Overexpression of CD26/DPPIV in mesothelioma tissue and mesothelioma cell lines

Mesothelioma, a highly aggressive cancer with poor prognosis and refractory to currently available therapies show increasing trends of its incidence in Japan and other developing countries. Although surgery is a gold standard for patients with early mesothelioma, most patients with advanced disease are not suitable for surgical resection and have option of palliative chemotherapy alone. One of the new treatment strategies for mesothelioma, the humanized anti-CD26 monoclonal antibody therapy is under development. CD26, a 110-kDa transmembrane glycoprotein with known dipeptidyl peptidase IV activity, plays a role in tumor development and its expression was reported in various human malignancies. This study determined the preliminary selection criteria for humanized monoclonal anti-CD26 antibody therapy. Eighty-one epithelioid (49 differentiated and 32 less differentiated), 34 sarcomatoid, 19 biphasic mesothelioma and 8 mesothelioma cell lines were immunohistochemically examined using 8 different commercially available anti-CD26 antibodies for membranous and cytoplasmic expression. The cytoplasmic expression of CD26 was observed in all histological types of mesothelioma, while the membranous expression of CD26 was found in 88% of differentiated and 69% of less differentiated epithelioid mesothelioma, and none of sarcomatoid mesothelioma with anti-CD26 antibodies with rabbit polyclonal anti-DPP4 antibody and similar results were also obtained with goat polyclonal anti-DPP4/CD26 antibody. These antibodies absorbed with soluble human CD26 proteins do not show CD26 expression in mesothelioma tissue, suggesting these two antibodies localize true CD26 protein. Seven mesothelioma cell lines, including sarcomatoid types, also showed membranous expression of CD26 in cellblock preparation.CD26 vector transfection to CD26-negative MSTO-211H cells showed membranous expression of CD26 by flow cytometry, but not in tumor developed in NOD/SCID mice with inoculation of CD26 vector transfected MSTO-211H cells. We found that both ra

Evaluation of Apoptosis and Immunohistochemical Expression of the Apoptosis-related Proteins in Mesothelioma

We evaluated apoptosis and the expression of apoptosis-related proteins in 3 mesothelioma cell lines and 34 paraffin-embedded tissue specimens. Apoptosis was evaluated by the TUNEL method, while expression of the apoptosis-related proteins, bax, bcl-2, survivin, caspase-3 and cleaved caspase-3 was evaluated by immunohistochemical staining. The mean apoptotic index of mesothelioma tissue was 17.6 (ranging from 0 to 41.9), which was significantly lower than that of other carcinomas. Thirty-one of 34 cases showed caspase-3 expression. However, the cleaved caspase-3 index in mesothelioma was only 14.7 (ranging from 0 to 36.5). There was a direct correlation between apoptotic index and cleaved caspase-3 index (p value = 0.03). All cases of mesothelioma tissue showed bax expression, while only 2 cases showed bcl-2 expression. Thirty of 31 mesothelioma cases showed cytoplasmic expression of survivin, and 16 cases out of 30 cases showed diffuse staining while 11 cases showed strong staining. Three mesothelioma cell lines also showed high cytoplasmic expression of bax, caspase-3 and survivin, while there was no expression of bcl-2, and apoptosis and cytoplasmic expression of cleaved caspase-3 were limited. mRNA expression of survivin was confirmed by RT-PCR and its protein was confirmed by western blotting. In conclusion, apoptosis is an uncommon event in mesothelioma and low mean cleaved caspase-3 index, suggesting the role of low activation of caspase-3 for inhibition of apoptosis. High expression of survivin in mesothelioma may play a role in inhibition of apoptosis

Immunohistochemical marker panels for distinguishing between epithelioid mesothelioma and lung adenocarcinoma

The distinction between epithelioid mesothelioma and lung adenocarcinoma remains an important diagnostic challenge for surgical pathologists. The aim of the present study was to select a limited and appropriate panel of antibodies that can differentiate between epithelioid mesothelioma and lung adenocarcinoma. Specimens of 90 epithelioid mesotheliomas and 51 lung adenocarcinomas obtained from Japanese cases were examined using calretinin, WT1, AE1/AE3, CAM5.2, cytokeratin (CK) 5/6, vimentin, epithelial membrane antigen (EMA), thrombomodulin, CEA, CA19-9, and CA125. Ninety-six percent of epithelioid mesotheliomas were positive for calretinin; 99% for WT1; 100% for AE1/AE; 97% for CAM5.2; 70% for CK 5/6; 91% for vimentin; 96% for EMA; 71% for thrombomodulin; 77% for mesothelin; 7% for CEA; 17% for CA19-9; and 85% for CA125. In contrast, 33% of lung adenocarcinomas were positive for calretinin; 16% for WT1; 100% for AE1/AE3, CAM5.2, and EMA; 41% for CK 5/6; 47% for vimentin; 20% for thrombomodulin; 69% for mesothelin; 98% for CEA; 73% for CA19-9; and 80% for CA125. For distinguishing between epithelioid mesothelioma and lung adenocarcinoma, the combination of CEA, calretinin and each WT1 or thrombomodulin was suggested to be the best panel of immunohistochemical markers