PLATELET-DERIVED GROWTH-FACTOR RECEPTOR IMMUNOREACTIVITY IN MESOTHELIOMA AND NONNEOPLASTIC MESOTHELIAL CELLS IN SEROUS EFFUSIONS

Expression of the platelet-derived growth factor receptor (PDGFR) was detected by immunocytochemistry in normal and malignant mesothelial ce lls from 14 benign effusions and 22 mesotheliomas. Two well-characteri zed antireceptor monoclonal antibodies to the PDGFR alpha-subunit (PR2 92) and beta-subunit (PR7212) were used. PDGFR alpha-subunit outlined cell membranes intensely in nonneoplastic mesothelial cells, whereas i t was focal in mesothelioma and limited to a few cases only. PDGFR bet a-subunit was weakly expressed in the cytoplasm of normal mesothelium; in contrast, malignant mesothelial cells showed strong cytoplasmic st aining. Our uesults show that normal mesothelium may be responsive to PDGF by the predominant expression of PDGFR-alpha and less by PDGFR-be ta and indicate the presence of growth-stimulation loops in mesothelio ma through PDGF/PDGFR-beta interaction. Also, scattered staining for t he PDGFR alpha-subunit suggests that a PDGF-A chain/PDGFR-alpha intera ction may also be active in mesothelioma cells growing in suspension.