A marker for ovarian cancer, capable of binding CA125, the ovarian cancer marker.
A binding domain on mesothelin for CA125/MUC16. Kaneko O et al. Ovarian cancer and malignant mesothelioma frequently express both mesothelin and CA125 (also known as MUC16) at high levels on the cell surface. The interaction between mesothelin and CA125 may facilitate the implantation and peritoneal spread of tumors by cell adhesion, whereas the detailed nature of this interaction is still unknown. Here, we used truncated mutagenesis and alanine replacement techniques to identify a binding site on mesothelin for CA125. We examined the molecular interaction by Western blot overlay assays and further quantitatively analyzed by enzyme-linked immunosorbent assay. We also evaluated the binding on cancer cells by flow cytometry. We identified the region (296-359) consisting of 64 amino acids at the N-terminal of cell surface mesothelin as the minimum fragment for complete binding activity to CA125. We found that substitution of tyrosine 318 with an alanine abolished CA125 binding. Replacement of tryptophan 321 and glutamic acid 324 with alanine could partially decrease binding to CA125, whereas mutation of histidine 354 had no effect. These results indicate that a conformation-sensitive structure of the region (296-359) is required and sufficient for the binding of mesothelin to CA125. In addition, we have shown that a single chain monoclonal antibody (SS1) recognizes this CA125-binding domain and blocks the mesothelin-CA125 interaction on cancer cells. The identified CA125-binding domain significantly inhibits cancer cell adhesion and merits evaluation as a new therapeutic agent for preventing or treating peritoneal malignant tumors.
NCBI Summary:
This gene encodes a precursor protein that is cleaved into two products, megakaryocyte potentiating factor and mesothelin. Megakaryocyte potentiation factor functions as a cytokine that can stimulate colony formation in bone marrow megakaryocytes. Mesothelian is a glycosylphosphatidylinositol-anchored cell-surface protein that may function as a cell adhesion protein. This protein is overexpressed in epithelial mesotheliomas, ovarian cancers and in specific squamous cell carcinomas. Alternative splicing results in multiple transcript variants.[provided by RefSeq, Apr 2010]
General function
Ligand
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Cellular localization
Secreted, Plasma membrane
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Ovarian function
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Expression regulated by
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Ovarian localization
Ovarian tumor
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Expression of mesothelin, fascin, and prostate stem cell antigen in primary ovarian mucinous tumors and their utility in differentiating primary ovarian mucinous tumors from metastatic pancreatic mucinous carcinomas in the ovary. Cao D et al. Metastatic pancreatic mucinous adenocarcinomas in the ovaries can be difficult to distinguish from primary ovarian mucinous neoplasms because the former can simulate the latter grossly and histologically and both tumor types share the same cytokeratin 7/cytokeratin 20 immunoprofile. We previously reported the utility of loss of Dpc4 expression in distinguishing metastatic pancreatic carcinomas from primary ovarian mucinous tumors. Recently several new pancreatic carcinoma markers have been identified, including mesothelin, fascin, and prostate stem cell antigen (PSCA). In this study we investigate the expression patterns of these markers in 35 primary ovarian mucinous tumors (28 atypical proliferative [borderline] tumors and 7 invasive carcinomas) and 11 metastatic pancreatic mucinous carcinomas in the ovary. Primary ovarian mucinous tumors expressed mesothelin (17%), fascin (26%), and PSCA (43%) less frequently than metastatic pancreatic adenocarcinomas (73%, 73%, and 82%, respectively). Expression of all three markers was seen only in metastatic pancreatic adenocarcinomas (45%), and coexpression of at least two markers was observed significantly more frequently in metastatic (82%) than primary ovarian mucinous tumors (17%). Our results indicate that an immunohistochemical panel including Dpc4, mesothelin, fascin, and PSCA is useful for evaluating difficult mucinous tumors in the ovary when the differential diagnosis includes metastatic pancreatic adenocarcinoma.