Experimental studies on the radiosensitizing agents against cultured human glioblastoma and human neurinoma

The radiosensitivity increasing effect of bromo-2'-deoxyuridine (BUdR) and 5-fluorouracil (5-FU), alone and in combination, was studied comparatively using tissue culture of brain tumor cells (No. 60 cells originating in human glioblastoma and N cells originating in human neurinoma) with colony formation and growth curve as the quantitative indices and the phase contrast microscope and scanning electron microscope for morphological observation. The inhibitive effect of BUdR on growth of the N cells was above 4μg/ml, while 3000μg/ml was required in the case of the No. 60 cells. This indicates that there is a large difference between the sensitivities of these two cell types against BUdR. Increased sensitivity can be anticipated by pretreatment of the No. 60 cells or the N cells with BUdR with a dose of no growth inhibition effect. N cells have a lower radiosensitivity than No. 60 cells; but when both cells are pretreated with BUdR, N cells have a higher radiosensitivity than No. 60 cells. This increasing radiosensitivity of the N cells, which is clinically benign, suggests the possibility of wider application for radiotherapy in the future. A dose of 2μg/ml of 5-FU alone showed no growth inhibiting effect on either the N cells or the No. 60 cells, but it intensified the effect of BUdR. Using a phase contrast microscope and a scanning electron microscope for morphological observation of the No. 60 cells and the N cells which had been exposed to BUdR+5-FU+X-ray, unique findings were observed on the surface structures of these two kinds of cells. (J.P.N.)