Notes to application of the V79 metabolic cooperation assay for detection of potential tumor promoters

Many chemicals which promote tumorigenesis in vivo have been observed to inhibit metabolic cooperation between 6-thioguanine-resistant (6TGr) and sensitive (6TGs) Chinese hamster lung V79 cells. The apparent correlation between inhibition of metabolic cooperation in V79 cells in vitro and promotion of oncogenesis in vivo has led to the suggested utilization of the assay as a screen for tumor promoters. Several parameters concerning the V79 metabolic cooperation assay were investigated for an improved understanding of the usefulness and limitations of the assay in our laboratory conditions. We have found that the recovery of 6TGr cells were dependent upon the number of 6TGs cells plated, upon the generation time, passage number, and upon the co-cultivation period until the addition of selective agent. The ability of this assay to detect tumor promoters has been determined by the known tumor promoter phorbol ester TPA.