Effects of Hydrodynamic Factors on Tumor Cell Arrest and Adhesion in the Microcirculation

Cuny City College, New York NY

Investigators

Abstract

CBET-0754158 Fu It is widely known that circulating tumor cells arrest in the microvasculature, but this arrest is not random. For example, breast cancer cells preferentially arrest in the small blood vessels of lung, liver, and bone. The underlying mechanisms responsible for this preferential arrest of breast cancer cells in distant organs are not well understood. Although both biochemical and mechanical factors are found to play a role in tumor cell arrest and adhesion in the microvasculature, the quantitative understanding of their contribution is poor. The long-term goal of our research is to elucidate the relationships between microcirculation-induced mechanical factors, microvascular permeability (vascular integrity), cell adhesion molecules, and tumor metastasis in intact microvessels. The objective of this project is to investigate the relationships between localized hydrodynamic factors in curved/stretched microvessels, VEGF (vascular endothelial growth factor)-induced microvascular hyperpermeability, and tumor cell arrest and adhesion in intact microvessels. On the basis of the preliminary studies, a newly developed in vivo single vessel perfusion/bending method, which can create non-uniformly distributed shear rates/stresses along the vessel wall, will be used to test two hypotheses: 1) Tumor cells prefer to arrest at the locations of the higher shear rates and shear rate gradients in the microvasculature. The higher shear rates/shear rate gradients activate the endothelial cells and the tumor cells to increase the binding of tumor cells to the vessel wall and to increase the accumulation of tumor cells; 2) Tumor cells prefer to arrest in the microvessel with increased permeability. The increased tumor cell adhesion to the microvessel wall with increased permeability is partially due to the radial pressure gradient that drives the cells towards the wall. A series of in vivo experiments will be performed on individually perfused microvessels in rat mesentery. Quantitative fluorescence video and confocal microscopy will be used to measure the adhesion rates of fluorescently dyed tumor cells in straight and curved/stretched microvessels under various flow and permeability conditions. Numerical simulation will be employed to quantify the profiles of shear rates and stresses, pressures, velocities and vorticities in the microvessel for each experimental condition. Specific aims are: 1) to measure the adhesion rates of normal, non-malignant (MCF-10A), and malignant (MDA-MB-435) breast epithelial cells in the straight microvessels under known bulk flow rates and a) under conditions of normal and increased permeability by VEGF; b) after pretreatment with the blocking antibodies to endothelial cell adhesion molecules, and c) after pretreatment with the blocking antibodies to tumor cell adhesion molecules; 2) to measure the adhesion rates of normal, MCF-10A, and MDA-MB-435 breast epithelial cells in the curved/stretched microvessels under known bulk flow rates and under the same conditions as in Aim 1; 3) to quantify the shear rate, shear stress, normal stress (pressure), velocity and vorticity profiles by numerical simulation in the straight and curved/stretched microvessels under known bulk flow rates and under conditions of normal and increased permeability by VEGF for two cases: a) when there are no tumor cells in the microvessel, and b) when there are tumor cells attached to the wall. This project provides a direct tool in the quantitative assessment of the role of hydrodynamic factors and adhesion molecules of tumor and endothelial cells in tumor metastasis under normal and inflammatory conditions, and hence helps define a new class of targets for therapeutic drug design for cancer. It is hoped that inhibitory reagents that prevent cancer cell arrest and adhesion in the microcirculation and reagents that enhance the microvessel wall integrity may be used in combination with traditional therapies to combat this malignant disease more effectively. Meanwhile, this project will provide an opportunity to train both graduate and undergraduate students in a new promising field, engineering approach to cancer therapy, as well as to broaden and diversify the research areas of the City College of New York, a minority serving institution.