| Mesothelin, also known as CAK1 and ERC, is a protein that is mainly expressed in the mesothelial cells lining the pleura, pericardium, and peritoneum. The Mesothelin gene encodes a precursor protein of 70kD that is cleaved into two products, including megakaryocyte potentiating factor (aa37-286) and Mesothelin (aa296-606). Megakaryocyte potentiation factor is a secreted protein of about 32kD, and it functions as a cytokine that can stimulate colony formation in bone marrow megakaryocytes. Mesothelin is a 40kD glycosylphosphatidylinositol-anchored cell-surface protein. Multiple transcription variants of Mesothelin, as a result of alternative splicing, have been described. Variant 1 is primarily expressed at the surface of the cells and can be shed. Compared to variant 1, variant 2 has an eight aa insertion between aa409-416 and variant 3 differs from aa601-630. Variant 1 is the predominant form that is expressed by both normal and tumor cells, while variants 2 and 3 exist at low levels. The biological functions of Mesothelin remain unclear. Bera et al. generated knockout mice in which the Mesothelin gene was inactivated. They found that these mice did not have any detectable abnormal phenotypes, and they produced offspring normally, suggesting that Mesothelin is not essential for growth and development. Other studies have reported that cells transfected with Mesothelin were more difficult to remove from the culture dishes than nontransfected cells. This indicates that Mesothelin might function as an adhesion molecule. This notion is further supported by the observation that Mesothelin is able to bind to CA125/MUC16 with a high affinity and that this interaction mediates cell adhesion. Mesothelin may thus play an important role in the peritoneal spread of ovarian cancer. The expression of Mesothelin is modulated by the Wnt proteins. In mouse mammary epithelial cells, Mesothelin is up-regulated by Wnt-1, while down-regulated by Wnt-5a. Under physiological conditions, the expression of Mesothelin is limited. However, overexpression of Mesothelin has been described in many types of malignancies, such as mesothelioma, ovarian cancer, and pancreatic cancer. Further studies have suggested that this cancer-specific overexpression of Mesothelin might be attributed to an upstream transcription enhancer. Mesothelin is detectable in many biological fluids, such as serum and urine. It has been demonstrated that quantification of Mesothelin in these biological fluids may serve as a useful biomarker for cancer diagnosis, prognosis, and monitoring response to therapy in patients with mesothelioma and ovarian cancer. Furthermore, due to its low expression in normal tissues and high expression in tumor cells, Mesothelin is an attractive candidate for cancer immunotherapy. Additionally, Mesothelin can elicit an autoimmune response in cancer patients. These therapies include agents that target cell surface Mesothelin or elicit an immune response against Mesothelin. Sample Type: Cell culture supernates, serum, plasma, saliva, and urine Intended Use: For the quantitative determination of human Mesothelin concentrations in cell culture supernates, serum, plasma, saliva, and urine. Sensitivity: Twenty assays were evaluated and the minimum detectable dose (MDD) of Mesothelin ranged from 0.005-0.022ng/ml. The mean MDD was 0.010ng/ml. The MDD was determined by adding two standard deviations to the mean optical density value of twenty zero standard replicates and calculating the corresponding concentration. Specificity: Recognizes recombinant and natural human Mesothelin. Test Principle: This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for Mesothelin has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any Mesothelin present is bound by the immobilized antibody. After washing away any unbound substances, an enzyme-linked monoclonal antibody specific for Mesot |