FIGURE 3: SFN increases the pH of endosomes of human A549 cells.(A) Cells from the A549 human alveolar adenocarcinoma cell line with and without overexpressed IFITM3 were cultured in media with and without 40 μM SFN and the pH-sensitive dye, Lysotracker Red. Interferon-inducible Transmembrane Protein 3 (IFITM3) is known to enlarge the late endosomes and lysosomal compartments as well as to increase their acidity. A549 cells grown with SFN were less positive for the dye than cells grown in the absence of the drug suggesting that they have more alkaline endosomes. (B) The viability of A549 cells with or without IFITM3 cultured in media with or without SFN was determined by Hoechst staining. Error bars indicate standard deviations for trials with at least three independent cultures. The difference in viabilities was deemed statistically significant by the Student's t-test comparing cells grown in drug with control cells grown in the absence of drug (** p<0.01).