Multicellular tumor spheroids in gene therapy and oncolytic virus therapy.

Multicellular clusters of cells, or spheroids, can be grown and sustained in vitro, facilitating various cancer research and treatment approaches. As spheroids are three-dimensional and retain many of the cell types and features present in the original clinical tissues, they provide an important link between two-dimensional cell lines and in vivo xenograft studies. With regards to gene therapy and replication-competent oncolytic viruses in particular, spheroids allow sustained viability of primary tumor cells in vitro, a requirement for reliable analysis of replication. Analysis of clinical samples is of paramount importance for preclinical evaluation of candidate anticancer agents.