טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentShachaf Yonatan
SubjectBiosynthetic Materials to Regulate Metastasizing Neoplastic
Cell Migration
DepartmentDepartment of Biomedical Engineering
Supervisor Professor Dror Seliktar
Full Thesis textFull thesis text - English Version


Abstract

Cell migration is one of the fundamental elements of many physiological and path-physiological processes in the body. Neoplastic or tumor cell migration is particularly important to understand in this regard, in order to develop therapeutic strategies that can limit tumor invasion or to design diagnostic tools that help identify tumor potency. In the body, the migratory of neoplastic cells is confined by the extracellular matrix (ECM), which is a complex 3D terrain of proteins and polysaccharides.  Therefore, the ECM plays a central role in the ability of metastasizing cells to move and remodel their microenvironment as part of the tumor invasion process. At the individual cell level, neoplastic cells migrate and invade the ECM using either an amoeboid or a mesenchymal migration mechanism. In order to manipulate these cells, customized cell-specific ECM biomaterial analogs can be engineered with a set of properties that precisely control these processes (e.g. modulus, biological motifs and architecture). Such an approach offers the ability to selectively enable or block the invasion of one specific cell type from a tissue that contains several types of migratory cells. This approach can readily be applied for developing in vitro drug screening diagnostic technique for evaluating chemosensitivity of metastasizing tumors.

Towards this goal we developed a biomimetic material that can harness the bioactive properties of serum proteins as fibrinogen, but still retain control over physical features of the material. We conjugated proteins to Pluronics or Tetronics copolymers to create a biosynthetic precursor with tunable physicochemical properties. Pluronics and Tetronics are synthetic block co-polymer that exhibit reverse thermal gelation properties. In their protein conjugated form, a hydrogel matrix is formed from the biocompatible protein-polymer adducts by free-radical polymerization using light activation. In addition, these materials display a reversible temperature-induced physical sol-gel transition.

We employ these biomaterials as a platform to study how to control neoplastic and non-malignant cell migration using defined physical, structural and biological features of the hydrogel 3D microenvironment. In this regards, we found that neoplastic (HeLa) cells are more adjustable to high modulus environments then non-malignant cells (fibroblasts). By utilizing this property we successfully induced selective cell outgrowth from a heterogonous cell cluster that simulated malignant tissue containing HeLa cells and fibroblasts. Furthermore, we found that cell adhesion motifs are essential components in the biomaterial, due to the need of the neoplastic cell to generate efficient traction forces that required for invading constrained spaces.