Abstract 5585: Generation of novel cell lines for analyzing the role of TLR4 in breast cancer

Abstract

Abstract Background: Toll like receptor 4 (TLR4) is a transmembrane receptor expressed in macrophages that plays a major role in pathogen recognition and activation of innate immunity. TLR4 signaling has been linked to tumorigenesis and promotion of metastasis in ovarian, lung, prostate and head-neck cancers through up-regulation of the expression of inflammatory cytokines (e.g., IL-6, IL-8 and TNF-alpha). These factors increase cancer cell survival and resistance to chemotherapy through up-regulation of anti-apoptotic and down-regulation of apoptotic proteins, respectively. The goal of this study was to generate new isogenic cell lines that would allow analysis of the TLR4 role in paclitaxel resistance in breast cancer. To this end, we used TLR4-positive and negative lines (MDA-MB-231 and HCC1806, respectively) to generate stable TLR4 knockdown and over-expressing line derivatives. Methods: To generate a TLR4 knockdown line, MDA-MB-231 cells were transfected with pisiRNA-TLR4 plasmid and selected with zeocin (50μg/ml). To generate a TLR4 over-expressing line, HCC1806 cells were transfected with pKT2-TLR4-PURO plasmid and selected with puromycin (1μg/ml). Ten to 20 monoclonal colonies were selected from each line and characterized for TLR4 expression and TLR4-dependent cell activities by qRT-PCR and western blot. Results: TLR4 mRNA expression was reduced by >90% as compared with parental line in five out of 8 MDA-MB-231TLR4− clones examined. One clone had 60% reduction and two clones had no effect on TLR4 mRNA determined by qRT-PCR. TLR4 mRNA was up-regulated 1,000-12,000 fold in five (out of 11) clones derived from HCC1806 line. Two clones overexpressed TLR4 mRNA by 300-500 fold and four clones had increased TLR4 expression by 1-6 fold. All selected clones were analyzed for TLR4 functional signaling by exposure to LPS (1μg/ml), which was reduced by 50-70% in MDA-MB-231TLR4− clones and increased by 15-25 folds in HCC1806TLR4+ sub-lines, as compared with cells transfected with empty vectors. Conclusions: These data show that we successfully created sub-lines of MDA-MB-231 with stable knockdown of TLR4 and sub-lines of breast carcinoma HCC1806 line with stable over-expression of TLR4. Ectopically expressed human TLR4 as well as TLR4 downregulating sequence had significant functional effects on the TLR4 signaling as demonstrated by increase and decrease of LPS-activated targets (IL-6, IL-8 and TNF-alpha) in MDA-MB-231TLR4− and HCC1806TLR4+ sub-lines, respectively. These new sub-lines will serve as excellent tools for analyzing the role of the TLR4 pathway signaling in breast cancer progression, metastasis and resistance to therapy. * These authors contributed equally in this work. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5585. doi:10.1158/1538-7445.AM2011-5585