Multi-center collaborative in vitro studies using a human cancer cell line: the EORTC Preclinical Therapeutic Models...

The EORTC Preclinical Therapeutic Models Group (PTMG), formerly known as the Clonogenic Assay Screening Study Group (CASSG), began experiments in 1982 to investigate the feasibility of doing collaborative studies using in vitro clonogenic assays. The human colon adenocarcinoma cell line WiDr was selected as the model with which all participating laboratories would work. During the course of these studies, representatives from 34 different institutions located in 10 European countries participated. The first two collaborative experiments attempted to standardize the assay techniques using a double layer agar clonogenic assay. The results indicated that it was not possible to truly standardize these techniques in an international setting. The overall results demonstrated that the WiDr cell line grew well under a variety of conditions and that cloning efficiencies were independent of cell concentration, provided that a concentration of about 3,000 cells/ml was not exceeded. For the next series of protocols, the overall objectives were modified so that each laboratory could use its preferred assay technique whereas the WiDr cells were standardized by being expanded in a single center and sent to participants as viable cells. Analysis of the pooled results indicated that there was steady improvement in reproducibility for the group as a whole with repetition of the protocol. Drug dose responses with doxorubicin and etoposide showed good reproducibility from experiment to experiment. The results with cisplatin suggested that the sensitivity of this cell line may be affected by the presence of reduced sulfhydryl in some tissue culture media. The overall experience of the group indicates that use of a cancer cell line can provide the framework within which collaborative in vitro studies can be performed, provided that the initial conditions such as cell and drug concentrations are carefully determined in advance through preliminary studies.