Dp44mT targets the AKT, TGF-β and ERK pathways via the metastasis suppressor NDRG1 in normal prostate epithelial cells and prostate cancer cells

Multi-modal mechanisms of the metastasis suppressor, NDRG1: Inhibition of WNT/β-catenin signaling by stabilization of protein kinase Cα

The metastasis suppressor, N-myc downstream regulated gene-1 (NDRG1), inhibits pro-oncogenic signaling in pancreatic cancer (PC). This investigation dissected a novel mechanism induced by NDRG1 on WNT/β-catenin signaling in multiple PC cell types. NDRG1 overexpression decreased β-catenin and downregulated glycogen synthase kinase-3β (GSK-3β) protein levels and its activation. However, β-catenin phosphorylation at Ser33, Ser37, and Thr41 are classically induced by GSK-3β was significantly increased after NDRG1 overexpression, suggesting a GSK-3β-independent mechanism. Intriguingly, NDRG1 overexpression upregulated protein kinase Cα (PKCα), with PKCα silencing preventing β-catenin phosphorylation at Ser33, Ser37, and Thr41, and decreasing β-catenin expression. Further, NDRG1 and PKCα were demonstrated to associate, with PKCα stabilization occurring after NDRG1 overexpression. PKCα half-life increased from 1.5 ± 0.8 h (3) in control cells to 11.0 ± 2.5 h (3) after NDRG1 overexpression. Thus, NDRG1 overexpression leads to the association of NDRG1 with PKCα and PKCα stabilization, resulting in β-catenin phosphorylation at Ser33, Ser37, and Thr41. The association between PKCα, NDRG1, and β-catenin was identified, with the formation of a potential metabolon that promotes the latter β-catenin phosphorylation. This anti-oncogenic activity of NDRG1 was multi-modal, with the above mechanism accompanied by the downregulation of the nucleo-cytoplasmic shuttling protein, p21-activated kinase 4 (PAK4), which is involved in β-catenin nuclear translocation, inhibition of AKT phosphorylation (Ser473), and decreased β-catenin phosphorylation at Ser552 that suppresses its transcriptional activity. These mechanisms of NDRG1 activity are important to dissect to understand the marked anti-cancer efficacy of NDRG1-inducing thiosemicarbazones that upregulate PKCα and inhibit WNT signaling.

Ubiquitination Process Mediates Prostate Cancer Development and Metastasis through Multiple Mechanisms

Prostate cancer (PCa) is a common malignant tumor in men, when the disease progresses to the advanced stage, most patients will develop distant metastasis and develop into castration-resistant prostate cancer (CRPC), resulting in increased mortality. Ubiquitination is a widespread protein post-translational modification process in the biological world, and it plays an important role in the development and transfer of PCa. E3 ubiquitin ligase plays an important role in the specific selection and role of substrates in the process of ubiquitination ligase. This review will briefly introduce the ubiquitination process and E3 ubiquitin ligase, focus on the recently discovered multiple mechanisms by which ubiquitination affects PCa development and metastasis, and a summary of the current emerging proteolysis-targeting chimeras (PROTAC) in the treatment of PCa.

Desulfurization of thiosemicarbazones: the role of metal ions and biological implications

Thiosemicarbazones are biologically active substances whose structural formula is formed by an azomethine, an hydrazine, and a thioamide fragments, to generate a R2C=N-NR-C(=S)-NR2 backbone. These compounds often act as ligands to generate highly stable metal-organic complexes. In certain experimental conditions, however, thiosemicarbazones undergo reactions leading to the cleavage of the chain. Sometimes, the breakage involves desulfurization processes. The present work summarizes the different chemical factors that influence the desulfurization reactions of thiosemicarbazones, such as pH, the presence of oxidant reactants or the establishment of redox processes as those electrochemically induced, the effects of the solvent, the temperature, and the electromagnetic radiation. Many of these reactions require coordination of thiosemicarbazones to metal ions, even those present in the intracellular environment. The nature of the products generated in these reactions, their detection in vivo and in vitro, together with the relevance for the biological activity of these compounds, mainly as antineoplastic agents, is discussed.

