Z-Guggulsterone Induces Ferroptosis in Chemoresistant Breast Cancer via a CDKN2B-Mediated Suppression of GTP Cyclohydrolase 1.

The development of tumor resistance remains a major challenge in breast cancer therapy, frequently leading to diminished treatment efficacy. Ferroptosis, a recently identified form of programmed cell death, has been associated with various treatment-resistant malignancies. This study aimed to explore the effect of Z-GS-a natural bioactive compound derived from myrrh-on inhibiting the growth of drug-resistant breast cancer cells via ferroptosis, and to elucidate its underlying molecular mechanisms. The growth of drug-resistant breast cancer cells was evaluated using CCK-8 and EdU assays. Ferroptosis was assessed by measuring reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH)/oxidized glutathione (GSSG) ratio, and FerroOrange fluorescence. A xenograft mouse model was established to compare tumor growth rates between transplanted and control groups. Gene screening was performed via RNA sequencing, and the involvement of the CDKN2B/CDK2/GCH1 pathway in Z-GS-induced growth inhibition was validated by Western blot analysis. Z-GS significantly suppressed tumor growth both in vitro and in vivo. It induced ferroptosis in drug-resistant breast cancer cells by promoting Fe2+ accumulation, ROS generation, and MDA production, while reducing the GSH/GSSG ratio. Mechanistically, Z-GS downregulated GCH1 protein expression. Genetic knockout of CDKN2B effectively reversed these effects and, through modulation of CDK2 and p53, restored GCH1 expression. These findings indicate that Z-GS upregulates CDKN2B, which in turn suppresses downstream GCH1 expression, ultimately triggering the ferroptosis pathway. Z-GS mediates ferroptosis in drug-resistant breast cancer cells by targeting the CDKN2B/CDK2/GCH1 pathway. These results highlight the potential of Z-GS as a natural small-molecule therapeutic candidate for overcoming chemotherapy resistance in breast cancer, providing a novel mechanistic strategy for further drug development.