[Spheroids: A reference model for in vitro culture of solid tumors?]

The recognition that solid tumors are complex entities composed of the tumor cell mass itself and a stromal micro-environnement providing a variety of cells from the host (fibroblasts, endothelial cells, immune cells) led to recognize that this heterogeneity could not be recapitulated in vitro by conventional bidimensional (2-D) cultures. This justified numerous attempts to develop tridimensional (3-D) cultures that provided better tools for approaching tumor complexity and more convincing drug testing systems. Among various 3-D technologies, tumor spheroids are more likely suited to provide in vitro platforms for apprehending specific aspects of different processes specifically defining each tumor category as well as testing drug delivery systems. This review summarizes current features of multicellular tumor spheroids and their suitability for studying different aspects of cancer cell biology, patient-specific therapies and drug treatment.