Assessing the Potential of Small Peptides for Altering Expression Levels of the Iron-Regulatory Genes FTH1 and TFRC and Enhancing Androgen Receptor Inhibitor Activity in In Vitro Prostate Cancer Models

Recent research highlights the key role of iron dyshomeostasis in the pathogenesis of prostate cancer (PCa). PCa cells are heavily dependent on bioavailable iron, which frequently results in the reprogramming of iron uptake and storage pathways. Although advanced-stage PCa is currently incurable, bioactive peptides capable of modulating key iron-regulatory genes may constitute a means of exploiting a metabolic adaptation necessary for tumor growth. Recent annual increases in PCa incidence have been reported, highlighting the urgent need for novel treatments. We examined the ability of LNCaP, PC3, VCaP, and VCaP-EnzR cells to form colonies in the presence of androgen receptor inhibitors (ARI) and a series of iron-gene modulating oligopeptides (FT-001-FT-008). The viability of colonies following treatment was determined with clonogenic assays, and the expression levels of FTH1 (ferritin heavy chain 1) and TFRC (transferrin receptor) were determined with quantitative polymerase chain reaction (PCR). Peptides and ARIs combined significantly reduced PCa cell growth across all phenotypes, of which two peptides were the most effective. Colony growth suppression generally correlated with the magnitude of concurrent increases in FTH1 and decreases in TFRC expression for all cells. The results of this study provide preliminary insight into a novel approach at targeting iron dysmetabolism and sensitizing PCa cells to established cancer treatments.

MAOA suppresses the growth of gastric cancer by interacting with NDRG1 and regulating the Warburg effect through the PI3K/AKT/mTOR pathway

OBJECTIVE

Previous studies have indicated that neurotransmitters play important roles in the occurrence and development of gastric cancer. MAOA is an important catecholamine neurotransmitter-degrading enzyme involved in the degradation of norepinephrine, epinephrine and serotonin. To find a potential therapeutic target for the treatment of gastric cancer, the biological functions of MAOA and the underlying mechanism in gastric cancer need to be explored.

METHODS

The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) datasets, Kaplan‒Meier (KM) plotter were used to identify the differentially expressed genes, which mainly involved the degradation and synthesis enzymes of neurotransmitters in gastric cancer. We also investigated the expression pattern of MAOA in human and mouse tissues and cell lines by immunohistochemistry and Western blotting analysis. Western blotting, quantitative real-time PCR, enzyme-linked immunosorbent assay (ELISA) and a Seahorse experiment were used to identify the molecular mechanism of cancer cell glycolysis. MAOA expression and patient survival were analysed in the Ren Ji cohort, and univariate and multivariate analyses were performed based on the clinicopathological characteristics of the above samples.

RESULTS

MAOA expression was significantly downregulated in gastric cancer tissue and associated with poor patient prognosis. Moreover, the expression level of MAOA in gastric cancer tissue had a close negative correlation with the SUXmax value of PET-CT in patients. MAOA suppressed tumour growth and glycolysis and promoted cancer cell apoptosis. We also reported that MAOA can interact with NDRG1 and regulate glycolysis through suppression of the PI3K/Akt/mTOR pathway. MAOA expression may serve as an independent prognostic factor in gastric cancer patients.

CONCLUSIONS

MAOA attenuated glycolysis and inhibited the progression of gastric cancer through the PI3K/Akt/mTOR pathway. Loss of function or downregulation of MAOA can facilitate gastric cancer progression. Overexpression of MAOA and inhibition of the PI3K/Akt/mTOR pathway may provide a potential method for gastric cancer treatment in clinical therapeutic regimens.

The Myc Family and the Metastasis Suppressor NDRG1: Targeting Key Molecular Interactions with Innovative Therapeutics

Cancer is a leading cause of death worldwide, resulting in ∼10 million deaths in 2020. Major oncogenic effectors are the Myc proto-oncogene family, which consists of three members including c-Myc, N-Myc, and L-Myc. As a pertinent example of the role of the Myc family in tumorigenesis, amplification of MYCN in childhood neuroblastoma strongly correlates with poor patient prognosis. Complexes between Myc oncoproteins and their partners such as hypoxia-inducible factor-1α and Myc-associated protein X (MAX) result in proliferation arrest and pro-proliferative effects, respectively. Interactions with other proteins are also important for N-Myc activity. For instance, the enhancer of zest homolog 2 (EZH2) binds directly to N-Myc to stabilize it by acting as a competitor against the ubiquitin ligase, SCFFBXW7, which prevents proteasomal degradation. Heat shock protein 90 may also be involved in N-Myc stabilization since it binds to EZH2 and prevents its degradation. N-Myc downstream-regulated gene 1 (NDRG1) is downregulated by N-Myc and participates in the regulation of cellular proliferation via associating with other proteins, such as glycogen synthase kinase-3β and low-density lipoprotein receptor-related protein 6. These molecular interactions provide a better understanding of the biologic roles of N-Myc and NDRG1, which can be potentially used as therapeutic targets. In addition to directly targeting these proteins, disrupting their key interactions may also be a promising strategy for anti-cancer drug development. This review examines the interactions between the Myc proteins and other molecules, with a special focus on the relationship between N-Myc and NDRG1 and possible therapeutic interventions. SIGNIFICANCE STATEMENT: Neuroblastoma is one of the most common childhood solid tumors, with a dismal five-year survival rate. This problem makes it imperative to discover new and more effective therapeutics. The molecular interactions between major oncogenic drivers of the Myc family and other key proteins; for example, the metastasis suppressor, NDRG1, may potentially be used as targets for anti-neuroblastoma drug development. In addition to directly targeting these proteins, disrupting their key molecular interactions may also be promising for drug discovery.

