Redeployment-based drug screening identifies the anti-helminthic niclosamide as anti-myeloma therapy that also reduces free light chain production

Niclosamide inhibits epithelial-mesenchymal transition with apoptosis induction in BRAF/ NRAS mutated metastatic melanoma cells

Malignant melanoma is considered a deadly aggressive form of skin cancer that frequently metastasizes to various distal organs, which harbors mutations of the BRAF or NRAS which occur in 30 to 50% of melanoma patients. The growth factors secreted by melanoma cells contribute to tumor angiogenesis with the acquisition of metastatic potential by epithelial-mesenchymal transition (EMT) and drive melanoma growth toward a more aggressive form. Niclosamide (NCL) is an FDA-approved anthelmintic drug and is reported to have strong anti-cancer properties against various solid and liquid tumors. Its role in BRAF or NRAS mutated cells is unknown. In this context, we uncovered the role of NCL in impeding malignant metastatic melanoma in vitro in SK-MEL-2 and SK-MEL-28 cell lines. We found that NCL induces significant ROS generation and apoptosis through a series of molecular mechanisms, such as depolarization of mitochondrial membrane potential, arresting the cell cycle at the sub G1 phase with a significant increase in the DNA cleavage via topoisomerase II in both cell lines. We also found that NCL potently inhibited metastasis, which was examined by scratch wound assay, Additionally, we found that NCL inhibits the most important markers involved in the EMT signaling cascade that are stimulated by TGF-β such as N-cadherin, Snail, Slug, Vimentin, α-SMA and p-Smad 2/3. This work provides useful insights into the mechanism of NCL in BRAF/NRAF mutant melanoma cells via inhibition of molecular signaling events involved in EMT signaling, and apoptosis induction.

A Dual-Responsive STAT3 Inhibitor Nanoprodrug Combined with Oncolytic Virus Elicits Synergistic Antitumor Immune Responses by Igniting Pyroptosis

Immune checkpoint blockade (ICB) therapy shows excellent efficacy against malignancies; however, insufficient tumor immunogenicity and the immunosuppressive tumor microenvironment (TME) are considered as the two major stumbling blocks to a broad ICB response. Here, a combinational therapeutic strategy is reported, wherein TME-reactive oxygen species/pH dual-responsive signal transducers and activators of transcription 3 inhibitor nanoprodrugs MPNPs are combined with oncolytic herpes simplex virus 1 virotherapy to synergistically ignite pyroptosis for enhancing immunotherapy. MPNPs exhibit a certain level of tumor accumulation, reduce tumor cell stemness, and enhance antitumor immune responses. Furthermore, the simultaneous application of oncolytic viruses (OVs) confers MPNPs with higher tumor penetration capacity and remarkable gasdermin-E-mediated pyroptosis, thereby reshaping the TME and transforming "cold" tumors into "hot" ones. This "fire of immunity" strategy successfully activates robust T-cell-dependent antitumor responses, potentiating ICB effects against local recurrence and pulmonary metastasis in preclinical "cold" murine triple-negative breast cancer and syngeneic oral cancer models. Collectively, this work may pave a new way and offer an unprecedented opportunity for the combination of OVs with nanomedicine for cancer immunotherapy.

Niclosamide is a potential candidate for the treatment of chemo-resistant osteosarcoma

Chemotherapy is the main treatment option for advanced osteosarcoma, which is the most common type of primary bone malignancy. However, patients develop resistance rapidly and many succumb to the disease. Niclosamide, an anthelmintic drug, has been recently identified to display potent and selective anti-cancer activity. In this work, we show that niclosamide at sub-micromolar concentrations inhibits proliferation and migration, and induces apoptosis in both parental and chemo-resistant osteosarcoma cells, with much less toxicity in normal osteoblastic cells. Interestingly, chemo-resistant osteosarcoma cells are more sensitive to niclosamide compared to parental cells. We further identify that inhibition of β-catenin is the underlying mechanism of niclosamide's action in osteosarcoma cells. In addition, we reveal that chemo-resistant osteosarcoma cells display increased β-catenin activity compared to parental cells, which might explain the hypersensitivity of chemo-resistant cells to niclosamide. Our work provides pre-clinical evidence that niclosamide can be repurposed for treating osteosarcoma. Our findings also suggest the therapeutic value of β-catenin to overcome osteosarcoma chemo-resistance.

Salicylanilides and Their Anticancer Properties

Salicylanilides are pharmacologically active compounds with a wide spectrum of biological effects. Halogenated salicylanilides, which have been used for decades in human and veterinary medicine as anthelmintics, have recently emerged as candidates for drug repurposing in oncology. The most prominent example of salicylanilide anthelmintic, that is intensively studied for its potential anticancer properties, is niclosamide. Nevertheless, recent studies have discovered extensive anticancer potential in a number of other salicylanilides. This potential of their anticancer action is mediated most likely by diverse mechanisms of action such as uncoupling of oxidative phosphorylation, inhibition of protein tyrosine kinase epidermal growth factor receptor, modulation of different signaling pathways as Wnt/β-catenin, mTORC1, STAT3, NF-κB and Notch signaling pathways or induction of B-Raf V600E inhibition. Here we provide a comprehensive overview of the current knowledge about the proposed mechanisms of action of anticancer activity of salicylanilides based on preclinical in vitro and in vivo studies, or structural requirements for such an activity.

Niclosamide as a Promising Therapeutic Player in Human Cancer and Other Diseases

Niclosamide is an FDA-approved anthelmintic drug for the treatment of parasitic infections. However, over the past few years, increasing evidence has shown that niclosamide could treat diseases beyond parasitic diseases, which include metabolic diseases, immune system diseases, bacterial and viral infections, asthma, arterial constriction, myopia, and cancer. Therefore, we systematically reviewed the pharmacological activities and therapeutic prospects of niclosamide in human disease and cancer and summarized the related molecular mechanisms and signaling pathways, indicating that niclosamide is a promising therapeutic player in various human diseases, including cancer.

Disturbance of the Warburg effect by dichloroacetate and niclosamide suppresses the growth of different sub-types of malignant pleural mesothelioma in vitro and in vivo

Background: Inhalation of asbestos fibers is the most common cause of malignant pleural mesothelioma (MPM). In 2004, the United States Food and Drug Administration approved a combination of cisplatin with pemetrexed to treat unresectable MPM. Nonetheless novel treatment is urgently needed. The objective of this study is to report the combination effect of dichloroacetate (DCA) or niclosamide (Nic) Nic in MPM.

Materials and methods: The effect of a combination of DCA and Nic was studied using a panel of MPM cell lines (H28, MSTO-211H, H226, H2052, and H2452). Cell viability was monitored by MTT assay. Glycolysis, oxidative phosphorylation, glucose, glycogen, pyruvate, lactate, citrate, succinate and ATP levels were determined by corresponding ELISA. Apoptosis, mitochondrial transmembrane potential, cell cycle analysis, hydrogen peroxide and superoxide were investigated by flow cytometry. Cell migration and colony formation were investigated by transwell migration and colony formation assays respectively. The in vivo effect was confirmed using 211H and H226 nude mice xenograft models.

Results and conclusion: Cell viability was reduced. Disturbance of glycolysis and/or oxidative phosphorylation resulted in downregulation of glycogen, citrate and succinate. DCA and/or Nic increased apoptosis, mitochondrial transmembrane depolarization, G2/M arrest and reactive oxygen species. Moreover, DCA and/or Nic suppressed cell migration and colony formation. Furthermore, a better initial tumor suppressive effect was induced by the DCA/Nic combination compared with either drug alone in both 211H and H226 xenograft models. In H226 xenografts, DCA/Nic increased median survival of mice compared with single treatment. Single drug and/or a combination disturbed the Warburg effect and activated apoptosis, and inhibition of migration and proliferation in vivo. In conclusion, dichloroacetate and/or niclosamide showed a tumor suppressive effect in MPM in vitro and in vivo, partially mediated by disturbance of glycolysis/oxidative phosphorylation, apoptosis, ROS production, G2/M arrest, and suppression of migration and proliferation.

