cancer cells through activation of YAP/TAZ signaling.

[CONCLUSION] Our findings establish the cardiac glycoside PPM as a novel ferroptosis sensitizer that targets ATP1A1 to activate the Src-YAP/TAZ-TFRC axis, providing mechanistic insights for repurposing cardiac glycosides as ferroptosis modulators in precision combinatorial cancer therapy.