Figure 7. Methionine restriction significantly reduces mammosphere formation in MCF7 cells.

Note that mammosphere formation was dramatically inhibited by methionine deprivation. Importantly, mammosphere formation was functionally restored to normal levels by the dose-dependent re-addition of methionine to the methionine-free culture media, with maximal effects occurring at 0.01 mM (10 μM). Mammosphere media normally contains 0.1 mM (100 μM). Parallel experiments with MCF7 cells grown as monolayer cultures are shown for comparison. Interestingly, mammosphere growth is 10-to18-fold more sensitive to the effects of methionine-restriction and replacement. (*)p <0.05.