When comparing the cell proliferation ability of these cell lines, we found that NNMT‐high expressing cell lines (MDA‐MB‐231, BT‐549, and Bcap37 cells) demonstrate a stronger proliferation ability compared to other NNMT‐low expressing (T47D, MDA‐MB‐468, and HCC1937 cells) and NNMT‐absent SKBR3 and MCF7 cells (Figure 2B), indicating the involvement of NNMT in breast cancer cell proliferation. This evidence concerns the gene NNMT and breast cancer.