Increased drug resistance of cultured human cancer cell lines in three-dimensional cellular growth assay using collagen gel matrix.

We have conducted a three-dimensional cellular growth assay using collagen gel matrix with an endpoint of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay, on four human gastric and colonic cancer cell lines. Three-dimensionally growing cells in collagen gel matrix were 2- to 180-fold more resistant to mitomycin C, doxorubicin, 5-fluorouracil, and cisplatin than those in monolayer culture, and these resistances were increased further when the cells increased their three-dimensionality. Furthermore, the influence of fibroblasts in the collagen gel matrix on the chemosensitivity of cancer cells was less than that in monolayer culture. Since this new assay using collagen gel matrix with an endpoint of the MTT assay was able to detect the increase of drug resistance of human cancer cell lines by three-dimensional cellular growth using a simple and convenient procedure, it was considered to be more useful than conventional monolayer cultures for evaluating the chemosensitivity of cancer cells.