MCF7-fibroblast co-cultures are a valuable model of resistance to apoptosis induced by hormonal therapies, such as Tamoxifen and Fulvestrant. These mixed co-cultures demonstrate the induction of mito-sternness and ribo-stemness features. Molecular therapeutic targets were identified through label-free proteomics of MCF7-fibroblast co-cultures, and independently validated using a bioinformatics approach. The resulting Mito-Signature is prognostic of endocrine treatment failure, tumor recurrence, and distant metastasis, and may be used to identify patients at risk of treatment failure. Such patients may be treated with a mitochondrial biogenesis inhibitor to reduce the risk of treatment failure, and/or to increase the effectiveness of the hormone therapy.