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Figure 1: Effect of STM on proliferation and cell death. (a) NL-20, A549, and NCI-H1650 cells were treated with the indicated concentrations of STM for 24 h and cell proliferation was determined by the MTT assay. Data are expressed as mean ± SEM of three different experiments. Columns not sharing the same superscript letter differ significantly (). (b) NL-20, A549, and NCI-H1650 cells were treated with the indicated concentrations of STM in the presence or absence of 3 mM NAC for 24 h. Cells’ morphological changes were observed under a phase-contrast microscope and images were captured. (c) NL-20, A549, and NCI-H1650 cells were treated with the indicated concentrations of STM for 24 h and live and dead cells were quantified using live/dead assay. Pretreatment of cells with NAC reversed STM-induced death in A549 cells. Data are expressed as mean ± SEM (). Columns not sharing the same superscript letters differ significantly ().