[Research Press Release] Medicine: Fasting linked to improved hormone therapy response for breast cancer in mice (Nature)

Therapies to mimic the metabolic effects of fasting might improve the effectiveness of hormone treatments for breast cancer, according to a study in Nature. The research, carried out in mouse cells, finds that the metabolites associated with fasting can boost anti-tumour properties involved in some cellular pathways. Further clinical studies are warranted to confirm this effect.

Endocrine therapies, the main treatment for breast cancers driven by abnormal oestrogen levels, work by lowering the levels of hormones in the body. However, tumours can become resistant to the hormone therapy and continue to grow. Previous studies in animal models have shown that periodic fasting can enhance the efficacy of endocrine therapies and delay resistance in certain types of breast cancer, but the mechanisms by which this happens have remained unclear.

Wilbert Zwart, Irene Caffa and colleagues investigated this effect by inducing human hormone receptor-positive (HR+) breast cancer in mice and commencing weekly cycles of 48-hour fasting in combination with tamoxifen (a common endocrine therapy). The authors also analysed samples from human patients with breast cancer undergoing a 5-day diet to mimic the metabolic effects of fasting in combination with tamoxifen. Analysis of the tumours found that fasting (in mice) and the fasting-mimicking diet (in humans) had induced widespread activation of glucocorticoid and progesterone receptors in HR+ breast cancer cells; these pathways are known to have tumour-suppressive effects. Removing the receptors from a line of mouse cells stopped the anti-tumour effect of the fasting and tamoxifen, validating the role of these receptors in the mechanism. Finally, the researchers administered dexamethasone (a therapeutic to mimic the effects of fasting through glucocorticoid receptor activation) to mouse cells in conjunction with tamoxifen. They observed that this treatment combination was able to induce the same anti-tumour effects as fasting, demonstrating its potential as a therapeutic alternative to fasting.  

The authors emphasize that future research must assess the long-term safety and efficacy of corticosteroid treatment in humans before any clinical applications can be made. 

• Article
• Open access
• Published: 10 December 2025

Padrão, N., Severson, T.M., Gregoricchio, S. et al. Fasting boosts breast cancer therapy efficacy via glucocorticoid activation. Nature (2025). https://doi.org/10.1038/s41586-025-09869-0

© 2025 Springer Nature Limited. All Rights Reserved.   

More Press Releases