Figure 2: STM induces apoptosis in A549 cells. (a) A549 cells were treated with 0 and 40 μM STM for 24 h. The cells treated with 40 μM STM were stained either with PI or with Annexin V-FITC, while untreated cells were not stained with either probe. The samples were run on flow cytometry for compensation controls (upper). A549 cells were treated with the indicated concentration of STM in the presence or absence of 3 mM NAC for 24 h. Cells were stained with Annexin V/PI and apoptosis was determined by flow cytometry (lower). (b) Statistical analysis of data from (a). Columns not sharing the same superscript letters within the same group differ significantly ().