Genomic alterations and enormous monoclonal immunoglobulin production cause multiple myeloma to heavily depend on proteostasis mechanisms, including protein folding and degradation. These findings support the use of proteasome inhibitors for treating multiple myeloma and mantle cell lymphoma. Myeloma treatment has evolved, especially with the availability of new drugs, such as proteasome inhibitors, into therapeutic strategies for both frontline and relapsed/refractory disease settings. However, proteasome inhibitors are generally not effective enough to cure most patients. Natural resistance and eventual acquired resistance led to relapsed/refractory disease and poor prognosis. Advances in the understanding of cellular proteostasis and the development of innovative drugs that also target other proteostasis network components offer opportunities to exploit the intrinsic vulnerability of myeloma cells. This review outlines recent findings on the molecular mechanisms regulating cellular proteostasis pathways, as well as resistance, sensitivity, and escape strategies developed against proteasome inhibitors and provides a rationale and examples for novel combinations of proteasome inhibitors with FDA-approved drugs and investigational drugs targeting the NRF1 (NFE2L1)-mediated proteasome bounce-back response, redox homeostasis, heat shock response, unfolding protein response, autophagy, and VCP/p97 to increase proteotoxic stress, which can improve the efficacy of antimyeloma therapy based on proteasome inhibitors.

• Keywords
• Autophagy, Heat shock response, Proteasome bounce-back response, Redox homeostasis, UPR, VCP/p97,
• MeSH
• Drug Resistance, Neoplasm MeSH
• Proteostasis * drug effects   MeSH
• Proteasome Inhibitors * therapeutic use   pharmacology   MeSH
• Humans MeSH
• Multiple Myeloma * drug therapy   metabolism   MeSH
• Antineoplastic Agents * therapeutic use   pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Proteasome Inhibitors * MeSH
• Antineoplastic Agents * MeSH

Advanced metastatic colorectal cancer (CRC) with deficient DNA mismatch repair (MMR-d), or immune-hot CRCs, show significantly improved clinical outcomes compared to MMR-proficient (MMR-p), or immune-cold CRCs. While the prior represents about 5% of all CRCs, the latter represent 95% and are characterized by low immunogenicity. This study investigates bis-diethyldithiocarbamate (CuET), a novel anticancer compound, and its impact on the colorectal cancer tumor microenvironment (TME). CuET is shown to convert immunologically inactive tumors into hotbeds of antitumor immune responses, marked by increased lymphocyte infiltration, heightened cytotoxicity of natural killer (NK) and T cells, and enhanced non-self recognition by lymphocytes. The potent anticancer cytotoxicity and in vivo safety and efficacy of CuET are established. In summary, CuET transforms the colorectal cancer TME, bolstering NK and T cell cytotoxicity and refining tumor cell recognition through non-classical activation via the NKG2D/NKG2DL axis. This study unveils a novel mechanism of action for CuET: a potent immunomodulator capable of turning cold tumors hot.

• Keywords
• NK cells, NKG2D, colorectal cancer, copper bis-diethyldithiocarbamate, disulfiram,
• MeSH
• Killer Cells, Natural immunology   drug effects   MeSH
• Cytotoxicity, Immunologic drug effects   MeSH
• Ditiocarb * pharmacology   chemistry   MeSH
• Colorectal Neoplasms * immunology   drug therapy   pathology   metabolism   MeSH
• Coordination Complexes * pharmacology   MeSH
• NK Cell Lectin-Like Receptor Subfamily K * metabolism   immunology   MeSH
• Humans MeSH
• Copper * chemistry   pharmacology   MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Tumor Microenvironment * drug effects   immunology   MeSH
• Antineoplastic Agents * pharmacology   MeSH
• Signal Transduction drug effects   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Ditiocarb * MeSH
• KLRK1 protein, human MeSH Browser
• Coordination Complexes * MeSH
• NK Cell Lectin-Like Receptor Subfamily K * MeSH
• Copper * MeSH
• Antineoplastic Agents * MeSH

Recent efforts to repurpose disulfiram, a drug used in alcohol-aversion therapy for decades, for other diseases suggest the molecule is almost an in vitro panacea: it seems to be effective against various cancers (by multiple mechanisms of action), Alzheimer's disease, obesity and metabolic syndrome, pythiosis, lyme borreliosis, COVID-19, and sepsis. The problem is that the molecule almost does not exist in the body after ingestion and, most importantly, is not the pharmacologically active entity in alcoholic patients, being rather a prodrug. This prodrug is widely and misleadingly used in many in vitro and in vivo experiments regardless of its physiologically reachable concentration or its metabolism in vivo.

