The design of the spheroids-based in vitro tumor model determines its biomimetic properties.

Cancer, one of the world's deadliest diseases, is expected to claim an estimated 16 million lives by 2040. Three-dimensional (3D) models of cancer have become invaluable tools for the study of tumor biology and the development of new therapies. The tumor microenvironment (TME) is a determinant of tumor progression and has implications for clinical therapies. Cancer-associated fibroblasts (CAFs) are one of the most important components of the TME. Modeling the interactions between cancer cells and CAFs in vitro can help to create biomimetic tumor equivalents for elucidating the causes of cancer growth and assessing the effectiveness of therapies. Here, we are investigated the effect of the mutual arrangement of tumor cells and fibroblasts on the formation of tumor models and their biomimetic properties. Pancreatic tumor models of three different designs were formed by the bioprinting method. Gelatin-alginate hydrogels with and without PANC-1 (pancreatic cancer) and NIH/3 T3 (mouse fibroblasts) cells, as well as their homo- and heterospheroids, were used as bioink. To enable bioprinting, we have chosen the most suitable compositions of alginate and gelatin that provide both good printability and cell proliferation activity. We also have investigated the kinetics of spheroid formation to identify the optimal cultivation parameters for achieving spheroid sizes suitable for bioprinting. All tumor models remained viable for 3-4 weeks. At the same time, the patterns of model development in the cultivation process and the biomimetic properties of the final tissue-engineered structures depended on the model design.