Although these findings may seem in contrast with previous evidence suggesting that HSP90 inhibition synergizes with trastuzumab in preclinical models of HER2+ breast cancer [37], it has to be noted that such evidence employed pharmacological HSP90 inhibition [37,38,39,40], rather than modulation of its expression, and mostly demonstrated activity of such inhibitors, alone or in combination with trastuzumab, in HER2+ models that had already become resistant to trastuzumab [38]. This evidence concerns the gene ERBB2 and breast carcinoma.