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It was found that a decrease in electrophoretic mobility of pyruvate kinase (PK) isoenzyme, and an increase of the sensitivity of this enzyme to L-cysteine, were markers of immortalization and tumorigenic properties, respectively, in human urothelial cell lines characterized by different grades of transformation (TGr) in vitro.

Quantitative changes in major histocompatibility class I antigen expression in tumour cells are believed to affect the host immune response against the tumour. In tumourigenic (TGrIII) human urothelial cell lines the apparent loss of polymorphic HLA-A,B epitopes has previously been demonstrated. In the present study, 3 non-tumourigenic (TGrII) and 6 tumourigenic (TGrIII) human urothelial cell lines have been investigated for their quantitative expression of monomorphic HLA-A,B,C and B2-microglobulin. Evidence is provided that an inverse correlation exists between tumourigenicity and HLA-A,B,C and B2-microglobulin expression. Furthermore, treatment of the cells with neuraminidase partly restored the expression of monomorphic HLA-A,B,C suggesting that at least some of the observed quantitative differences could be due to masking of the membrane bound HLA antigens by sialic acid-containing glycoconjugates.

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