Two clinical drugs deubiquitinase inhibitor auranofin and aldehyde dehydrogenase inhibitor disulfiram trigger synergistic anti-tumor effects in vitro and in vivo.

Hongbiao Huang,Changshan Yang,Xiaoying Lan,Xianliang Hua,Jianyu Cai,Xuejun Wang,Yuning Liao,Ningning Liu,Chong Zhao,Jinbao Liu,Huidan Long,Xianping Shi,Xiaofen Li,Jinjie Wu,Dan Zang,Xin Chen

doi:10.18632/oncotarget.6425

Abstract

Inhibition of proteasome-associated deubiquitinases (DUBs) is emerging as a novel strategy for cancer therapy. It was recently reported that auranofin (Aur), a gold (I)-containing compound used clinically to treat rheumatoid arthritis, is a proteasome-associated DUB inhibitor. Disulfiram (DSF), an inhibitor of aldehyde dehydrogenase, is currently in clinical use for treating alcoholism. Recent studies have indicated that DSF can also act as an antitumor agent. We investigated the effect of combining DSF and Aur on apoptosis induction and tumor growth in hepatoma cancer cells. Here we report that (i) the combined treatment of Aur and DSF results in synergistic cytotoxicity to hepatoma cells in vitro and in vivo; (ii) Aur and DSF in combination induces caspase activation, endoplasmic reticulum (ER) stress, and reactive oxygen species (ROS) production; (iii) pan-caspase inhibitor z-VAD-FMK could efficiently block apoptosis but not proteasome inhibition induced by Aur and DSF combined treatment, and ROS is not required for Aur+DSF to induce apoptosis. Collectively, we demonstrate a model of synergism between DSF and proteasome-associated DUB inhibitor Aur in the induction of apoptosis in hepatoma cancer cells, identifying a potential novel anticancer strategy for clinical use in the future.

Highlights

Disulfiram (DSF) is currently in clinical use for the treatment of alcoholism by irreversibly inhibiting aldehyde dehydrogenase
Both Z-VAD-FMK and NAC prevented Aur+DSF co-treatment from inducing cell death (Figure 5B and 5C). These findings are consistent with the proteasome inhibition effects of Aur observed in our previous reports [23]. These results demonstrate that ubiquitinated proteins (Ub-prs) accumulation, prior to caspase activation, is critical to the induction of cell death by the combined treatment
Here we found that DSF and Aur synergistically enhanced reactive oxygen species (ROS) production (Figure 6A), which was blocked by using another antioxidant agent, Vitamin C (100 μM; Figure 6B); to our prior report, the scavenging of ROS by Vitamin C failed to block cell death (Figure 6C), Ub-prs accumulation, or PARP cleavage (Figure 6D) induced by the DSF and Aur www.impactjournals.com/oncotarget co-treatment

Summary

Introduction

Disulfiram (DSF) is currently in clinical use for the treatment of alcoholism by irreversibly inhibiting aldehyde dehydrogenase. Several studies have shown that DSF possesses an anticancer activity in various cancer cells [26,27,28]. It was reported that DSF, as a cooper-binding agent, induced apoptosis in breast cancer via proteasome inhibition [29]. It was reported that DSF, when complexed with copper, could induce ROS-dependent apoptosis of prostate cancer cells [30]. It was reported that DSF and its metabolites could be used as a chemosensitizer of some anti-cancer agents [31]. We report that the combination of Aur and DSF synergistically enhances their cytotoxicity and cell apoptosis of hepatoma cancer cells in both cultures and xenograft models and the synergistic effect is associated with enhancement of proteasome inhibition, induction of ER stress, loss of MMP, and caspase activation

Methods

Results

Conclusion