Actionable cancer vulnerability due to translational arrest, p53 aggregation and ribosome biogenesis stress evoked by the disulfiram metabolite CuET

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.

Drug-Drug Interactions of Cannabidiol with Standard-of-Care Chemotherapeutics

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.

Cannabidiol-induced activation of the metallothionein pathway impedes anticancer effects of disulfiram and its metabolite CuET

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.

Abstract 1251: Dithiocarb-copper complex, CuET, demonstrates anti-neoplastic activity in mouse model of prostate cancer and prevents recurrence of tumors

INTRODUCTION Prostate cancer (PCa) is the most common cancer in the North-American man. It was responsible for about 192,000 new cases and 33,000 deaths in the USA in 2020. Surgical resection and systemic androgen deprivation therapy are standard approaches to treat both localized and metastatic PCa (mPCa). The five-year survival from prostate cancer (PCa) without bone metastasis is 56% versus 3% with metastasis There is no cure for the metastatic prostate cancer (mPCa) which often spreads to the hip, spine, and pelvis bones. Therefore, new approaches and combination therapy need to be developed to improve patients's survival. Disulfiram's anti-cancer activity was previously explored and its metabolite ditiocarb-copper complex (CuET) was found to have high anti-cancer activity. The mechanism of action of CuET involves NPL4 aggregation and activation of ER stress, leading to preferential apoptosis of cancer cells. Since altered protein degradation is targeted by CuET, it might display high efficacy in highly mutated PCa. Consequently, we want to propose CuET for the treatment of mPCa.

METHODS Survival curve and colony-formation assays in murine dKO cell line harboring PTEN and Rb driver mutations as well as in the human metastatic PC3 cell line, were performed. Anti-metastatic effect of CuET in vitro was assessed through Boyden chamber. In vivo efficacy of systemic treatment with CuET, was studied in dKO model of C57BL/6 mice.

RESULTS Our results demonstrate that CuET displays cytotoxicity in dKO and PC3 cells at very low concentrations with respective IC50 of 46.2nM and 90.5nM. In vitro, CuET significantly reduced both the clonogenicity and migration ability of cells. In vivo, systemic treatment with CuET significantly reduced growth of dKO tumor and prevented recurrence of tumors.

CONCLUSION Given these positive pre-clinical results, CuET should be investigated for its antineoplastic activity in clinical setting as an adjuvant therapy for mPCa.

Citation Format: Daciana Catalina Dumut, Juan B. DeSanctis, Martin Mistrik, Zdenek Skrott, Petr Dzubak, Jiri Bartek, Marian Hajduch, Danuta Radzioch. Dithiocarb-copper complex, CuET, demonstrates anti-neoplastic activity in mouse model of prostate cancer and prevents recurrence of tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1251.

Microthermal-induced subcellular-targeted protein damage in cells on plasmonic nanosilver-modified surfaces evokes a two-phase HSP-p97/VCP response

Despite proteotoxic stress and heat shock being implicated in diverse pathologies, currently no methodology to inflict defined, subcellular thermal damage exists. Here, we present such a single-cell method compatible with laser-scanning microscopes, adopting the plasmon resonance principle. Dose-defined heat causes protein damage in subcellular compartments, rapid heat-shock chaperone recruitment, and ensuing engagement of the ubiquitin-proteasome system, providing unprecedented insights into the spatiotemporal response to thermal damage relevant for degenerative diseases, with broad applicability in biomedicine. Using this versatile method, we discover that HSP70 chaperone and its interactors are recruited to sites of thermally damaged proteins within seconds, and we report here mechanistically important determinants of such HSP70 recruitment. Finally, we demonstrate a so-far unsuspected involvement of p97(VCP) translocase in the processing of heat-damaged proteins. Overall, we report an approach to inflict targeted thermal protein damage and its application to elucidate cellular stress-response pathways that are emerging as promising therapeutic targets.

