The Effect of Glutathione Depletion by Diamide, Diethyl Maleate or Buthione Sulfoximine on the Surface Structure of Mouse L-Cells

Radiosensitizers that act by reducing glutathione levels have been studied by many workers as agents to enhance the killing of hypoxic tumour cells. In this paper we describe a scanning electron microscope (SEM) study of the surface morphology of mouse L-cells after exposure to three of these: diazenedicarboxylic acid bis N, N-dimethylamide (diamide), DL-buthionine-S, R-sulfoximine (BSO) and diethyl maleate (DEM). Diamide at 0.1 to 0.6 mMol/L for 10 min produced large blebs on the cell surface as seen in the SEM. Transmission electron microscope (TEM) images show that these are clear, featureless regions of cytoplasm. BSO treatment for 24 hat 0.5 to 2.0 mMol/L, by contrast, left the surface similar to control cells. DEM at 0.5 mMol/L for 2 h produces small blebs over the cell surface and a reduction in the number of microvilli. A combined 24 h BSO treatment with 2 h of DEM produced large blebs, which were similar in TEM micrographs to those produced by diamide. Thus, although all three sensitizers reduce glutathione levels, they have different effects on cellular morphology and hence such secondary effects may account for the different degrees of radiation sensitization seen with these agents

Morphological Effects of Lonidamine on Two Human-Tumor Cell Culture Lines

Lonidamine, 1-(2-4-dichlorobenzyl)-1-H-indazol-3-carboxylic acid. is an anticancer drug that has its primary action on cellular metabolism rather than cell division. Since lonidamine is not effective in all tumor cells, we have tested it in two human-tumor cell culture lines: MOLT-4, a T-leukemia and U-87 MG. a glioma. Lonidamine exposure of MOLT-4 cells at 50 μg/mL and pH 6.7 disrupted the mitochondria within 1 h of treatment. The mitochondria were swollen and the cristae were disrupted. When the treated cells were re-incubated in fresh medium at pH 7.4 the mitochondria rapidly returned to their normal morphology. The U-87 MG glioma cells did not show ultrastructural disruption after 1-h treatment with lonidamine at concentrations up to 200 μg/mL at pH 6.7 In the concentration range of 25 μg/mL to 200 μg/mL. lonidamine did not produce any cell killing in MOLT-4 after a 1-h exposure at pH 7.4, although the drug had some limited effectiveness at pH 6.7. Compared to sham-treated controls, long exposures to 100 μg/mL of lonidamine at pH 6.7 reduced survival in MOLT-4 to 92% and 53% after 6-h and 24-h exposures, respectively. Survival of U-87 MG glioma cells was also strongly pH dependent, a 2-h exposure to 50 μg/mL lonidamine at pH 7.4 did not cause cell death; however, survival dropped to 84% of the control at pH 6.65