ASMT and breast cancer: In contrast, a different trend was observed for ASMT protein levels (responsible for converting NAS into melatonin), which were significantly lower in HR+HER2- (3.04 ng/mL ± 1.05) and HR+HER2+ (2.74 ng/mL ± 1.30) BC patients than in controls (4.46 ng/mL ± 1.52) (p < 0.01) (Figure 8b).