Malignant transformation of human bladder epithelial cells by DNA transfection with the v-raf oncogene

Deregulation in trans or c-myc expression in immortalized human urothelial cells and in T24 bladder carcinoma cells

The expression of a number of cellular oncogenes was investigated in human urothelial cell lines with different in vitro growth properties. Constitutively elevated levels of expression of c-myc RNA were found in Hu609, an immortalized, nontumorigenic cell line that was derived from normal urothelium, and in the bladder carcinoma cell line T24. Potential mechanisms that might underlie deregulation of c-myc expression in these cells were investigated. It was found that the c-myc gene was apparently intact and not amplified in Hu609 and T24. No increased stability of c-myc RNA was detected. A c-myc-CAT fusion construct containing 2.5 kb of normal c-myc 5' sequences showed levels of expression that paralleled the overexpression of the endogenous gene, indicating that the high constitutive levels of c-myc expression were due, at least in part, to alterations in the activities of cellular trans-acting transcriptional regulators.

Angiogenesis induced by urothelial cells (HCV-29) and their v-ras and v-raf transfectants

The angiogenic ability of human urothelial cells (HCV-29) and their v-ras and v-raf transfectants was studied. The most pronounced angiogenesis, observed in vivo, induced v-raf-transfected cells. The lowest degree of induction of neovascularization presented cells of the parental line. The increased extent of angiogenesis correlated with the presence of VEGF mRNA as measured by RT-PCR as well as the level of VEGF as visualized by the method of Western blotting.

The Reducing Agent Dithiothreitol (DTT) Increases Expression of c-myc and c-fos Proto-oncogenes in Human Cells

— The objective of the present study was to assess the possible tumour promoting activity of the food mutagen 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5- b]pyridine ( N-OH-PhIP), by studying its influence on the expression of three genes considered to be of relevance in the tumour promotion step. The genes were two proto-oncogenes, c- fos and c- myc, and the tumour suppressor gene, p53. We observed that the expression of the c- fos and c- myc genes was induced when human bladder epithelial cells were treated with a standard solution of N-OH-PhIP and dithiothreitol (DTT), previously shown to be genotoxic. However, when cells were treated with DTT alone, the expression of c- fos and c- myc was also transiently induced. We therefore conclude that DTT, and not N-OH-PhIP, induced oncogene expression. Induction of both c- fos and c- myc expression by a reducing agent, DTT, which is frequently used in in vitro toxicology studies, is a novel observation that suggests the need for a cautious interpretation of such studies.

Two phorbol ester receptor affinities in partially transformed human urothelial cells and decrease of receptor binding in desensitized cells

The presence of specific binding sites for phorbol esters was studied in a transformed but non-tumorigenic human urothelial cell line HCV-29 by assay of specific binding of 3H-phorbol-12,13-dibutyrate (3H-PDBu) to intact living cells. 3H-PDBu bound specifically to HCV-29 cells in a saturable and competitive manner. Scatchard plot analysis of specific binding yielded a curved plot consistent with two binding sites with Kd of 11 nM and 102 nM, respectively. At saturation the corresponding PDBu binding capacities (Bmax) were 8.8 pmol/10(6) cells (5.2 x 10(6) molecules bound per cell) and 2.8 pmol/10(6) cells (1.7 x 10(6) molecules bound per cell). 3H-PDBu binding was displaced by biologically active phorbol ester tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and mezerein, but not by tumor promoters such as L-tryptophan, anthranilic acid and sodium saccharin. In cells desensitized by pretreatment with 1 microgram/ml (2 microM) TPA or PDBu for 24 h the level of binding was reduced to 28% of the level in non-exposed cells. The ability of desensitized cells to bind 3H-PDBu was gradually restored within 5-6 days. At the same time the cells became sensitive to the morphological alteration induced by PDBu. This suggests that desensitization of HCV-29 cells is due to a decreased receptor-ligand binding capacity probably associated with down regulation of the phorbol ester receptors.

