Figure 1: Morphological changes of A549 lung cancer cells after 48 hr ATO exposure. A-Untreated control; B – 2 µg/ml ATO; C – 4 µg/ml ATO; and D - 6 µg/ml ATO. A549 cells were observed using an Olympus Inverted Phase Contrast Microscope with camera (C-Squared), at (20x) magnification for Panel A and Panel B, and (40x) magnification for Panel C and Panel D. Cells in Panels A and B maintained normal morphological features. The black arrow shows an example of cell shrinkage in Panel C, and an evidence of chromatin condensation and membrane blebbing in Panel D; bo`th of which are indicative of apoptosis.