Background: Ovarian cancer (OV) is associated with high mortality and poses challenges in diagnosis and prognosis prediction. Ubiquitin-related genes (UbRGs) are involved in the initiation and progression of cancers, but have still not been utilized for diagnosis and prognosis of OV. Methods: K48-linked ubiquitination in ovarian tissues from our OV and control cohort was assessed using immunohistochemistry. UbRGs, including ubiquitin and ubiquitin-like regulators, were screened based on the TCGA-OV and GTEx database. Univariate Cox regression analysis identified survival-associated UbRGs. A risk model was established using the LASSO regression and multivariate Cox regression analysis. The relationship between UbRGs and immune cell infiltration, tumor mutational burden, drug sensitivity, and immune checkpoint was determined using the CIBERSORT, ESTIMATE, and Maftools algorithms, based on the Genomics of Drug Sensitivity in Cancer and TCGA-OV databases. GEPIA2.0 was used to analyze the correlation between FBXO9/UBD and DNA damage repair-related genes. Finally, FBXO9 and UBD were accessed in tissues or cells using immunohistochemistry, qPCR, and Western blot. Results: We confirmed the crucial role for ubiquitination in OV as a significant decrease of K48-linked ubiquitination was observed in primary OV lesions. We identified a prognostic signature utilizing two specific UbRGs, FBXO9 and UBD. The risk score obtained from this signature accurately predicted the overall survival of TCGA-OV training dataset and GSE32062 validation dataset. Furthermore, this risk score also showed association with immunocyte infiltration and drug sensitivity, revealing potential mechanisms for ubiquitination mediated OV risk. In addition, FBXO9, but not UBD, was found to be downregulated in OV and positively correlated with DNA damage repair pathways, suggesting FBXO9 as a potential cancer suppressor, likely via facilitating DNA damage repair. Conclusions: We identified and validated a signature of UbRGs that accurately predicts the prognosis, offers valuable guidance for optimizing chemotherapy and targeted therapies, and suggests a potential role for FBXO9 in OV.

Background: Ovarian cancer (OC) remains the most common cause of gynecological cancer-related death, and about 70% of these deaths are from advanced high-grade serous ovarian cancer (HGSOC). Cysteine-rich secretory protein 3 (CRISP3) is related to various human diseases; however, the roles and mechanisms of CRISP3 in HGSOC remain unclear. Methods: The clinical significance of CRISP3 in patients with OC was analyzed using the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus databases. CRISP3 expression in OC tissues was validated by RNA-sequencing (RNA-seq), quantitative PCR, and immunohistochemistry. Furthermore, we explored the effect of CRISP3 expression modulation on the biological behavior of HGSOC through CCK-8, EdU, and Transwell assays in vitro, and the differences in CRISP3 during the progression of HGSOC in vivo. We utilized RNA-seq, GSEA and Western blotting to detect CRISP3’s regulatory mechanisms. Finally, we employed data from the IMvigor210 cohort and TCGA to assess the correlation of CRISP3 with clinical response to immunotherapy, and the landscape of immune cell infiltration. Results: CRISP3 expression was markedly reduced in HGSOC. In vitro studies demonstrated that CRISP3 knockdown significantly enhanced proliferation, migration, and invasion of HGSOC cells, whereas its overexpression suppressed these malignant phenotypes. Moreover, CRISP3 expression was found to be downregulated during OC progression in vivo. Mechanistically, CRISP3 acted as a tumor suppressor through the PI3K/AKT signaling pathway to inhibit the progression and metastasis of HGSOC. Additionally, we observed an association between CRISP3 expression and CD8⁺ T cell, macrophage, neutrophil and Th1 cell infiltration. Conclusions: We demonstrate that CRISP3 suppresses tumorigenesis in HGSOC by regulating the PI3K/AKT pathway, and that alterations in its expression correlate with disease progression, supporting its utility as a biomarker.