13C and 31P NMR investigation of effect of 6-aminonicotinamide on metabolism of RIF-1 tumor cells in vitro.
The effect of 6-aminonicotinamide on the metabolism of RIF-1 tumor cells was investigated using 13C and 31P NMR spectroscopy. 6-Aminonicotinamide can be metabolized to 6-amino-NAD(P), a competitive inhibitor of NAD(P)-requiring processes. 40 microM 6-aminonicotinamide led to an inhibition of 6-phosphogluconate dehydrogenase and an accumulation of 6-phosphogluconate. A subsequent accumulation of the 6-phosphogluconate precursor 6-phosphoglucono-delta-lactone was observed in the 13C NMR spectrum. These metabolites were shown to be intracellular, although a small amount of leakage of 6-phosphoglucono-delta-lactone occurred. The intracellular concentrations of 6-phosphogluconate and 6-phosphoglucono-delta-lactone were 1.9 +/- 0.8 micromol/108 cells (+/-1 standard deviation) and 0.8 +/- 0.4 micromol/10(8) cells, respectively, after 15 h. Glucose utilization and lactate production were significantly inhibited by 6-aminonicotinamide (both p < 0.05), indicating inhibition of glycolysis. 31P NMR data showed that phosphocreatine was significantly depleted in cells exposed to 6-aminonicotinamide (p < 0.05). Exposure of RIF-1 cells to 6-aminonicotinamide prior to 3- or 6-Gy x-irradiation induced a supra-additive cell kill, indicating that 6-aminonicotinamide is acting as a radiosensitizer. There was no effect of 6-aminonicotinamide alone or when the drug was given postradiation, suggesting that its mechanism of action may be by inhibition of radiation-induced repair.
Street
J C
JC
Department of Medical Physics, Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Mahmood
U
U
Ballon
D
D
Alfieri
A A
AA
Koutcher
J A
JA
D015120:6-Aminonicotinamide / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002247:Carbon Isotopes; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005354:Fibrosarcoma; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis / Q000187:drug effects*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009381:Neoplasms, Radiation-Induced; D010758:Phosphorus; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014965:X-Rays
D002247:Carbon Isotopes; D010758:Phosphorus; D015120:6-Aminonicotinamide; D005947:Glucose