Influence of hyaluronic acid binding on the actin cortex measured by optical forces.

Melanoma cells are often surrounded by hyaluronic acid (HA) rich environments, which are considered to promote tumor progression and metastasis. Induced effects in compound materials consisting of cells embedded in an extracellular matrix have been studied, however, alterations of the single cells have never been addressed. Here, we explicitly addressed single cell properties and measured HA-induced biomechanical changes via deformations induced solely by optical forces. With the optical stretcher setup, cells were deformed after culturing them in either the presence or absence of HA revealing the crucial interplay of HA with the CD44 receptor. To assess the role of CD44 in transducing effects of HA, we compared a CD44 expressing variant of the melanoma cell line RPM-MC to its natural CD44-negative counterpart. Our measurements revealed a significant stiffness change, which we attribute to changes of the actin cytoskeleton.