Metabolic signatures associated with a NAD synthesis inhibitor-induced tumor apoptosis identified by 1H-decoupled-31P magnetic resonance spectroscopy.
OBJECTIVE
Attempts to selectively initiate tumor cell death through inducible apoptotic pathways are increasingly being exploited as a potential anticancer strategy. Inhibition of NAD+ synthesis by a novel agent FK866 has been recently reported to induce apoptosis in human leukemia, hepatocarcinoma cells in vitro, and various types of tumor xenografts in vivo. In the present study, we used 1H-decoupled phosphorus (31P) magnetic resonance spectroscopy (MRS) to examine the metabolic changes associated with FK866 induced tumor cell death in a mouse mammary carcinoma.


METHODS
Induction of apoptosis in FK866-treated tumors was confirmed by histology and cytofluorometric analysis. FK866-induced changes in mammary carcinoma tumor metabolism in vivo were investigated using 1H-decoupled 31P MRS. To discern further the changes in metabolic profiles of tumors observed in vivo, high-resolution in vitro 1H-decoupled 31P MRS studies were carried out with perchloric acid extracts of mammary carcinoma tumors excised after similar treatments. In addition, the effects of FK866 on mammary carcinoma tumor growth and radiation sensitivity were studied.


RESULTS
Treatment with FK866 induced a tumor growth delay and enhanced radiation sensitivity in mammary carcinoma tumors that was associated with significant increases in the 31P MR signal in the phosphomonoester region and a decrease in NAD+ levels, pH, and bioenergetic status. The 31P MRS of perchloric acid extracts of treated tumors identified the large unresolved signal in the phosphomonoester region as the resultant of resonances originating from intermediates of tumor glycolysis and guanylate synthesis in addition to alterations in pyridine nucleotide pools and phospholipid metabolism.


CONCLUSIONS
The present results suggest that FK866 interferes with multiple biochemical pathways that contribute to the increased cell death (apoptosis) and subsequent radiation sensitivity observed in the mammary carcinoma that could be serially monitored by 31P MRS.
Muruganandham
Manickam
M
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Alfieri
Alan A
AA
Matei
Cornelia
C
Chen
Yuchun
Y
Sukenick
George
G
Schemainda
Isabel
I
Hasmann
Max
M
Saltz
Leonard B
LB
Koutcher
Jason A
JA
D000178:Acrylamides / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D006019:Glycolysis / Q000187:drug effects; D006150:Guanine Nucleotides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D008938:Mitosis / Q000187:drug effects; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009368:Neoplasm Transplantation; D054409:Nicotinamide Phosphoribosyltransferase; D010430:Pentosyltransferases / Q000037:antagonists & inhibitors; D010743:Phospholipids / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology* / Q000627:therapeutic use; D011485:Protein Binding / Q000187:drug effects; D013997:Time Factors
D000178:Acrylamides; D017304:Annexin A5; D006150:Guanine Nucleotides; C480543:N-(4-(1-benzoylpiperidin-4-yl)butyl)-3-(pyridin-3-yl)acrylamide; D010743:Phospholipids; D010880:Piperidines; D009243:NAD; D009249:NADP; D010430:Pentosyltransferases; D054409:Nicotinamide Phosphoribosyltransferase