The pH Dependence of Niclosamide Solubility, Dissolution, and Morphology: Motivation for Potentially Universal Mucin-Penetrating Nasal and Throat Sprays for COVID19, its Variants and other Viral Infections

Motivation

With the coronavirus pandemic still raging, prophylactic-nasal and early-treatment throat-sprays could help prevent infection and reduce viral load. Niclosamide has the potential to treat a broad-range of viral infections if local bioavailability is optimized as mucin-penetrating solutions that can reach the underlying epithelial cells.

Experimental

pH-dependence of supernatant concentrations and dissolution rates of niclosamide were measured in buffered solutions by UV/Vis-spectroscopy for niclosamide from different suppliers (AK Sci and Sigma), as precipitated material, and as cosolvates. Data was compared to predictions from Henderson-Hasselbalch and precipitation-pH models. Optical-microscopy was used to observe the morphologies of original, converted and precipitated niclosamide.

Results

Niclosamide from the two suppliers had different polymorphs resulting in different dissolution behavior. Supernatant concentrations of the “AKSci-polymorph” increased with increasing pH, from 2.53μM at pH 3.66 to 300μM at pH 9.2, reaching 703μM at pH 9.63. However, the “Sigma-polymorph” equilibrated to much lower final supernatant concentrations, reflective of more stable polymorphs at each pH. Similarly, when precipitated from supersaturated solution, or as cosolvates, niclosamide also equilibrated to lower final supernatant concentrations. Polymorph equilibration though was avoided by using a solvent-exchange technique to make the solutions.

Conclusions

Given niclosamide’s activity as a host cell modulator, optimized niclosamide solutions could represent universal prophylactic nasal and early treatment throat sprays against COVID19, its more contagious variants, and other respiratory viral infections. They are the simplest and potentially most effective formulations from both an efficacy standpoint as well as manufacturing and distribution, (no cold chain). They now just need testing.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03112-x.

The Hyperlipidaemic Drug Fenofibrate Significantly Reduces Infection by SARS-CoV-2 in Cell Culture Models

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic has caused a significant number of fatalities and worldwide disruption. To identify drugs to repurpose to treat SARS-CoV-2 infections, we established a screen to measure the dimerization of angiotensin-converting enzyme 2 (ACE2), the primary receptor for the virus. This screen identified fenofibric acid, the active metabolite of fenofibrate. Fenofibric acid also destabilized the receptor-binding domain (RBD) of the viral spike protein and inhibited RBD binding to ACE2 in enzyme-linked immunosorbent assay (ELISA) and whole cell-binding assays. Fenofibrate and fenofibric acid were tested by two independent laboratories measuring infection of cultured Vero cells using two different SARS-CoV-2 isolates. In both settings at drug concentrations, which are clinically achievable, fenofibrate and fenofibric acid reduced viral infection by up to 70%. Together with its extensive history of clinical use and its relatively good safety profile, this study identifies fenofibrate as a potential therapeutic agent requiring an urgent clinical evaluation to treat SARS-CoV-2 infection.

Anthelminthic niclosamide inhibits tumor growth and invasion in cisplatin-resistant human epidermal growth factor receptor 2-positive breast cancer

Chemotherapy-resistant breast cancer displays aggressive clinical behavior, is poorly differentiated and is associated with the occurrence of epithelial-mesenchymal transition and the presence of cancer stem cells. The anthelmintic drug niclosamide has been shown to have numerous clinical applications in the treatment of malignant tumors, in addition to its traditional use in tapeworm disease. Our previous study demonstrated that niclosamide had an antiproliferative effect and could inhibit the stem-like phenotype of the breast cancer cells, suggesting that it might have the potential to be used in the treatment of triple-negative breast cancer. However, the specific function and underlying mechanism of action of niclosamide in chemoresistant human epidermal growth factor receptor 2 (HER2)-positive breast cancer remain unknown. The present study aimed to determine whether niclosamide can inhibit cell proliferation, invasion and epithelial-to-mesenchymal transition, as well as the stem-like phenotype in cisplatin-resistant HER2-positive breast cancer. Alamar Blue and Annexin V/7-AAD staining, mammosphere formation and Transwell assays were performed to assess the viability, apoptosis, stem-like phenotype and invasion ability of breast cancer cell lines, respectively. Signaling molecule expression was detected via western blotting and a xenograft model was used to verify the inhibitory effect of niclosamide in vivo. The results from the present study demonstrated that niclosamide inhibited the resistance of HER2-positive breast cancer to cisplatin both in vitro and in vivo. Furthermore, niclosamide combined with cisplatin could inhibit breast cancer cell invasion, epithelial-mesenchymal transition and cell stemness. The inhibitory effect of niclosamide was mediated by apoptosis induction and Bcl-2 downregulation. Taken together, the results of the present study suggested that niclosamide combined with cisplatin may be considered as a novel treatment for chemoresistant HER2-positive breast cancer.

Targeting the crosstalk between canonical Wnt/β-catenin and inflammatory signaling cascades: A novel strategy for cancer prevention and therapy

Emerging scientific evidence indicates that inflammation is a critical component of tumor promotion and progression. Most cancers originate from sites of chronic irritation, infections and inflammation, underscoring that the tumor microenvironment is largely orchestrated by inflammatory cells and pro-inflammatory molecules. These inflammatory components are intimately involved in neoplastic processes which foster proliferation, survival, invasion, and migration, making inflammation the primary target for cancer prevention and treatment. The influence of inflammation and the immune system on the progression and development of cancer has recently gained immense interest. The Wnt/β-catenin signaling pathway, an evolutionarily conserved signaling strategy, has a critical role in regulating tissue development. It has been implicated as a major player in cancer development and progression with its regulatory role on inflammatory cascades. Many naturally-occurring and small synthetic molecules endowed with inherent anti-inflammatory properties inhibit this aberrant signaling pathway, making them a promising class of compounds in the fight against inflammatory cancers. This article analyzes available scientific evidence and suggests a crosslink between Wnt/β-catenin signaling and inflammatory pathways in inflammatory cancers, especially breast, gastrointestinal, endometrial, and ovarian cancer. We also highlight emerging experimental findings that numerous anti-inflammatory synthetic and natural compounds target the crosslink between Wnt/β-catenin pathway and inflammatory cascades to achieve cancer prevention and intervention. Current challenges, limitations, and future directions of research are also discussed.

The anti-tumour activity of DNA methylation inhibitor 5-aza-2'-deoxycytidine is enhanced by the common analgesic paracetamol through induction of oxidative stress

The DNA demethylating agent 5-aza-2'-deoxycytidine (DAC, decitabine) has anti-cancer therapeutic potential, but its clinical efficacy is hindered by DNA damage-related side effects and its use in solid tumours is debated. Here we describe how paracetamol augments the effects of DAC on cancer cell proliferation and differentiation, without enhancing DNA damage. Firstly, DAC specifically upregulates cyclooxygenase-2-prostaglandin E2 pathway, inadvertently providing cancer cells with survival potential, while the addition of paracetamol offsets this effect. Secondly, in the presence of paracetamol, DAC treatment leads to glutathione depletion and finally to accumulation of ROS and/or mitochondrial superoxide, both of which have the potential to restrict tumour growth. The benefits of combined treatment are demonstrated here in head and neck squamous cell carcinoma (HNSCC) and acute myeloid leukaemia cell lines, further corroborated in a HNSCC xenograft mouse model and through mining of publicly available DAC and paracetamol responses. The sensitizing effect of paracetamol supplementation is specific to DAC but not its analogue 5-azacitidine. In summary, the addition of paracetamol could allow for DAC dose reduction, widening its clinical usability and providing a strong rationale for consideration in cancer therapy.