Stromal-epithelial interaction induces GALNT14 in prostate carcinoma cells

Introduction

Cell-cell communication is an important process in healthy tissue but also gains enhanced attention regarding pathological tissue. To date, the tumor microenvironment is gradually brought into focus when studying tumorigenesis. In the prostate gland, stromal and epithelial cells greatly interact to maintain homeostasis or tissue integrity. This study focuses on an indirect communication via soluble factors.

Methods

To investigate the cell-cell interaction via soluble factors, the prostate carcinoma cell line LNCaP and the stromal primary cells p21 were co-cultured without direct contact and RNA was isolated at defined time points. Differences in gene expression were finally analyzed by RNA sequencing.

Results

RNA sequencing revealed a time-depending differential expression profile. Selected factors were subsequently characterized at molecular level and analyzed in human prostate tissue of different developmental stages as well as pathology. GALNT14 was one of the highest induced co-culture-specific genes in LNCaP cells. Detection in healthy tissue and BPH revealed an age-dependent decrease in GALNT14 expression. Moreover, in prostate carcinoma, GALNT14 expression heavily varied independent of the Gleason score.

Conclusion

Overall, this work provides a basis for further studies related to paracrine stromal-epithelial interaction in prostate carcinoma and highlights the importance of GALNT14.

A review on the role of NDRG1 in different cancers

NDRG1 is a member of the α/β hydrolase superfamily that resides in the cytoplasm and participates in the stress responses, hormone response, cell growth, and differentiation. Several studies have pointed to the importance of NDRG1 in the carcinogenesis. This gene has been found to be up-regulated in an array of cancer types such as bladder, esophageal squamous cell carcinoma, endometrial, lung and liver cancers, but being down-regulated in other types of cancers such as colorectal, gastric and ovarian cancers. The current study summarizes the evidence on the role of NDRG1 in the carcinogenic processes in different types of tissues.

Role of KLF4/NDRG1/DRP1 axis in hypoxia-induced pulmonary hypertension

N-myc downstream regulated gene 1 (NDRG1) has recently drawn increasing attention because of its involvement in angiogenesis, cell proliferation, and differentiation. We used in vitro [human pulmonary artery smooth muscle cells (hPASMCs)] and in vivo (rat) models under hypoxic conditions and found a vital role of NDRG1 in reducing apoptosis and increasing proliferation and migration by overexpressing and knocking down NDRG1. We also proved that hypoxia induced the protein expression of dynamin-related protein 1 (DRP1) and stimulated The phosphatidylinositol-3-kinase (PI3K)/ Protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathways, and these effects were reversed by NDRG1 knockdown. The relationship between NDRG1 and DRP1 and the PI3K/Akt/mTOR pathway was further evaluated by adding mdivi-1 (DRP1 inhibitor) or LY294002 (PI3K inhibitor). NDRG1 was found to regulate the proliferation, apoptosis, and migration of hypoxia-treated hPASMCs via DRP1 and PI3K/Akt/mTOR signaling pathways. We explored the upstream regulators of NDRG1 using in vivo and in vitro hypoxia models. Hypoxia was found to upregulate and downregulate KLF transcription factor 4 (KLF4) protein expression in the cytoplasm and nucleus, respectively. Further, we showed that KLF4 regulated the proliferation and migration of hypoxia-treated hPASMCs via NDRG1. These results indicated a link between KLF4, NDRG1, and DRP1 for the first time, providing new ideas for treating hypoxic pulmonary hypertension.

