Cytotoxicity and characterization of an active metabolite of benzamide riboside, a novel inhibitor of IMP dehydrogenase

K. Gharehbaghi, K. D. Paull, J. A. Kelley, J. J. Barchi, V. E. Marquez, D. A. Cooney, A. Monks, D. Scudiero, K. Krohn, H. N. Jayaram

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Abstract

Benzamide riboside exhibits significant cytotoxicity against a variety of human tumor cells in culture. On the basis of metabolic studies, the primary target of this drug's action appears to be IMP dehydrogenase (IMPDH). Incubation of human myelogenous leukemia K562 cells with an IC50 concentration of benzamide riboside resulted in an expansion of IMP pools (5.9-fold), with a parallel reduction in the concentration of GMP (90%), GDP (63%), GTP (55%) and dGTP (40%). On kinetic grounds, it was deduced that benzamide riboside (whose K(i) versus IMPDH is 6.4 mM, while that of its 5'-monophosphate is 3.9 mM) or its 5'-monophosphate were unlikely to be responsible for inhibition of this target enzyme, IMPDH, since only micromolar concentrations of benzamide riboside were needed to exert potent inhibition of tumor-cell growth. Studies on the metabolism of this C-nucleoside have revealed the presence of a new peak eluting in the nucleoside diphosphate area on HPLC. Treatment of this peak with venom phosphodiesterase degraded it and concurrently nullified its inhibitory activity versus IMPDH; alkaline phosphatase, on the other hand, totally failed to digest the anabolite. These results suggest that the metabolite in question is the phosphodiester, benzamide adenine dinucleotide (BAD). Evidence that the inhibitor was an analog of NAD, wherein the nicotinamide moiety has been replaced by benzamide, was provided by both NMR and mass spectrometric analysis and confirmed by enzymatic synthesis. Further insight into the nature of the active principle was obtained from kinetic studies, which established that BAD competitively inhibited NAD utilization by partially purified IMPDH from K562 cells with a K(i) of 0.118 μM. In concert, these studies establish that benzamide riboside exhibits potent antiproliferative activity by inhibiting IMPDH through BAD.

Original languageEnglish
Pages (from-to)892-899
Number of pages8
JournalInternational Journal of Cancer
Volume56
Issue number6
StatePublished - 1994

Fingerprint

IMP Dehydrogenase
Adenine
K562 Cells
Nucleosides
NAD
Inosine Monophosphate
Myeloid Leukemia
Niacinamide
Diphosphates
Venoms
Phosphoric Diester Hydrolases
Guanosine Triphosphate
Inhibitory Concentration 50
Alkaline Phosphatase
3-(1-deoxyribofuranosyl)benzamide
Neoplasms
Cell Culture Techniques
High Pressure Liquid Chromatography
benzamide
Enzymes

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Gharehbaghi, K., Paull, K. D., Kelley, J. A., Barchi, J. J., Marquez, V. E., Cooney, D. A., ... Jayaram, H. N. (1994). Cytotoxicity and characterization of an active metabolite of benzamide riboside, a novel inhibitor of IMP dehydrogenase. International Journal of Cancer, 56(6), 892-899.

Cytotoxicity and characterization of an active metabolite of benzamide riboside, a novel inhibitor of IMP dehydrogenase. / Gharehbaghi, K.; Paull, K. D.; Kelley, J. A.; Barchi, J. J.; Marquez, V. E.; Cooney, D. A.; Monks, A.; Scudiero, D.; Krohn, K.; Jayaram, H. N.

In: International Journal of Cancer, Vol. 56, No. 6, 1994, p. 892-899.