Development of a nano-luciferase based assay to measure the binding of SARS-CoV-2 spike receptor binding domain to ACE-2

To identify drugs that could potentially be used to treat infection with SARS-CoV-2, a high throughput 384-well assay was developed to measure the binding of the receptor binding domain (RBD) of the viral S1 protein to its main receptor, angiotensin converting enzyme 2 (ACE2). The RBD was fused to both a HiBIT tag and an IL6 secretion signal to enable facile collection from the cell culture media. The addition of culture media containing this protein, termed HiBIT-RBD, to cells expressing ACE2 led to binding that was specific to ACE2 and both time and concentration dependant, Binding could be inhibited by both RBD expressed in E. coli and by a full length S1 - Fc fusion protein (Fc-fused S1) expressed in eukaryotic cells. The mutation of residues that are known to play a role in the interaction of RBD with ACE2 also reduced binding. This assay may be used to identify drugs which inhibit the viral uptake into cells mediated by binding to ACE2.

1.A high-throughput, 384-well plate assay was developed to measure the binding S1 RBD to ACE2;

2.HiBIT-RBD binds to cells expressing ACE2 specifically and in a time dependant fashion;

3.The binding of HiBIT-RBD to ACE2 can be inhibited using recombinantly expressed SARS-CoV-2 RBD and full-length, Spike S1;

4.Site specific mutations within the RBD demonstrate the specificity of this assay.

Ring-Substituted 1-Hydroxynaphthalene-2-Carboxanilides Inhibit Proliferation and Trigger Mitochondria-Mediated Apoptosis

Ring-substituted 1-hydroxynaphthalene-2-carboxanilides were previously investigated for their antimycobacterial properties. In our study, we have shown their antiproliferative and cell death-inducing effects in cancer cell lines. Cell proliferation and viability were assessed by WST-1 assay and a dye exclusion test, respectively. Cell cycle distribution, phosphatidylserine externalization, levels of reactive oxygen or nitrogen species (RONS), mitochondrial membrane depolarization, and release of cytochrome c were estimated by flow cytometry. Levels of regulatory proteins were determined by Western blotting. Our data suggest that the ability to inhibit the proliferation of THP-1 or MCF-7 cells might be referred to meta- or para-substituted derivatives with electron-withdrawing groups -F, -Br, or -CF₃ at anilide moiety. This effect was accompanied by accumulation of cells in G1 phase. Compound 10 also induced apoptosis in THP-1 cells in association with a loss of mitochondrial membrane potential and production of mitochondrial superoxide. Our study provides a new insight into the action of salicylanilide derivatives, hydroxynaphthalene carboxamides, in cancer cells. Thus, their structure merits further investigation as a model moiety of new small-molecule compounds with potential anticancer properties.

Nanoliposomal Encapsulation Enhances In Vivo Anti-Tumor Activity of Niclosamide against Melanoma

BACKGROUND

Niclosamide is an FDA-approved and old anti-helminthic drug used to treat parasitic infections. Recent studies have shown that niclosamide has broad anti-tumor effects relevant to the treatment of cancer. However, this drug has a low aqueous solubility hindering its systemic use. Herein, we report the preparation and characterization of niclosamide nanoliposomes and their in vivo anti-tumor effects.

METHODS

Nanoliposomes were prepared using thin-film method and the drug was encapsulated with a remote loading method. The nanoliposomes were investigated by the observation of morphology, analysis of particle size and zeta potential. Additionally, qualitative and quantitative analyses were performed using HPLC. We assessed the in vitro cytotoxicity of the nanoliposomal niclosamide on B16F10 melanoma cells. Inhibition of tumor growth was investigated in C57BL/6 mice bearing B16F0 melanoma cancer.

RESULTS

Analytical results indicated that the nanoliposomal system is a homogeneous and stable colloidal dispersion of niclosamide particles. Atomic force microscopy images and particle size analysis revealed that all niclosamide particles had a spherical shape with a diameter of approximately 108nm. According to in vitro and in vivo studies, nanoliposomal niclosamide exhibited a better anti-tumor activity against B16F10 melanoma tumor compared with free niclosamide.

CONCLUSION

Nanoliposomal encapsulation enhanced the aqueous solubility of niclosamide and improved its anti-tumor properties.

Niclosamide inhibits ovarian carcinoma growth by interrupting cellular bioenergetics

Background: Ovarian carcinoma is a common malignant tumor of the female reproductive organs with an incidence rate second only to cervical and endometrial cancers. In the past 10 years, anticancer therapy has focused on Niclosamide, an anthelmintic teniacide that is commonly used against tapeworms and has been approved for use in humans for nearly 50 years. Importantly, Niclosamide has been confirmed to target the Wnt/β-catenin, mTOR, STAT3, NF-κB, and Notch pathways has been widely investigated in multiple cancer types. However, the potential benefits of Niclosamide therapy for treatment of ovarian carcinoma have not been established.

Methods: CCK-8 colony formation assays were performed to evaluate cell viability and tumor growth. Cell apoptosis was measured by flow cytometry. A Seahorse XF96 analyzer was used to measure cellular bioenergetics. Mito-tracker stained mitochondria were visualized by confocal microscopy. Western blotting was used to detect expressed proteins. A nude mouse transplanted-tumor model was used to evaluate the antitumor activity of Niclosamide in ovarian carcinoma.

Result: Niclosamide treatment significantly suppressed ovarian carcinoma growth and induced cell apoptosis by inactivating MEK1/2-ERK1/2 mediated signal transduction. Overall, mitochondrial respiration and aerobic glycolysis were both decreased by Niclosamide treatment. Niclosamide dramatically enhanced ROS-activated and JNK-mediated apoptosis in cells subjected to glucose deprivation. Niclosamide also showed in vivo antitumor activity in the nude mouse transplanted-tumor model.

Conclusion: Collectively, these data highlight a novel anti-tumor mechanism of Niclosamide that involves an interruption of cell metabolism. The finding also indicates a potential for the application of Niclosamide in ovarian carcinoma therapy.

Pharmacological Inhibition of Oncogenic STAT3 and STAT5 Signaling in Hematopoietic Cancers

Signal Transducer and Activator of Transcription (STAT) 3 and 5 are important effectors of cellular transformation, and aberrant STAT3 and STAT5 signaling have been demonstrated in hematopoietic cancers. STAT3 and STAT5 are common targets for different tyrosine kinase oncogenes (TKOs). In addition, STAT3 and STAT5 proteins were shown to contain activating mutations in some rare but aggressive leukemias/lymphomas. Both proteins also contribute to drug resistance in hematopoietic malignancies and are now well recognized as major targets in cancer treatment. The development of inhibitors targeting STAT3 and STAT5 has been the subject of intense investigations during the last decade. This review summarizes the current knowledge of oncogenic STAT3 and STAT5 functions in hematopoietic cancers as well as advances in preclinical and clinical development of pharmacological inhibitors.

