Central nervous system tumors and three-dimensional cell biology: Current and future perspectives in modeling

Table 3 Characteristics of three-dimensional modeling technologies

Modeling technology	Methods of generation	Applications	Limitations
Spheroids[37-39]	Static suspension; Hanging drops; Spinner and rotational bioreactor; Magnetic levitation; Microfluidic system; Gel embedding (Matrigel, etc.)	Radioresistance through hypoxia and cell-cell contacts; Chemosensitivity and drug screening; Migration and invasion; Propagation and analysis of CSCs	Tumor heterogeneity; Immune system response; Interaction with normal non-tumor cells; Lack organ-like histology
Organoids[14,17,37,40,41]	Culturing done on matrices (Matrigel, collagen I, hyaluronic acid, etc.); Addition of culture supplements including FGF, EGF, Noggin, N2, B27, etc.	Disease mechanism; Drug discovery and toxicology; Developmental, stem cell biology and regenerative medicine; Infectious disease	Oxygen and nutrient distribution underdeveloped; Cellular microenvironments are challenging to replicate; Imaging difficulties; Expensive and time consuming assay

CSC: Cancer stem cell; EGF: Endothelial growth factor; FGF: Fibroblast growth factor.