Anticancer response to disulfiram may be enhanced by co-treatment with MEK inhibitor or oxaliplatin: modulation by tetrathiomolybdate, KRAS/BRAF mutations and c-MYC/p53 status

Targeting aldehyde dehydrogenase enzymes in combination with chemotherapy and immunotherapy: An approach to tackle resistance in cancer cells

Modern cancer chemotherapy originated in the 1940s, and since then, many chemotherapeutic agents have been developed. However, most of these agents show limited response in patients due to innate and acquired resistance to therapy, which leads to the development of multi-drug resistance to different treatment modalities, leading to cancer recurrence and, eventually, patient death. One of the crucial players in inducing chemotherapy resistance is the aldehyde dehydrogenase (ALDH) enzyme. ALDH is overexpressed in chemotherapy-resistant cancer cells, which detoxifies the generated toxic aldehydes from chemotherapy, preventing the formation of reactive oxygen species and, thus, inhibiting the induction of oxidative stress and the stimulation of DNA damage and cell death. This review discusses the mechanisms of chemotherapy resistance in cancer cells promoted by ALDH. In addition, we provide detailed insight into the role of ALDH in cancer stemness, metastasis, metabolism, and cell death. Several studies investigated targeting ALDH in combination with other treatments as a potential therapeutic regimen to overcome resistance. We also highlight novel approaches in ALDH inhibition, including the potential synergistic employment of ALDH inhibitors in combination with chemotherapy or immunotherapy against different cancers, including head and neck, colorectal, breast, lung, and liver.

Design and Synthesis of Orally Active Quinolyl Pyrazinamides as Sigma 2 Receptor Ligands for the Treatment of Pancreatic Cancer

Sigma 2 receptor (σ2R) is overexpressed in select cancers and is regarded as a biomarker for tumor proliferation. σ2R ligands are emerging as promising theranostics for cancer and neurodegenerative diseases. Herein, we describe the design and synthesis of a series of novel quinolyl pyrazinamides as selective and potent σ2R ligands that show sub-micromolar potency in pancreatic cancer cell lines. Compounds 14 (JR1-157) and 17 (JR2-298) bind σ2R with K_i of 47 and 10 nM, respectively. Importantly, compound 14 has an oral bioavailability of 60% and shows significant in vivo efficacy without obvious toxicity in a syngeneic model of pancreatic cancer. The cytotoxicity of the quinolyl pyrazinamides significantly enhanced in the presence of copper and diminished in the presence of the copper-chelator tetrathiomolybdate. In conclusion, compound 14 is water-soluble, metabolically stable, orally active, and increases the expression of the autophagy marker LC3B and warrants further development for the treatment of pancreatic cancer.

Anticancer effects of disulfiram: a systematic review of in vitro, animal, and human studies

BACKGROUND AND OBJECTIVES

Cancer morbidity and mortality rates remain high, and thus, at present, considerable efforts are focused on finding drugs with higher sensitivity against tumor cells and fewer side effects. Disulfiram (DSF), as an anti-alcoholic drug, kills the cancer cells by inducing apoptosis. Several preclinical and clinical studies have examined the potential of repurposing DSF as an anticancer treatment. This systematic review aimed to assess evidence regarding the antineoplastic activity of DSF in in vitro and in vivo models, as well as in humans.

METHODS

Two authors independently conducted this systematic review of English and Chinese articles from the PubMed, Embase, and the Cochrane Library databases up to July 2019. Eligible in vitro studies needed to include assessments of the apoptosis rate by flow cytometry using annexin V/propidium iodide, and studies in animal models and clinical trials needed to examine tumor inhibition rates, and progression-free survival (PFS) and overall survival (OS), respectively. Data were analyzed using descriptive statistics.

RESULTS

Overall, 35 studies, i.e., 21 performed in vitro, 11 based on animal models, and three clinical trials, were finally included. In vitro and animal studies indicated that DSF was associated with enhanced apoptosis and tumor inhibition rates, separately. Human studies showed that DSF prolongs PFS and OS. The greatest anti-tumor activity was observed when DSF was used as combination therapy or as a nanoparticle-encapsulated molecule. There was no noticeable body weight loss after DSF treatment, which indicated that there was no major toxicity of DSF.

