HSP90 expression, which was not modulated by single-agent docetaxel, was also upregulated (in HER2+ breast cancer models) with the combination of trastuzumab and docetaxel under conditions that induced the expected growth inhibitory synergism [24], further strengthening the observed relationship between HER2 and HSP90 expression and its potential therapeutic relevance. Here, HSP90AA1 is linked to breast cancer.