Figure 8. Pre-treatment of MCF7 cell monolayers with methionine restriction significantly reduces mammosphere formation.

MCF7 cell monolayers were pre-treated with various concentrations of methionine (0, 0.001, 0.01 and 0.1 mM) for 4 days and then trypsinized and re-plated for mammosphere assays (in the presence of normal levels of methionine (0.1 mM)). Note that under these conditions, mammosphere-forming activity was significantly reduced by up to 3-fold (compare 0 vs. 0.1 mM). As such, methionine restriction is also effective at reducing “stemness” in the context of MCF7 cell monolayers.