Fig. 3.

Breast cancer models for in vitro research. Traditional 2D cancer cell lines are easy to work with but lack tumour stroma, and adaptation to in vitro culture conditions results in loss of the original tumour phenotypic signature. Spheroids form from cellular aggregates which may be cultured from one or more cell types in suspension or within a hydrogel. Transwell systems involve the compartmentalisation of different cell populations, limited by the lack of direct cellular and cell-ECM interactions. 3D breast organotypic cancer models entail a specialised hydrogel approach in which cancer cells are seeded into a hydrogel laden with cell populations such as fibroblasts. Organotypic models are now widely used as they are a physiologically relevant system and closely resemble the original tumour. Co-culture systems containing fibroblasts, endothelial cells or immune cells have extended the predictive capabilities of these systems. Organoids self-assemble in multicellular structures which closely resemble the organisation of host tissue. Tissue explants are isolated tissue segments, capable of being cultured ex vivo, and retain physiological characteristics of the breast tumour. Microfluidic systems entail bespoke bioengineered chips facilitating fluid flow and recapitulating circulation. Original schematic created in Adobe Illustrator