CONCLUSIONS

This systematic review provides evidence regarding the anti-tumor activity of DSF in vitro, in animals, and in humans and indicates the optimal forms of treatment to be evaluated in future research.

Disruption of Redox Homeostasis by Alterations in Nitric Oxide Synthase Activity and Tetrahydrobiopterin along with Melanoma Progression

Cutaneous melanoma emerges from the malignant transformation of melanocytes and is the most aggressive type of skin cancer. The progression can occur in different stages: radial growth phase (RGP), vertical growth phase (VGP), and metastasis. Reactive oxygen species contribute to all phases of melanomagenesis through the modulation of oncogenic signaling pathways. Tetrahydrobiopterin (BH4) is an important cofactor for NOS coupling, and an uncoupled enzyme is a source of superoxide anion (O2•-) rather than nitric oxide (NO), altering the redox homeostasis and contributing to melanoma progression. In the present work, we showed that the BH4 amount varies between different cell lines corresponding to distinct stages of melanoma progression; however, they all presented higher O2•- levels and lower NO levels compared to melanocytes. Our results showed increased NOS expression in melanoma cells, contributing to NOS uncoupling. BH4 supplementation of RGP cells, and the DAHP treatment of metastatic melanoma cells reduced cell growth. Finally, Western blot analysis indicated that both treatments act on the PI3K/AKT and MAPK pathways of these melanoma cells in different ways. Disruption of cellular redox homeostasis by the altered BH4 concentration can be explored as a therapeutic strategy according to the stage of melanoma.

The Double-Edged Sword of Oxidative Stress in Skin Damage and Melanoma: From Physiopathology to Therapeutical Approaches

The skin is constantly exposed to exogenous and endogenous sources of reactive oxygen species (ROS). An adequate balance between ROS levels and antioxidant defenses is necessary for the optimal cell and tissue functions, especially for the skin, since it must face additional ROS sources that do not affect other tissues, including UV radiation. Melanocytes are more exposed to oxidative stress than other cells, also due to the melanin production process, which itself contributes to generating ROS. There is an increasing amount of evidence that oxidative stress may play a role in many skin diseases, including melanoma, being the primary cause or being a cofactor that aggravates the primary condition. Indeed, oxidative stress is emerging as another major force involved in all the phases of melanoma development, not only in the arising of the malignancy but also in the progression toward the metastatic phenotype. Furthermore, oxidative stress seems to play a role also in chemoresistance and thus has become a target for therapy. In this review, we discuss the existing knowledge on oxidative stress in the skin, examining sources and defenses, giving particular consideration to melanocytes. Therefore, we focus on the significance of oxidative stress in melanoma, thus analyzing the possibility to exploit the induction of oxidative stress as a therapeutic strategy to improve the effectiveness of therapeutic management of melanoma.

Disulfiram/copper induces antitumor activity against gastric cancer cells in vitro and in vivo by inhibiting S6K1 and c-Myc

PURPOSE

Disulfiram (DSF) is an approved drug for the treatment of alcohol dependence. Accumulating evidence indicates that DSF, alone or in combination with copper (Cu), possesses strong antitumor activity in various malignancies. This study investigated the effects of DSF on gastric cancer (GC) and the potential mechanisms involved.

METHODS

GC cell proliferation and apoptosis upon treatment with DSF with or without copper were analyzed using CCK-8 assay, colony formation assay, and flow cytometry. Glucose metabolism was investigated using glucose consumption and lactate production assays. The expression of caspase-3, Bcl-2, LC-3, P62, S6K1, c-Myc, GLUT1, PKM2, and LDHA was analyzed using western blot assay. In vivo nude mice studies were performed to verify the findings from in vitro analyses.

RESULTS

Our study showed that DSF was highly toxic to GC cells in a Cu-dependent manner. Nontoxic concentrations of Cu enhanced the inhibitory effects of DSF on cell viability and colony formation. DSF also induced apoptotic and autophagic cell death in the presence of Cu. In addition, DSF/Cu inhibited glycolysis and xenograft growth of GC cells by suppressing the expression of S6K1, c-Myc, and their downstream molecules, including GLUT1, PKM2, and LDHA.