Research output: Contribution to journalArticle

Gharehbaghi, K, Paull, KD, Kelley, JA, Barchi, JJ, Marquez, VE, Cooney, DA, Monks, A, Scudiero, D, Krohn, K & Jayaram, HN 1994, 'Cytotoxicity and characterization of an active metabolite of benzamide riboside, a novel inhibitor of IMP dehydrogenase', International Journal of Cancer, vol. 56, no. 6, pp. 892-899.
Gharehbaghi, K. ; Paull, K. D. ; Kelley, J. A. ; Barchi, J. J. ; Marquez, V. E. ; Cooney, D. A. ; Monks, A. ; Scudiero, D. ; Krohn, K. ; Jayaram, H. N. / Cytotoxicity and characterization of an active metabolite of benzamide riboside, a novel inhibitor of IMP dehydrogenase. In: International Journal of Cancer. 1994 ; Vol. 56, No. 6. pp. 892-899.
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abstract = "Benzamide riboside exhibits significant cytotoxicity against a variety of human tumor cells in culture. On the basis of metabolic studies, the primary target of this drug's action appears to be IMP dehydrogenase (IMPDH). Incubation of human myelogenous leukemia K562 cells with an IC50 concentration of benzamide riboside resulted in an expansion of IMP pools (5.9-fold), with a parallel reduction in the concentration of GMP (90{\%}), GDP (63{\%}), GTP (55{\%}) and dGTP (40{\%}). On kinetic grounds, it was deduced that benzamide riboside (whose K(i) versus IMPDH is 6.4 mM, while that of its 5'-monophosphate is 3.9 mM) or its 5'-monophosphate were unlikely to be responsible for inhibition of this target enzyme, IMPDH, since only micromolar concentrations of benzamide riboside were needed to exert potent inhibition of tumor-cell growth. Studies on the metabolism of this C-nucleoside have revealed the presence of a new peak eluting in the nucleoside diphosphate area on HPLC. Treatment of this peak with venom phosphodiesterase degraded it and concurrently nullified its inhibitory activity versus IMPDH; alkaline phosphatase, on the other hand, totally failed to digest the anabolite. These results suggest that the metabolite in question is the phosphodiester, benzamide adenine dinucleotide (BAD). Evidence that the inhibitor was an analog of NAD, wherein the nicotinamide moiety has been replaced by benzamide, was provided by both NMR and mass spectrometric analysis and confirmed by enzymatic synthesis. Further insight into the nature of the active principle was obtained from kinetic studies, which established that BAD competitively inhibited NAD utilization by partially purified IMPDH from K562 cells with a K(i) of 0.118 μM. In concert, these studies establish that benzamide riboside exhibits potent antiproliferative activity by inhibiting IMPDH through BAD.",
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AU - Gharehbaghi, K.

AU - Paull, K. D.

AU - Kelley, J. A.

AU - Barchi, J. J.

AU - Marquez, V. E.

AU - Cooney, D. A.

AU - Monks, A.

AU - Scudiero, D.

AU - Krohn, K.

AU - Jayaram, H. N.

PY - 1994

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N2 - Benzamide riboside exhibits significant cytotoxicity against a variety of human tumor cells in culture. On the basis of metabolic studies, the primary target of this drug's action appears to be IMP dehydrogenase (IMPDH). Incubation of human myelogenous leukemia K562 cells with an IC50 concentration of benzamide riboside resulted in an expansion of IMP pools (5.9-fold), with a parallel reduction in the concentration of GMP (90%), GDP (63%), GTP (55%) and dGTP (40%). On kinetic grounds, it was deduced that benzamide riboside (whose K(i) versus IMPDH is 6.4 mM, while that of its 5'-monophosphate is 3.9 mM) or its 5'-monophosphate were unlikely to be responsible for inhibition of this target enzyme, IMPDH, since only micromolar concentrations of benzamide riboside were needed to exert potent inhibition of tumor-cell growth. Studies on the metabolism of this C-nucleoside have revealed the presence of a new peak eluting in the nucleoside diphosphate area on HPLC. Treatment of this peak with venom phosphodiesterase degraded it and concurrently nullified its inhibitory activity versus IMPDH; alkaline phosphatase, on the other hand, totally failed to digest the anabolite. These results suggest that the metabolite in question is the phosphodiester, benzamide adenine dinucleotide (BAD). Evidence that the inhibitor was an analog of NAD, wherein the nicotinamide moiety has been replaced by benzamide, was provided by both NMR and mass spectrometric analysis and confirmed by enzymatic synthesis. Further insight into the nature of the active principle was obtained from kinetic studies, which established that BAD competitively inhibited NAD utilization by partially purified IMPDH from K562 cells with a K(i) of 0.118 μM. In concert, these studies establish that benzamide riboside exhibits potent antiproliferative activity by inhibiting IMPDH through BAD.

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