Three-dimensional culture systems in cancer research: Focus on tumor spheroid model

Abstract

Cancer cells propagated in three-dimensional (3D) culture systems exhibit physiologically relevant cell-cell and cell-matrix interactions, gene expression and signaling pathway profiles, heterogeneity and structural complexity that reflect in vivo tumors. In recent years, development of various 3D models have improved the study of host-tumor interaction and use of high-throughput screening platforms for anti-cancer drug discovery and development. This review attempts to summarize the various 3D culture systems, with an emphasis on the most well characterized and widely applied model - multicellular tumor spheroids. This review also highlights the various techniques to generate tumor spheroids, methods to characterize them, and its applicability in cancer research.

Spheroid-based 3D Cell Cultures Enable Personalized Therapy Testing and Drug Discovery in Head and Neck Cancer

“…A main precondition for high-throughput screening is the reproducibility of uniform spheroids as size and heterogeneity may influence the validity of end-point assays (45). We showed that spheroids grow in a linear pattern with higher proliferation rates in ULA plates resulting in significant increased spheroid sizes compared to HD.…”

“…Typical spheroid architecture, consisting of a an inner layer of quiescent cells and an outer layer of proliferating cells, respectively, was detected in MCTS lager than 500 μm in diameter, an indication of nutrition, oxygen and, thus, proliferation gradients responsible for cell heterogeneity (29,32,47). These limited diffusion gradients of oxygen, nutrients, metabolic waste products and soluble factors, such as cytokines and growth factors, were shown to be similar to micro-metastases and avascular tumors measuring 0.5-1.0 mm 3 (37,45,48).…”

“…Pickl et al recently pointed out a good example for the role of such microenvironments in which trastuzumab was tested in 2D and 3D environments of breast cancer cells (51). Cells in 3D spheroids where much more vulnerable to the antibody as they depended significantly more on their physiological human epidermal growth factor receptor 2 (HER2) signaling in the spheroid formation, the target of the antibody (45). Therefore, predicting clinical response of new agents tested in 2D cellular assays is limited (32).…”

“…Among a wide range of different 3D models with variable complexity, it seems important to focus on scaffold-free MCTS like the HD and the ULA method, respectively, as they represent an auspicious tradeoff between easy handling for high-throughput screening and enhanced reflection of tumor physiology (32,45). One of the major limitations that 2D and 3D cultures have in common is the lack of examining migration and invasion of the malignant cells.…”

“…One of the major limitations that 2D and 3D cultures have in common is the lack of examining migration and invasion of the malignant cells. As spheroids consist of a distinct construction (hypoxic core enriched with a quiescent viable central zone with tendency to necrosis, as well as the outer proliferating zone) the rates of proliferation of several tumor cell lines might be reduced compared to its behavior in a 2D model (45). The underlying mechanisms include different oxygen/nutrient/growth factor gradients, stromal cell and extracellular matrix influence (30,(55)(56)(57)(58).…”