A New Method to Prepare Multicellular Spheroids in Cancer Cell Lines Using a Thermo-Reversible Gelation Polymer

: The purpose of this study is to utilize the thermo‐reversible gelation polymer in which the sol‐gel transitting phase is reversibly changed by temperature in a three‐dimensional culture system. Human cancer cells have been observed to form multicellular spheroids, whereas fibroblasts slowly develop into small spheroids with the culture medium including this polymer. This polymer has some advantages for use as a culture material, as follows: first, cancer cells grow three‐dimensionally in the aqueous solution of this polymer; second, it is easy to harvest cells or spheroids in the aqueous solution of this polymer by simply cooling down the temperature; and third, the culture medium including this polymer is so translucent that the cells or spheroids can be observed through a phase‐contrast microscope. We thus conclude that this polymer is a very useful material for three‐dimensional cultures.