Evaluation of the Anti-Tumor Activity of Niclosamide Nanoliposomes Against Colon Carcinoma

BACKGROUND AND AIMS

Niclosamide is an established anti-helminthic drug, which has recently been shown to inhibit the growth of various cancer cells. To exploit the potential anti-tumor activity of this drug for systemic use, the problem of low aqueous solubility should be addressed. The present study tested the in vivo anti-tumor effects of a recently developed nanoliposomal preparation of niclosamide in an experimental model of colon carcinoma.

METHODS

The cytotoxicity of nanoliposomal niclosamide on CT26 colon carcinoma cells was evaluated using the MTT test. Inhibition of tumor growth was investigated in BALB/c mice bearing CT26 colon carcinoma cells. The animals were randomly divided into 4 groups including: 1) untreated control, 2) liposomal doxorubicin (15 mg/kg; single intravenous dose), 3) liposomal niclosamide (1 mg/kg/twice a week; intravenously for 4 weeks), and 4) free niclosamide (1 mg/kg/twice a week; intravenously for 4 weeks). To study therapeutic efficacy, tumor size and survival were monitored in 2-day intervals for 40 days.

RESULTS

In vitro results indicated that nanoliposomal and free niclosamide could exert cytotoxic effects with IC50 values of 4.5 and 2.5 μM, respectively. According to in vivo studies, nanoliposomal niclosamide showed a higher growth inhibitory activity against CT26 colon carcinoma cells compared with free niclosamide as revealed by delayed tumor growth and prolongation of survival.

CONCLUSION

Nnaoliposomal encapsulation enhanced anti-tumor properties of niclosamide in an experimental model of colon carcinoma.

Screening a library of approved drugs reveals that prednisolone synergizes with pitavastatin to induce ovarian cancer cell death

The survival rate for patients with ovarian cancer has changed little in the past three decades since the introduction of platinum-based chemotherapy and new drugs are needed. Statins are drugs used for the treatment and prevention of cardiovascular diseases. Recent work from our laboratory has shown that pitavastatin has potential as a treatment for ovarian cancer if dietary geranylgeraniol is controlled. However, relatively high doses of statins are required to induce apoptosis in cancer cells, increasing the risk of myopathy, the most common adverse effect associated with statins. This makes it desirable to identify drugs which reduce the dose of pitavastatin necessary to treat cancer. A drug-repositioning strategy was employed to identify suitable candidates. Screening a custom library of 100 off-patent drugs for synergistic activity with pitavastatin identified prednisolone as the most prominent hit. Prednisolone potentiated the activity of pitavastatin in several assays measuring the growth, survival or apoptosis in several ovarian cancer cells lines. Prednisolone, alone or in some cases in combination with pitavastatin, reduced the expression of genes encoding enzymes in the mevalonate pathway, providing a mechanistic explanation for the synergy.

Control of invasive sea lampreys using the piscicides TFM and niclosamide: Toxicology, successes & future prospects

The invasion of the Laurentian Great Lakes of North America by sea lampreys (Petromyzon marinus) in the early 20th century contributed to the depletion of commercial, recreational and culturally important fish populations, devastating the economies of communities that relied on the fishery. Sea lamprey populations were subsequently controlled using an aggressive integrated pest-management program which employed barriers and traps to prevent sea lamprey from migrating to their spawning grounds and the use of the piscicides (lampricides) 3-trifluoromethyl-4-nitrophenol (TFM) and niclosamide to eliminate larval sea lampreys from their nursery streams. Although sea lampreys have not been eradicated from the Great Lakes, populations have been suppressed to less than 10% of their peak numbers in the mid-1900s. The ongoing use of lampricides provides the foundation for sea lamprey control in the Great Lakes, one of the most successful invasive species control programs in the world. Yet, significant gaps remain in our understanding of how lampricides are taken-up and handled by sea lampreys, how lampricides exert their toxic effects, and how they adversely affect non-target invertebrate and vertebrates species. In this review we examine what has been learned about the uptake, handling and elimination, and the mode of TFM and niclosamide toxicity in lampreys and in non-target animals, particularly in the last 10 years. It is now clear that the mode of TFM toxicity is the same in non-target fishes and lampreys, in which TFM interferes with oxidative phosphorylation by the mitochondria leading to decreased ATP production. Vulnerability to TFM is related to abiotic factors such as water pH and alkalinity, which we propose changes the relative amounts of the bioavailable un-ionized form of TFM in the gill microenvironment. Niclosamide, which is also a molluscicide used to control snails in areas prone to schistosomiasis infections of humans, also likely works by uncoupling oxidative phosphorylation, but less is known about other aspects of its toxicology. The effects of TFM include reductions in energy stores, particularly glycogen and high energy phosphagens. However, non-target fishes readily recover from sub-lethal TFM exposure as demonstrated by the rapid restoration of energy stores and clearance of TFM. Although both TFM and niclosamide are non-persistent in the environment and critical for sea lamprey control, increasing public and institutional concerns about pesticides in the environment makes it imperative to explore other means of sea lamprey control. Accordingly, we also address possible "next-generation" strategies of sea lamprey control including genetic tools such as RNA interference and CRISPR-Cas9 to impair critical physiological processes (e.g. reproduction, digestion, metamorphosis) in lamprey, and the use of green chemistry to develop more environmentally benign chemical methods of sea lamprey control.

STAT3: A Promising Therapeutic Target in Multiple Myeloma

Multiple myeloma (MM) is an incurable plasma cell malignancy for which novel treatment options are required. Signal Transducer and Activator of Transcription 3 (STAT3) overexpression in MM appears to be mediated by a variety of factors including interleukin-6 signaling and downregulation of Src homology phosphatase-1 (SHP-1). STAT3 overexpression in MM is associated with an adverse prognosis and may play a role in microenvironment-dependent treatment resistance. In addition to its pro-proliferative role, STAT3 upregulates anti-apoptotic proteins and leads to microRNA dysregulation in MM. Phosphatase of regenerating liver 3 (PRL-3) is an oncogenic phosphatase which is upregulated by STAT3. PRL-3 itself promotes STAT-3 phosphorylation resulting in a positive feedback loop. PRL-3 is overexpressed in a subset of MM patients and may cooperate with STAT3 to promote survival of MM cells. Indirectly targeting STAT3 via JAK (janus associated kinase) inhibition has shown promise in early clinical trials. Specific inhibitors of STAT3 showed in vitro efficacy but have failed in clinical trials while several STAT3 inhibitors derived from herbs have been shown to induce apoptosis of MM cells in vitro. Optimising the pharmacokinetic profiles of novel STAT3 inhibitors and identifying how best to combine these agents with existing anti-myeloma therapy are key questions to be addressed in future clinical trials.

Molecules targeting the androgen receptor (AR) signaling axis beyond the AR-Ligand binding domain

Prostate cancer (PCa) is the second most common cause of cancer-related mortality in men in the United States. The androgen receptor (AR) and the physiological pathways it regulates are central to the initiation and progression of PCa. As a member of the nuclear steroid receptor family, it is a transcription factor with three distinct functional domains (ligand-binding domain [LBD], DNA-binding domain [DBD], and transactivation domain [TAD]) in its structure. All clinically approved drugs for PCa ultimately target the AR-LBD. Clinically active drugs that target the DBD and TAD have not yet been developed due to multiple factors. Despite these limitations, the last several years have seen a rise in the discovery of molecules that could successfully target these domains. This review aims to present and comprehensively discuss such molecules that affect AR signaling through direct or indirect interactions with the AR-TAD or the DBD. The compounds discussed here include hairpin polyamides, niclosamide, marine sponge-derived small molecules (eg, EPI compounds), mahanine, VPC compounds, JN compounds, and bromodomain and extraterminal domain inhibitors. We highlight the significant in vitro and in vivo data found for each compound and the apparent limitations and/or potential for further development of these agents as PCa therapies.