• Publication type
• Journal Article MeSH

Drug repurposing is a versatile strategy to improve current therapies. Disulfiram has long been used in the treatment of alcohol dependency and multiple clinical trials to evaluate its clinical value in oncology are ongoing. We have recently reported that the disulfiram metabolite diethyldithiocarbamate, when combined with copper (CuET), targets the NPL4 adapter of the p97VCP segregase to suppress the growth of a spectrum of cancer cell lines and xenograft models in vivo. CuET induces proteotoxic stress and genotoxic effects, however important issues concerning the full range of the CuET-evoked tumor cell phenotypes, their temporal order, and mechanistic basis have remained largely unexplored. Here, we have addressed these outstanding questions and show that in diverse human cancer cell models, CuET causes a very early translational arrest through the integrated stress response (ISR), later followed by features of nucleolar stress. Furthermore, we report that CuET entraps p53 in NPL4-rich aggregates leading to elevated p53 protein and its functional inhibition, consistent with the possibility of CuET-triggered cell death being p53-independent. Our transcriptomics profiling revealed activation of pro-survival adaptive pathways of ribosomal biogenesis (RiBi) and autophagy upon prolonged exposure to CuET, indicating potential feedback responses to CuET treatment. The latter concept was validated here by simultaneous pharmacological inhibition of RiBi and/or autophagy that further enhanced CuET's tumor cytotoxicity, using both cell culture and zebrafish in vivo preclinical models. Overall, these findings expand the mechanistic repertoire of CuET's anti-cancer activity, inform about the temporal order of responses and identify an unorthodox new mechanism of targeting p53. Our results are discussed in light of cancer-associated endogenous stresses as exploitable tumor vulnerabilities and may inspire future clinical applications of CuET in oncology, including combinatorial treatments and focus on potential advantages of using certain validated drug metabolites, rather than old, approved drugs with their, often complex, metabolic profiles.

• MeSH
• Zebrafish metabolism   MeSH
• Disulfiram * metabolism   MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Tumor Suppressor Protein p53 genetics   metabolism   MeSH
• Neoplasms * metabolism   MeSH
• Ribosomes metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Disulfiram * MeSH
• Tumor Suppressor Protein p53 MeSH

Cannabidiol (CBD) is an easily accessible and affordable Marijuana (Cannabis sativa L.) plant derivative with an extensive history of medical use spanning thousands of years. Interest in the therapeutic potential of CBD has increased in recent years, including its anti-tumour properties in various cancer models. In addition to the direct anticancer effects of CBD, preclinical research on numerous cannabinoids, including CBD, has highlighted their potential use in: (i) attenuating chemotherapy-induced adverse effects and (ii) enhancing the efficacy of some anticancer drugs. Therefore, CBD is gaining popularity as a supportive therapy during cancer treatment, often in combination with standard-of-care cancer chemotherapeutics. However, CBD is a biologically active substance that modulates various cellular targets, thereby possibly resulting in unpredictable outcomes, especially in combinations with other medications and therapeutic modalities. In this review, we summarize the current knowledge of CBD interactions with selected anticancer chemotherapeutics, discuss the emerging mechanistic basis for the observed biological effects, and highlight both the potential benefits and risks of such combined treatments. Apart from the experimental and preclinical results, we also indicate the planned or ongoing clinical trials aiming to evaluate the impact of CBD combinations in oncology. The results of these and future trials are essential to provide better guidance for oncologists to judge the benefit-versus-risk ratio of these exciting treatment strategies. We hope that our present overview of this rapidly advancing field of biomedicine will inspire more preclinical and clinical studies to further our understanding of the underlying biology and optimize the benefits for cancer patients.

