The influence of stromal cells on the MTT assay (II)--Study on the nude mouse system.

A fresh surgical specimen from colon carcinoma was tested by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide assay (MTT assay) and transplanted into nude mice. After 5 transfers in male BALB/c nude mice, the xenograft was then tested again by the MTT assay. It was found that the in vivo chemosensitivity pattern of the xenograft was essentially identical to that of the in vitro fresh surgical specimen, whereas the sensitivity of the xenograft was increased. To exclude the stromal cells from the nude mouse, anti-BALB/c serum was added to the primarily cultured colon carcinoma xenograft, and its chemosensitivity to mitomycin C (MMC) assessed. Although the sensitivity of the serum-treated group to MMC was slightly higher than that of the untreated group, the dose-response curves of the tumor cells to MMC were similar to each other. Thus, the chemosensitivity pattern of tumor cells seemed to be stable with or without normal cells, although the sensitivity itself was reduced by the presence of normal cells.