ERBB2 and cancer: mTOR signaling may be related to estrogen receptor (ER) activation and adaptive estrogen hypersensitivity.[31] mTOR pathway signaling is increased in HER2+ tumor cells resistant to endocrine therapy.[32] mTOR activation predicts a worse clinical outcome for patients treated with endocrine therapy.[33] mTOR controls the supply of nutrients to cancer cells by regulating nutrient uptake, cell metabolism, and angiogenesis.