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T. Sueda

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    P1.02 - Biology/Pathology (ID 614)

    • Event: WCLC 2017
    • Type: Poster Session with Presenters Present
    • Track: Biology/Pathology
    • Presentations: 1
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      P1.02-052 - Identification of DAB2 and Intelectin-1 as Novel Positive Immunohistochemical Markers of Epithelioid Mesothelioma (ID 9299)

      09:30 - 16:00  |  Author(s): T. Sueda

      • Abstract

      Malignant mesothelioma is a fatal malignant tumor. It is often difficult to diagnose and to differentiate from other carcinomas, especially pulmonary adenocarcinoma. As there are currently no absolute immunohistochemical positive markers for the definite diagnosis of epithelioid mesothelioma, the identification of additional “positive” markers that may facilitate this diagnosis becomes of clinical importance.

      Gene Expression Analysis Formalin-fixed paraffin-embedded tissue sections from 6 epithelioid mesothelioma and 6 pulmonary adenocarcinoma cases were used for gene expression analysis. RNA extraction for gene expression analysis was performed from papillary or solid growth of tumor cells in each specimen. The Human Transcriptome 2.0 GeneChip Array containing gene transcript sets of 44,699 protein coding and 22,829 nonprotein coding clusters was used to analyze gene expression profiles. Validation by Real-time RT PCR & Western Blotting The increased mRNA expression of DAB2 and Intelectin-1 was validated by reverse transcriptase polymerase chain reaction of RNA from tumor tissue and protein expression was validated by Western blotting of 5 mesothelioma cell lines. Immunohistochemical Procedures and Evaluation of Expression of DAB2 and Intelectin-1 The utility of DAB2 and Intelectin-1 in the differential diagnosis of epithelioid mesothelioma and pulmonary adenocarcinoma was examined by an immunohistochemical study of 75 cases of epithelioid mesothelioma and 67 cases of pulmonary adenocarcinoma.

      Differential Gene Expression Of the 44,699 protein coding and 22,829 nonprotein coding transcripts on the Human Transcriptome 2.0 GeneChip Array, 902 statistically significant mRNA transcripts were differentially expressed, with a greater than 1.3-fold difference, between epithelioid mesothelioma and pulmonary adenocarcinoma. Validation Realtime RT-PCR showed relative mRNA expression of DAB2 and Intelectin-1 was significantly higher in epithelioid mesothelioma than that in pulmonary adenocarcinoma. Western blot analysis showed DAB2 and Intelectin-1 protein expression in all 5 commercially available mesothelioma cells lines with anti-DAB2 and anti-Intelectin-1 antibody. Immunohistochemical Expression Profiles in Epithelioid Mesothelioma and Pulmonary Adenocarcinoma The expression of DAB2 and Intelectin-1 was localized in the cytoplasm of tumor cells in epithelioid mesothelioma cases. Positive DAB2 expression was observed in 60 of 75 epithelioid mesotheliomas (80.0%) and 2 of 67 pulmonary adenocarcinomas (3.0%). In half of epithelioid mesotheliomas, DAB2 immunoreactivity was generally strong and diffuse (score 3+). In contrast, pulmonary adenocarcinomas showing DAB2 expression was focal (score 1+).

      We identified 2 novel positive markers of epithelioid mesothelioma, DAB2 and Intelectin-1, by using gene expression microarray analysis and confirmed their utility to differentiate epithelioid mesothelioma from pulmonary adenocarcinoma by immunohistochemical study.