Three-Dimensional In Vitro Hydro- and Cryogel-Based Cell-Culture Models for the Study of Breast-Cancer Metastasis to Bone.

Laura Bray,Petra Welzel,Jana Sievers,Carsten Werner,Constanze Secker,Marcus Binner,Berline Murekatete

doi:10.3390/cancers10090292

Abstract

Bone is the most common site for breast-cancer invasion and metastasis, and it causes severe morbidity and mortality. A greater understanding of the mechanisms leading to bone-specific metastasis could improve therapeutic strategies and thus improve patient survival. While three-dimensional in vitro culture models provide valuable tools to investigate distinct heterocellular and environmental interactions, sophisticated organ-specific metastasis models are lacking. Previous models used to investigate breast-to-bone metastasis have relied on 2.5D or singular-scaffold methods, constraining the in situ mimicry of in vitro models. Glycosaminoglycan-based gels have demonstrated outstanding potential for tumor-engineering applications. Here, we developed advanced biphasic in vitro microenvironments that mimic breast-tumor tissue (MCF-7 and MDA-MB-231 in a hydrogel) spatially separated with a mineralized bone construct (human primary osteoblasts in a cryogel). These models allow distinct advantages over former models due to the ability to observe and manipulate cellular migration towards a bone construct. The gels allow for the binding of adhesion-mediating peptides and controlled release of signaling molecules. Moreover, mechanical and architectural properties can be tuned to manipulate cell function. These results demonstrate the utility of these biomimetic microenvironment models to investigate heterotypic cell–cell and cell–matrix communications in cancer migration to bone.

Highlights

The development of breast cancer is a multistep process involving epigenetic and genetic cellular changes, irregular interactions within the microenvironment, as well as the deregulation of proliferation, survival, differentiation, and migration [1]
The response of MCF-7 and MDA-MB-231 cells to in situ hydrogels with varying stiffness was evaluated for the two types of starPEG–heparin networks
The hydrogels formed from HM6 and PEG–matrix metalloproteinase (MMP)–GFOGER, which includes the collagen I-derived

Summary

Introduction

The development of breast cancer is a multistep process involving epigenetic and genetic cellular changes, irregular interactions within the microenvironment, as well as the deregulation of proliferation, survival, differentiation, and migration [1]. The mineralized bone matrix contains numerous growth factors, calcium ions, cell-adhesion molecules, cytokines, and chemokines, which are released during physiological bone remodeling This makes the bone an attractive site for breast-cancer metastasis. Direct and indirect bidirectional interactions play a major role in attracting the breast-cancer cells to bone sites and in conditioning the cells to adapt to the bone microenvironment In this manner, numerous chemoattractants, such as transforming growth factor β (TGF-β), vascular endothelial growth factor (VEGF), RANK-ligand, and C-X-C chemokine receptor type 4 (CXCR4) have been associated with the homing of circulating tumor cells to bone and providing a fertile ‘soil’ for these cells in secondary sites [2,3,4]. It is crucial to design relevant cell-culture systems that mimic key features of the in vivo situation in order to unravel the complex interactions between breast-cancer cells and the bone/bone environment

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