Abstract 1333: Upregulation of chemokines including RANTES/CCL5 upon Toll-like receptor 3 activation in breast cancer: Association with leukocyte infiltration

Abstract

Abstract The association of leukocytes with the microenvironment of different tumors and their role in disease progression is well-documented. However, the mechanism of recruitment of leukocytes to the tumor microenvironment remains unclear. In particular, we have previously demonstrated the capability of tumor-associated dendritic cells to promote neovascularization. In this light, toll-like receptors (TLR) have recently been identified as potential players in different cancers such as malignant melanomas, thyroid cancer and pancreatic cancer. These are a family of pattern-recognition receptors that, when activated by a ligand, trigger signaling pathways involved chiefly in the inflammation process of the innate immune system. Here, we investigated the role of TLR-3 in the capability of the tumor cells to generate chemokines capable of attracting leukocytes to the tumor microenvironment. For this purpose we used the 4T1 model of breast cancer in BALB/c mouse. First, we were able to determine the expression of TLR-3 in these cells by PCR analysis. Then, 4T1 mouse breast cancer cells were treated with poly(I:C), a well-known ligand for TLR-3, and the supernatants were checked for the presence of different chemokines (RANTES, SDF-1α, MIP-3α, MIP-3β) by sandwich ELISA. These molecules were selected taking into account that their receptors are present in dendritic cells. Further, a reverse transcription quantitative PCR was performed to detect the RNA expression levels of these chemokines. In both cases, a significant increase in RANTES levels upon TLR-3 activation was observed. Further, a chemokine PCR array showed upregulation of 10 chemokines, RANTES among them, on 4T1 cells stimulated with poly(I:C). A subsequent protein array analysis of different mouse cytokines in poly(I:C)-treated 4T1 cells revealed also an increase in RANTES, IL-6 and MIP-2 and a decrease in the matrix metalloprotease inhibitor TIMP-1. Interestingly, IL-6 upregulation was further confirmed by ELISA. These results are supportive of our hypothesis that TLR-3 activation could lead to the release of chemokines that assist in leukocyte recruitment. Further in vivo studies are required to observe the effect of knocking down TLR-3 in cancer cells on the capability of the tumor to promote leukocyte infiltration. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1333.