CHARACTERIZATION OF A SPECIFIC SIGNAL FROM HUMAN PANCREATIC TUMORS HETEROTRANSPLANTED INTO NUDE-MICE - STUDY BY HIGH-RESOLUTION H-1-NMR ANDHPLC

In a previous study, we demonstrated the existence of a 3.2 +/- 0.2 pp m peak in the H-1 NMR spectrum at 60 MHz from human pancreatic adenoca rcinomas (Capan-1 cell) heterotransplanted into nude mice. This peak, which is not present in normal human pancreas, was attributed to enhan ced membrane fluidity and/or an increase in phospholipid turnover. The present study was designed to identify this signal by comparing the H -1 NMR spectra recorded in vivo at 100 MHz from Capan-1 tumors, after suppression of the tissular water proton peak, to those recorded from normal pancreatic tissue, and to those recorded at 300 MHz from lipid extracts. The H-1 NMR spectra at 100 MHz of the Capan-1 tumors in vivo exhibited three main peaks in the 3.2 +/- 0.2 ppm region: 1. A peak a t 2.8 +/- 0.1 ppm from CH2 protons of the acyl chains of unsaturated p hospholipids; 2. A peak at 3.2 +/- 0.1 ppm from the protons of the N(C H3)3 group of choline; and 3 A peak at 3.5 +/- 0.1 ppm attributed to G PC. The NMR H-1 300 MHz spectrum of phospholipid extracts of Capan-1 t umors displayed 12 principal resonances, of which only the N(CH3)3 pea k of PC had a similar chemical shift to that observed at low resolutio n (3.2 +/- 0.2 ppm). This peak had a higher intensity in the xenograft s than in normal human pancreatic tissue. HPLC analysis of the same li pid extracts from Capan-1 cells in culture, of tumors derived from the se cells and from normal pancreas showed: 1. Identical concentrations of the different phospholipids from cancerous human pancreatic cells i n vivo and in culture; and 2. A significantly higher level of PC in th e extracts of normal human pancreatic tissue. The increase in intensit y of the N(CH3)3 peak of PC in the Capan-1 tumors was not thought to b e caused by an increase in PC concentration, but to a difference in co nformation or mobility of the PC protons in the xenografts. The increa se in relaxation time in cancerous tissue (from 60 to 125 ms) was also taken to be evidence in favor of a high mobility of protons. The peak observed at 3.2 +/- 0.2 ppm in the low resolution NMR spectra from th e Capan-1 tumors in vivo thus represents a combination of several phen omena:1. An increase in membrane fluidity as a result of an enhanced m obility of the N(CH3)3 protons of PC; 2. An increase in concentration of unsaturated fatty acids; and 3. A rise in GPC levels from an increa se in turnover of phospholipids or from tumor necrosis.