Effect of concentration and time of drug exposure on clonal growth of murine bladder cancer

The use of a tumor colony assay was evaluated for its ability to predict anticancer drug response in an N[4-(5-nitro-2 furyl)-2-thiazolyl] formamide mouse bladder tumor model. One-hour and continuous drug exposure were compared to determine what effect altering drug concentration and time of exposure would have on the predictability of t he tumor colony assay in the murine model. Ten anticancer drugs were tested in the murine model, and tumor cells removed from control mice were used for in vitro drug testing. One-hour and continuous drug exposure (using the one-hour drug level) were performed simultaneously and the in vitro and in vivo data compared. Using one-hour drug incubation in the tumor colony assay resulted in a true positive predictive rate of 54 per cent and a true negative predictive rate of 70 per cent. Continuousdrug incubation overestimated drug sensitivity resulting in a drop in the predictability of the tumor colony assay. We conclude that using one-hour drug exposure the tumor colony assay is predictive of chemotherapeutic drug response in this murine bladder tumor model.