Re-Shaping the Pancreatic Cancer Tumor Microenvironment: A New Role for the Metastasis Suppressor NDRG1

Pancreatic cancer (PaC) is a highly aggressive disease, with poor response to current treatments and 5-year survival rates of 10-15%. PaC progression is facilitated by its interaction with the complex and multifaceted tumor microenvironment (TME). In the TME, cancer cells and surrounding stromal cells constantly communicate with each other via the secretion and uptake of factors including cytokines, chemokines, growth factors, metabolites, and extracellular vesicles (EVs), reshaping the landscape of PaC. Recent studies demonstrated that the metastasis suppressor N-myc downstream regulated 1 (NDRG1) not only inhibits oncogenic signaling pathways in PaC cells but also alters the communication between PaC cells and the surrounding stroma. In fact, NDRG1 was found to influence the secretome of PaC cells, alter cancer cell metabolism, and interfere with intracellular trafficking and intercellular communication between PaC cells and surrounding fibroblasts. This review will present recent advancements in understanding the role of NDRG1 in PaC progression, with a focus on how this molecule influences PaC-stroma communication and its potential for re-shaping the PaC TME.

Designing Tailored Thiosemicarbazones with Bespoke Properties: The Styrene Moiety Imparts Potent Activity, Inhibits Heme Center Oxidation, and Results in a Novel "Stealth Zinc(II) Complex"

A novel, potent, and selective antitumor agent, namely (E)-3-phenyl-1-(2-pyridinyl)-2-propen-1-one 4,4-dimethyl-3-thiosemicarbazone (PPP44mT), and its analogues were synthesized and characterized and displayed strikingly distinctive properties. This activity was mediated by the inclusion of a styrene moiety, which through steric and electrochemical mechanisms prevented deleterious oxy-myoglobin or oxy-hemoglobin oxidation relative to other potent thiosemicarbazones, i.e., di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) or di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT). Structure-activity relationship analysis demonstrated specific tuning of PPP44mT electrochemistry further inhibited oxy-myoglobin or oxy-hemoglobin oxidation. Both PPP44mT and its Cu(II) complexes showed conspicuous almost immediate cytotoxicity against SK-N-MC tumor cells (within 3 h). In contrast, [Zn(PPP44mT)₂] demonstrated a pronounced delay in activity, taking 48 h before marked antiproliferative efficacy was apparent. As such, [Zn(PPP44mT)₂] was designated as a "stealth Zn(II) complex" that overcomes the near immediate cytotoxicity of PPP44mT or its copper complexes. Upon examination of the suppression of oncogenic signaling, [Zn(PPP44mT)₂] was superior at inhibiting cyclin D1 expression compared to DpC or Dp44mT.

Antitumor Activity of Piceamycin by Upregulation of N-Myc Downstream-Regulated Gene 1 in Human Colorectal Cancer Cells

Piceamycin (1), a macrocyclic lactam isolated from the silkworm's gut (Streptomyces sp. SD53 strain), reportedly possesses antibacterial activity. However, the potential anticancer activity and molecular processes underlying 1 have yet to be reported. Colorectal cancer (CRC) is high-risk cancer and accounts for 10% of all cancer cases worldwide. The high prevalence of resistance to radiation or chemotherapy means that patients with advanced CRC have a poor prognosis, with high recurrence and metastasis potential. Therefore, the present study investigated the antitumor effect and underlying mechanisms of 1 in CRC cells. The growth-inhibiting effect of 1 in CRC cells was correlated with the upregulation of a tumor suppressor, N-myc downstream-regulated gene 1 (NDRG1). Additionally, 1 induced G₀/G₁ cell cycle arrest and apoptosis and inhibited the migration of CRC cells. Notably, 1 disrupted the interaction between NDRG1 and c-Myc in CRC cells. In a mouse model with HCT116-implanted xenografts, the antitumor activity of 1 was confirmed by NDRG1 modulation. Overall, these findings show that 1 is a potential candidate for CRC treatment through regulation of NDGR1-mediated functionality.

NDRG1 in Cancer: A Suppressor, Promoter, or Both?

N-myc downregulated gene-1 (NDRG1) has been variably reported as a metastasis suppressor, a biomarker of poor outcome, and a facilitator of disease progression in a range of different cancers. NDRG1 is poorly understood in cancer due to its context-dependent and pleiotropic functions. Within breast cancer, NDRG1 is reported to be either a facilitator of, or an inhibitor of tumour progression and metastasis. The wide array of roles played by NDRG1 are dependent on post-translational modifications and subcellular localization, as well as the cellular context, for example, cancer type. We present an update on NDRG1, and its association with hallmarks of cancer such as hypoxia, its interaction with oncogenic proteins such as p53 as well its role in oncogenic and metastasis pathways in breast and other cancers. We further comment on its functional implications as a metastasis suppressor and promoter, its clinical relevance, and discuss its therapeutic targetability in different cancers.

