SHMT1 and breast cancer: The SHMT1 protein, mainly responsible for the cytoplasmic conversion of glycine to serine, does not appear to be generally overexpressed in brain metastasis deriving from breast cancer; however, a specific shmt1 expressing subtype has been recently identified, showing a dramatically negative association with the overall survival (p = 0.002), strikingly suggesting that adaptation to cytoplasmic serine production confers a key advantage for these cells [44].