Rapamycin-regulated gene expression signatures predict breast cancer prognosis. Researchers identified a gene expression signature, called the Rapamycin Metagene Index (RMI), which is associated with better survival in breast cancer patients. The RMI is a set of 31 genes upregulated by rapamycin treatment in both in vitro and in vivo settings. Analysis of three independent breast cancer datasets showed that high RMI values were linked to longer survival, while low RMI values were associated with shorter survival. The RMI was also prognostic for metastasis-free survival in some datasets. These findings suggest that mTOR signaling plays a central role in breast cancer biology and support the development of mTOR-targeted therapies. The study highlights the importance of identifying gene expression signatures that can predict clinical outcomes in cancer patients. The RMI provides a potential biomarker for identifying patients who may benefit from mTOR inhibitors. The study also emphasizes the need for further research to determine the clinical relevance of RMI and its potential as a predictive marker for treatment response in breast cancer.Rapamycin-regulated gene expression signatures predict breast cancer prognosis. Researchers identified a gene expression signature, called the Rapamycin Metagene Index (RMI), which is associated with better survival in breast cancer patients. The RMI is a set of 31 genes upregulated by rapamycin treatment in both in vitro and in vivo settings. Analysis of three independent breast cancer datasets showed that high RMI values were linked to longer survival, while low RMI values were associated with shorter survival. The RMI was also prognostic for metastasis-free survival in some datasets. These findings suggest that mTOR signaling plays a central role in breast cancer biology and support the development of mTOR-targeted therapies. The study highlights the importance of identifying gene expression signatures that can predict clinical outcomes in cancer patients. The RMI provides a potential biomarker for identifying patients who may benefit from mTOR inhibitors. The study also emphasizes the need for further research to determine the clinical relevance of RMI and its potential as a predictive marker for treatment response in breast cancer.