CONCLUSION

Our study demonstrated that DSF/Cu exerted antitumor activity against GC cells both in vitro and in vivo. DSF/Cu may represent a promising therapeutic strategy for the treatment of GC.

Disulfiram as a Therapeutic Agent for Metastatic Malignant Melanoma-Old Myth or New Logos?

Simple Summary

In recent years, disulfiram has gained in attention as an anticancer drug due to its broad activity against various cancers, and its mechanisms and molecular targets have been deciphered in vitro and in vivo. One of these cancers is melanoma. Initial data from human studies show some benefit, but do not confirm its broad efficacy as a monotherapy. However, combination approaches could pave the way for exploiting the beneficial effects of disulfiram for cancer patients, including those with melanoma.

Abstract

New therapeutic concepts such as anti-PD-1-based immunotherapy or targeted therapy with BRAF and MEK inhibitors have significantly improved the survival of melanoma patients. However, about 20% of patients with targeted therapy and up to 50% with immunotherapies do not respond to their first-line treatment or rapidly develop resistance. In addition, there is no approved targeted therapy for certain subgroups, namely BRAF wild-type melanomas, although they often bear aggressive tumor biology. A repurposing of already approved drugs is a promising strategy to fill this gap, as it will result in comparatively low costs, lower risks and time savings. Disulfiram (DSF), the first drug to treat alcoholism, which received approval from the US Food and Drug Administration more than 60 years ago, is such a drug candidate. There is growing evidence that DSF has great potential for the treatment of various human cancers, including melanoma. Several mechanisms of its antitumor activity have been identified, amongst them the inhibition of the ubiquitin-proteasome system, the induction of reactive oxygen species and various death signaling pathways. This article provides an overview of the application of DSF in humans, its molecular mechanisms and targets in cancer therapy with a focus on melanoma. The results of clinical studies and experimental combination approaches of DSF with various cancer therapies are discussed, with the aim of exploring the potential of DSF in melanoma therapy.

Cancer Pro-oxidant Therapy Through Copper Redox Cycling: Repurposing Disulfiram and Tetrathiomolybdate

Background:

Copper (Cu) is a transition metal active in Fenton redox cycling from reduced Cu+ and H2O2, to oxidized Cu2+ and the hydroxyl radical (·OH) highly reactive oxygen species (ROS). At homeostatic Cu levels, ROS promote cell proliferation, migration, angiogenesis, and wound repair. To limit ROS toxicity, cells use Cu-dependent chaperone proteins, Cu-binding ceruloplasmin, and Cu-modulated enzymes like superoxide dismutases (SOD) like SOD1 and SOD3 to scavenge excess superoxide anions which favour Cu+ reduction, and mitochondrial cytochrome c oxidase, important in aerobic energy production. Because Cu helps drive tumor cell proliferation by promoting growth factor-independent receptor tyrosine kinase signaling, and Cu-dependent MEK1 involved in oncogenic BRAF-V600E signaling, further augmenting bioavailable Cu may promote ROS overproduction, cancer progression and eventually tumor cell death. For these reasons, the following clinically approved copper chelators are being repurposed as anti-cancer agents: a) ammonium tetrathiomolybdate (TTM) used to treat Wilson’s disease (copper overload) and Menkes disease (copper deficiency); b) Disulfiram (DSF), used against alcoholism, since it inhibits Aldehyde Dehydrogenase (ALDH1) enzyme, important in ethanol detoxification, and a key target against cancer stem cells. Moreover, TTM and DSF are also relevant in cancer clinical trials, because they increase the uptake of both Cu and Platinum (Pt)-containing anti-cancer drugs, since Pt and Cu share the same CTR1 copper transporter.

Purpose:

The majority of reports on Cu chelators dealt separately with either TTM, DSF or others. Here, we compare in parallel, the anti-cancer efficacy of low doses of TTM and DSF, asking whether they can be synergistic or antagonistic. The relevance of their unequal ROS inducing abilities and their different behavior as ionophores is also addressed.

Significance:

The potential of Cu chelators as repurposed anti-cancer drugs, should be greater in patients with higher endogenous Cu levels. Since platinum and Cu share uptake receptors, the synergism by drugs containing these metals should not be under-estimated. The potential of disulfiram or its metabolically active Cu-containing form, to inhibit ALDH1-positive tumor cells is therapeutically very important.