Drug repurposing for antimicrobial discovery

Antimicrobial resistance continues to be a public threat on a global scale. The ongoing need to develop new antimicrobial drugs that are effective against multi-drug-resistant pathogens has spurred the research community to invest in various drug discovery strategies, one of which is drug repurposing-the process of finding new uses for existing drugs. While still nascent in the antimicrobial field, the approach is gaining traction in both the public and private sector. While the approach has particular promise in fast-tracking compounds into clinical studies, it nevertheless has substantial obstacles to success. This Review covers the art of repurposing existing drugs for antimicrobial purposes. We discuss enabling screening platforms for antimicrobial discovery and present encouraging findings of novel antimicrobial therapeutic strategies. Also covered are general advantages of repurposing over de novo drug development and challenges of the strategy, including scientific, intellectual property and regulatory issues.

Repositioning salicylanilide anthelmintic drugs to treat adenovirus infections

The repositioning of drugs already approved by regulatory agencies for other indications is an emerging alternative for the development of new antimicrobial therapies. The repositioning process involves lower risks and costs than the de novo development of novel antimicrobial drugs. Currently, infections by adenovirus show a steady increment with a high clinical impact in immunosuppressed and immunocompetent patients. The lack of a safe and efficacious drug to treat these infections supports the search for new antiviral drugs. Here we evaluated the anti-adenovirus activity of niclosanide, oxyclozanide, and rafoxanide, three salicylanilide anthelmintic drugs. Also, we carried out the cytotoxicity evaluation and partial characterization of the mechanism of action of these drugs. The salicylanilide anthelmintic drugs showed significant anti-adenovirus activity at low micromolar concentrations with little cytotoxicity. Moreover, our mechanistic assays suggest differences in the way the drugs exert anti-adenovirus activity. Niclosamide and rafoxanide target transport of the HAdV particle from the endosome to the nuclear envelope, whilst oxyclozanide specifically targets adenovirus immediately early gene E1A transcription. Data suggests that the studied salicylanilide anthelmintic drugs could be suitable for further clinical evaluation for the development of new antiviral drugs to treat infections by adenovirus in immunosuppressed patients and in immunocompetent individuals with community-acquired pneumonia.

Chemical Strategies for Activating PINK1, a Protein Kinase Mutated in Parkinson's Disease

PINK1 is a ubiquitously expressed mitochondrial serine/threonine protein kinase that has emerged as a key player in mitochondrial quality control. This protein kinase came to prominence in the mid-2000s, when PINK1 mutations were found to cause early onset Parkinson's disease (PD). As most of the PD-related mutations occurred in the kinase domain and impaired PINK1's catalytic activity, it was suggested that small molecules that activated PINK1 would maintain mitochondrial quality control and, as a result, have neuroprotective effects. Working on this hypothesis, a few small-molecule PINK1 activators that offer critical insights and distinct approaches for activating PINK1 have been discovered. Herein, we briefly highlight the discovery of these small molecules and offer insight into the future development of small-molecule PINK1 activators as potential treatments for PD.

A phase I study of niclosamide in combination with enzalutamide in men with castration-resistant prostate cancer

BACKGROUND

Niclosamide, an FDA-approved anti-helminthic drug, has activity in preclinical models of castration-resistant prostate cancer (CRPC). Potential mechanisms of action include degrading constitutively active androgen receptor splice variants (AR-Vs) or inhibiting other drug-resistance pathways (e.g., Wnt-signaling). Published pharmacokinetics data suggests that niclosamide has poor oral bioavailability, potentially limiting its use as a cancer drug. Therefore, we launched a Phase I study testing oral niclosamide in combination with enzalutamide, for longer and at higher doses than those used to treat helminthic infections.

METHODS

We conducted a Phase I dose-escalation study testing oral niclosamide plus standard-dose enzalutamide in men with metastatic CRPC previously treated with abiraterone. Niclosamide was given three-times-daily (TID) at the following dose-levels: 500, 1000 or 1500mg. The primary objective was to assess safety. Secondary objectives, included measuring AR-V expression from circulating tumor cells (CTCs) using the AdnaTest assay, evaluating PSA changes and determining niclosamide's pharmacokinetic profile.

RESULTS

20 patients screened and 5 enrolled after passing all screening procedures. 13(65%) patients had detectable CTCs, but only one was AR-V+. There were no dose-limiting toxicities (DLTs) in 3 patients on the 500mg TID cohort; however, both (N = 2) subjects on the 1000mg TID cohort experienced DLTs (prolonged grade 3 nausea, vomiting, diarrhea; and colitis). The maximum plasma concentration ranged from 35.7 to 182 ng/mL and was not consistently above the minimum effective concentration in preclinical studies. There were no PSA declines in any enrolled subject. Because plasma concentrations at the maximum tolerated dose (500mg TID) were not consistently above the expected therapeutic threshold, the Data Safety Monitoring Board closed the study for futility.

CONCLUSIONS

Oral niclosamide could not be escalated above 500mg TID, and plasma concentrations were not consistently above the threshold shown to inhibit growth in CRPC models. Oral niclosamide is not a viable compound for repurposing as a CRPC treatment.

CLINICAL TRIAL REGISTRY

Clinicaltrials.gov: NCT02532114.

Preferential Inhibition of Wnt/β-Catenin Signaling by Novel Benzimidazole Compounds in Triple-Negative Breast Cancer

Wnt/β-catenin signaling is upregulated in triple-negative breast cancer (TNBC) compared to other breast cancer subtypes and normal tissues. Current Wnt/β-catenin inhibitors, such as niclosamide, target the pathway nonspecifically and exhibit poor pharmacokinetics/pharmacodynamics in vivo. Niclosamide targets other pathways, including mTOR, STAT3 and Notch. Novel benzimidazoles have been developed to inhibit Wnt/β-catenin signaling with greater specificity. The compounds SRI33576 and SRI35889 were discovered to produce more cytotoxicity in TNBC cell lines than in noncancerous cells. The agents also downregulated Wnt/β-catenin signaling mediators LRP6, cyclin D1, survivin and nuclear active β-catenin. In addition, SRI33576 did not affect mTOR, STAT3 and Notch signaling in TNBC and noncancerous cells. SRI35889 inhibited mTOR signaling less in noncancerous than in cancerous cells, while not affecting STAT3 and Notch pathways. Compounds SRI32529, SRI35357 and SRI35361 were not selectively cytotoxic against TNBC cell lines compared to MCF10A cells. While SRI32529 inhibited Wnt/β-catenin signaling, the compound also mitigated mTOR, STAT3 and Notch signaling. SRI33576 and SRI35889 were identified as cytotoxic and selective inhibitors of Wnt/β-catenin signaling with therapeutic potential to treat TNBC in vivo.

Niclosamide, a Drug with Many (Re)purposes

Niclosamide is an anthelmintic drug that has been used for over 50 years mainly to treat tapeworm infections. However, with the increase in drug repurposing initiatives, niclosamide has emerged as a true hit in many screens against various diseases. Indeed, from being an anthelmintic drug, it has now shown potential in treating Parkinson's disease, diabetes, viral and microbial infections, as well as various cancers. Such diverse pharmacological activities are a result of niclosamide's ability to uncouple mitochondrial phosphorylation and modulate a selection of signaling pathways, such as Wnt/β-catenin, mTOR and JAK/STAT3, which are implicated in many diseases. In this highlight, we discuss the plethora of diseases that niclosamide has shown promise in treating.

