Figure 1.

(A–D) Illustrative scheme of the methods for the preparation of multicellular tumor spheroid (MCTS):: the hanging drop method, where the cells come together at the bottom of a hanging drop (A), the liquid overlay method, where the surface of plates or (conical) wells is coated with a non-adhesive material (B), spinner flasks (stirred or rotating vessel), where the cells are kept in suspension (C) and magnetic culture, where, after the addition of magnetic particles, the cells are brought together through magnetic forces (D). (E) Schematic representation of the spheroid physiology depicting the distribution of proliferating (orange, outside layer), quiescent (violet, middle layer) and necrotic cells (purple, at the core). The cellular density is lower in the outside layer.