MMP9 and cancer: Unlike MSI proteins that sustain cancer stemness in triple-negative breast cancer or HuR’s regulation of Snail/MMP9-driven metastasis in HER2+ tumors (Chen et al., 2022), CELF1 uniquely drives metabolic reprogramming in luminal A. This aligns with its role in reshaping mitochondrial metabolism in diabetic cardiomyopathy (Belanger et al., 2018), suggesting tissue-agnostic metabolic functions.