Expression of a 130-kDa mesothelial and ciliated cell Ag (MCp130) in normal and developing human and rat lung and its role as a diagnostic marker for mesotheliomas and tumors of the female reproductive system

BACKGROUND: Proteins in human lung lavage were analyzed to identify cell- specific markers for potential use in the study of the biology and pathology of pulmonary cells. EXPERIMENTAL DESIGN: Proteins associated with pulmonary surfactant were used to raise mAb. An Ab to a 130-kDa protein (MCp130) was reactive with ciliated and mesothelial cells. Expression of this Ag in normal organs, developing lung, and tumors was investigated. RESULTS: By Western blotting, the Ab stained a protein of about 130 kDa. In formalin-fixed, paraffin-embedded tissues from adult human and rat organs, the Ab specifically stained the luminal/apical surfaces of pulmonary and nonpulmonary ciliated and mesothelial cells. Staining of fetal airway cells was independent of ciliation. Airway cell staining was detectable in human fetal lungs at 12 weeks of gestation and at Day 18 of gestation in fetal rat. The Ab reacted with human and rat fetal mesothelial cells at the gestational ages of 15 weeks and 17 days, respectively. It also stained ciliated cells in endosalpinx and endometrium. Human epithelial mesotheliomas and ovarian and endometrial carcinomas stained selectively, whereas other pulmonary tumors and tumors of other organs did not react with the Ab. CONCLUSIONS: This 130- kDa mesothelial and ciliated cell plasma membrane protein appears in developing lung at an earlier age than secretory proteins. The marker is of potential use in the study of development of the different cell lineages in the lung and female reproductive tract. The Ab is expected to be useful in the diagnosis of epithelial mesotheliomas and ovarian/endometrial carcinomas, because it selectively stains these tumors and is reactive with formalin- fixed, paraffin-embedded tissues.