Biochemical pharmacology
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Biochemical pharmacology · May 2000
Differential cytotoxicity and induction of apoptosis in tumor and normal cells by hydroxymethylacylfulvene (HMAF).
This investigation compared the effects of hydroxymethylacylfulvene (HMAF), a novel antitumor drug with alkylating properties, in eight human tumor (prostate, colon, and leukemia) cell lines, and five human normal (prostate and renal proximal tubule epithelial, colon mucosa, fibroblasts, and endothelial) cell lines. Drug-induced growth inhibition paralleled the uptake of HMAF into both tumor and normal cells, although normal cells were 3- to 4-fold more tolerant to the accumulated drug. In both tumor and normal cells, approximately two-thirds of internalized [(14)C]HMAF-derived radioactivity was bound covalently to macromolecules. ⋯ This resistance of normal cells to apoptosis could not be accounted for by differences in drug accumulation or drug covalent binding to macromolecules. The qualitatively different responses of the tumor and normal cells studied suggest a greater tolerance of normal cells to HMAF-macromolecular adducts. The demonstrated differential cytotoxic/cytostatic and apoptotic effects of HMAF can be of significance for the clinical use of this promising new agent.
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Biochemical pharmacology · May 2000
Specificity of inhibitors of serine palmitoyltransferase (SPT), a key enzyme in sphingolipid biosynthesis, in intact cells. A novel evaluation system using an SPT-defective mammalian cell mutant.
In the present study, we demonstrate a model cell system for evaluating the specificity of inhibitors of serine palmitoyltransferase (SPT), the enzyme that catalyzes the first step of sphingolipid biosynthesis. The LY-B strain is a Chinese hamster ovary (CHO) cell mutant defective in SPT, and the LY-B/cLCB1 strain is a genetically corrected revertant of the mutant. Although LY-B cells grew only slightly in sphingolipid-deficient medium, their growth was restored to the level of LY-B/cLCB1 cells under sphingosine-supplied conditions, indicating that, in CHO cells, the growth inhibition caused by SPT inactivation was rescued almost fully by the metabolic complementation of sphingolipids. ⋯ Similar cytotoxic patterns of these inhibitors also were observed on the growth of SPT-defective LY-B cells cultured under sphingosine-supplied conditions. The SPT inhibitors did not affect metabolic conversion of exogenous [(3)H]sphingosine to complex sphingolipids. Thus, the cytotoxicity of sphingofungin B and ISP-1, but not L-cycloserine or beta-chloro-L-alanine, is due largely to inhibition of sphingolipid synthesis by inhibiting the SPT activity.