Three-dimensional spheroid model in tumor biology

It is becoming more and more apparent that monolayer cultures of tumor cell s cannot completely represent the characteristics of three-dimensional soli d tumors. Consequently, the multicellular tumor spheroid model, which is of intermediate complexity between in vivo tumors and monolayer cultures, was developed. In this review,the major similarities between spheroids and sol id tumors are discussed. After a brief survey of the different spheroid cul turing techniques, the general morphological and growth characteristics of these systems are examined and compared to solid tumors. Finally, selected studies regarding the use of tumor spheroids to examine cell response to an tineoplastic agents and radiation, cell death including both necrosis and a poptosis and cell adhesion in spheroids are reviewed.