Though cancer cells typically have a higher than normal content of ROS due to relative anoxia, additional oxidative stress is lethal due to oxidation and disruption of membrane lipids, proteins, and DNA [23]. To assess the involvement of ROS in apoptosis following sigma-2 receptor CH5183284 mouse ligand Ivacaftor cell line treatement, we examined the influence of antioxidants on cell death. ROS production in Bxpc3 cells following 24 hour treatment with SW43 (60 μM), PB282 (90 μM), and H2O2(100 μM) was detected with 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate acetyl ester (CM-H2DCFDA) as described in the Materials and Methods. Substantial amounts of ROS were

detected with SW43 and H2O2, but no ROS was detectable after treatment with PB282. ROS was decreased following SW43 treatment in the presence of antioxidants α-tocopherol (α-toco) and n-acetylcysteine (NAC), while ROS from H2O2 was only decreased by NAC (Figure 6A). The impact of antioxidants on cell viability was

assessed following 24 hour treatment Rabusertib with SW43 and PB282. Antioxidants protected against sigma-2 receptor ligand induced cell death, with NAC protecting against SW43 to a greater extent than α-toco. Interestingly, while PB282 treatment did not result in detectable ROS release, both antioxidants increased tumor cell viability after PB282 exposure (Figure 6B). Figure 6 Antioxidants are protective of much cellular toxicity. (A) ROS detection by flow cytometry in Bxpc3 cells with 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA) following 24 hour treatment with SW43 (60 μM), PB282 (90 μM), or hydrogen peroxide (H2O2, 100 μM) in the presence of lipophilic antioxidant α-tocopherol (α-toco) or hydrophilic antioxidant N-acetylcyteine (NAC). (B) Cell viability following 24 hour treatment with SW43 or PB282 in the presence of α-toco or NAC. Data

represents percent viability compared to DMSO treated cells, n = 3, * p < 0.05. Caspase-3 inhibition by lipophilic antioxidant correlates with caspase dependence Caspase-3 has been extensively studied as a mechanism of sigma-2 receptor ligand mediated apoptosis, and we wished to examine the impact of ROS stimulation by structurally different ligands. Basal caspase-3 activity by SW43, PB282, and HCQ treatment following 24 hours was detected by cleavage of Z-DEVD-AMC as previously described [10] (Figure 7A). This activation was inhibited by α-toco following PB282 treatment, but not following SW43 or HCQ treatment. NAC, however, decreased caspase-3 activation by all compounds. DEVD-FMK caspase-3 inhibitor was used as a positive control for inhibition in all experiments.