Features of squamous and adenocarcinoma in the same cell in a xenografted human transitional cell carcinoma: evidence of a common histogenesis?

Ultrastructural features of squamous differentiation have been found in adenocarcinomatous cells in a xenografted line (UCRU-BL-17) established in nude mice from a primary human bladder transitional cell carcinoma (grade III, stage T4) with a tetraploid DNA component. The line has been characterized by light and electron microscopy, flow cytometry and immunocytochemistry. The initial xenograft showed predominantly adenocarcinomatous differentiation with mucin secretion, whilst the subsequent passages also contained cells showing squamous differentiation. A xenograft subline established from a cell culture of the initial xenograft shows the emergence of a population of cells with near triploid DNA, which are less differentiated, grow more quickly, show decreased expression of carcinoembryonic antigen, and a change in the distribution of staining with peanut lectin from cell surface to cytoplasm. These lines offer an unusual opportunity to study the histogenetic relationships between the histological subtypes of bladder cancer.