HTR1A and breast cancer: Furthermore, the demethylation drug 5‐aza‐2′‐deoxycytidine (1 × 10−6m, 5‐AZA‐CdR, ZdCyd, decitabine) was utilized for 7 d, after which the expression of HTR1A was significantly upregulated in breast cancer cells (Figure 6c, all p < 0.01).