Abstract 5246: Disulfiram anticancer metabolite, dithiocarb-copper complex, demonstrates anti-neoplastic activity against hypermutated colorectal cancers

Introduction: Colorectal cancer (CRC) is the third leading cause of cancer related deaths in the United States. It was responsible for about 51,000 deaths during 2019. Surgical resection and systemic chemotherapy are standard approaches to treat both localized and metastatic CRC (mCRC). However, the effect of the chemotherapy depends on the characteristics of the individual tumor, for instance CRC subtypes with a microsatellite instability (MSI) tend to have better prognosis and response to both chemotherapy and immune check-point inhibition. Recently, Disulfiram's anti-cancer activity was explored and its metabolite ditiocarb-copper complex (CuET) was found to have high anti-cancer activity. The mechanism of action of CuET was proposed to act through p97 segregase adaptor NPL4 and activation of endoplasmic reticulum stress leading to preferential apoptosis of cancer cells. Since altered protein degradation pathway is targeted by CuET, this compound might display high efficacy in highly mutated colorectal cancers.

Methods: To assess CuET anti-cancer activity in vitro, we performed survival curve assays and colony-formation assays in both murine hypermutated colorectal cancer cell line MC-38 as well as in human KRAS mutant and MSI HCT116 cell line. We also evaluated anti-metastatic effect of CuET on both cell lines through migration-invasion assays in Boyden chamber setting. We assessed in vivo efficacy of systemic treatment with CuET alone or in combination with irinotecan, against MC-38 model in immunocompetent C57BL/6 mice. We characterized tumor growth, mice survival and tumor histopathology.

Results: Our results demonstrate that CuET displays cytotoxicity in MC-38 and HCT116 cells at very low doses with respective IC50 of 46nM and 88nM. CuET also significantly reduces the ability of both cell lines to grow and form colonies under sustained treatment. Additionally, CuET is effective in significantly reducing cancer cell migration and invasion through porous membrane in vitro. Furthermore, systemic treatment with CuET significantly reduced tumor growth in mice and prolonged survival when compared to controls.

Conclusion: CuET demonstrates cytotoxic activity against hypermutated colorectal cancer cells both in vitro and in vivo and should be further investigated in clinical trials.

Citation Format: Daciana Catalina Dumut, Juan B. De Sanctis, Martin Mistrik, Zdenek Skrott, Petr Dzubak, Jiri Bartek, Marian Hajduch, Danuta Radzioch. Disulfiram anticancer metabolite, dithiocarb-copper complex, demonstrates anti-neoplastic activity against hypermutated colorectal cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5246.

Targeting the NPL4 Adaptor of p97/VCP Segregase by Disulfiram as an Emerging Cancer Vulnerability Evokes Replication Stress and DNA Damage while Silencing the ATR Pathway

Research on repurposing the old alcohol-aversion drug disulfiram (DSF) for cancer treatment has identified inhibition of NPL4, an adaptor of the p97/VCP segregase essential for turnover of proteins involved in multiple pathways, as an unsuspected cancer cell vulnerability. While we reported that NPL4 is targeted by the anticancer metabolite of DSF, the bis-diethyldithiocarbamate-copper complex (CuET), the exact, apparently multifaceted mechanism(s) through which the CuET-induced aggregation of NPL4 kills cancer cells remains to be fully elucidated. Given the pronounced sensitivity to CuET in tumor cell lines lacking the genome integrity caretaker proteins BRCA1 and BRCA2, here we investigated the impact of NPL4 targeting by CuET on DNA replication dynamics and DNA damage response pathways in human cancer cell models. Our results show that CuET treatment interferes with DNA replication, slows down replication fork progression and causes accumulation of single-stranded DNA (ssDNA). Such a replication stress (RS) scenario is associated with DNA damage, preferentially in the S phase, and activates the homologous recombination (HR) DNA repair pathway. At the same time, we find that cellular responses to the CuET-triggered RS are seriously impaired due to concomitant malfunction of the ATRIP-ATR-CHK1 signaling pathway that reflects an unorthodox checkpoint silencing mode through ATR (Ataxia telangiectasia and Rad3 related) kinase sequestration within the CuET-evoked NPL4 protein aggregates.

Targeting genotoxic and proteotoxic stress-response pathways in human prostate cancer by clinically available PARP inhibitors, vorinostat and disulfiram

BACKGROUND

Castration-resistant prostate cancer (PCa) represents a serious health challenge. Based on mechanistically-supported rationale we explored new therapeutic options based on clinically available drugs with anticancer effects, including inhibitors of PARP1 enzyme (PARPi), and histone deacetylases (vorinostat), respectively, and disulfiram (DSF, known as alcohol-abuse drug Antabuse) and its copper-chelating metabolite CuET that inhibit protein turnover.

