Differential induction of transcription of c-myc and c-fos proto-oncogenes by 12-O-tetradecanoylphorbol-13-acetate in mortal and immortal human urothelial cells

Cell cycle perturbation by sodium butyrate in tumorigenic and non-tumorigenic human urothelial cell lines assessed by flow cytometric bromodeoxyuridine/DNA analysis

The effect of sodium butyrate on cell proliferation was studied in eight human urothelial cell lines differing in transformation grade (TGr): Hu 1752 (mortal, TGr I); HCV29 (immortal and tumorigenic, TGr II); HCV29T, T24, T24A, T24B, Hu 961A and Hu 1703He (tumorigenic, TGr III). In all cell lines, except Hu 1752, addition of 4 mM sodium butyrate at 18 h after replating resulted in a significantly decreased population of adherent cells after a further 24-48 h. This might partially be explained by detachment of cells, probably mainly S phase cells, from the substrate in the lines HCV29, HCV 29T, Hu 961A and Hu 1703He. Flow cytometric DNA analysis of the adherent cell population showed that all TGr II and III urothelial cell lines were DNA aneuploid, and that butyrate perturbed the cell cycle distribution in these cell lines, mainly by a decrease of the S phase fraction. Flow cytometric bromodeoxyuridine (BrdUrd)/DNA analysis of continuously BrdUrd labelled cultures, using a 'washless' BrdUrd/DNA staining technique, showed that butyrate inhibited the G0/1-S phase transition, indicated by a delayed depletion of BrdUrd negative G0/1 cells in the cell lines HCV29, HCV29T, T24B, Hu 961A and Hu 1703He. BrdUrd/DNA analysis further showed that butyrate inhibited the G2M-G0/1 phase transition, indicated by a pronounced accumulation of BrdUrd positive G2M cells in the cell lines HCV 29T, T24B, Hu 961A and Hu 1703He. Microscopy of HCV29T and Hu 961A cells indicated that this block did not occur in mitosis. The parental cell line T24 and the cell line T24A did not show an accumulation of BrdUrd negative G0/1 cells or BrdUrd positive G2M cells like that occurring in the derived cell line T24B.

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.

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.

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

Transfection of the v-raf oncogene into immortalized, nontumorigenic human bladder epithelial cells resulted in the isolation of two tumorigenic transformants. Both were identified as human and of the same origin as the parent cell line by human leukocyte antigen typing and Southern blot analysis. Both the primary tumorigenic transfectants and the cell lines established from the induced tumors expressed v-raf mRNA and v-raf protein. In both tumorigenic transformants the level of c-myc mRNA was enhanced compared with that of the parent cell line.