To investigate the function role of MTAP in breast cancer cells, we initially examined the protein expression of MTAP in 9 BC cell lines (BT20, BT474, BT549, MCF-7, MDA-MB-231, MDA-MB-453, MDA-MB-468, SW527 and T47D) and a human breast epithelial cell line (Hs 578Bst) by Western blot (Figure S1). The gene discussed is MTAP; the disease is breast carcinoma.