SLC1A5 and breast cancer: This revealed that high SHMT2 protein expression is an independent negative prognostic factor for OS (p = 0.011; Table 4) and both high SHMT2 and high ASCT2 protein expression levels are independent negative prognostic factors for RFS (SHMT2, p = 0.003; ASCT2, p = 0.042; Table 5) in patients with BC.