Abstract 1096: Murine mammary carcinoma produce more CCL2 in response to TLR agonist treatment than dendritic cells because of differences in NF-kB levels
Authors: Phuong Tiffany , Jones Carli B. , Kurt Robert A. , Liew Chun Wai 
Published: August 2015

Previously we reported that murine mammary carcinoma and dendritic cells elicit distinct responses to Toll-like receptor (TLR) agonists. Here we used a combination of computational biology and molecular analysis to identify the reason for the distinct responses. For this purpose we created a Netlogo model of the TLR4-Myd88 signaling pathway from TLR4 through nuclear translocation of NF-kB culminating in CCL2 transcription. Assessing CCL2 allowed us to validate our model by comparing how much CCL2 was generated by the model versus how much CCL2 was produced in our lab experiments. CCL2 was also of interest because previous studies have shown that CCL2 expression correlates with breast cancer progression. The 4T1 murine mammary carcinoma was used for these studies because it represents a model for stage IV breast cancer and also produces CCL2. Bone marrow derived CD11c+ dendritic cells (DC), which elicit a prototypical TLR agonist response, were used as a control. The model was developed by incorporating qRT-PCR data of the relative mRNA concentrations from each cell type. The experimental values were then used as the starting concentration of proteins in the model. The model of the TLR4-Myd88 signaling cascade allowed us to make predictions by running computational experiments that generate CCL2 expression data over a set amount of time. For instance, the model could be used to predict what happens in response to a TLR agonist if any of the TLR signaling proteins are up- or down-regulated. So far, the model predicted that the tumor cells would produce significantly more CCL2 than DC, results that were validated with experimental data. These results were surprising because most of the TLR signaling proteins were expressed at greater levels by the DC. Since only Tab3 and NF-kB were expressed at greater levels by the tumor cells we used the model to address whether the increased amount of NF-kB in the tumor cells was responsible for the greater level of CCL2 production by the tumor cells. The model showed that when the level of NF-kB in the tumor cells was reduced to the level found in the DC the tumor cells produced lower levels of CCL2. These data suggest that the level of NF-kB in the tumor cells was responsible for the greater production of CCL2 by the tumor cells relative to the DC. Thus, our computational model successfully predicted the experimental data and revealed that NF-kB may be a critical protein responsible for tumor-derived CCL2 expression. Collectively, a more thorough understanding of the differences in TLR signaling between the tumor cells and DC may reveal how targeting the TLR4 signaling cascade can be used to slow tumor progression.

Citation Format: Tiffany Phuong, Carli B. Jones, Robert A. Kurt, Chun Wai Liew. Murine mammary carcinoma produce more CCL2 in response to TLR agonist treatment than dendritic cells because of differences in NF-kB levels. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1096. doi:10.1158/1538-7445.AM2015-1096