The Measure of DAMPs and a role for S100A8 in recruiting suppressor cells in breast cancer lung metastasis.

To determine whether there was a relationship between damage associated molecular pattern molecule (DAMP) expression and recruitment of suppressor cells to sites of metastasis we measured relative expression of DAMPs, regulatory T cells (Tregs), and myeloid derived suppressor cells (MDSC) in mice at various stages of breast cancer progression using the 4T1 model. Although S100A8 was expressed at relatively low levels in the tumor cells, expression was 100-fold higher in the lung and liver which are common sites of metastasis for this tumor. Despite the relatively high level of S100A8 expression in the lungs of naïve mice, the level of expression increased further and was significantly elevated after only 7 days of tumor growth. The same pattern was observed for MDSC, and both S100A8 and MDSC expression peaked in the lungs of mice following 21 days of tumor growth. Characterization of MDSC from the lungs revealed expression of RAGE, and the cells were capable of migrating in a dose-dependent manner toward S100A8. In addition, the MDSC expressed low levels of MHC Class I, MHC Class II, CD80, and secreted TGF-ß. Taken together, these data suggest that expression of S100A8 in the lungs may facilitate recruitment of MDSC, which may in turn aid in establishing a metastatic niche capable of suppressing a localized immune response.

A computational approach to unraveling TLR signaling in murine mammary carcinoma.

We developed an agent-based model to simulate a signaling cascade which allowed us to focus on the behavior of each class of agents independently of the other classes except when they were in physical contact. A critical piece was the ratio of the populations of agents that interact with one another, not their absolute values. This ratio reflects the effects of the density of each agent in the biological cascade as well as their size and velocity. Although the system can be used for any signaling cascade in any cell type, to validate the system we modeled Toll-like receptor (TLR) signaling in two very different types of cells; tumor cells and white blood cells. The iterative process of using experimental data to improve a computational model, and using predictions from the model to design additional experiments strengthened our understanding of how TLR signaling differs between normal white blood cells and tumor cells. The model and experimental data showed that some of the differences between the tumor cells and normal white blood cells were related to NFκB and TAB3 levels, and also suggested that tumor cells lacked IRAKM-dependent feedback inhibition as a negative regulator of TLR signaling. Finally, we found that these different cell types had distinctly different responses when exposed to two signals indicating that a more biologically relevant model and experimental system should address activation of multiple interconnected signaling cascades, the complexity of which further reinforces the need for a combined computational and molecular approach.

A Multifaceted Role for Myd88-Dependent Signaling in Progression of Murine Mammary Carcinoma.

Previous data obtained in our laboratory suggested that there may be constitutive signaling through the myeloid differentiation primary response gene 88 (Myd88)-dependent signaling cascade in murine mammary carcinoma. Here, we extended these findings by showing that, in the absence of an added Toll-like receptor (TLR) agonist, the myddosome complex was preformed in 4T1 tumor cells, and that Myd88 influenced cytoplasmic extracellular signal-regulated kinase (Erk)1/Erk2 levels, nuclear levels of nuclear factor-kappaB (NFκB) and signal transducer and activator of transcription 5 (STAT5), tumor-derived chemokine (C-C motif) ligand 2 (CCL2) expression, and in vitro and in vivo tumor growth. In addition, RNA-sequencing revealed that Myd88-dependent signaling enhanced the expression of genes that could contribute to breast cancer progression and genes previously associated with poor outcome for patients with breast cancer, in addition to suppressing the expression of genes capable of inhibiting breast cancer progression. Yet, Myd88-dependent signaling in tumor cells also suppressed expression of genes that could contribute to tumor progression. Collectively, these data revealed a multifaceted role for Myd88-dependent signaling in murine mammary carcinoma.