Investigation of cancer cell adhesion and migration from a mechanobiological perspective

Understanding the role of mechanical forces in modulating the interactions of cancer cells with their microenvironment during the process of cancer metastasis is key to designing successful therapeutics. Shear stress in the bloodstream affects the lifetime of receptor-ligand bonds involved in the adhesion of circulating tumor cells to vessel walls. Cancerous cells themselves exert traction forces using their cytoskeletal machinery to navigate through the complex tissues in vivo. In this work, we have investigated the forces involved in cancer cell adhesion and migration.;CD44v is the major functional P-selectin ligand and fibrin receptor on metastatic colon carcinoma cells. I used single-molecule force spectroscopy to provide a molecular interpretation for the CD44v-mediated firm adhesion to immobilized fibrin at low shear versus CD44v-mediated transient rolling at elevated shear stresses and low P-selectin site densities. CD44v-P-selectin binding has a longer unstressed equilibrium lifetime and a higher tensile strength relative to CD44v-fibrin. Increasing the receptor-ligand contact duration does not affect the micromechanical properties of CD44v-P-selectin bond, but it increases the tensile strength of CD44v-fibrin bond.;I further delineated the biophysical and molecular requirements of CD44-HA and CD44s-fibrin(ogen) interactions at the single-molecule level. Although the HA binding motif on CD44, that is common to all the isoforms, is the primary binding site, O-, N-linked glycans and sulfation contribute to the tensile strength of the CD44-HA bond. Unlike CD44-HA binding, the molecular interaction between CD44s and fibrin(ogen) is predominantly mediated by the chondroitin sulfate and dermatan sulfate on CD44.;Finally, I fabricated a microfluidic migration device to measure the traction forces exerted by cancer cells moving towards a chemoattractant through confined microchannels. My results highlight the reduced role of actomyosin contractility in confined migration.;Collectively, force spectroscopy in conjunction with biochemical interventions enable us to identify the biophysical parameters and molecular constituents of CD44-counter receptor interactions and predict the shear-dependent cell-substrate adhesive interactions observed in vitro and in vivo. Moreover, microfluidics offers exciting opportunities to investigate nanonewton scale traction forces exerted by migrating cancer cells. The studies presented here enable us to gain a comprehensive and quantitative understanding of the intricacies of cancer metastasis.