Siramesine, one of the most potent selective S2R ligands, has potential antitumor activity against various tumor cell lines as follows: (1) in breast tumors, (2) in neck tumors, (3) in lung tumors, (4) in prostate tumors, (5) in fibrosarcoma, and (6) in breast cancer grafts in mice [46,47]. Here, TMEM97 is linked to breast cancer.