Expression of polymorphic HLA-A,B epitopes in human urothelial cell lines.

Malignant human urothelial cell lines propagated in vitro have previously been demonstrated to express low amounts of monomorphic HLA-A,B,C as compared to premalignant urothelial cells. In this study the expression of polymorphic HLA-A,B epitopes in human urothelial cell lines have been investigated in greater detail. The expression of HLA-B locus coded epitopes in malignant TGrIII cells was demonstrated to be low or absent as compared to pre-malignant TGrII or slightly transformed TGrI cells, suggesting a mechanism by which malignant cells could escape from the host immune response. The extreme polymorphism of HLA-A,B,C antigens suggests that HLA typing could be used as a method to identify the origin of cell lines which is essential in the study of the process of malignant transformation in vitro, or when correlating in vitro data with clinical observations of the patient. Two urothelial cell lines classified as slightly transformed (TGrI) and two as pre-malignant (TGrII) could, according to their expression of polymorphic HLA-A,B epitopes, be identified as genuine independent cell lines. One TGrII cell line previously designated Hu1734 shared the same HLA-A,B phenotype as the genuine HCV29 (TGrII) cell line and is therefore suspected to be a subline of the latter. Out of 18 cell lines and sublines classified as TGrIII the fidelity of four (Hu1922 and three sublines of T24) was proved by their HLA-A,B phenotype. Mistaken identity either by contamination or false labelling of the cultures was suspected in samples of six TGrIII cell lines and sublines. In four of these the HLA-A,B type characteristic for the T24 cell line could be demonstrated, but in general HLA typing of TGrIII cell lines as a method to identify the origin of the individual cell lines failed, primarily due to the decreased expression of HLA-A,B,C antigens and the apparent selective loss of HLA-B locus coded antigens.