Niclosamide sensitizes nasopharyngeal carcinoma to radiation by downregulating Ku70/80 expression

The aim of the present study was to investigate whether niclosamide could sensitize the nasopharyngeal carcinoma cells to radiation and further explore the underlying mechanisms. CCK-8 assay was used to determine the effect of niclosamide on the proliferation of NPC cells. Colony formation assay was used to evaluate the radiosensitizing effect of niclosamide on NPC cells. Flow cytometry analysis was used to determine the apoptosis of NPC cells induced by niclosamide. Immunofluorescent staining was used to detect the formation of γ-H2AX foci and the localization of Ku70/80 proteins in NPC cells. Real-time PCR quantification analysis was used to examine the level of Ku70/80 mRNA. DNA damage repair-related proteins were detected by western blot analysis. Our results showed that niclosamide markedly suppressed the proliferation of NPC cells. Niclosamide pretreatment followed by irradiation reduced the colony forming ability of NPC cells. Niclosamide in combination with irradiation significantly increased the apoptotic rate of NPC cells. Niclosamide significantly reduced the transcriptional level of K70/80 but not the translocation of Ku70/80 protein induced by irradiation. In conclusion, our study demonstrated that niclosamide could inhibit the growth of NPC cells and sensitize the NPC cells to radiation via suppressing the transcription of Ku70/80.

The Anthelmintic Drug Niclosamide and Its Analogues Activate the Parkinson's Disease Associated Protein Kinase PINK1

Mutations in PINK1, which impair its catalytic kinase activity, are causal for autosomal recessive early‐onset Parkinson's disease (PD). Various studies have indicated that the activation of PINK1 could be a useful strategy in treating neurodegenerative diseases, such as PD. Herein, it is shown that the anthelmintic drug niclosamide and its analogues are capable of activating PINK1 in cells through the reversible impairment of the mitochondrial membrane potential. With these compounds, for the first time, it is demonstrated that the PINK1 pathway is active and detectable in primary neurons. These findings suggest that niclosamide and its analogues are robust compounds for the study of the PINK1 pathway and may hold promise as a therapeutic strategy in PD and related disorders.

Inhibition of Wnt/β-catenin by anthelmintic drug niclosamide effectively targets growth, survival, and angiogenesis of retinoblastoma

Retinoblastoma is an angiogenesis-dependent ocular tumor, the clinical management of which remains a challenge. Agents that can target tumor cells and angiogenesis, as well as augment current chemotherapy efficacy, present a promising therapeutic strategy for retinoblastoma. We demonstrated that niclosamide, an FDA-approved anthelmintic drug, is effective against multiple aspects of retinoblastoma. Niclosamide inhibited proliferation via causing cell cycle arrest at the G2/M phase and induced caspase-dependent apoptosis in a panel of retinoblastoma cell lines, including Y79, RB116, and WERI-Rb-1. In addition, niclosamide inhibited retinoblastoma angiogenesis by disrupting capillary network formation, decreasing migration and proliferation, and inducing apoptosis of human primary retinal microvascular endothelial cells. We also demonstrated that niclosamide specifically suppresses the levels of p-LRP6, Dvl2, and β-catenin, but not p-STAT3, in Y79 cells. It decreased β-catenin activity and the mRNA expression levels of Wnt/β-catenin target genes. Stabilization of β-catenin with the Wnt activator lithium or overexpression of β-catenin reversed the inhibitory effects of niclosamide in Y79 cells, confirming Wnt/β-catenin as the molecular target of niclosamide in retinoblastoma cells. Importantly, niclosamide significantly enhanced the in vitro and in vivo efficacy of carboplatin and inhibited Wnt/β-catenin signaling in a retinoblastoma xenograft mouse model. Our data suggest that niclosamide is a promising candidate for the treatment armamentarium for retinoblastoma. Our work also highlights that targeting Wnt/β-catenin is a potential therapeutic strategy in retinoblastoma.

[Antineoplastic mechanisms of niclosamide-loaded nanoparticles in human colorectal cancer cells]

Using poly(lactic-co-glycolic) acid we developed a polymeric form of niclosamide (PFN) and investigated molecular mechanisms underlying its antitumor activity against human colorectal cancer cell lines (SW837, Caco-2, COLO 320 HSR). PFN was shown to be more cytotoxic against cancer cells and less cytotoxic against normal cells (human embryonic lung fibroblasts) as compared to niclosamide. Both niclosamide and its polymeric form caused mitochondrial damage (evaluated as a decrease in rhodamine 123 accumulation) and increased the levels of reactive oxygen species, particularly mitochondrial superoxide, resulting in the oxidative damage to biomolecules. Furthermore, niclosamide and PFN induced G0/G1 cell cycle arrest.

The antihelmenthic phosphate niclosamide impedes renal fibrosis by inhibiting homeodomain-interacting protein kinase 2 expression

Renal fibrosis is the final common pathway of all varieties of progressive chronic kidney disease. However, there are no effective therapies to prevent or slow the progression of renal fibrosis. Niclosamide is a US Food and Drug Administration-approved oral antihelminthic drug used for treating most tapeworm infections. Here, we demonstrated that phosphate niclosamide, the water-soluble form of niclosamide, significantly reduced proteinuria, glomerulosclrotic lesions, and interstitial fibrosis in a murine model of adriamycin nephropathy. In addition, phosphate niclosamide significantly ameliorated established renal interstitial fibrosis a murine model of unilateral ureteral obstruction. Mechanistically, phosphate niclosamide directly inhibited TGF-β-induced expression of homeodomain-interacting protein kinase 2 (HIPK2) by interfering with the binding of Smad3 to the promoter of the HIPK2 gene, and subsequently mitigated the activation of its downstream signaling pathways including Smad, Notch, NF-κB and Wnt/β-catenin pathway both in vitro and in vivo. Thus, phosphate niclosamide mitigates renal fibrosis at least partially by inhibiting HIPK2 expression. Hence, phosphate niclosamide might be a potential therapeutic agent for renal fibrosis.

Benzimidazole inhibitors from the Niclosamide chemotype inhibit Wnt/β-catenin signaling with selectivity over effects on ATP homeostasis

The Wnt signaling pathway plays a key role in organ and tissue homeostasis, and when dysregulated, can become a major underlying mechanism of disease, particularly cancer. We reported previously that the anthelmintic drug Niclosamide inhibits Wnt/β-catenin signaling and suppresses colon cancer cell growth in vitro and in vivo. To define Niclosamide's mechanism of Wnt/β-catenin inhibition, and to improve its selectivity and pharmacokinetic properties as an anticancer treatment, we designed a novel class of benzimidazole inhibitors of Wnt/β-catenin signaling based on SAR studies of the Niclosamide salicylanilide chemotype. Niclosamide has multiple biological activities. To address selectivity in our design, we interrogated a protonophore SAR model and used the principle of conformational restriction to identify novel Wnt/β-catenin inhibitors with less effect on ATP cellular homeostasis. These studies led to the identification of 4-chloro-2-(5-(trifluoromethyl)-1H-benzo[d]imidazol-2-yl) phenol (4) and related derivatives with greater selectivity for Wnt/β-catenin signaling inhibition vs. differential effects on cellular ATP homeostasis. This is the first report that the Wnt signaling inhibitory activity of Niclosamide can be translated into a new chemical class and to show that its effects on ATP homeostasis can be separated from its inhibitory effects on Wnt signaling. These compounds could be useful tools to elucidate the mechanism of Niclosamide's inhibition of Wnt signaling, and aid the discovery of inhibitors with improved pharmacologic properties to treat cancer and diseases in which Niclosamide has important biological activity.

