New screening system for selection of anticancer drugs for treatment of human colorectal cancer.

We report an evaluation of a new radiometric technique (BACTEC assay) as a potential screening system for cytotoxic compounds with activity against cancer of the large bowel. Exponentially growing cells of nine different human colorectal cancer cell lines were exposed to a variety of standard anticancer agents with or without documented clinical activity. Each drug was tested in a series of 1-h and continuous exposure studies utilizing three different concentrations. Antineoplastic effects were analyzed as a function of in vivo achievable serum concentrations, namely by a ratio of the concentration required to decrease cell growth to 10% of control to one-tenth of the peak plasma concentration in humans. Our results suggest that COLO 320DM, OM-1, and Ht-29 cells manifest responsiveness to anticancer drugs consistent with that noted in clinical studies with most agents tested. The radiometric technique provides several advantages for a screening system, including reproducibility, a good agreement with the cloning assay, speed, and low costs. The combined use of the BACTEC technique and the three colon cancer cell lines could prove useful as a screen for new anticancer compounds with activity in colorectal cancer.