ESR1 and breast cancer: Moreover, a higher expression of LAT1/SLC7A5 in tumors compared to normal tissue was confirmed for colorectal cancer in absolute protein level [36,37], glioblastoma in protein level [38], triple-negative and human epidermal growth factor receptor 2 (HER2)-positive breast cancers, as well as for MYC driver estrogen receptor (ER)-positive breast cancer, in the mRNA and protein levels [39].