The authors have evaluated the antiproliferative activity of verapamil, alone or in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in brain-tumor cells. These effects were studied in vitro using four human glioma cell lines and in vivo using glioblastoma multiforme cells transplanted to athymic nude mice. The results showed that verapamil when used alone produced inhibition of tumor growth; however, when verapamil was used in combination with BCNU (in vitro), significant dose-dependent suppression of proliferation occurred in all four cell lines. The in vivo results were far more dramatic. Mice treated with BCNU (25 mg/kg) plus verapamil (50 mg/kg) achieved a 200-fold decrease in tumor growth with a greater than 80% regression in tumor size. Complete cures were achieved in 80% of the mice observed for at least 50 days following the completion of therapy. These findings support the use of verapamil in overcoming drug resistance in malignant brain tumors.
This report describes a new fluorescent microcarrier cytostasis assay. Human glioma cell lines and primary cultures were attached to microcarrier tissue culture beads and treated with various chemotherapeutic drugs. After treatment, the cells were labelled with two vital fluorescent dyes in order to measure cellular viability. The uptake of hydroethidine and Hoechst 33342 was evaluated alone and in combination as probes for determining metabolic activity and cellular proliferation. Hydroethidine was found to be superior when compared to trypan blue and tritiated thymidine. The use of the microcarrier technique allows for the direct cellular measurement of fluorescence without the need of extensive extraction procedures. The fluorescent assay is a sensitive, rapid and an effective way to screen for potential antiproliferative compounds.
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