Association of downregulation of toll-like receptor 3 (TLR3) expression with aggressive breast cancer (BC).

Abstract

11035 Background: Inflammation in the tumor microenvironment plays a key role in human breast cancer. We previously showed that a high proportion of alternatively-activated, tumor-associated macrophages (M2) are associated with increased microvessel density (MVD) and worse outcomes in BC. The anti-tumor effect of TLR3 is well recognized. To our knowledge, there are no studies evaluating TLR3 expression and characteristics of inflammation in primary breast tumors. Methods: 48 breast tumors were obtained from the University of Chicago Breast Cancer SPORE tissue bank under IRB approved protocols. Tissue microarrays were constructed and molecular subtypes assigned based on immunohistochemical (IHC) staining into: luminal A, luminal B, HER2-like, and basal-like. Macrophage density was determined using double staining with CD68/CD163. MVD was measured by IHC using anti-CD34. Staining quantification was done by a pathologist. To evaluate the association between M2 macrophages, TLR3 and MVD, Spearman's rho correlation coefficients were calculated. Survival comparison analysis was done using Wilcoxon statistic. Results: Of the tumors studied, 46% were LumA, 38% basal-like, 4% HER2-like, 2% LumB. We found a significant association between high MVD and high M2 content in tumors (p<0.000). Tumors with high MVD exhibited shorter survival (Wilcoxon statistic 4.845, p=0.028). Spearman’s rho nonparametric correlations showed low TLR3 expression correlated with higher MVD (p=0.014), advanced pathologic tumor stage (p=0.046) and a trend for nodal disease (p=0.069). There was no statistically significant association between TLR3 expression and number of M2 macrophages (p=0.21). Conclusions: Neovascularization is promoted by tumor-associated macrophages and in turn poorer prognosis in BC. Our results suggest that reduced TLR3 expression is associated with more aggressive breast cancer. Future studies are needed to elucidate a mechanism by which TLR3 is downregulated in highly angiogenic BC. Thus, activation of TLR3 with TLR3-ligands such as poly (A:U) can potentially be coupled with anti-angiogenic therapies in patients with BC exhibiting low TLR3 expression and high MVD to improve treatment outcomes.