Using gene expression profiling of breast cancer biopsy samples between responders and nonresponders to docetaxel, Iwao-Koizumi et al. devised a diagnostic system that was able to predict the clinical response to docetaxel treatment, and identified molecular targets for therapy.23 As an extension of their report, we previously performed a study of RNAi-induced gene knockdown in docetaxel-resistant breast cancer cells, and identified the RPN2 gene, which is part of the N-oligosaccharyl transferase complex, as a new target for overcoming the drug resistance of breast cancer. This evidence concerns the gene RPN2 and breast cancer.