Augmentation of oxidative stress-induced apoptosis in MCF7 cells by ascorbate–tamoxifen and/or ascorbate–juglone treatments

Abstract

Since reactive oxygen species (ROS) play diverse roles in cancer, modulating the redox status of cancerous cells seems to be a promising therapeutic approach. Oxidant-targeted therapy appears logical for intervention with the acquired adaptive response to oxidative stress in cancer. In this study, we investigated the cytotoxic effects of juglone (J) and tamoxifen (T) and also the combination of each with ascorbate (A): tamoxifen/ascorbate (TA) and/or juglone/ascorbate (JA) on MCF7 cancerous cells. The results revealed that the growth inhibitory effects of juglone and tamoxifen were each associated with enhanced levels of ROS production and lipid peroxidation. These effects were markedly intensified in tamoxifen/ascorbate and juglone/ascorbate co-treatments. On the other hand, the intracellular anti-oxidant components such as reduced glutathione (GSH), catalase, superoxide dismutase (SOD), and glutathione peroxidase significantly declined in cells subjected to combination treatments compared to that in cells exposed solely to tamoxifen, juglone, and the untreated control cells. In addition, ascorbate association induced more apoptotic and necrotic or necrotic-like cell death than cells treated with each drug alone. These results were further confirmed by comparing the Bax/Bcl2 ratio in combination-treated cells. Additionally, ascorbate was able to potentiate the cytotoxic effects of combination therapy via activation of ROS-responsive factors including Foxo family members.

Natural Products to Fight Cancer: A Focus on Juglans regia

“…Glutathione (GSH), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase protein levels diminished, validating the hypothesis of their consumption by juglone-induced ROS formation [ 93 ]. Juglone-mediated oxidative stress triggered forkhead box O3 (FOXO3), that, in turn, modulated p53 and altered the cellular homeostatic balance, prompting apoptosis [ 93 ]. Another interesting study showed that juglone cytotoxicity is, at least partially, ascribed to DNA damage.…”

“…Juglone ( Figure 1 ) is a member of this family, acting as a growth-stunting agent [ 136 ] and apoptosis inducer. It exhibits antitumour activity on many types of tumours, such as breast [ 92 , 93 , 94 , 95 , 137 ], skin [ 99 , 100 , 137 ], glial cells [ 109 , 110 , 111 , 135 , 138 ], lung [ 137 , 138 ], prostate [ 105 , 106 , 107 , 137 ], pancreas [ 97 ], bladder [ 108 ], stomach [ 98 ], cervix [ 102 , 103 , 139 , 140 ], ovary [ 104 ], and blood [ 113 , 114 ]. For some of them, the mechanism of action has been investigated.…”

“…Juglone exhibited anticancer effects on different breast cancer models. On MCF-7, doxo-resistant MCF-7 (MCF-7Adr) and transtuzumab-resistant SKBR3, juglone promoted G1 cell-cycle arrest [ 94 , 95 ] and ROS-driven apoptosis [ 92 , 93 , 95 ]. An exhaustive study on MCF-7 proved that juglone increased Bax/Bcl2 ratio , intracellular calcium (Ca 2+ ) levels, ΔΨ disruption, cytochrome c (Cyt-c) release and caspase 3 activation, demonstrating the activation of the intrinsic apoptotic pathway [ 92 ].…”

“…An exhaustive study on MCF-7 proved that juglone increased Bax/Bcl2 ratio , intracellular calcium (Ca 2+ ) levels, ΔΨ disruption, cytochrome c (Cyt-c) release and caspase 3 activation, demonstrating the activation of the intrinsic apoptotic pathway [ 92 ]. On MCF-7 and SKBR3, it inhibited cell proliferation, colony formation, and migration capability [ 93 , 94 ], while on MCF-7Adr, angiogenesis was inhibited by decreased levels of VEGF-A, -B and -C [ 94 ]. The prooxidant profile of juglone was investigated on MCF-7.…”

Overview of biological mechanisms of human carcinogens

“…Tamoxifen induced a significant reduction in fat mass in adipose mice and transiently stimulated the production of reactive oxygen species (ROS) in these mice in vivo, and in murine adipocytes exposed in vitro (Liu et al 2015). The growth-inhibitory effects of tamoxifen on MCF7 human breast cancer cells were associated with enhanced levels of ROS production and lipid peroxidation (Sajadimajd, Yazdanparast, and Roshanzamir 2016).…”