Abstract. a large-scale screening involving the measurement of n-Erc/mesothelin levels in blood using an EliSa system for the early diagnosis of malignant mesothelioma (mm) was carried out in individuals with a history of employment at construction sites. approximately 30,000 subjects were screened. Of the 80 subjects with high-risk values, one male patient was diagnosed as having mm based on a pEt study and histopathology. This is the first report of the pre-clinical diagnosis of mm based on blood test screening. in addition, plasma levels of n-Erc/mesothelin may be effectively used for monitoring relapse after surgery. Introductionmesothelioma is an aggressive tumor arising from the mesothelium, a membrane lining various body cavities, including the pleura, peritoneum and pericardium, and is usually associated with asbestos exposure. due to the long incubation period and the short survival time after the onset of asbestos-induced malignant mesothelioma (mm), an early diagnostic system for individuals with a history of asbestos exposure is critically required. recently, soluble mesothelin-related protein (1) and serum mesothelin have been reported to be potentially useful markers for the early diagnosis of mm (2,3). a 71-kda precursor protein of human Erc/mesothelin can be cleaved into a 40-kda c-terminal fragment as a surface Gpi-anchored glycoprotein and a 31-kda n-terminal fragment as a secreted protein. We focused on this n-Erc/ mesothelin, as it is physiologically secreted into the blood, and as a specific ELISA system has been developed for N-ERC/ mesothelin (2,3).in the present study, to develop a pre-clinical diagnostic system for the early detection of mm, the levels of n-Erc/ mesothelin, the n-terminal 31-kda fragment of mesothelin, in blood samples was measured by EliSa as a primary screening method. chest radiography, chest ct and positron emission tomography (pEt) examinations, and also histopathology, were then used as secondary screening examinations for individuals with a history of exposure to asbestos and consequently, a high risk of developing of mm. Materials and methods Establishment of ELISA for N-ERC/mesothelin and measurement of blood samples.the sandwich EliSa system used in this report were established as described previously (3). the 7E7 moab was used as the capture antibody and the 16K16 moab was used as the detecting antibody after conjugation with horseradish peroxidase. recombinant n-Erc/mesothelin was used as the standard. the protein in the EliSa system was purified from culture supernatants of CHO-K1 cells transfected with Erc/mesothelin cdna using an anti-Erc/ mesothelin poab. Edta plasma was used for this EliSa.the present study was approved by the institutional review Board of Juntendo university School of medicine, its hospital and immuno-Biological laboratories. Written informed consent for participation in the study was obtained from all of the subjects. Results Case reports of three patientsPatient A: clinical history. the subject was a 71-year-old male who had a history...

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