Our laboratory has developed nuclear magnetic resonance (NMR) techniques for detecting cancer. Using water-suppressed proton (H-1) NMR spectroscopy, we observed that the linewidths of the resonances of methyl and methylene moieties in lipoprotein lipids were consistently narrower in plasma samples from cancer patients than in those from controls. These findings have been corroborated by a number of independent laboratories, but other investigators have been unable to reproduce our results. One reason for the variability of results obtained with H-1 NMR may be that hypertriglyceridemia also induces linewidth narrowing of lipoprotein lipid methyl and methylene resonances, and can cause false positive results. We show that this ambiguity can be circumvented by using a second test based on the carbon-13 (C-13) NMR spectrum of plasma. Here we postulate that the cancer-associated changes seen in H-1 and C-13 NMR spectra are caused by peroxidation of lipoprotein lipids, an effect that may be induced by tumor necrosis factor-alpha released during malignancy.
