CGB2 encodes the beta subunit of human chorionic gonadotropin (hCG), a hormone with critical roles in reproduction and disease. Originally classified as a pseudogene, CGB2 is transcriptionally active 1, though its protein product remains uncharacterized. In normal physiology, CGB2 expression peaks during early pregnancy, particularly at the implantation stage, suggesting involvement in placental development and trophoblast function 2. CGB2 mRNA is detectable in testicular tissues at levels proportional to gene dosage, indicating potential roles in male reproduction 3. CGB2 exhibits evolutionary conservation between humans and chimpanzees with minimal population-level diversity, consistent with functional importance 4. Clinically, CGB2 shows significant disease relevance as a cancer-testis antigen. CGB2 transcripts are present in 20-41% of ovarian cancers but absent in normal ovarian tissue 56. CGB2 is also expressed in diverse cancers including bladder, cervical, esophageal, lung, and pancreatic malignancies 1. Notably, CGB2 expression specifically correlates with secretion of ectopic free hCGβ protein in epithelial cancer cells, and siRNA silencing of CGB2 reduces both protein secretion and cancer cell survival 7, suggesting functional importance in cancer-associated hCG production and potentially anti-apoptotic signaling.