[Chemosensitivity to mitomycin C and cell kinetics of human tumor xenografts serially transplanted into nude mice].

Different chemosensitivity to mitomycin C (MMC) and cell kinetics were studied by using human tumor xenografts serially transplanted into nude mice. Two gastric adenocarcinomas (St-4; poorly differentiated, St-40; well differentiated) and two colon adenocarcinomas (Co-3; well differentiated, Co-4; poorly differentiated) were transplanted into the back of BALB/c nude mice subcutaneously. Three mg/kg of MMC was administered, q4d X 3, intraperitoneally. The effect of MMC in vivo was evaluated according to the protocol of Battelle Memorial Institute. The primary cultured tumor cells of the same strains were used for the chemosensitivity test in vitro, and the effect of MMC in vitro was tested by the inhibition rate of 3H-thymidine (3H-TdR) incorporation to cancer cells. Cell kinetics were analyzed by percent labeled mitosis curves obtained from 3H-TdR pulse labeling in vivo and by 3H-TdR incorporation to cancer cells in vitro. Although MMC suppressed the growth of St-40 and Co-4, it was found that St-4 and Co-3 were less sensitive to MMC in vivo. St-4, St-40 and Co-4 were observed to be sensitive to MMC in vitro. Growth fractions of transplanted tumors in vivo were correlated well to the chemosensitivity to MMC with statistical significance. St-4, which was insensitive to MMC in vivo and sensitive in vitro, showed low growth fraction in vivo and increased 3H-TdR incorporation in vitro, suggesting the recruitment of G0 cells to growth fraction in vitro. The chemosensitivity of 4 tumors to MMC was revealed to be correlated well to each growth fraction in vivo and in vitro.