Abstract
Mouse neuroblastoma cells (NB) have been adapted for growth in 1 mM mycophenolic acid (NB-myco) by incremental increases in drug concentration with each passage without mutagenesis. 50% growth inhibition occurred at 0.1 uM and 1 mM for NB and NB-myco cells respectively representing a 10,000-fold increase in resistance. There were increases in IMP dehydrogenase activity, 25-fold, and a 56.7K dalton protein, 200-500 fold, in NB-myco as compared to NB cells. The resistant phenotype was also unstable. In the absence of drug there were decreases in the 56.7K dalton protein, 4-fold over 90 days, and IMP dehydrogenase activity, 3-fold over 80 days. These findings are characteristic of amplification, others are indicative of a mutation. The substrate Km's were unchanged but the Ki's have increased in the NB-myco cells: 2400-fold for mycophenolic acid, and 4-fold for XMP, The kinetic studies are consistent with an ordered bi bi reaction where IMP binds first and XMP is released last; mycophenolic acid and NAD+ exhibit uncompetitive inhibition with IMP. Guanine nucleotide synthesis was also perturbed. The ATP concentration was unchanged, GTP and UTP were increased 2- and 1.5-fold respectively in NB-myco cells as compared to NB cells. Upon removal of mycophenolic acid, ATP did not change, but within hours GTP increased to 4.5-fold that of NB cells. Supported by the Medical Research Council of Canada grant MT-8665.
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Snyder, F., Hodges, S. & Fung, E. 145 MYCOPHENOLIC ACID INDUCED AMPLIFICATION AND MUTATION OF INOSINATE DEHYDROGENASE IN MOUSE NEUROBLASTOMA CELLS. Pediatr Res 24, 135 (1988). https://doi.org/10.1203/00006450-198807000-00169
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DOI: https://doi.org/10.1203/00006450-198807000-00169
