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- Genre: Masters Thesis
Description
Breast cancer cell invasion is a highly orchestrated process driven by a myriad of complex microenvironmental stimuli. These complexities make it difficult to isolate and assess the effects of specific parameters including matrix stiffness and tumor architecture on disease progression. In this regard, morphologically accurate tumor models are becoming instrumental to perform fundamental studies on cancer cell invasion within well-controlled conditions. In this study, the use of photocrosslinkable hydrogels and a novel, two-step photolithography technique was explored to microengineer a 3D breast tumor model. The microfabrication process presented herein enabled precise localization of the cells and creation of high stiffness constructs adjacent to a low stiffness matrix. To validate the model, breast cancer cell lines (MDA-MB-231, MCF7) and normal mammary epithelial cells (MCF10A) were embedded separately within the tumor model and cellular proliferation, migration and cytoskeletal organization were assessed. Proliferation of metastatic MDA-MB-231 cells was significantly higher than tumorigenic MCF7 and normal mammary MCF10A cells. MDA-MB-231 exhibited highly migratory behavior and invaded the surrounding matrix, whereas MCF7 or MCF10A cells formed clusters that were confined within the micropatterned circular features. F-actin staining revealed unique 3D protrusions in MDA-MB-231 cells as they migrated throughout the surrounding matrix. Alternatively, there were abundance of 3D clusters formed by MCF7 and MCF10A cells. The results revealed that gelatin methacrylate (GelMA) hydrogel, integrated with the two-step photolithography technique, has great promise in creating 3D tumor models with well-defined features and tunable stiffness for detailed studies on cancer cell invasion and drug responsiveness.
ContributorsSam, Feba Susan (Author) / Nikkhah, Mehdi (Thesis advisor) / Ros, Robert (Committee member) / Smith, Barbara (Committee member) / Arizona State University (Publisher)
Created2015
Description
Adsorption of fibrinogen on various surfaces, including biomaterials, dramatically reduces the adhesion of platelets and leukocytes. The mechanism by which fibrinogen renders surfaces non-adhesive is its surface-induced self-assembly leading to the formation of a nanoscale multilayer matrix. Under the applied tensile force exerted by cellular integrins, the fibrinogen matrix extends as a result of the separation of layers which prevents the transduction of strong mechanical forces, resulting in weak intracellular signaling and feeble cell adhesion. Furthermore, upon detachment of adherent cells, a weak association between fibrinogen molecules in the superficial layers of the matrix allows integrins to pull fibrinogen molecules out of the matrix. Whether the latter mechanism contributes to the anti-adhesive mechanism under the flow is unclear. In the present study, using several experimental flow systems, it has been demonstrated that various blood cells as well as model HEK293 cells expressing the fibrinogen receptors, were able to remove fibrinogen molecules from the matrix in a time- and cell concentration-dependent manner. In contrast, insignificant fibrinogen dissociation occurred in a cell-free buffer, and crosslinking fibrinogen matrix significantly reduced cell-mediated dissociation of adsorbed fibrinogen. Surprisingly, cellular integrins contributed minimally to fibrinogen dissociation since function-blocking anti-integrin antibodies did not significantly inhibit this process. In addition, erythrocytes that are not known to express functional fibrinogen receptors and naked liposomes caused fibrinogen dissociation, suggesting that the removal of fibrinogen from the matrix may be caused by nonspecific low-affinity interactions of cells with the fibrinogen matrix. These results indicate that the peeling effect exerted by flowing cells upon their contact with the fibrinogen matrix is involved in the anti-adhesive mechanism.
ContributorsMursalimov, Aibek (Author) / Ugarova, Tatiana (Thesis advisor) / Chandler, Douglas (Committee member) / Podolnikova, Nataly (Committee member) / Ros, Robert (Committee member) / Arizona State University (Publisher)
Created2022