Optimization of three-dimensional (3D) in vitro assays for breast cancer drug screening

Abstract

Matrix stiffness is recognized as a major factor when it comes to tumor progression and cancer cell migration. Obtaining a relevant matrix stiffness when developing 3D in vitro models is therefore key in order to accurately replicate the cellular behavior exhibited in human breast cancer tissue. In this study, DLP-bioprinting and grayscale image projection was used to create a multi-material, multi-stiffness 3D model with a stiffness range similar to that of tumorous and tumor-adjacent breast tissue. By using the BIONOVA X grayscale function, PhotoGel-INK 50% (CELLINK, Gothenburg Sweden) was exposed to an energy range between 70% and 100% (corresponding to approximately 224 mJ/cm2 - 320 mJ/cm2) which generated a matrix with a stiffness gradient between 3.5 - 5.2 kPa. The generated matrix promoted MDA-MB-231 cells to form spheroids and caused a progressive matrix reconstruction through both proteolyticdependent and proteolytic-independent invasion mechanisms. The cells in the MDAMB- 231 spheroids also exhibited a migratory behavior consistent with literature as they migrated towards the softer parts of the surrounding matrix. This study shows that DLP-bioprinting and grayscale image projection can be used to create viable, multistiffness, 3D in vitro models that accurately mimic the behavior of native breast cancer tissue. These findings suggest that this model has the potential to serve as a stepping stone for future development of high-throughput in vitro assays for breast cancer drug screening.