3':5'-stimulation of cyst formation by dibutyryl cyclic adenosine monophosphate in human urinary bladder tumors cultured in vitro.

Ten cases of human urinary bladder tumors, varying from histological Grades I to III, were cultured as fragments on a gyratory shaker. Low-grade tumors formed cysts spontaneously, and dibutyryl cyclic adenosine 3':5'-monophosphate stimulated both the number and the size of cysts. Grade III tumors did not form any cysts in culture, and, with light microscopy, dibutyryl cyclic adenosine 3':5'-monophosphate had no visible effect on the fragments. The cells lining the cysts that occurred in the aggregates were characterized by the appearance of zonula occludens on the aspect of the cells facing the culture medium. Two types of cysts were observed: some were lined by a monolayer of cells; and some were lined by a multilayer. In the former, zonula occludens appeared on the aspect facing the culture medium; in the latter, zonula occludens appeared on both the aspect facing the culture medium and that facing the cavities. These specialized structures functioned as tight intercellular junctions as one component of the complex of functions required for effective transport by sheets of epithelium.