Abstract LB277: β1-integrin and CD44 may both be required in modulating traction force transmission in collagen-hyaluronic acid hydrogels
Authors: Cheung Brian C.H. , Chen Xingyu , Davis Hannah J. , Toth Joshua , Shenoy Vivek B. , Segall Jeffrey E. , Wu Mingming 
Published: April 2023

Abstract
Mechanics of the tumor microenvironment (TME) has long been recognized as a key aspect of the tumor invasion cascade. The TME contains a mesh of fibrous proteins such as collagen fibers, elastin, and fibronectin, and glycosaminoglycans (GAGs) that fill the interstitial space. As tumor cells migrate and invade throughout the extracellular matrix (ECM), they can communicate with each other mechanically by utilizing biophysical cues such as contractile forces and fiber alignment. For example, leader cells emerging from tumor spheroids can align ECM fibers to guide follower cells. In breast cancer, hyaluronic acid (HA), one of the GAGs found in the tumor stroma, is often overexpressed in pathological tissues, and stromal HA has been correlated with poor survival. Mechanically, while cells can guide their way by aligning matrix fibers through traction force generation, it is reported that HA may impact force transmission by altering matrix microstructure in the TME. It is therefore crucial to understand how HA impacts the interaction between tumor cells and the TME.
In this study, we first investigated the bulk mechanical properties and micro-architecture of collagen-HA hydrogels (Col-HA). Our rheology measurements show that HA softens the collagen network while increasing the onset strain for strain-stiffening. Structurally, together with smaller pore sizes and thinner fibers as revealed by reflectance confocal microscopy, fiber alignment in Col-HA becomes less favorable. We then questioned how MDA-MB-231 cells generate traction forces in Col-HA using 3-dimensional traction force microscopy (3D TFM). Along with less fiber alignment around cells in Col-HA, we found that force transmission distance is reduced in Col-HA, as revealed by a shorter propagation of matrix deformation. In Col-HA, while the matrix resists alignment as the fiber network becomes more isotropic, we hypothesized that force transmission is also adhesion-dependent. Specifically, we investigated the role of β1-integrin and CD44, the key adhesion molecules to collagen fiber and HA respectively, in traction force generation. Immunofluorescence staining shows a significant increase in colocalization between actin and the two adhesion molecules in Col-HA, compared to pure collagen matrix. Interestingly, CD44 is colocalized with β1-integrin in Col-HA, but not in pure collagen. While it is widely recognized that cells transmit forces via β1-integrin in collagen matrices, we suspect that, in parallel with β1-integrin, CD44 may also be involved in traction force transmission because of its linkage between actin and HA. To examine how β1-integrin and CD44 contribute to force transmission in Col-HA, we neutralized them with antibodies and performed 3D TFM experiments. Preliminary data shows that matrix deformation decreases significantly when either β1-integrin and CD44 is blocked. In conclusion, we have demonstrated that HA reduces the mechanical communication between breast tumor cells by reducing force transmission distance. And in addition to β1-integrin, CD44 may also be required in traction force transmission in Col-HA. In the future, we will explore the differential role of β1-integrin and CD44 on tumor invasion in the presence of HA.
Citation Format: Brian C.H. Cheung, Xingyu Chen, Hannah J. Davis, Joshua Toth, Vivek B. Shenoy, Jeffrey E. Segall, Mingming Wu. β1-integrin and CD44 may both be required in modulating traction force transmission in collagen-hyaluronic acid hydrogels [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB277.