Niclosamide and its analogs are potent inhibitors of Wnt/β-catenin, mTOR and STAT3 signaling in ovarian cancer

Epithelial ovarian cancer (EOC) is the leading cause of gynecologic cancer mortality worldwide. Platinum-based therapy is the standard first line treatment and while most patients initially respond, resistance to chemotherapy usually arises. Major signaling pathways frequently upregulated in chemoresistant cells and important in the maintenance of cancer stem cells (CSCs) include Wnt/β-catenin, mTOR, and STAT3. The major objective of our study was to investigate the treatment of ovarian cancer with targeted agents that inhibit these three pathways. Here we demonstrate that niclosamide, a salicylamide derivative, and two synthetically manufactured niclosamide analogs (analog 11 and 32) caused significant inhibition of proliferation of two chemoresistant ovarian cancer cell lines (A2780cp20 and SKOV3Trip2), tumorspheres isolated from the ascites of EOC patients, and cells from a chemoresistant patient-derived xenograft (PDX). This work shows that all three agents significantly decreased the expression of proteins in the Wnt/β-catenin, mTOR and STAT3 pathways and preferentially targeted cells that expressed the ovarian CSC surface protein CD133. It also illustrates the potential of drug repurposing for chemoresistant EOC and can serve as a basis for pathway-oriented in vivo studies.

Identification of small-molecule inhibitors of Zika virus infection and induced neural cell death via a drug repurposing screen

In response to the current global health emergency posed by the Zika virus (ZIKV) outbreak and its link to microcephaly and other neurological conditions, we performed a drug repurposing screen of ∼6,000 compounds that included approved drugs, clinical trial drug candidates and pharmacologically active compounds; we identified compounds that either inhibit ZIKV infection or suppress infection-induced caspase-3 activity in different neural cells. A pan-caspase inhibitor, emricasan, inhibited ZIKV-induced increases in caspase-3 activity and protected human cortical neural progenitors in both monolayer and three-dimensional organoid cultures. Ten structurally unrelated inhibitors of cyclin-dependent kinases inhibited ZIKV replication. Niclosamide, a category B anthelmintic drug approved by the US Food and Drug Administration, also inhibited ZIKV replication. Finally, combination treatments using one compound from each category (neuroprotective and antiviral) further increased protection of human neural progenitors and astrocytes from ZIKV-induced cell death. Our results demonstrate the efficacy of this screening strategy and identify lead compounds for anti-ZIKV drug development.

High-Throughput Screening Assay Identifies Small Molecules Capable of Modulating the BMP-2 and TGF-β1 Signaling Pathway

Modulating the bone morphogenetic protein 2 (BMP-2) and transforming growth factor-β1 (TGF-β1) signaling pathways is essential during tendon/ligament (T/L) healing. Unfortunately, growth factor delivery in situ is far from trivial and, in many cases, the necessary growth factors are not approved for clinical use. Here we used a BMP-2 and a TGF-β1 reporter cell line to screen a library of 1280 Food and Drug Administration-approved small molecules and identify modulators of both signaling pathways. We identified four compounds capable of modulating BMP and TGF signaling on primary human tendon-derived cells (huTCs) and describe their effects on proliferation and differentiation of these cells.

Niclosamide suppresses renal cell carcinoma by inhibiting Wnt/β-catenin and inducing mitochondrial dysfunctions

PURPOSE

To investigate the effects of anthelminthic drug niclosamide in renal cell carcinoma (RCC) and the underlying mechanisms of its action.

METHODS

The effects of niclosamide on the proliferation and apoptosis of RCC cells were examined in vitro and in vivo by using MTS, colony formation assay, flow cytometry and xenograft cancer mouse model. Mechanism studies were performed by analyzing Wnt/β-catenin signaling and mitochondrial functions in a panel of RCC cell lines.

RESULTS

We show that niclosamide effectively targets two RCC cell lines through inhibiting proliferation and anchorage-independent colony formation, and inducing apoptosis. It also enhances the inhibitory effects of chemotherapeutic drug cisplatin in two independent in vivo RCC xenograft mouse models. Mechanistically, niclosamide decreases β-catenin levels and therefore suppresses Wnt/β-catenin activities. Overexpression of β-catenin partially reverses the inhibitory effects of niclosamide in RCC cells, demonstrating that besides β-catenin, other mechanisms are involved in niclosamide's anti-cancer activity. Indeed, we further show that niclosamide induces mitochondrial dysfunctions as shown by the decreased level of mitochondrial membrane potential and respiration, resulting in decreased ATP levels and increased reactive oxygen species (ROS) levels.

CONCLUSIONS

Our findings support the inhibitory effects of niclosamide in cancer and provide better understanding on its underlying mechanism. Our data suggests that niclosamide is a useful addition to the treatment armamentarium for RCC.

Niclosamide As a Potential Nonsteroidal Therapy for Endometriosis That Preserves Reproductive Function in an Experimental Mouse Model

Endometriosis causes severe chronic pelvic pain and infertility. Because the standard medication and surgical treatments of endometriosis show high recurrence of symptoms, it is necessary to improve current treatment options. In the initial study, we examined whether niclosamide can be a useful drug for endometriosis in a preclinical setting. Endometriotic implants were induced using an established mouse model involving transimplantation of mouse endometrial fragments to the peritoneal wall of recipient mice. When the recipient mice were treated with niclosamide for 3 weeks, niclosamide reduced the size of endometriotic implants with inhibition of cell proliferation, and inflammatory signaling including RELA (NFKB) and STAT3 activation, but did not alter expression of steroid hormone receptors. To identify genes whose expression is regulated by niclosamide in endometriotic implants, RNA-sequencing was performed, and several genes downregulated by niclosamide were related to inflammatory responses, WNT and MAPK signaling. In a second study designed to assess whether niclosamide affects reproductive function, the recipient mice started receiving niclosamide after the induction of endometriosis. Then, the recipient mice were mated with wild type males, and treatments continued until the pups were born. Niclosamide treated recipient mice became pregnant and produced normal size and number of pups. These results suggest that niclosamide could be an effective therapeutic drug, and acts as an inhibitor of inflammatory signaling without disrupting normal reproductive function.

Extracellular pH Modulates Neuroendocrine Prostate Cancer Cell Metabolism and Susceptibility to the Mitochondrial Inhibitor Niclosamide

Neuroendocrine prostate cancer is a lethal variant of prostate cancer that is associated with castrate-resistant growth, metastasis, and mortality. The tumor environment of neuroendocrine prostate cancer is heterogeneous and characterized by hypoxia, necrosis, and numerous mitoses. Although acidic extracellular pH has been implicated in aggressive cancer features including metastasis and therapeutic resistance, its role in neuroendocrine prostate cancer physiology and metabolism has not yet been explored. We used the well-characterized PNEC cell line as a model to establish the effects of extracellular pH (pH 6.5, 7.4, and 8.5) on neuroendocrine prostate cancer cell metabolism. We discovered that alkalinization of extracellular pH converted cellular metabolism to a nutrient consumption-dependent state that was susceptible to glucose deprivation, glutamine deprivation, and 2-deoxyglucose (2-DG) mediated inhibition of glycolysis. Conversely, acidic pH shifted cellular metabolism toward an oxidative phosphorylation (OXPHOS)-dependent state that was susceptible to OXPHOS inhibition. Based upon this mechanistic knowledge of pH-dependent metabolism, we identified that the FDA-approved anti-helminthic niclosamide depolarized mitochondrial potential and depleted ATP levels in PNEC cells whose effects were enhanced in acidic pH. To further establish relevance of these findings, we tested the effects of extracellular pH on susceptibility to nutrient deprivation and OXPHOS inhibition in a cohort of castrate-resistant prostate cancer cell lines C4-2B, PC-3, and PC-3M. We discovered similar pH-dependent toxicity profiles among all cell lines with these treatments. These findings underscore a potential importance to acidic extracellular pH in the modulation of cell metabolism in tumors and development of an emerging paradigm that exploits the synergy of environment and therapeutic efficacy in cancer.

