PURPOSE: The adherence of bacillus Calmette-Guerin (BCG) to the surface of transitional carcinoma tumor cells initiates nuclear factor (NF)-kappa B signal transduction pathways that modulate the expression of proteins important in the antitumor response to BCG. We tested the hypothesis that BCG initiates NF-kappa B signaling as a consequence of cross-linking alpha 5 beta 1 integrin receptors present on the tumor cell surface. MATERIALS AND METHODS: The effect of alpha 5 beta 1 antibody mediated cross-linking on interleukin (IL)-6 mRNA expression, IL-6 promoter activation and activation of a specific NF-kappa B reporter construct was determined. A series of reporter constructs containing nonfunctional mutations in the AP-1, NF-IL-6 and NF-kappa B sites were used to determine the relative importance of these response elements in alpha 5 beta 1 cross-linking mediated activation of the IL-6 promoter. A final series of experiments assessed the role of alpha 5 beta 1 receptor occupancy by fibronectin (FN) in initiating antibody or BCG mediated signaling. RESULTS: Anti alpha 5 and anti beta 1 mediated cross-linking of alpha 5 beta 1 integrin initiated NF-kappa B signaling, IL-6 promoter activation and IL-6 mRNA expression. Deletion mutants demonstrated that alpha 5 beta 1 cross-link initiated, IL-6 promoter transactivation required intact NF-kappa B and AP-1 response elements. Receptor occupancy by FN was required for BCG but not for antibody initiated signaling. CONCLUSIONS: Cross-linking the alpha 5 beta 1 receptor present on the surface of human transitional carcinoma cells lines initiates signal transduction in a manner identical to that observed for BCG. We propose a model in which multiple FN binding sites present on BCG interact with alpha 5 beta 1 receptor bound FN molecules to cross-link alpha 5 beta 1 receptors and initiate intracellular signaling.
PURPOSE: The adherence of bacillus Calmette-Guerin (BCG) to the surface of transitional carcinoma tumor cells initiates nuclear factor (NF)-kappa B signal transduction pathways that modulate the expression of proteins important in the antitumor response to BCG. We tested the hypothesis that BCG initiates NF-kappa B signaling as a consequence of cross-linking alpha 5 beta 1 integrin receptors present on the tumor cell surface. MATERIALS AND METHODS: The effect of alpha 5 beta 1 antibody mediated cross-linking on interleukin (IL)-6 mRNA expression, IL-6 promoter activation and activation of a specific NF-kappa B reporter construct was determined. A series of reporter constructs containing nonfunctional mutations in the AP-1, NF-IL-6 and NF-kappa B sites were used to determine the relative importance of these response elements in alpha 5 beta 1 cross-linking mediated activation of the IL-6 promoter. A final series of experiments assessed the role of alpha 5 beta 1 receptor occupancy by fibronectin (FN) in initiating antibody or BCG mediated signaling. RESULTS: Anti alpha 5 and anti beta 1 mediated cross-linking of alpha 5 beta 1 integrin initiated NF-kappa B signaling, IL-6 promoter activation and IL-6 mRNA expression. Deletion mutants demonstrated that alpha 5 beta 1 cross-link initiated, IL-6 promoter transactivation required intact NF-kappa B and AP-1 response elements. Receptor occupancy by FN was required for BCG but not for antibody initiated signaling. CONCLUSIONS: Cross-linking the alpha 5 beta 1 receptor present on the surface of human transitional carcinoma cells lines initiates signal transduction in a manner identical to that observed for BCG. We propose a model in which multiple FN binding sites present on BCG interact with alpha 5 beta 1 receptor bound FN molecules to cross-link alpha 5 beta 1 receptors and initiate intracellular signaling.
Authors: L Lima; P F Severino; M Silva; A Miranda; A Tavares; S Pereira; E Fernandes; R Cruz; T Amaro; C A Reis; F Dall'Olio; F Amado; P A Videira; L Santos; J A Ferreira Journal: Br J Cancer Date: 2013-09-24 Impact factor: 7.640