Human breast cancer invasion and aggression correlates with ECM stiffening and immune cell infiltration

Abstract

Tumors are stiff and data suggest that the extracellular matrix stiffening that correlates with experimental mammary malignancy drives tumor invasion and metastasis. Nevertheless, the relationship between tissue and extracellular matrix stiffness and human breast cancer progression and aggression remains unclear. We undertook a biophysical and biochemical assessment of stromal-epithelial interactions in noninvasive, invasive and normal adjacent human breast tissue and in breast cancers of increasingly aggressive subtype. Our analysis revealed that human breast cancer transformation is accompanied by an incremental increase in collagen deposition and a progressive linearization and thickening of interstitial collagen. The linearization of collagen was visualized as an overall increase in tissue birefringence and was most striking at the invasive front of the tumor where the stiffness of the stroma and cellular mechanosignaling were the highest. Amongst breast cancer subtypes we found that the stroma at the invasive region of the more aggressive Basal-like and Her2 tumor subtypes was the most heterogeneous and the stiffest when compared to the less aggressive Luminal A and B subtypes. Intriguingly, we quantified the greatest number of infiltrating macrophages and the highest level of TGF beta signaling within the cells at the invasive front. We also established that stroma stiffness and the level of cellular TGF beta signaling positively correlated with each other and with the number of infiltrating tumor-activated, macrophages, which was highest in the more aggressive tumor subtypes. These findings indicate that human breast cancer progression and aggression, collagen linearization and stromal stiffening are linked and implicate tissue inflammation and TGF beta.

Dynamic microtubules regulate cellular contractility during T-cell activation

“…Interestingly, the lymph node itself is also mechanically active, because Rho inactivation in fibroblastic reticular cells enables lymph node expansion during inflammation (77). Understanding the mechanobiology of T-cell activation is important for immunotherapy design against cancer because the tumor microenvironment is known to undergo significant extracellular matrix remodeling and stiffness changes during disease progression (78). The molecular mechanisms linking cytoskeletal forces with TCR-mediated signaling initiation will be the subject of future investigation.…”

Association between lysyl oxidase and fibrotic focus in relation with inflammation in breast cancer

“…Also, it has been implicated that LOX-mediated collagen cross-linking is critical in ECM stiffness (2,5). Acerbi et al (4) have shown that both ECM stiffness and cellular TGF-β signaling correlated positively with immune cell infiltration in human breast cancer. Leight et al have demonstrated that increased matrix stiffness regulates TGF-β signaling, a potent inducer of EMT in tumor cells (24).…”

“…Recently, it has been described that inflammation plays an important role in fibrosis as an inducer of epithelial-mesenchymal transition (EMT) in cancer (19). Also, it has been suggested that invasion and aggression of breast cancer correlates with ECM stiffening and immune cell infiltration (4).…”

“…The ECM provides structural and mechanical support to cells and tissues (1). During carcinogenesis, the composition and the overall content of the ECM change and the ECM is progressively stiffened (3,4). ECM stiffness has been implicated to promote tumor progression (5) and is partially associated with lysyl oxidase (LOX)-mediated collagen cross-linking (2,5).…”

“…ECM stiffness is caused by collagen deposition and linearization and bundling of interstitial collagen (4) and LOX has a crucial role in stiffness-associated tumor progression (5,10,14). ECM remodeling including stiffness contributes to fibrotic changes in tumor (15), which is defined as fibrotic focus (FF).…”