METHODS

Drugs and their combination with ionizing radiation (IR) were tested in various cytotoxicity assays in three human PCa cell lines including radio-resistant stem-cell like derived cells. Mechanistically, DNA damage repair, heat shock and unfolded protein response (UPR) pathways were assessed by immunofluorescence and immunoblotting.

RESULTS

We observed enhanced sensitivity to PARPi/IR in PC3 cells consistent with lower homologous recombination (HR) repair. Vorinostat sensitized DU145 cells to PARPi/IR and decreased mutant p53. Vorinostat also impaired HR-mediated DNA repair, as determined by Rad51 foci formation and downregulation of TOPBP1 protein, and overcame radio-resistance of stem-cell like DU145-derived cells. All PCa models responded well to CuET or DSF combined with copper. We demonstrated that DSF interacts with copper in the culture media and forms adequate levels of CuET indicating that DSF/copper and CuET may be considered as comparable treatments. Both DSF/copper and CuET evoked hallmarks of UPR in PCa cells, documented by upregulation of ATF4, CHOP and phospho-eIF2α, with ensuing heat shock response encompassing activation of HSF1 and HSP70. Further enhancing the cytotoxicity of CuET, combination with an inhibitor of the anti-apoptotic protein survivin (YM155, currently undergoing clinical trials) promoted the UPR-induced toxicity, yielding synergistic effects of CuET and YM155.

CONCLUSIONS

We propose that targeting genotoxic and proteotoxic stress responses by combinations of available drugs could inspire innovative strategies to treat castration-resistant PCa.

Abstract LB-264: Alcohol-aversion drug disulfiram targets cancer via p97 segregase adaptor NPL4

Cancer incidence is rising and this global challenge is further exacerbated by resistance of advanced tumors to standard-of-care and emerging precision medicines. A promising approach to such unmet need for innovative and cost-effective cancer treatments is drug repurposing, exploitation of drugs already approved for other indications that show anticancer activity. Here we highlight the potential for repurposing disulfiram (Antabuse), an old alcohol-aversion drug that kills a broad range of cancer types in preclinical studies. Our nationwide population study reveals that patients who continued using disulfiram have a lower risk of death from cancer compared to those who stopped using the drug at their diagnosis. More importantly, we identify ditiocarb-copper complex as the metabolite of disulfiram responsible for anticancer effects, present methods to detect its preferential accumulation in tumors and candidate biomarkers of impact in cells and tissues. Finally, our functional and biophysical analyses reveal the long-thought molecular target: NPL4 adapter of the p97/VCP segregase essential for protein recycling involved in multiple stress-response cellular pathways.

Citation Format: Martin Mistrik, Zdenek Skrott, Marian Hajduch, Søren Friis, Petr Dzubak, Jan Gursky, Dusana Majera, Tomas Ozdian, Jana Vaclavkova, Martina Michalova, Pavla Pouckova, Boris Cvek, Klaus Kaae Andersen, Jiři Bartek. Alcohol-aversion drug disulfiram targets cancer via p97 segregase adaptor NPL4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-264.

Alcohol-abuse drug disulfiram targets cancer via p97 segregase adaptor NPL4

Cancer incidence is rising and this global challenge is further exacerbated by tumour resistance to available medicines. A promising approach to such unmet need for improved cancer treatment is drug repurposing. Here we highlight the potential for repurposing disulfiram (Antabuse), an old alcohol-aversion drug effective against diverse cancer types in preclinical studies. Our nationwide epidemiological study reveals that patients who continuously used disulfiram have a lower risk of death from cancer compared to those who stopped using the drug at their diagnosis. Moreover, we identify ditiocarb-copper complex as the metabolite of disulfiram responsible for anticancer effects, and provide methods to detect its preferential accumulation in tumours and candidate biomarkers for impact in cells and tissues. Finally, our functional and biophysical analyses reveal the long-sought molecular target of disulfiram’s tumour suppressing effects as NPL4, an adapter of p97/VCP segregase essential for protein turnover involved in multiple regulatory and stress-response cellular pathways.