Examining OST4's impact on tumorigenesis and immune microenvironment in ovarian cancer

IntroductionOvarian cancer remains one of the deadliest malignancies in gynecology, characterized by a high tendency for metastasis, strong drug resistance, and limited response to immunotherapy. Protein glycosylation plays a critical role in these processes, making it an attractive target for therapeutic development. The oligosaccharidyltransferase (OST) complex, which catalyzes a central step in N-linked glycosylation, is of particular importance. Among OST subunits, OST4 serves as a key regulatory element. Previous studies indicate that OST4 expression modulates the efficiency of protein N-glycosylation and has been recognized as a prognostic marker in head and neck cancers, with connections to PD-L1 expression. However, the role of glycosylation-related genes such as OST4 in ovarian cancer development and immune cell activity within the tumor microenvironment remains unclear. This study explores the function of OST4 in ovarian cancer and assesses its potential as a therapeutic target.MethodsWe employed comprehensive data mining of The Cancer Genome Atlas (TCGA) and single-cell RNA sequencing datasets to identify pathways linked to OST4 in ovarian cancer and its immune-related effects. OST4 expression was knocked down in ovarian cancer cell lines (OVCAR4 and OVCAR8) using siRNA. Cell migration and invasion were measured to evaluate metastatic potential, and proliferation was assessed via XTT assays. Western blot analysis was performed to examine associated signaling pathways and downstream effectors. Tumor Conditioned Medium (TCM) was collected from ovarian cancer cells transfected with OST4 siRNA and scRNA, incubated in complete medium for 48 hours. The transwell migration assay was used to determine the infiltration of T cells cultured with the TCM. ResultsOST4 was found to be highly expressed in ovarian cancer. Patient stratification based on OST4 expression levels revealed associations with macrophage and T-cell infiltration. Pathway analysis indicated that OST4 may regulate the unfolded protein response (UPR). Silencing OST4 suppressed ovarian cancer cell migration, invasion, and proliferation. Western blot analysis further demonstrated that OST4 knockdown decreased the expression of IRE1alpha, a central component of the UPR pathway. The number of infiltrated CD8 + T cells increased in the presence of TCM derived from OST4-silenced OC cells compared to control TCM.ConclusionIn conclusion, OST4 influences ovarian cancer progression and CD8 + T cell infiltration, potentially through activation of the UPR pathway. Targeting OST4 may offer a promising therapeutic approach for ovarian cancer.