Specific binding of bacillus Calmette-Gu�rin to urothelial tumor cells in vitro

Abstract

Intravesical immunotherapy with bacillus Calmette-Guérin (BCG) against recurrences of superficial bladder cancer and carcinoma in situ is a highly effective regimen in urology. Despite intensive efforts to clarify the immunological mechanisms of the most successful immunotherapy known today, the cellular mechanism of its antitumor activity remains unknown. In our approach to elucidate the way of action of intravesical BCG, we applied an in vitro adhesion assay to investigate the interaction of radiolabeled BCG with urothelial bladder-tumor cells. We demonstrated a BCG dose-dependent binding to bladder-tumor cell lines derived from tumors of different gradings. The binding of BCG is apparently specific, since competition experiments showed an inhibition by nonradioactive BCG but not by Escherichia coli. We also found that there was no difference between the binding of living or heat-killed mycobacteria. Control experiments showed only a low affinity of BCG for fibroblasts, smooth-muscle cells, and endothelial cells in comparison with the tumor cells. Furthermore, we investigated the role of fibronectin as an adhesion molecule that is also present in the bladder wall. We demonstrated that BCG was capable of binding to fibronectin-coated surfaces in a dose-dependent manner. However, competitive binding assays failed to reveal an inhibition of the binding of BCG to bladder-tumor cells by anti-fibronectin. Furthermore, binding was not influenced by soluble fibronectin. These data suggest that the in vitro attachment of BCG to bladder-tumor cells appears not to be mediated by fibronectin. In electron microscope studies an adhesion of BCG to bladder-tumor cells was observed after an incubation period of ony 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary Fibronectin Levels in Patients Treated with Intravesical Bacillus Calmette-Guérin for Superficial Bladder Cancer

“…Our patient population is not large enough to draw certain results but this observation suggests that the binding of BCG to bladder tumor cells is not influenced by soluble fibronectin. In confirmation of this finding, Schneider et al [17] have shown that in vitro interaction of radiolabeled BCG with urothelial tumor cells was not effected by soluble FN.…”

Response of high-risk of recurrence/progression bladder tumours expressing sialyl-Tn and sialyl-6-T to BCG immunotherapy

“…Thus, sTn may contribute to a more efficient binding of the bacillus to tumour cells and consequently a better response to BCG. The bacillus may also directly target cells in a fibronectin-independent manner (Schneider et al , 1994), namely by binding sTn or specific carbohydrates residues such as α 2,6 sialic acids. On the other hand, sTn is a product of incomplete O -glycosylation of proteins (Dall'Olio et al , 2012), a reduction in the structural complexity of O -glycan may allow the bacillus to bind more efficiently to tumour cells.…”

Role of urothelial cells in BCG immunotherapy for superficial bladder cancer

“…Pretreatment of T24 cells, a human TCC cell line, with anti-FN or anti-a5b1-receptor antibodies resulted in an impaired BCG attachment to and internalisation in these cells. However, other investigators could not inhibit BCG internalisation with anti-FN antibodies (Schneider et al, 1994;Bevers et al, 2000). The current available data do not suggest a mandatory role of FN in BCG internalisation.…”

“…The current available data do not suggest a mandatory role of FN in BCG internalisation. It seems that BCG internalisation is mediated by additional molecule(s), possibly coexpressed with FN, such as heparan sulphate-containing proteoglycans interacting with the mycobacterial heparin-binding haemagglutinin adhesin (HBHA) (Schneider et al, 1994;Bevers et al, 2000).…”