Disulfiram Facilitates Intracellular Cu Uptake and Induces Apoptosis in Human Melanoma Cells

Abstract

The alcohol-abuse deterrent disulfiram (DSF) is shown to have a highly selective toxicity against melanoma in culture, inducing a largely apoptotic response, with much lower toxicity against several other cell lines. Melanoma cell lines derived from different stages (radial, vertical, and metastatic phase) were all sensitive to DSF treatment in vitro; melanocytes were only slightly affected. A required role of extracellular Cu is demonstrated for DSF toxicity. Low concentrations of DSF alone decreased the number of viable cells, and the addition of CuCl2 significantly enhanced the DSF-induced cell death to less than 10% of control. Significantly, the intracellular Cu concentration of melanoma cells increased rapidly upon DSF treatment. Both the intracellular Cu uptake and the toxicity induced by DSF were blocked by co-incubation with bathocuproine disulfonic acid (BCPD, 100 μM), a non-membrane-permeable Cu chelator. Chemical studies demonstrated a complicated, extracellular redox reaction between Cu(II) and DSF, which forms the complex Cu(deDTC)2 in high yield, accompanied by oxidative decomposition of small amounts of disulfiram. The Cu complex has somewhat higher activity against melanoma and is suggested to be the active agent in DSF-induced toxicity. The redox conversion of DSF was unique to Cu(II) and not engendered by the other common biological metal ions Fe(II or III), Mn(III), and Zn(II). The implications of this work are significant both in the possible treatment of melanoma as well as in limiting the known side-effects of DSF, which we propose may be diminished by cotreatment to decrease adventitious Cu.

Disulfiram when Combined with Copper Enhances the Therapeutic Effects of Temozolomide for the Treatment of Glioblastoma

“…Recently, several independent groups, including this study, have identified DSF through high-throughput screens as a potential therapeutic for the treatment of various cancers including glioblastoma (14)(15)(16)(17)(18)(19). As DSF has been used clinically for over 60 years to treat alcoholism, its pharmacokinetics has been extensively studied and shown to have an excellent safety record at FDArecommended doses (20,21).…”

“…DSF is available, inexpensive, safe, and overall well-tolerated making it an attractive candidate for "repurposing" in the context of glioblastoma. Although the anticancer mechanisms of DSF are still not well-understood (22), published data indicate that the cytotoxicity of DSF is enhanced in the presence of copper (14,15,23). DSF chelates bivalent metals such as copper (Cu) and zinc (Zn) to form DSF metal complexes that inhibit proteasome activity and block the degradation of IkB and NFkB nuclear translocation (24)(25)(26).…”

NQO1-activated phenothiazinium redox cyclers for the targeted bioreductive induction of cancer cell apoptosis

“…According to this hypothesis, pro-oxidant pharmacological agents that substantially increase cellular ROS would induce deviations from redox homeostasis that do not reduce viability of untransformed cells, but cannot be tolerated by malignant cells that are already under high constitutive oxidative stress [1,12]. Indeed, prooxidant redox agents including metal-based drugs such as dithiocarbamate chelates [13] and therapeutics in advanced clinical development such as texaphyrins [14] can achieve cancer cell-selective cytotoxicity [15,16].…”

Development and characterisation of disulfiram-loaded PLGA nanoparticles for the treatment of non-small cell lung cancer

“…The anticancer effect of DSF has been shown to be Cu dependent [37][38] However, the level of protection does depend on the formulation and sonication time used. The choice of PLGA has no significant (p > 0.05) influence on the level of DSF protection that the nanoparticles provide ( Figure 4A), which is due to the size of the nanoparticles being similar (Figure 2A).…”

“…This anticancer effect is copper (Cu) dependent [37][38] as Cu plays a crucial role in redox reactions which trigger the generation of reactive oxygen species (ROS) inducing apoptosis in human cells [39]. A recent phase IIb study demonstrated that DSF in combination with cisplatin and vinorelbine was well tolerated and prolonged the survival of patients with newly diagnosed NSCLC [40].…”