Magnetic resonance detects metabolic changes associated with chemotherapy-induced apoptosis

Apoptosis was induced by treating L1210 leukaemia cells with mechlorethamin e, and SW620 colorectal cells with doxorubicin. The onset and progression o f apoptosis were monitored by assessing caspase activation, mitochondrial t ransmembrane potential, phosphatidylserine externalization, DNA fragmentati on and cell morphology. In parallel, P-31 magnetic resonance (MR) spectra o f cell extracts were recorded. In L1210 cells, caspase activation was detec ted at 4 h. By 3 h, the MR spectra showed a steady decrease in NTP and NAD, and a significant build-up of fructose 1,6-bisphosphate (F-1,6-P) dihydrox yacetonephosphate and glycerol-3-phosphate, indicating modulation of glycol ysis, Treatment with iodoacetate also induced a build-up of F-1,6-P, while preincubation with two poly(ADP-ribose) polymerase inhibitors, 3-aminobenza mide and nicotinamide, prevented the drop in NAD and the build-up of glycol ytic intermediates, This suggested that our results were due to inhibition of glyceraldehyde-3-phosphate dehydrogenase, possibly as a consequence of N AD depletion following poly(ADP-ribose) polymerase activation. Doxorubicin treatment of the adherent SW620 cells caused cells committed to apoptosis t o detach. F-1,6-P was observed in detached cells, but not in treated cells that remained attached. This indicated that our observations were not cell line- or treatment-specific, but were correlated with the appearance of apo ptotic cells following drug treatment. The P-31 MR spectrum of tumours resp onding to chemotherapy could be modulated by similar effects.