PRMT1 plays a pivotal role in tumor progression, primarily by methylating target proteins to modulate their activity or stability.[23] For example, PRMT1 promotes HCC growth by methylating PHGDH, enhancing its enzymatic activity, and driving serine synthesis and oxidative stress resistance.[22, 24] Similarly, PRMT1 stabilizes DDX3 through arginine methylation, preserving mitochondrial homeostasis and facilitating breast cancer metastasis.[23] However, its non‐enzymatic functions remain largely unexplored. Here, PHGDH is linked to breast cancer.