• Keywords
• cancer, cannabidiol, chemotherapy, drug–drug interaction,
• MeSH
• Cannabis * MeSH
• Cannabidiol * pharmacology   therapeutic use   MeSH
• Cannabinoids * therapeutic use   MeSH
• Drug Interactions MeSH
• Humans MeSH
• Neoplasms * drug therapy   MeSH
• Antineoplastic Agents * pharmacology   therapeutic use   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Cannabidiol * MeSH
• Cannabinoids * MeSH
• Antineoplastic Agents * MeSH

The current Coronavirus 2019 (COVID-19) pandemic has shown us that the pharmaceutical research community can organize and administer large nonprofit clinical trials (RECOVERY and SOLIDARITY) and achieve the swift development of common, unpatentable drugs for a new indication: in this case an old, inexpensive drug, dexamethasone, for COVID-19. Why is it that such nonprofit efforts are so rare and are not organized as a systemic, routine part of drug development in the public interest? Based on my own experience with repurposing the alcohol-abuse drug disulfiram (Antabuse) for cancer, I identify at least four serious deadlocks to development of nonprofit drugs. All of these obstacles should be addressed to leverage the potential of the COVID-19 pandemic for better future healthcare systems in all countries around the world.

• Keywords
• Biomedicine, COVID-19, Clinical trials, Dexamethasone, Disulfiram, Nonprofit drugs,
• MeSH
• COVID-19 * MeSH
• Disulfiram MeSH
• Humans MeSH
• Organizations, Nonprofit MeSH
• Pandemics * MeSH
• Delivery of Health Care MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Disulfiram MeSH

Disulfiram (DSF), an established alcohol-aversion drug, is a candidate for repurposing in cancer treatment. DSF's antitumor activity is supported by preclinical studies, case reports, and small clinical trials; however, ongoing clinical trials of advanced-stage cancer patients encounter variable results. Here, we show that one reason for the inconsistent clinical effects of DSF may reflect interference by other drugs. Using a high-throughput screening and automated microscopy, we identify cannabidiol, an abundant component of the marijuana plant used by cancer patients to mitigate side effects of chemotherapy, as a likely cause of resistance to DSF. Mechanistically, in cancer cells, cannabidiol triggers the expression of metallothioneins providing protective effects by binding heavy metal-based substances including the bis-diethyldithiocarbamate-copper complex (CuET). CuET is the documented anticancer metabolite of DSF, and we show here that the CuET's anticancer toxicity is effectively neutralized by metallothioneins. Overall, this work highlights an example of undesirable interference between cancer therapy and the concomitant usage of marijuana products. In contrast, we report that insufficiency of metallothioneins sensitizes cancer cells toward CuET, suggesting a potential predictive biomarker for DSF repurposing in oncology.

• Keywords
• CuET, cancer, cannabidiol, disulfiram, metallothionein,
• MeSH
• Disulfiram * chemistry   pharmacology   therapeutic use   MeSH
• Cannabidiol * pharmacology   therapeutic use   MeSH
• Humans MeSH
• Copper chemistry   pharmacology   MeSH
• Metallothionein MeSH
• Cell Line, Tumor MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Disulfiram * MeSH
• Cannabidiol * MeSH
• Copper MeSH
• Metallothionein MeSH

The metal complex copper diethyldithiocarbamate (CuET) induces cancer cell death by inhibiting protein degradation and induces proteotoxic stress, making CuET a promising cancer therapeutic. However, no clinical formulation of CuET exists to date as the drug is insoluble in water and exhibits poor bioavailability. To develop a scalable formulation, nanoliposomal (LP) CuET was synthesized using ethanol injection as a facile one-step method that is suitable for large-scale manufacturing. The nanoparticles are monodispersed, colloidally stable, and approximately 100 nm in diameter with an encapsulation efficiency of over 80%. LP-CuET demonstrates excellent stability in plasma, minimal size change, and little drug release after six-month storage at various temperatures. Additionally, melanoma cell lines exhibit significant sensitivity to LP-CuET and cellular uptake occurs predominantly through endocytosis in YUMM 1.7 cancer cells. Intracellular drug delivery is mediated by vesicle acidification with more nanoparticles being internalized by melanoma cells compared with RAW 264.7 macrophages. Additionally, the nanoparticles preferentially accumulate in YUMM 1.7 tumors where they induce cancer cell death in vivo. The development and characterization of a stable and scalable CuET formulation illustrated in this study fulfils the requirements needed for a potent clinical grade formulation.