Identification of Novel Small-Molecule Kinase Modulators for the Treatment of Neuroblastoma

Neuroblastoma represents 8-10% of all childhood cancer cases and is responsible for 15% of all cancer-related deaths in infants. Even though patients with low- and intermediate-risk disease have a good prognosis, the 5-year survival rate of the vast majority of patients with high-risk neuroblastoma is 50%. Despite extensive research efforts to find a cure for neuroblastoma, current treatment options are still limited. The aim of our study was to identify novel therapeutic compounds using high-throughput drug screening of a small molecule kinase inhibitor library containing 960 compounds. This screening resulted in the identification of two compounds, ST013381 and ST022328, that showed pronounced cytotoxic effects in six human neuroblastoma cell lines in vitro while having reduced effects in the BJ-5ta control cell line. These effects were observed in both MYCN-amplified and -non-amplified cells, indicating that these compounds can affect a wide range of neuroblastomas. Our experiments also revealed that several signaling pathways underlie the selective elimination of neuroblastoma cells by the ST013381 and ST022328 compounds. In summary, we have identified two novel compounds with a strong cytotoxic effect in vitro as promising agents for the treatment of neuroblastoma.

Repurposing Disulfiram as An Anti-Cancer Agent: Updated Review on Literature and Patents

BACKGROUND

Despite years of success of most anti-cancer drugs, one of the major clinical problems is inherent and acquired resistance to these drugs. Overcoming the drug resistance or developing new drugs would offer promising strategies in cancer treatment. Disulfiram, a drug currently used in the treatment of chronic alcoholism, has been found to have anti-cancer activity.

OBJECTIVE

To summarize the anti-cancer effects of Disulfiram through a thorough patent review.

METHODS

This article reviews molecular mechanisms and recent patents of Disulfiram in cancer therapy.

RESULTS

Several anti-cancer mechanisms of Disulfiram have been proposed, including triggering oxidative stress by the generation of reactive oxygen species, inhibition of the superoxide dismutase activity, suppression of the ubiquitin-proteasome system, and activation of the mitogen-activated protein kinase pathway. In addition, Disulfiram can reverse the resistance to chemotherapeutic drugs by inhibiting the P-glycoprotein multidrug efflux pump and suppressing the activation of NF-kB, both of which play an important role in the development of drug resistance. Furthermore, Disulfiram has been found to reduce angiogenesis because of its metal chelating properties as well as its ability to inactivate Cu/Zn superoxide dismutase and matrix metalloproteinases. Disulfiram has also been shown to inhibit the proteasomes, DNA topoisomerases, DNA methyltransferase, glutathione S-transferase P1, and O6- methylguanine DNA methyltransferase, a DNA repair protein highly expressed in brain tumors. The patents described in this review demonstrate that Disulfiram is useful as an anti-cancer drug.

CONCLUSION

For years the FDA-approved, well-tolerated, inexpensive, orally-administered drug Disulfiram was used in the treatment of chronic alcoholism, but it has recently demonstrated anti-cancer effects in a range of solid and hematological malignancies. Its combination with copper at clinically relevant concentrations might overcome the resistance of many anti-cancer drugs in vitro, in vivo, and in patients.

Current Biomedical Use of Copper Chelation Therapy

Copper is an essential microelement that plays an important role in a wide variety of biological processes. Copper concentration has to be finely regulated, as any imbalance in its homeostasis can induce abnormalities. In particular, excess copper plays an important role in the etiopathogenesis of the genetic disease Wilson's syndrome, in neurological and neurodegenerative pathologies such as Alzheimer's and Parkinson's diseases, in idiopathic pulmonary fibrosis, in diabetes, and in several forms of cancer. Copper chelating agents are among the most promising tools to keep copper concentration at physiological levels. In this review, we focus on the most relevant compounds experimentally and clinically evaluated for their ability to counteract copper homeostasis deregulation. In particular, we provide a general overview of the main disorders characterized by a pathological increase in copper levels, summarizing the principal copper chelating therapies adopted in clinical trials.