ECRG4 encodes a cytokine-like tumor suppressor that plays critical roles in cancer progression and cellular homeostasis. The protein likely functions as a hormone that attenuates cell proliferation by inducing G1 cell cycle arrest and cellular senescence through mechanisms involving RB1 dephosphorylation and cyclin degradation 1. ECRG4 is widely expressed across human tissues and regulated by counter-balancing mechanisms: promoter hypermethylation provides negative regulation while Sp1 transcription factor binding provides positive regulation 1. ECRG4 acts as a tumor suppressor frequently silenced in multiple cancer types through epigenetic hypermethylation. In breast cancer, ECRG4 is downregulated in 94.3% of cases, with expression restoration inhibiting proliferation and migration while promoting G0/G1 arrest and apoptosis via the mitochondrial pathway 2 3. Similar suppressive effects occur in nasopharyngeal carcinoma, gastric cancer, and colorectal cancer, where low ECRG4 correlates with poor prognosis, advanced tumor stage, and lymph node metastasis 4 5 6. ECRG4 can be detected in liquid biopsy and possesses promising diagnostic and therapeutic potential in precision medicine 7. Pharmacologic demethylation restores ECRG4 expression and chemosensitivity in cancer cells 4, positioning ECRG4 as both a prognostic biomarker and candidate therapeutic target.