The effects of biomimetic proteoglycans on interstitial flow-induced cancer invasion

Local microenvironments play a crucial role in cancer biology and the regulation of cellular behavior. A challenge that remains to be studied is the role of the extracellular matrix in the transition from normal physiology to a cancerous niche. The matrix of the basement membrane and interstitium is made up of fibrous proteins, glycoproteins, proteoglycans, and polysaccharides. Proteoglycans are one of the three most abundantly found molecules in the extracellular matrix. These proteoglycans interact with soluble factors such as chemokines, cytokines, growth factors, and other matrix macromolecules, thereby playing an important role in cell interactions with the matrix. Biomimetic proteoglycans that mimic natural proteoglycan structure were synthesized in the Drexel Biomaterials Laboratory and consisted of a biologically inert polyacrylic acid (PAA) core and natural chondroitin sulfate bristles. This novel macromolecule was used to determine the influence of matrix chondroitin sulfate proteoglycans found in tumor microenvironments on interstitial flow-induced invasion through an in vitro 3D invasion assay. Characterization of the in vitro environment was done to quantify changes in matrix permeability, as well as qualitatively assess structural and morphological changes of the collagen fiber network and melanoma cells. We proposed that the presence of these biomimetic chondroitin sulfate proteoglycans (with PAA core molecular weights of 10 and 250 kDa) would decrease the permeability of the matrix and lead to greater flow-induced invasion of melanoma cells due to growth factor binding to the chondroitin sulfate side chains, thereby promoting formation of a chemokine gradient. Lower concentrations of biomimetic proteoglycans increased matrix permeability and dramatically altered collagen fiber matrix structure; however, there was no effect on invasion of melanoma cells. High concentrations ([greater than or equal to]20mg/ml) of biomimetic proteoglycans had no effect on collagen matrix permeability, but the 250 kDa core proteoglycan increased flow-induced invasion compared to the 10 kDa core proteoglycan. The significant differences in matrix structure may be the cause of the increase in permeability when biomimetic proteoglycans were present in the matrices. The difference in flow-induced invasion between the two sizes of biomimetic proteoglycans led us to hypothesize that the size of the proteoglycan and the degree of chondroitin sulfate decoration impacts invasive characteristics of melanoma cells through growth factor binding. These studies have advanced the possibility of using these biomimetic proteoglycans to generate more defined in vitro matrix microenvironments. Moving forward, using biomimetic proteoglycans to better mimic the tumor microenvironment can help determine how a multitude of factors influence cellular behavior and disease progression.