December 10, 2025

expert reaction to study in mice looking at fasting and hormone therapy response for breast cancer

A study published in Nature looks at fasting and hormone therapy response for breast cancer in mice. 

Dr Charlie Birts, Lecturer in Antibody Therapeutics at the University of Southampton, said:

“This is a well-designed and thorough study that provides valuable insight into how metabolic changes during fasting might enhance hormone therapy in oestrogen-receptor-positive breast cancer. The authors use a powerful combination of genomic and functional approaches, and the consistent activation of glucocorticoid and progesterone receptor pathways across models is a particularly interesting mechanistic finding. These data offer a promising direction for future research into fasting-mimicking strategies or glucocorticoid-based therapeutic approaches.

“However, several important limitations need to be considered when interpreting the results. The work is largely preclinical, and although supported by small patient cohorts, the human data are preliminary and lack control groups. The mouse studies were performed primarily in immuno-deficient models, which limits our ability to assess how fasting or glucocorticoid signalling might interact with the immune system in a clinically relevant setting. In addition, key endocrine and pharmacokinetic variables, such as oestrogen levels and tamoxifen metabolite exposure, were not measured, so it remains uncertain how much of the observed effect reflects direct mechanistic action versus broader hormonal changes.

“Overall, this is an intriguing and thoughtful study that advances our understanding of metabolic influences on endocrine therapy, opening the door to exciting avenues of research, including whether glucocorticoid-based fasting mimetics could be tested safely and effectively in humans. But it remains too early to know whether these findings will translate into meaningful benefit for patients, and clinical recommendations should not change until robust trials in humans have been completed.”

Dr Dimitrios Koutoukidis, Associate Professor in Diet, Obesity, and Behavioural Sciences; and dietitian, University of Oxford, said:

“These results are in mice and a small number of patients in an uncontrolled study. Although they provide data to inform future research on diet restriction in some cancer patients, they are not sufficient to tell us what the effect of fasting-mimicking diets in humans could be.”

‘Fasting boosts breast cancer therapy efficacy via glucocorticoid activation’ by Nuno Padrão et al. was published in Nature at 16:00 UK time on Wednesday 10 December 2025.

DOI: 10.1038/s41586-025-09869-0

Declared interests

Dr Dimitrios Koutoukidis: No DOIs.

Dr Charlie Birts: “I have no conflicts of interest to declare.”

For all other experts, no reply to our request for DOIs was received.