M.Sc Thesis

M.Sc StudentSchvartzer Maayan
SubjectEvaluation of Intracellular Transport; Mechanics and
Dynamics of Breast Cancer Cells
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Daphne Weihs
Full Thesis textFull thesis text - English Version



The main cause of death from cancer is metastases formed at distant sites. One of the key steps in metastases formation is entrance and exit of tumor cells into blood vessels. The ability of tumor cells to penetrate blood vessels walls is highly related to its intracellular structure, mechanics and dynamics. Understanding the mechanical aspects of the penetration process may lead to developments in diagnosis and treatment of cancer.

In this research we assessed the role of cytoskeletal elements in intracellular transport in tumor cells of varying metastatic potential. Previously collected data of spontaneously internalized nano-particles motion in single, living cells was analyzed. To reveal cell elements involved in transport we have disrupted the dynamics of actin, microtubules, molecular motors, and ATP-dependent processes. Following disruption, the transport of particles changed depending on both treatment and cell type. Using a variety of trajectory and displacement analysis procedures we identify cell-specific structural and dynamic changes. Specifically, we utilize statistical-analysis procedures including the time-dependent mean-square displacement (MSD), directional persistence, quantification of deviation from Gaussianity and presence of driven transport.

We observed differences relating to cell type that provide insight into the microenvironment structure and main driving mechanisms inside each cell type. Intracellular transport in highly metastatic tumor cells is suggested to origin from dynamicity of microtubule network as well as from direct and indirect interactions between particles and microtubules associated molecular motors. In the low MP cells we suggest that the origin is direct interactions between particles and microtubules associated molecular motors, moving along the filaments as well as indirect interactions were molecular motors push particles in gap of the microtubules network. The benign cells, however, reveal involvement of the actomyosin network, where we associate particles motion to network contractions.

During tumor cells penetration, cells are required to undergo morphological changes and to apply force; both call for intracellular mechanical involvement. We have generated a model-vasculature system simulating the extravasation process. The set-up consists of soft substrate modeling the basal membrane with endothelial cells growing in a monolayer on it. Tumor cells can be added on top of the monolayer to imitate tumor cells in the blood stream. This model is designed to enable measurements of traction forces and can be used for further exploration of the extravasation process as well as the role of the CSK elements in the process.