Thus, Sathparthy et al. analyzed core needle biopsies from HER2-positive breast cancers before and 48–72 h after the start of therapy with Trastuzumab: greater suppression of HER2 protein and of both phosphorylated HER2 and mTOR levels in tumor cases associated with complete pathological response was observed; androgen receptor signaling, low HER2 activity, and the absence of HER2 amplification were identified as the mechanisms of drug resistance [382]. This evidence concerns the gene ERBB2 and breast cancer.