Magnetic resonance spectroscopy detection of increased total and de novo PC in live, perfused cells following 17-AAG treatment. (a) 31P spectra of live, perfused MCF-7 cells illustrating an increase in PC after 48 hours of 17-AAG treatment. (b) 13C spectral array depicting the build-up of [1,2-13C]-PC in perfused MCF-7 cells over a 14-hour period. (c) Graph of build-up of de novo [1,2-13C]-PC in control (blue) and 17-AAG-treated (red) MCF-7 cells over 14 hours of exposure to [1,2-13C]-choline. The data represent an average of three repeats. 17-AAG, 17-allyamino-17-demethoxygeldanamycin; GPC, glycerophosphocholine; NTP, nucleoside triphosphate; PC, phosphocholine; Pi, inorganic phosphate; PPM, parts per million.