Brain tumour samples obtained during neurosurgery for HER2 + and triple-negative breast cancer, revealed that brain metastasis of breast cancer has GABAergic characteristics; that is, the brain metastatic cells have high expression of GABA-related proteins, including GABAA receptors, GABA transporters, GABA transaminase and glutamate decarboxylase [101]. Here, ERBB2 is linked to breast cancer.