Abstract: Tissue Engineering a Biomimetic Platform for the Study of Breast Cancer Metastasis

Abstract

INTRODUCTION: Current tissue engineering efforts are aimed towards recreating tissues to repair those that have been lost or damaged – such as the development of in vitro 3D biomimetic platforms to recapitulate in vivo conditions. Specifically, in breast cancer research, surrounding ECM in vivo has a profound effect on malignant invasion of cancer cells and it has also been clinically observed that breast tumor tissue is denser than normal tissue. However, traditional cell culture systems employed to study tumor cell behavior are limited by the significantly different cell phenotype induced under 2D culture conditions. We have created intact functional vascularized channels in biocompatible collagen constructs with proper in vivovascular physiology and alter collagen stiffness to study factors that influence tumor progression, and vascular remodeling. METHODS: Type-I collagen was enzymatically stiffened with ribose solution to create a stock collagen solution. Pluronic F127 fibers, were sacrificed in the collagen, creating a central looped microchannel with a tumor spheroid embedded in the collagen bulk. A cell suspension of human aortic smooth muscle cells (HASMC) and human umbilical vein endothelial cells (HUVEC) was seeded into the microchannel. Mechanical compression testing was completed by ElectroForce-3200 Series III. RESULTS: Confocal reflectance values showed no statistical changes of fiber length or pore area in enzymatically altered collagen, suggesting changing the stiffness would not affect bulk cell migration. Biomechanical testing of stiffened collagen revealed that 200mM of ribose dosed collagen increased the stiffness of the hydrogels to appropriate “tumor” stiffness (4kPa).1 After all time points, non-cancer containing constructs contained microchannels consisting of an anatomically correct robust vascular channel lining with increasing proliferation. However, in cancer constructs, degradation of the vascular lining and aberrantly organized HUVEC and HASMC were present. IHC and MPM imaging revealed the presence of breast cancer cells invading the endoluminal lining. Permeability studies using TexasRed Dextran revealed an increase of neovessel permeability correlating with increasing stiffness, suggesting metastatic potential of cancer also increased. CONCLUSION: This model overcomes the limitations of previous 2D and 3D culture models and may be used to investigate any type of tumor cell and can lead to the further understanding of breast cancer signaling pathways, as well as potentially provide an effective platform for high throughput analysis of patient specific breast cancer cells. Reference Citations: 1. Plewes, D., et al. Elastic moduli of normal and pathological human breast tissues: an inversion-technique-based investigation of 169 samples. Physics in Medicine and Biology. 52 (2007). 1565–76. doi:10.1088/0031-9155/52/6/002.