Evaluation of in vitro chemosensitivity using human lung cancer cell lines

The use of well-characterized human lung cancer cell lines has allowed for new opportunities in preclinical and clinical drug evaluation. Development of semiautomated tests of in vitro cytotoxicity such as the MTT assay, which utilizes the formazan salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), has allowed for preclinical evaluation of novel chemotherapeutic agents and drug combinations. In addition, techniques such as this make possible the testing of sufficient data sets to allow determination of true biochemical drug synergy. Assessment of drug combinations which possess in vitro synergy or supraadditive effects can suggest chemotherapeutic regimens for further clinical testing. Using the MTT assay in conjunction with isobolographic analysis, it is possible to test commonly used regimens which are based on presumed or apparent in vivo drug synergy, such as the combination of etoposide and cis-platinum. This frequently prescribed combination was found to lack in vitro biochemical synergy when tested with human lung cancer cell lines, indicating that the observed clinical benefits of this drug combination may be due to factors in the tumor microenvironment, drug metabolism, or non-overlapping toxicities. Finally, although it remains to be determined if a significant role for in vitro drug testing will be found in direct clinical applications, preclinical drug evaluation during the drug development process using cultured tumor cell lines may ultimately allow for disease or patient specific therapies for testing.