Frozen don cells as a source for a cell cycle assay of antitumor agents

This study was intended to determine the feasibility of using frozen mitotic mammalian cells as a source of synchronous cultures to determine the cell cycle phase specificity of cytotoxic agents. We first found that the relative effectiveness of different additives in protecting cells during freezing was DMSO > glycerol of polyvinyl pyrolidone > sucrose > 50% serum. We also found that mitotic cells frozen in glycerol did not progress synchronously through the cell cycle when thawed. However, mitotic cells frozen in DMSO had approximately the same cell cycle time as non-frozen mitotic cells and therefore could be thawed and cultured to determine phase specific cytotoxicity of compounds. However, better results were obtained when cells frozen in different phases were used to determine phase specific toxicity of compounds. The pattern of sensitivity to cytotoxic agents of cells frozen in different phases was the same as that of the non-frozen controls.