The in vivo 31P NMR spectrum of T47D human breast cancer cells grown as spheroids shows changes in the phosphomonoester lipid precursors as a function of spheroid size. The ratio of phosphorylethanolamine (PE) to phosphorylcholine (PC) was 1.0±0.3 for 3-day-old, 150 μm spheroids. This ratio increased to 2.4±0.4 for spheroids 7 days and older and which were at least 300 μm in diameter. To investigate the phosphatidylethanolamine to phosphatidylcholine (PdyIE/Pdy1C) ratio in the membranes, chloroform/methanol extracts of spheroids were performed. The 31P spectrum of these extracts showed no change with spheroid size, namely the PdyIE/Pdy1C ratio was 0.5±0.06 for spheroids of all ages suggesting that membrane composition is strongly regulated at the precursor level.
