Regarding the catecholamine biosynthesis, Pearson’s analysis revealed that (i) ADRA2A and ADRB2 were negatively related, while ADRA1B and ADRA2C were positively correlated with the levels of TH; (ii) ADRA1A, ADRA2A, ADRA2B, ADRB1, ADRB2, ADRB3 were positively correlated with the levels of DBH; and interestingly, (iii) the three mostly expressed ADRs in BC tissue, ADRA2A, ADRA2C, and ADRB2, were positively related with PNMT (an enzyme responsible for the synthesis of EPI). The gene discussed is ADRA2A; the disease is breast cancer.