A multi-cellular 3D model of human breast tissue to replace rodent xenograft models in breast cancer research.

Lead Research Organisation: University of Nottingham
Department Name: School of Medicine

Abstract

The cells that make up the tissues of your body are surrounded by a matrix of proteins and sugars. Cells interact with this matrix environment helping organs fulfil their function reacting to the elasticity and stiffness of the matrix and secreting messenger molecules into the matrix leaving specific information for other cells. This complex communication is crucial during development of an embryo driving the segmentation of the body into organs and to divide organs into functional regions. The matrix also plays an important role in disease progression where cells digest proteins or sugars within the matrix to release cryptic fragments that can instruct cells to multiply or to migrate, both features that are exaggerated in the progression to cancer.

Scientists have specialised techniques that can interpret messages within cells, these are often carried out in human cells grown on plastic (2D) which would not include matrix interactions. To understand 3D matrix-driven signalling they often rely on animal-derived artificial matrices that can be hard to work with due to high variability or use animal models including the growth of human cells transplanted as a xenograft into a mouse. Although these 3D assays are an improvement from 2D culture neither fully reproduce the complex human tissue matrix. There is a need to improve the 3D growth of cells within the laboratory and reduce the need for animal models that do not represent human tissue. To this end we have developed a fully synthetic, highly reproducible gel that can be decorated with proteins and sugars to mimic the matrix of human tissues. Cancer cells, along with other cells types found in native tissues, can then be encapsulated in the gels and easily grown in the lab.

The development of our bespoke human matrix will provide scientists with cheap, functional and robust test environments where cancer cell behaviour can be studied in a human body mimick. This allows researchers to test theories of how cancers develop, discover new targets for intervention and additionally will provide more realistic test environments for screening therapeutics. To test our bespoke gel environments we are using breast cancer as a model system, which can we investigated in its normal, pre-invasive and invasive cancer forms. We will characterise the differences in matrix between dense and non-dense breast tissue (normal and cancer) as evidence shows that dense breast tissue is a major risk factor for breast cancer. We will then use this information to decorate gels with specific proteins and sugars to mimic these distinct matrix environments, by encapsulating cancer cells and pre-cancerous cells in the gels (along with other cell types typical of the tissue) we hope to better understand why this is and what role is played by specific proteins and sugars in the matrix. This project brings together an interdisciplinary team of cancer biologists, materials scientists and clinicians to develop a new solution that we hope will have impact for the study multiple cancer types once proven as a robust model for breast cancer we anticipate significantly reducing the numbers of animals used in xenograft studies across the world.

Technical Summary

We aim to reduce the number of rodent models investigating the biology of the breast by developing a superior in vitro matrix incorporating bespoke human breast extracellular matrix (ECM) components, providing a robust culture model as the go-to platform for exploring the biology of the breast and breast cancer. Drs Merry and Meade have developed a simple peptide hydrogel system originally optimised for the culture of stem cells. In collaboration with Dr Farnie and Prof Howell, who provide expertise in primary breast cell culture, ductal carcinoma in situ (DCIS) and breast ECM/density, we have pilot data demonstrating that the hydrogel is suitable for the growth of typical in vitro 3D normal and DCIS breast structures. As with the vast majority of cancers, the interaction of DCIS cells with their local microenvironment, the surrounding stroma and ECM, is fundamental in defining their proliferation, transformation to malignancy and invasion. Our hydrogel is well positioned to replicate aspects of the complex mixture of proteins and glycans that embeds and supports cells, and can also be manipulated to mimic ECM stiffness (breast density) which is a key predictor of DCIS recurrence and primary invasive breast cancer development. We will use a combination of proteomics and glycomics to identify the key ECM components defining dense and non-dense breast tissue in normal, DCIS and invasive breast cancer conditions. The proteins and glycans will then be combined to generate a panel of 6 bespoke hydrogel environments modelling the range of tissue types. We will validate the model using multicellular 3D culture and assay for ECM remodelling by encapsulated cells, directly assessing the ability of our in vitro model system to replicate human breast tissue. Finally, we will incorporate immune cells into the gels, thereby addressing a key feature of animal models that currently separates them from in vitro systems.

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