[Molecular mechanisms of niclosamide antitumor activity]

In this review the recent data regarding the antitumor activity of niclosamide and the molecular mechanisms of its antitumor activity are presented. Niclosamide has been used in the clinic for the treatment of intestinal parasite infections. In recent years in several screening investigations of various drugs and chemical compounds niclosamide was identified as a potential anticancer agent. Niclosamide not only inhibits the Wnt/β-catenin, mTORC1, STAT3, NF-κB and Notch signaling pathways, but also targets mitochondria in cancer cells to induce growth inhibition and apoptosis. A number of studies have established the anticancer activity of niclosamide in both in vitro and in vivo in xenotransplantation models using human tumors and immunodeficient mice. It is important that niclosamide is active not only against tumor cells but also cancer stem cells. Normal cells are resistant to niclosamide. The accumulated experimental data suggest niclosamide is a promising drug for the treatment of various types of cancer.

The anthelmintic niclosamide inhibits colorectal cancer cell lines via modulation of the canonical and noncanonical Wnt signaling pathway

BACKGROUND

Wnt/β-catenin signaling is known to play an important role in colorectal cancer (CRC). Niclosamide, a salicylamide derivative used in the treatment of tapeworm infections, targets the Wnt/β-catenin pathway. The objective of this study was to investigate niclosamide as a therapeutic agent against CRC.

METHODS

The antiproliferative effects of 1, 3, 10, and 50 μM concentrations of niclosamide on human (SW480 and SW620) and rodent (CC531) CRC cell lines were determined by MTS assay and direct cell count. The lymphoid enhancer-binding factor 1/transcription factor (LEF/TCF) reporter assay monitored the activity of Wnt signaling. Immunofluorescence staining demonstrated the expression pattern of active β-catenin. Gene expression of canonical and noncanonical Wnt signaling components was analyzed using qRT-PCR. Western blot analysis was performed with antibodies detecting nuclear localization of β-catenin and c-jun.

RESULTS

Cell proliferation in CRC cell lines was blocked dose dependently after 12 and 24 h of incubation. The Wnt promoter activity of LEF/TCF significantly decreased with niclosamide concentrations of 10 and 50 μM after 12 h of incubation. Active β-catenin did not shift from the nuclear to the cytosolic pool. However, canonical target genes (met, MMP7, and cyclin D1) as well as the coactivating factor Bcl9 were downregulated, whereas the noncanonical key player c-jun was clearly activated.

CONCLUSIONS

Niclosamide treatment is associated with an inhibitory effect on CRC development and reduced Wnt activity. It may exert its effect by interfering with the nuclear β-catenin-Bcl9-LEF/TCF triple-complex and by upregulation of c-jun representing noncanonical Wnt/JNK signaling. Thus, our findings warrant further research into this substance as a treatment option for patients with advanced CRC.

Repositioning of drugs for intervention in tumor progression and metastasis: Old drugs for new targets

The increasing unraveling of the molecular basis of cancer offers manifold novel options for intervention strategies. However, the discovery and development of new drugs for potential clinical applications is a tremendously time-consuming and costly process. Translating a novel lead candidate compound into an approved clinical drug takes often more than a decade, and the success rate is very low due to versatile efforts including defining its pharmacokinetics, pharmacodynamics, side effects as well as lack of sufficient efficacy. Thus, strategies are needed to minimize time and costs, while maximizing success rates. A very attractive strategy for novel cancer therapeutic options is the repositioning of already approved drugs. These medicines, approved for the treatment of non-malignant disorders, have already passed some early costs and time, have been tested in humans and are ready for clinical trials as anti-cancer drugs. Here we discuss the repositioning of nonsteroidal anti-inflammatory drugs (NSAID), statins, anti-psychotic drugs, anti-helminthic drugs and vitamin D as anti-tumor agents. We focus on their novel actions and potential for inhibition of cancer growth and metastasis by interfering with target molecules and pathways, which drive these malignant processes. Furthermore, important pre-clinical and clinical data are reviewed herein, which elucidate their therapeutic mechanisms which enable their repositioning for cancer therapy and disruption of metastasis.

The role of STAT3 in autophagy

Autophagy is an evolutionarily conserved process in eukaryotes that eliminates harmful components and maintains cellular homeostasis in response to a series of extracellular insults. However, these insults may trigger the downstream signaling of another prominent stress responsive pathway, the STAT3 signaling pathway, which has been implicated in multiple aspects of the autophagic process. Recent reports further indicate that different subcellular localization patterns of STAT3 affect autophagy in various ways. For example, nuclear STAT3 fine-tunes autophagy via the transcriptional regulation of several autophagy-related genes such as BCL2 family members, BECN1, PIK3C3, CTSB, CTSL, PIK3R1, HIF1A, BNIP3, and microRNAs with targets of autophagy modulators. Cytoplasmic STAT3 constitutively inhibits autophagy by sequestering EIF2AK2 as well as by interacting with other autophagy-related signaling molecules such as FOXO1 and FOXO3. Additionally, the mitochondrial translocation of STAT3 suppresses autophagy induced by oxidative stress and may effectively preserve mitochondria from being degraded by mitophagy. Understanding the role of STAT3 signaling in the regulation of autophagy may provide insight into the classic autophagy model and also into cancer therapy, especially for the emerging targeted therapy, because a series of targeted agents execute antitumor activities via blocking STAT3 signaling, which inevitably affects the autophagy pathway. Here, we review several of the representative studies and the current understanding in this particular field.

Combined niclosamide with cisplatin inhibits epithelial-mesenchymal transition and tumor growth in cisplatin-resistant triple-negative breast cancer

Women with triple-negative breast cancer have worse prognosis compared to other breast cancer subtypes. Acquired drug resistance remains to be an important reason influencing triple-negative breast cancer treatment efficacy. A prevailing theory postulates that the cancer resistance and recurrence results from a subpopulation of tumor cells with stemness program, which are often insensitive to cytotoxic drugs such as cisplatin. Recent studies suggested that niclosamide, an anti-helminthic drug, has potential therapeutic activities against breast cancer stem cells, which prompts us to determine its roles on eliminating cisplatin-resistant cancer cells. Hence, we established a stable cisplatin-resistant MDA-MB-231 cell line (231-CR) through continuously exposure to increasing concentrations of cisplatin (5-20 μmol/l). Interestingly, 231-CR exhibited properties associated to epithelial-mesenchymal transition with enhanced invasion, preserved proliferation, increased mammosphere formation, and reduced apoptosis compared to naive MDA-MB-231 sensitive cells (231-CS). Importantly, niclosamide or combination with cisplatin inhibited both 231-CS and 231-CR cell proliferation in vitro. In addition, niclosamide reversed the EMT phenotype of 231-CR by downregulation of snail and vimentin. Mechanistically, niclosamide treatment in combination with or without cisplatin significantly inhibited Akt, ERK, and Src signaling pathways. In vivo study showed that niclosamide or combination with cisplatin could repress the growth of xenografts originated from either 231-CS or 231-CR cells, with prominent suppression of Ki67 expression. These findings suggested that niclosamide might serve as a novel therapeutic strategy, either alone or in combination with cisplatin, for triple-negative breast cancer treatment, especially those resistant to cisplatin.