Figure 4. The antioxidant NAC induces apoptotic cell death in BRCA-null human breast cancer cells. Homotypic HCC1937 cell culture and co-culture with GFP fibroblasts was performed for 48 h. Then, vehicle or 10 mM NAC was added to the cell culture media 48 h prior to measurement of apoptosis with annexin V-APC and PI. Six hours prior to measuring apoptosis, the media was changed to HBSS with and without 10 mM NAC. Note that NAC increases the apoptotic rates of HCC1937 cells by 3.6-fold (p < 4E-5) in homotypic culture (A), and by 1.4-fold in co-culture (B) (p < 0.001).