Thiosemicarbazones and selected tyrosine kinase inhibitors synergize in pediatric solid tumors: NDRG1 upregulation and impaired prosurvival signaling in neuroblastoma cells

Tyrosine kinase inhibitors (TKIs) are frequently used in combined therapy to enhance treatment efficacy and overcome drug resistance. The present study analyzed the effects of three inhibitors, sunitinib, gefitinib, and lapatinib, combined with iron-chelating agents, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) or di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC). Simultaneous administration of the drugs consistently resulted in synergistic and/or additive activities against the cell lines derived from the most frequent types of pediatric solid tumors. The results of a detailed analysis of cell signaling in the neuroblastoma cell lines revealed that TKIs inhibited the phosphorylation of the corresponding receptor tyrosine kinases, and thiosemicarbazones downregulated the expression of epidermal growth factor receptor, platelet-derived growth factor receptor, and insulin-like growth factor-1 receptor, leading to a strong induction of apoptosis. Marked upregulation of the metastasis suppressor N-myc downstream regulated gene-1 (NDRG1), which is known to be activated and upregulated by thiosemicarbazones in adult cancers, was also detected in thiosemicarbazone-treated neuroblastoma cells. Importantly, these effects were more pronounced in the cells treated with drug combinations, especially with the combinations of lapatinib with thiosemicarbazones. Therefore, these results provide a rationale for novel strategies combining iron-chelating agents with TKIs in therapy of pediatric solid tumors.

Supplementation with High or Low Iron Reduces Colitis Severity in an AOM/DSS Mouse Model

The relationship between colitis-associated colorectal cancer (CAC) and the dysregulation of iron metabolism has been implicated. However, studies on the influence of dietary iron deficiency on the incidence of CAC are limited. This study investigated the effects of dietary iron deficiency and dietary non-heme iron on CAC development in an azoxymethane/dextran sodium sulfate (AOM/DSS) mouse model. The four-week-old mice were divided into the following groups: iron control (IC; 35 ppm iron/kg) + normal (NOR), IC + AOM/DSS, iron deficient (ID; <5 ppm iron/kg diet) + AOM/DSS, and iron overload (IOL; approximately 2000 ppm iron/kg) + AOM/DSS. The mice were fed the respective diets for 13 weeks, and the AOM/DSS model was established at week five. FTH1 expression increased in the mice’s colons in the IC + AOM/DSS group compared with that observed in the ID and IOL + AOM/DSS groups. The reduced number of colonic tumors in the ID + AOM/DSS and IOL + AOM/DSS groups was accompanied by the downregulated expression of cell proliferation regulators (PCNA, cyclin D1, and c-Myc). Iron overload inhibited the increase in the expression of NF-κB and its downstream inflammatory cytokines (IL-6, TNFα, iNOS, COX2, and IL-1β), likely due to the elevated expression of antioxidant genes (SOD1, TXN, GPX1, GPX4, CAT, HMOX1, and NQO1). ID + AOM/DSS may hinder tumor development in the AOM/DSS model by inhibiting the PI3K/AKT pathway by increasing the expression of Ndrg1. Our study suggests that ID and IOL diets suppress AOM/DSS-induced tumors and that long-term iron deficiency or overload may negate CAC progression.

Targeting Wnt/tenascin C-mediated cross talk between pancreatic cancer cells and stellate cells via activation of the metastasis suppressor NDRG1

A major barrier to successful pancreatic cancer (PC) treatment is the surrounding stroma, which secretes growth factors/cytokines that promote PC progression. Wnt and tenascin C (TnC) are key ligands secreted by stromal pancreatic stellate cells (PSCs) that then act on PC cells in a paracrine manner to activate the oncogenic β-catenin and YAP/TAZ signaling pathways. Therefore, therapies targeting oncogenic Wnt/TnC cross talk between PC cells and PSCs constitute a promising new therapeutic approach for PC treatment. The metastasis suppressor N-myc downstream-regulated gene-1 (NDRG1) inhibits tumor progression and metastasis in numerous cancers, including PC. We demonstrate herein that targeting NDRG1 using the clinically trialed anticancer agent di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) inhibited Wnt/TnC-mediated interactions between PC cells and the surrounding PSCs. Mechanistically, NDRG1 and DpC markedly inhibit secretion of Wnt3a and TnC by PSCs, while also attenuating Wnt/β-catenin and YAP/TAZ activation and downstream signaling in PC cells. This antioncogenic activity was mediated by direct inhibition of β-catenin and YAP/TAZ nuclear localization and by increasing the Wnt inhibitor, DKK1. Expression of NDRG1 also inhibited transforming growth factor (TGF)-β secretion by PC cells, a key mechanism by which PC cells activate PSCs. Using an in vivo orthotopic PC mouse model, we show DpC downregulated β-catenin, TnC, and YAP/TAZ, while potently increasing NDRG1 expression in PC tumors. We conclude that NDRG1 and DpC inhibit Wnt/TnC-mediated interactions between PC cells and PSCs. These results further illuminate the antioncogenic mechanism of NDRG1 and the potential of targeting this metastasis suppressor to overcome the oncogenic effects of the PC-PSC interaction.

