This study investigates the prognostic value of a gene expression signature regulated by rapamycin in breast cancer. Rapamycin, a serine/threonine kinase inhibitor, is a promising treatment for breast cancer due to its ability to inhibit the mammalian target of rapamycin (mTOR) pathway, which is often aberrantly activated in breast cancers. The researchers identified a set of 31 genes, termed the rapamycin metagene index (RMI), that were upregulated by rapamycin treatment in both in vitro and in vivo models. In three independent breast cancer datasets, high RMI levels were significantly associated with longer survival rates. Multivariate analysis showed that RMI, along with tumor size and lymph node status, was a significant prognostic factor for overall survival. The study concludes that the RMI is a reliable predictor of clinical outcomes in breast cancer, highlighting the central role of mTOR signaling in breast cancer biology and supporting the development of mTOR-targeted therapies.This study investigates the prognostic value of a gene expression signature regulated by rapamycin in breast cancer. Rapamycin, a serine/threonine kinase inhibitor, is a promising treatment for breast cancer due to its ability to inhibit the mammalian target of rapamycin (mTOR) pathway, which is often aberrantly activated in breast cancers. The researchers identified a set of 31 genes, termed the rapamycin metagene index (RMI), that were upregulated by rapamycin treatment in both in vitro and in vivo models. In three independent breast cancer datasets, high RMI levels were significantly associated with longer survival rates. Multivariate analysis showed that RMI, along with tumor size and lymph node status, was a significant prognostic factor for overall survival. The study concludes that the RMI is a reliable predictor of clinical outcomes in breast cancer, highlighting the central role of mTOR signaling in breast cancer biology and supporting the development of mTOR-targeted therapies.