Gautam et al. [11] found that the level of TPH1 expressed by triple-negative breast cancer (TNBC) cell lines was higher than that of hormone-responsive breast cancer cell lines, revealing that the effect of 5-hydroxytryptamine (5-HT) on the progression of breast cancer is due to TPH1 that promotes the production of 5-HT. Here, TPH1 is linked to triple-negative breast carcinoma.