BackgroundHigh-grade serous ovarian cancer (HGSOC) is the most common and aggressive subtype of epithelial ovarian cancer, characterized by rapid progression and poor prognosis. Despite advances in treatment, most cases are diagnosed at an advanced stage, and current diagnostic markers such as CA-125 have limited utility for early detection or treatment stratification. This study aimed to investigate the clinical significance and biological Function of phospholipase C delta 1 (PLCD1) in HGSOC.MethodsPLCD1 expression was assessed by immunohistochemistry (IHC) using tissue microarrays (TMA) comprising normal, borderline, and HGSOC tissues. Survival analyses were performed using Kaplan-Meier methods. PLCD1 expression in HGSOC cell lines was evaluated by Western blotting. Functional studies were conducted using PLCD1 knockdown and overexpression cell lines. Cell proliferation, invasion, and 3D spheroid assays were used to assess tumor cell behavior. A xenograft mouse model was used to evaluate the effect of PLCD1 overexpression on tumor growth in vivo.ResultsPLCD1 expression was significantly elevated in HGSOC tissues compared to normal and borderline tissues. Low PLCD1 expression was associated with significantly worse overall and disease-free survival in patients with HGSOC (n = 101). In vitro, PLCD1 knockdown increased proliferation in OVCA429 cells, while overexpression in OVCAR3 cells suppressed colony formation. In vivo, PLCD1 overexpression significantly reduced tumor growth in a xenograft model.ConclusionPLCD1 functions as a tumor suppressor in HGSOC and is associated with improved clinical outcomes. These findings suggest that PLCD1 may serve as a prognostic biomarker and potential therapeutic target in ovarian cancer.