Preferential expression of immunoreactive fucosylceramide in adenocarcinoma of the lung

The expression of fucosylceramide (PC47H antigen) in 97 lung cancers and 4 extrapulmonary squamous cell carcinomas was examined with the use of a novel monoclonal antibody, PC47H, recognizing fucosylceramide specifically. The observed variation in fucosylceramide content was dependent on the degree of glandular differentiation in adenocarcinoma of the lung. Fucosylceramide was abundantly expressed in well differentiated adenocarcinoma of the lung and poorly expressed in poorly differentiated adenocarcinoma. Some squamous cell carcinomas of the lung reacted with this monoclonal antibody weakly, but the reaction was noted only at the periphery of the epithelial sheets. Extrapulmonary squamous cell carcinoma and small-cell carcinomas did not react with monoclonal antibody PC47H. Interestingly, large cell carcinomas of uncertain cell origin were all positive for fucosylceramide, which accumulated in the cytoplasm. At the ultrastructural level, fucosylceramide was located in the plasma membrane and unit membrane of the rough endoplasmic reticulum. On the other hand, carcinoembryonic antigen as an adenocarcinoma-associated tumor marker was expressed significantly in squamous cell carcinomas as well as adenocarcinomas. Taken together, fucosylceramide seems to be expressed preferentially in adenocarcinomas, and is closely linked to glandular differentiation. Thus it may be a better tumor marker than carcinoembryonic antigen.