PSG5 (pregnancy-specific beta-1-glycoprotein 5) is a plasma membrane protein involved in cell-cell adhesion during pregnancy. PSG5 functions as a transcriptional enhancer of important placental genes and is regulated by endogenous retroviruses in human trophoblast 1. Specifically, LTR10A and other primate-specific transposable elements act as transcriptional enhancers of PSG5 expression, contributing to human trophoblast gene regulation and potentially affecting pregnancy outcomes 1. PSG5 demonstrates protein binding capacity and both homophilic and heterophilic cell-cell adhesion activities, consistent with its role in placental development. Beyond pregnancy physiology, PSG5 has emerged as a disease-relevant biomarker in non-pregnancy contexts. In endometrial cancer, PSG5 was identified as one of six overlapping proteins associated with nonendometrioid subtype pathogenesis through multiomics analysis 2. Additionally, PSG5 was incorporated into a six-gene-based risk score model for laryngeal cancer prognosis, where elevated PSG5 expression correlated with poorer overall survival 3. These findings suggest PSG5 has dual significance: as a critical regulator of normal placental development and as a potential prognostic biomarker in human malignancies.