PHGDH and breast carcinoma: Based on our PHGDH protein expression analysis together with previous findings reporting PHGDH overexpression in a subset of ER- breast cancer cell lines, we chose to further assess the effect of PHGDH knockdown in three different breast cancer cell lines [4, 7]: two that over-express PHGDH (MDA-MB-468, Hs578T) and one that expresses relatively little PHGDH (MDA-MB-231).