Autocrine over expression of fibronectin by human transitional carcinoma cells impairs bacillus Calmette-Guerin adherence and signaling.
OBJECTIVE
Bacillus Calmette-Guerin (BCG) binds to the tumor cell as a result of mycobacterial receptors for fibronectin (FN). Cell surface bound FN serves as a bridge through which BCG attaches to the tumor cell. Despite the importance of FN studies have demonstrated an idiosyncratic decrease in BCG adherence in response to exogenous FN. We evaluated the effect of exogenous and autocrine FN on the ability of BCG to adhere to the tumor cell surface and initiate cellular signaling.


METHODS
BCG adherence to parental 253J and FN over expressing 253JTGFbeta1-8 cells as well as to the intrinsic FN expressing cell line 647V was quantified using green fluorescent protein-BCG. Experiments were performed to assess the effect of FN on BCG initiated signal transduction through nuclear factor kappaB and AP1. Finally, the integrity of the BCG activated signaling pathway in transforming growth factor-beta1/FN over expressors was assessed using antibody mediated cross-linking of the FN receptor.


RESULTS
BCG adherence was decreased in cell lines with high autocrine expression of FN. Exogenous FN prevented BCG induced transactivation of nuclear factor kappaB and AP1 reporter constructs. No BCG stimulated signaling to these reporters could be detected in FN over expressing 253J cells. NonFN dependent alpha5beta1 cross-linking initiated signal transduction in FN over expressing cells.


CONCLUSIONS
We propose that by saturating cellular and BCG receptors excess FN expression decreases the ability of cellular or mycobacterial bound FN to bind vacant receptors on BCG or on the cell. Excess FN inhibits BCG adherence and BCG initiated signal transduction.
Zhang
Guangjian
G
Department of Urology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Chen
Fanghong
F
Xu
Yong
Y
Cao
Yanli
Y
Crist
Scott
S
McKerrow
Amy
A
Iwamoto
Yoshiki
Y
See
William A
WA
D019898:Autocrine Communication / Q000276:immunology*; D001422:Bacterial Adhesion / Q000276:immunology*; D002295:Carcinoma, Transitional Cell / Q000276:immunology*; D045744:Cell Line, Tumor; D005353:Fibronectins / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism; D009163:Mycobacterium bovis / Q000276:immunology*; D016328:NF-kappa B / Q000378:metabolism; D017469:Receptors, Fibronectin / Q000276:immunology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000276:immunology*; D001749:Urinary Bladder Neoplasms / Q000276:immunology*
D005353:Fibronectins; D039081:Integrin alpha5beta1; D016328:NF-kappa B; D017469:Receptors, Fibronectin; D018808:Transcription Factor AP-1