Investigation of HEG1, VISTA (VSIR) and PD-L1 expression levels in malignant mesothelioma by immunohistochemical methods and their relationship with histological subtypes

Abstract

Malignant Mesothelioma is a primary malignant tumor of the mesothelium lining the pleura, pericardium, peritoneum and tunica vaginalis of the testis with a poor prognosis. The epithelioid subtype is graded as high and low grade in the 2021 WHO classification of thoracic tumors. Recently, promising results from clinical trials of treatment with immune checkpoint inhibitors are reported. The aim of our study was to shed light on clinical studies on potential immune checkpoint inhibitors by examining VISTA and PD-L1 expression levels as well as HEG1 in malignant mesothelioma subtypes. Our study included 69 cases diagnosed with ‘malignant mesothelioma, well-differentiated papillary mesothelial tumor, atypical mesothelial hyperplasia’ at Dicle University Faculty of Medicine Department of Pathology between 2015 and 2021. Primary antibodies against HEG1, VISTA, and PD-L1 were used in the immunohistochemical study. The results showed a significant relationship between PD-L1 expression and sarcomatoid and high-grade epithelioid malignant mesotheliomas. VISTA was detected at a high rate in epithelioid malignant mesotheliomas and was negative in non-mesothelial tumors. HEG1 was positively monitored in mesothelial-derived tumors and negatively monitored in non-mesothelial tumors. The obtained results suggest that HEG1 could be further explored as a useful marker in determining mesothelial origin and that the expression levels of VISTA and PD-L1 markers may vary in histological subtypes in the selection of drugs for the treatment of malignant mesothelioma.