Introduction

Although Bacillus Calmette-Guerin (BCG) is the most effective agent for non-muscle-invasive bladder cancers, approximately 30% of patients treated with intravesical BCG fail to respond to this agent. Previous studies from our lab showed the potential linkage of estrogen/estrogen receptor signaling with the efficacy of BCG, yet the detailed mechanisms remain unclear. Our new data showed the combination of BCG and the anti-estrogen ICI 182,780 (ICI) or tamoxifen could lead to a better suppression of bladder cancer (BCa) than BCG alone.

Methods

We first applied PCR to detect BCG internalization in two ERα positive BCa cell lines to investigate the potential effect of anti-estrogen ICI. Then, we used Q-PCR and western blot and examined the E2/ER effects on the integrin-α5β1 expression and the BCG attachment/internalization to BCa cells. To examine whether ICI can help the recruitment of macrophages toward BCa cells, we applied the transwell migration assay and in vivo mouse BCG model. Q-PCR, Elisa assay and MTT assay were used to detect the cytokine profile changes and BCa cell viability. For our in vivo studies, we applied the BBN-induced mouse BCa model, HE staining, BrdU and F4/80 staining to show the changes of macrophage infiltration and to prove the better efficacy of combining BCG plus anti-estrogen.

Results

We found treatment with either 1 μM ICI or tamoxifen significantly increased the BCG attachment/internalization, and the neutralization of integrin-α5β1 could reduce the ability of the ICI enhanced BCG attachment/internalization to BCa cells (Figure 1). Mechanism dissection revealed ICI could promote BCG attachment/internalization to the BCa cells through targeting ERα and increased the integrin-α5β1 expression and IL-6 secretion. The increased cytokine production may enhance BCG-mediated suppression of BCa cell growth and TNF-α production via recruiting more monocytes/macrophages to BCa cells (Figure 2-3). Consistently, in vivo studies found ICI could potentiate the anti-BCa effects of BCG in the carcinogen-induced mouse BCa models (Figure 4).

Conclusions

Taken together, these in vitro and in vivo results suggest that combining BCG with the anti-estrogen may become a new therapeutic approach with better efficacy to suppress BCa progression and recurrence.

Funding

none