Variable response to 1,3-bis(2-chloroethyl)-1-nitrosourea of human glioma cells sorted according to DNA content

Malignant gliomas, especially glioblastoma multiforme, are composed of a considerable number of cells undergoing DNA synthesis and cells that contain various amounts of DNA. We have characterized cells dissociated from biopsy specimens of such tumors by sorting vital cell populations on the basis of DNA content and have determined the sensitivity of sorted cells to BCNU. Cultured human glioma cells from seven malignant gliomas were stained with Hoechst 33342 dye; the colony-forming efficiency (CFE) of stained tumor cells ranged from 2-50%. Stained cells were sorted on a fluorescence-activated cell sorter (FACS-III). The surviving fraction of each population was determined after exposure to graded doses (2.5-10 micrograms/ml X 2 h) of BCNU. Sorted populations of cells from 5 tumors had dose-response curves that were similar, although differences in cell kill of up to a half-log were commonly found between cells from different DNA peaks treated with the same BCNU dose. For two tumors, cells from the first peak (smallest DNA content) had distinct BCNU sensitivity compared to cells from the second and third peaks (largest DNA content); compared to other tumors in the series, cell kill differences were significant and greater than 1 log in magnitude for one anaplastic astrocytoma. This lack of uniformity in the response of cells within a tumor demonstrates the problem imposed by heterogeneity with regard to the interpretation of chemosensitivity testing of all cells within a single tumor.