Bacillus Calmette Guerin Induces Fibroblast Activation Both Directly and through Macrophages in a Mouse Bladder Cancer Model

Abstract

BackgroundBacillus Calmette-Guerin (BCG) is the most effective treatment for non-muscle invasive bladder cancer. However, a failure in the initial response or relapse within the first five years of treatment has been observed in 20% of patients. We have previously observed that in vivo administration of an inhibitor of nitric oxide improved the response to BCG of bladder tumor bearing mice. It was described that this effect was due to a replacement of tumor tissue by collagen depots. The aim of the present work was to clarify the mechanism involved in this process.Methodology/Principal FindingsWe demonstrated that BCG induces NIH-3T3 fibroblast proliferation by activating the MAPK and PI3K signaling pathways and also differentiation determined by alpha-smooth muscle actin (alpha-SMA) expression. In vivo, intratumoral inoculation of BCG also increased alpha-SMA and collagen expression. Oral administration of L-NAME enhanced the pro-fibrotic effect of BCG. Peritoneal macrophages obtained from MB49 tumor-bearing mice treated in vivo with combined treatment of BCG with L-NAME also enhanced fibroblast proliferation. We observed that FGF-2 is one of the factors released by BCG-activated macrophages that is able to induce fibroblast proliferation. The involvement of FGF-2 was evidenced using an anti-FGF2 antibody. At the same time, this macrophage population improved wound healing rate in normal mice and FGF-2 expression was also increased in these wounds.Conclusions/SignificanceOur findings suggest that fibroblasts are targeted by BCG both directly and through activated macrophages in an immunotherapy context of a bladder murine model. We also described, for the first time, that FGF-2 is involved in a dialog between fibroblasts and macrophages induced after BCG treatment. The fact that L-NAME administration improves the BCG effect on fibroblasts, NO inhibition, might represent a new approach to add to the conventional BCG therapy.

FGFR3 Down-Regulation is Involved in bacillus Calmette-Guérin Induced Bladder Tumor Growth Inhibition

“…Furthermore, we have shown in murine models that BCG inhibits BC growth 6 and induces stromal remodeling involving fibroblast proliferation and differentiation, increasing collagen fiber deposits and macrophage activation 6,7 .…”

“…FGF-2 acts on stromal cells, favoring its activation and proliferation to the detriment of tumor cells growth. Thus it is part of BCG mechanism of action in BC 6 .…”

Animal Models for Basic and Preclinical Research in Bladder Cancer

“…We also found that in vivo BCG therapy reduces tumor growth with a concomitant increase in collagen deposition and expression of alpha-smooth muscle actin and FGF-2. These results suggest that tissue repair mechanisms similar to healing are involved in BCG immunotherapy of bladder cancer (Lodillinsky et al, 2010).…”

iNOS expression and NO production contribute to the direct effects of BCG on urothelial carcinoma cell biology

“…Antioxidants or inducers of iNOS had a positive impact on the in vitro and in vivo effects of BCG respectively [7,8,22]. While one study has suggested that inhibition of iNOS may improve the tumor response to BCG [23], more studies have suggested that increasing iNOS production may be beneficial [7,8,22,24].…”