PREDICTION OF DRUG CYTOTOXICITY IN 9L RAT-BRAIN TUMOR BY USING FLOW-CYTOMETRY WITH A DEOXYRIBONUCLEIC ACID-BINDING DYE

OBJECTIVE: Flow cytometry (FCM) with a deoxyribonucleic acid (DNA)-bin ding dye, propidium iodide, provides a rapid and quantitative method t o detect apoptotic cell death. This technique was used to examine the sensitivity of tumor cells to anticancer agents, asa novel test of che mosensitivity in vitro, METHODS: The in vitro chemosensitivity of 9L g liosarcoma cells to a panel of anticancer agents (cisplatin, nimustine , adriamycin, cyclophosphamide, vincristine, 5-fluorouracil, and metho trexate) was investigated by both FCM, yielding DNA histograms, and a microtiter tetrazolium test, measuring cellular metabolism. Clinically achievable concentrations of the agents were used for the analysis of DNA histograms and proliferation of 9L cells in vitro. Rats intracran ially inoculated with 9L cells were treated with the agents, and tumor masses were visually monitored by using magnetic resonance imaging wi th gadolinium-diethylenetriaminepentaacetic acid enhancement. RESULTS: The cytotoxic effect of anticancer agents examined by the microtiter tetrazolium test correlated with a decreased G(0)/G(1) peak in the DNA histograms. Serial FCM analysis showed that the decrease in the G(0)/ G(1) peak was subsequently accompanied by increased hypodiploid areas, suggesting DNA fragmentation induced by the agents. The in vitro chem osensitivity test and cell proliferation examination showed that all a gents except cisplatin were effective. Growth retardation of inoculate d brain tumors and prolonged survival of inoculated rats were observed with treatment with the anticancer agents, except cisplatin. CONCLUSI ON: The present study shows that FCM analysis with a DNA-binding dye c an detect DNA damage induced by anticancer agents, and it suggests tha t this technique is a novel method to test chemosensitivity in vitro.