Hydrodynamic Behaviors Of A Moving Melanoma Adhering To The Vascular Wall In A Blood Flow

Adhesion of tumor cells to the endothelium monolayer is a very critical step in extravasation of the circulation-mediated tumor metastasis in the human body. The previous studies indicated that polymorphonuclear neutrophils(PMNs) played an important role in the tumor cell metastasis. This thesis focuses on the movement of a moving melanoma around a PMN attached to the endothelium substrate of a blood vessel in the near-wall region. The current investigation demonstrates that the local flow environment, especially the local shear rate, influences greatly the melanoma-PMN hydrodynamic interaction. This will help us better understand the mechanism behind the metastasis of cancers and further improve the method of the control of cancers.The Fluent commercial code is adopted in the present research as a simulating tool in order to perform the following work.Firstly, the local shear rates around a melanoma and a PMN are numerically investigated at 5 different fixed near-wall positions. The simulation shows that the numerical results agree well with the experimental data, which demonstrates the validity of the numerical calculation.Secondly, in order to explore a melanoma-PMN hydrodynamically adhesive process without consideration for the effects of biochemical bonds on their cytomembranes, the situation of a moving melanoma around a nearby PMN in the near-wall region is discussed. Two different tumor trajectories of detachment and adhesion patterns are found in the dynamical simulation of the tumor cell, one exhibits that the tumor cell rolls approaching a PMN cell, then runs on its symmetric surface and keeps in touch until rolls away, and the other shows that when the tumor cell gradually rolls over the top of the PMN, it would detach from the surface of the PMN up to blood flows.Finally, several trajectories of a melanoma around a nearby PMN are calculated at the different initial positions. We shall show some complicated dynamical behaviors of the tumor cell in its subsequent evolution and provide the shear rates of the flow field at several corresponding positions. The authors propose an explanation based on the hydrodynamic viewpoint that the shear rate of a blood flow has a significant influence on tethering of a melanoma on a PMN.