The sialosyl Lewis a ganglioside is present in tumorigenic human urothelial cell lines

The sialosyl Lewis a antigen was identified in a ganglioside extract from a malignant human urothelial cell line (Hu 1703He) by fast atom bombardment mass spectrometry. The presence of this antigen in urothelial cell lines with varying tumorigenic properties was further studied using the 19-9 monoclonal antibody (MAb). The sialosyl Lewis a ganglioside was expressed only in the tumorigenic cell lines. Thus, the expression of this antigen is a marker of malignancy for human urothelial cell lines. Mass spectrometry also suggests that the fucosyl GM1 ganglioside was expressed in the Hu 1703He cell line. This was confirmed using the F12 MAb, specific for fucosyl GM1. However, the expression of this antigen was not confined to cell lines with tumorigenic properties.

Reduced HLA-A,B,C expression in tumourigenic v-raf transfected human urothelial cells

Tumourigenic (TGrIII) human urothelial cells grown in vitro have previously been demonstrated to have a markedly decreased expression of beta 2-microglobulin and HLA-A,B,C antigens as compared to non-tumourigenic (TGrII) human urothelial cell lines. Furthermore, during 'spontaneous' in vitro transformation of a non-tumourigenic (TGrII) human urothelial cell line Hu609 into a tumourigenic (TGrIII) subline Hu609T/LLH, changes in morphology and tumourigenicity have been demonstrated to be accompanied by a decreased HLA-A,B,C expression. After malignant transformation of the non-tumourigenic (TGrII) human urothelial cell line HCV29 by DNA transfection with the v-raf oncogene, four sublines could be isolated. In this study we have investigated these sublines for their expression of membrane bound HLA-A,B,C antigens and provide further evidence that an inverse relationship exists between tumourigenicity and monomorphic HLA-A,B,C expression. Treatment of the cells with recombinant human interferon alpha for 3 days increased the expression of HLA-A,B,C antigens by 50-150% indicating that at least some of the reduced HLA-A,B,C expression could be due to decreased synthesis of HLA-A,B,C antigens. All the transfected cell lines overexpress v-raf and c-myc.

Recombinant human interferon gamma exerts an anti-proliferative effect and modulates the expression of human leukocyte antigens A,B,C and DR in human urothelial cell lines

In this study we have treated three malignant (TGrIII) and two pre-malignant (TGrII) urothelial cell lines with recombinant human interferon gamma (rHu-INF gamma). The malignant cells (HCV29-T112C1, Hu1703He and T24) were inhibited in growth by more than 50% after treatment with 100-1000 units of rHu-INF gamma/ml for 4 days as compared to untreated controls. The growth of the pre-malignant cell lines (HCV29 and Hu609) was not influenced to the same extent in the presence of rHu-INF gamma in the culture medium. Treatment with rHu-INF gamma increased the expression of monomorphic human leukocyte antigens (HLA) A,B,C as well as beta 2-microglobulin in all the cell lines tested, as demonstrated using a quantitative immunofluorescence assay. The tumourigenic cell lines increased their expression of HLA in a dose-dependent way, whereas treatment of the non-tumourigenic cells with higher concentrations of rHu-INF gamma than 10 units/ml, did not increase the HLA-A,B,C expression further. None of the cell lines expressed HLA-DR unless treated with rHu-INF gamma. No correlation between tumourigenicity and the dose of rHu-INF gamma required for "de novo" induction of HLA-DR could be demonstrated. After removal of rHu-INF gamma from the medium, the expression of HLA-DR gradually decreased in less than 14 days, indicating that the expression of HLA-DR is not constitutive but dependent upon the presence of rHu-INF gamma. We conclude that human urothelial cells grown in vitro are sensitive to the anti-proliferative and major-histocompatibility-complex-modulating effects of rHu-INF gamma, and that malignant urothelial cells are more sensitive than pre-malignant cells. Finally, our data indicate a possible role for rHu-INF gamma in the management of human bladder cancer.