Analysis of the Secreted Peptidome from Omental Adipose Tissue in High-Grade Serous Ovarian Cancer.

High-grade serous ovarian cancer (HGSOC) is a preferential omental metastasis malignancy. Since omental adipose tissue is an endocrine organ, we used liquid chromatography tandem mass spectrometry (LC-MS/MS) to compare the peptides secreted from omental adipose tissues of HGSOC and benign serous ovarian cysts (BSOC). Among the differentially secreted peptides, we detected 58 upregulated peptides, 197 downregulated peptides, 24 peptides that were only in the HGSOC group and 20 peptides that were only in the BSOC group (absolute fold change ≥ 2 and P < 0.05). Then, the basic characteristics of the differential peptides were analyzed, such as lengths, molecular weights, isoelectric points, and cleavage sites. Furthermore, we summarized the possible functions according to the precursor protein functions of the differentially expressed peptides by Gene Ontology (GO) analysis with the Annotation, Visualization, and Integrated Discovery (DAVID) database and canonical pathway analysis with IPA. For the GO analysis, the differentially secreted peptides were mainly associated with binding in molecular function and cellular processes in biology process. For the canonical pathways, the differentially secreted peptides were related to calcium signaling, protein kinase A signaling, and integrin-linked kinase (ILK) signaling. We also identified 67 differentially secreted peptides that located in the functional domains of the precursor proteins. These functional domains were mainly related to energy metabolism and immunoregulation. Our study might provide drugs that could potentially treat HGSOC or omental metastases of HGSOC cells.

Differential effects of the LncRNA RNF157-AS1 on epithelial ovarian cancer cells through suppression of DIRAS3- and ULK1-mediated autophagy.

Analyses of several databases showed that the lncRNA RNF157 Antisense RNA 1 (RNF157-AS1) is overexpressed in epithelial ovarian cancer (EOC) tissues. In our study, suppressing RNF157-AS1 strikingly reduced the proliferation, invasion, and migration of EOC cells compared with control cells, while overexpressing RNF157-AS1 greatly increased these effects. By RNA pulldown assays, RNA binding protein immunoprecipitation (RIP) assays, and mass spectrometry, RNF157-AS1 was further found to be able to bind to the HMGA1 and EZH2 proteins. Chromatin immunoprecipitation (ChIP) assays showed that RNF157-AS1 and HMGA1 bound to the ULK1 promoter and prevented the expression of ULK1. Additionally, RNF157-AS1 interacted with EZH2 to bind to the DIRAS3 promoter and diminish DIRAS3 expression. ULK1 and DIRAS3 were found to be essential for autophagy. Combination autophagy inhibitor and RNF157-AS1 overexpression or knockdown, a change in the LC3 II/I ratio was found using immunofluorescence (IF) staining and western blot (WB) analysis. The autophagy level also was confirmed by autophagy/cytotoxicity dual staining. However, the majority of advanced EOC patients require platinum-based chemotherapy, since autophagy is a cellular catabolic response to cell stress. As a result, RNF157-AS1 increased EOC cell sensitivity to chemotherapy and death under cis-platinum (DDP) treatment by suppressing autophagy, as confirmed by cell count Kit-8 (CCK8) assays, flow cytometry, and autophagy/cytotoxicity dual staining. Therefore, the OS and PPS times were longer in EOC patients with elevated RNF157-AS1 expression. RNF157-AS1-mediated autophagy has potential clinical significance in DDP chemotherapy for EOC patients.