• Keywords
• cancer therapeutics, copper diethyldithiocarbamate, drug delivery, ethanol injection, liposomes, melanoma, protein corona,
• Publication type
• Journal Article MeSH

Despite several approved therapeutic modalities, multiple myeloma (MM) remains an incurable blood malignancy and only a small fraction of patients achieves prolonged disease control. The common anti-MM treatment targets proteasome with specific inhibitors (PI). The resulting interference with protein degradation is particularly toxic to MM cells as they typically accumulate large amounts of toxic proteins. However, MM cells often acquire resistance to PIs through aberrant expression or mutations of proteasome subunits such as PSMB5, resulting in disease recurrence and further treatment failure. Here we propose CuET-a proteasome-like inhibitor agent that is spontaneously formed in-vivo and in-vitro from the approved alcohol-abuse drug disulfiram (DSF), as a readily available treatment effective against diverse resistant forms of MM. We show that CuET efficiently kills also resistant MM cells adapted to proliferate under exposure to common anti-myeloma drugs such as bortezomib and carfilzomib used as the first-line therapy, as well as to other experimental drugs targeting protein degradation upstream of the proteasome. Furthermore, CuET can overcome also the adaptation mechanism based on reduced proteasome load, another clinically relevant form of treatment resistance. Data obtained from experimental treatment-resistant cellular models of human MM are further corroborated using rather unique advanced cytotoxicity experiments on myeloma and normal blood cells obtained from fresh patient biopsies including newly diagnosed as well as relapsed and treatment-resistant MM. Overall our findings suggest that disulfiram repurposing particularly if combined with copper supplementation may offer a promising and readily available treatment option for patients suffering from relapsed and/or therapy-resistant multiple myeloma.

• MeSH
• Bortezomib pharmacology   therapeutic use   MeSH
• Drug Resistance, Neoplasm MeSH
• Disulfiram pharmacology   MeSH
• Proteasome Inhibitors pharmacology   therapeutic use   MeSH
• Humans MeSH
• Neoplasm Recurrence, Local drug therapy   MeSH
• Multiple Myeloma * pathology   MeSH
• Cell Line, Tumor MeSH
• Drug Repositioning MeSH
• Proteasome Endopeptidase Complex metabolism   MeSH
• Antineoplastic Agents * pharmacology   therapeutic use   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Bortezomib MeSH
• Disulfiram MeSH
• Proteasome Inhibitors MeSH
• Proteasome Endopeptidase Complex MeSH
• Antineoplastic Agents * MeSH

Multiple myeloma (MM) is a malignant disease of the plasma cells representing approximately 10% of all hemato-oncological diseases. Detection of the disease is most probable at around 65 years of age, and the average survival of patients is estimated to be 5-10 years, specifically due to frequent relapses and resistance to the therapy used. Thus, the search for new therapeutic approaches is becoming a big challenge. Disulfiram (DSF), a substance primarily known as a medication against alcoholism, has often been mentioned in recent years in relation to cancer treatment for its secondary anti-cancer effects. Recent studies performed on myeloma cell lines confirm high inhibition of the cell growth activity if a complex of disulfiram and copper is used. Its significant potential is now being seen in the cure of haematological malignities.

• Keywords
• disulfiram, multiple myeloma, pharmacoresistant, relapses, therapy,
• MeSH
• Disulfiram * therapeutic use   MeSH
• Humans MeSH
• Neoplasm Recurrence, Local MeSH
• Copper MeSH
• Multiple Myeloma * drug therapy   MeSH
• Cell Line, Tumor MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Disulfiram * MeSH
• Copper MeSH