XBP1 and breast cancer: Similarly, estrogen receptor β 1 (ERβ1) promotes HRD1-mediated ERAD of IRE1α, which attenuates the ER stress-induced IRE1α-XBP1 pathway in breast cancer.474 RNF5 ubiquitinates and promotes the degradation of phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in serine synthesis and a factor upregulated in human breast cancer, attenuating breast cancer cell proliferation.475