Evaluation of the relative cytotoxic effects of anticancer agents in serum-supplemented versus serum-free media using a tetrazolium colorimetric assay

Most cell culture and in vitro drug sensitivity assays utilize serum-supplemented media (SSM). However, fully defined serum-free media (SFM) offer several advantages and are being used increasingly for initiation and maintenance of cell cultures. Because serum inhibits the in vitro cytotoxicity of certain antineoplastic agents, we investigated the inter-relationships between medium type, cell proliferation and cytotoxic effect. Twenty-four human lung cancer cell lines were tested with nine anticancer agents in both media types. A semi-automated tetrazolium (MTT) colorimetric assay was used for assaying cell survival. Cell lines initiated and maintained in SFM preferentially proliferated in that medium type or proliferated equally well in both media types. In contrast, cell lines established in SSM varied considerably in their medium of preference. There appeared to be a direct correlation or trend between cell proliferative rate and cytotoxicity of all drugs with the possible exceptions of methotrexate and carmustine. In general, the cell lines were more sensitive to anticancer agents when they were exposed in the culture medium in which they preferentially proliferated. Therefore, to determine the influence of culture media on cytotoxicity, we analyzed the data only from lines that replicated equally efficiently in both media. After correction for cell proliferative rate, SSM had a negative effect on the cytotoxic action of some drugs (especially methotrexate, 5-fluorouracil and, to a lesser extent, mitomycin-C). Our results demonstrate that fully defined SFM may be suitable for initiating cell lines and for use in in vitro cytotoxicity assays for selection of individualized therapy or for screening of new anti-neoplastic agents, and thus may increase the number of antineoplastic agents that can be tested satisfactorily.