Increases in NMR-visible lipid and glycerophosphocholine during phenylbutyrate-induced apoptosis in human prostate cancer cells

DU145 human prostatic carcinoma cells were treated with 3 the differentiating agents phenylacetate (PA) and phenylbutyrate (PB) and examined in perfused cultures by diffusion-weighted H-1 and P-31 nuclear magnetic resonance spectroscopy (NMR). PA and PB (10 mM) induced significant (> 3-fold) time-dependent increases in the level of NMR-visible lipids and total choline in 1H spectra, and glycerophosphocholine levels in the P-31 spectra, with the increases being greater for PB. These effects were accompanied by significant increases in cytoplasmic lipid droplets and intracellular lipid volume fraction as observed by morphometric analysis of Oil Red O-stained cells. PB treatment caused cell cycle arrest in the G, phase and induction of apoptosis. In contrast, PA-treated DU145 cells showed all accumulation of cells in G(2)/M and no evidence of apoptosis. These results demonstrate that significant differences exist in the mechanism of PA and PB activity, although both compounds cause similar, but graded alterations in lipid metabolism. The simultaneous accumulation of mobile lipid and glycerophosphocholine suggests that PB and PA induce phospholipid catabolism via a phospholipase-mediated pathway. The mobile lipid accumulation following the induction of either apoptosis and cytostasis by related differentiating agents indicate that the presence of NMR-visible lipids may not be a specific event causally resulting from the induction of apoptosis. (c) 2005 Elsevier B.V. All rights reserved.