PHGDH and breast cancer: However, these results are opposite those of recent studies in which RNF5 inhibits breast cancer progression through the RNF5 association with the glutamine carriers SLC1A5 and SLC38A2 [40] or phosphoglycerate dehydrogenase [47]; unfortunately, these studies used MDA-MB-231 breast cancer cells that is estrogen receptor-negative subtype and carry mutated TP53, and then mutated p53 may not serve as a tumor suppressor but act as a tumor accelerator.