Fibronectin in the Tumor Microenvironment Activates a TLR4-dependent Inflammatory Response in Lung Cancer Cells

Abstract

The microenvironment of solid tumors plays an essential role in tumor progression. In lung cancer, the stromal cells produce a fibronectin rich extracellular matrix which is known to contribute to both tumor metastasis and drug resistance. Due to its conformational lability, fibronectin is considerably remodeled by the contractile forces of the fibrotic microenvironment within the tumor stroma. As a result, the secondary structure of fibronectin's Type III domains is disrupted and the molecule becomes highly stretched. The contribution/impact of these strained forms of fibronectin on tumor growth and metastasis is not known. In the current study we show that the partially unfolded first Type III domain of fibronectin, III-1c, activates a toll-receptor/NF-κB pathway leading to an increase in the expression of IL-8. Using a 3-D model of tumor-associated extracellular matrix, we demonstrate that lung cancer cells seeded onto this matrix activate a TLR4/NF-κB signaling pathway leading to a robust increase in the release of IL-8. Cytokine release by these cells is completely dependent on the presence of fibronectin in the extracellular matrix. These findings suggest that paracrine signaling between the tumor and the stromal myofibroblasts causes a remodeling of the matrix fibronectin into a strained conformation which supports the activation of a TLR4/NF-κB signaling pathway resulting in the upregulation of fibro-inflammatory cytokines.

Mechanobiological Principles Influence the Immune Response in Regeneration: Implications for Bone Healing

“…Whether these higher fibronectin levels contribute to the osteoporotic pathology via immunomodulatory mechanisms, has not yet been fully elucidated. However, lung cells and dermal fibroblasts have been shown to bind the stretched fibronectin conformation via TLR4, which led to increased IL-8 levels (Cho et al, 2020;Zheng et al, 2020). Since IL-8 also seems to play an important role in bone healing (Lin et al, 2019), mechanical manipulation of the fibronectin conformation may also be an attractive therapeutic target (Figure 5B).…”

“…In most situations, unphysiological mechanical stimuli or mechanical overstimulation resulted in the release of common pro-inflammatory mediators. Specific ECM components are actively involved in immune regulation, either by acting as DAMPs [LMW-HA (Jiang et al, 2005;Black et al, 2013), fibronectin (Cho et al, 2020), and biglycan (Schaefer et al, 2005)], or by stabilizing ECM-cell interactions [fibulin-5 (Nakasaki et al, 2015), and agrin (Haak et al, 2019)]. In all the tissues described, non-hematopoietic cells often respond to abnormal mechanical stimuli by secreting chemoattractants and cytokines that lure immune cells out from the vasculature and in most cases the secreted cytokines create a pro-inflammatory niche.…”

“…Moreover, LMW-HA has been shown to be sufficient for inducing epithelial to mesenchymal transition (EMT) of AEIIs, often associated with aberrant wound healing and fibrosis (Heise et al, 2011). Interestingly, stretched fibronectin conformation has been found to bind to TLR4 on lung cancer cells and increased IL-8 expression and release (Cho et al, 2020).…”

Downregulation of LINC00115 inhibits the proliferation and invasion of lung cancer cells in vitro and in vitro

“…Further molecular mechanism studies showed that knockdown of LINC00115 significantly inhibited the expression of the EMT-related proteins N-cadherin, vimentin, and fibronectin, and upregulated the expression of E-cadherin. In the tumor microenvironment, fibronectin activates the TLR4-dependent inflammatory response in lung cancer cells, thereby leading to the upregulation of fibroinflammatory cytokines by activating the TLR4/ (27). Therefore, LINC00115 may be involved in the regulation of the lung cancer microenvironment and the inflammatory response of tumors.…”

EGFR-Dependent Extracellular Matrix Protein Interactions Might Light a Candle in Cell Behavior of Non-Small Cell Lung Cancer

“…It is primarily synthesized by CAFs and polymerized into ECM fibrils that act as scaffolds for ECM binding molecules such as growth factors and cell surface receptors ( 63 ). FN is overexpressed in the stroma of NSCLC and can promote cancer cell adhesion, growth, differentiation, migration, invasion, survival, and resistance to chemotherapy ( 64 ). FN-dependent molecular pathways can control the tumor cell response to the stromal matrix and represent potential targets for managing chemo-resistant tumors ( 65 ).…”