Patients with triple-negative breast cancer often have increased risk for recurrence and metastasis as well as decreased 5-year survival. Since triple-negative breast cancers don’t depend on hormone receptors or HER for growth, triple-negative cancers do not respond to hormone or HER dependent therapies. Jennifer Richer and her research team have developed a miRNA screen for identifying triple-negative breast cancers. By screening for miRNA levels that are related to estrogen and growth factor signaling molecules and comparing them to miRNA expression levels of luminal breast cancer cells the inventors are able to classify a cancer as triple-negative or ER positive. From the screening results, miRNA treatment to correct the misregulated miRNAs can be tailored to each patient.