Abstract
The effects of fibroblasts and lymphocytes on the 3- (4, 5-dimethylthiazol-2-yl) -2, 5-diphenyl tetrazolium bromide (MTT) assay (Original), a typical in vitro anti-cancer drug sensitivity test, and the liquid top agarose layer MTT (Liquid) and MTT hybrid assays (Hybrid), which are modified methods, using Cis-platin, were evaluated. Lymphocytes had little effect on the MTT assay. A mixture of 50% or more of the fibroblasts (HF) with the tumor cells (HOSM-1) significantly decreased anti-cancer drug sensitivity. On the other hand, anti-cancer drug sensitivity significantly increased in an in vivo tumor treated with anti-nude mouse serum to eliminate mouse-derived cells. These findings suggested that the inhibition of the activity of cells such as fibroblasts is important in sensitivity tests using fresh tumors. Regarding fibroblast proliferation, HF increased by 2.9 fold in the Original assay. Compared with the Original assay, HF proliferation was 66% in the Liquid assay and 55% in the Hybrid assay (top layer, 0.25%) . Thus, the MTT hybrid assay using 0.25% agar as the top layer may be most appropriate when fresh tumor specimens are used.
