As depicted in Figure 8a, there was an increase in serum AANAT protein levels (responsible for converting serotonin into NAS) in HR+HER2- (means ± SDs: 8.59 ng/mL ± 3.05) and HR+HER2+ (means ± SDs: 7.34 ng/mL ± 1.39) BC patients compared to controls (means ± SDs: 4.96 ng/mL ± 1.94) (p < 0.001 and p < 0.05, respectively). Here, ERBB2 is linked to breast cancer.