Transforming growth factor-beta (TGF-β) in prostate cancer: A dual function mediator?

Transforming growth factor-beta (TGF-β) is a member of a family of secreted cytokines with vital biological functions in cells. The abnormal expression of TGF-β signaling is a common finding in pathological conditions, particularly cancer. Prostate cancer (PCa) is one of the leading causes of death among men. Several genetic and epigenetic alterations can result in PCa development, and govern its progression. The present review attempts to shed some light on the role of TGF-β signaling in PCa. TGF-β signaling can either stimulate or inhibit proliferation and viability of PCa cells, depending on the context. The metastasis of PCa cells is increased by TGF-β signaling via induction of EMT and MMPs. Furthermore, TGF-β signaling can induce drug resistance of PCa cells, and can lead to immune evasion via reducing the anti-tumor activity of cytotoxic T cells and stimulating regulatory T cells. Upstream mediators such as microRNAs and lncRNAs, can regulate TGF-β signaling in PCa. Furthermore, some pharmacological compounds such as thymoquinone and valproic acid can suppress TGF-β signaling for PCa therapy. TGF-β over-expression is associated with poor prognosis in PCa patients. Furthermore, TGF-β up-regulation before prostatectomy is associated with recurrence of PCa. Overall, current review discusses role of TGF-β signaling in proliferation, metastasis and therapy response of PCa cells and in order to improve knowledge towards its regulation, upstream mediators of TGF-β such as non-coding RNAs are described. Finally, TGF-β regulation and its clinical application are discussed.

N-myc downstream regulated family member 1 (NDRG1) is enriched in myelinating oligodendrocytes and impacts myelin degradation in response to demyelination

The N-myc downstream regulated gene family member 1 (NDRG1) is a gene whose mutation results in peripheral neuropathy with central manifestations. While most of previous studies characterized NDRG1 role in Schwann cells, the detection of central nervous system symptoms and the identification of NDRG1 as a gene silenced in the white matter of multiple sclerosis brains raise the question regarding its role in oligodendrocytes. Here, we show that NDRG1 is enriched in oligodendrocytes and myelin preparations, and we characterize its expression using a novel reporter mouse (TgNdrg1-EGFP). We report NDRG1 expression during developmental myelination and during remyelination after cuprizone-induced demyelination of the adult corpus callosum. The transcriptome of Ndrg1-EGFP+ cells further supports the identification of late myelinating oligodendrocytes, characterized by expression of genes regulating lipid metabolism and bioenergetics. We also generate a lineage specific conditional knockout (Olig1^cre/+ ;Ndrg1^fl/fl ) line to study its function. Null mice develop normally, and despite similar numbers of progenitor cells as wild type, they have fewer mature oligodendrocytes and lower levels of myelin proteins than controls, thereby suggesting NDRG1 as important for the maintenance of late myelinating oligodendrocytes. In addition, when control and Ndrg1 null mice are subject to cuprizone-induced demyelination, we observe a higher degree of demyelination in the mutants. Together these data identify NDRG1 as an important molecule for adult myelinating oligodendrocytes, whose decreased levels in the normal appearing white matter of human MS brains may result in greater susceptibility of myelin to damage.

Iron-Chelation Treatment by Novel Thiosemicarbazone Targets Major Signaling Pathways in Neuroblastoma

Despite constant advances in the field of pediatric oncology, the survival rate of high-risk neuroblastoma patients remains poor. The molecular and genetic features of neuroblastoma, such as MYCN amplification and stemness status, have established themselves not only as potent prognostic and predictive factors but also as intriguing targets for personalized therapy. Novel thiosemicarbazones target both total level and activity of a number of proteins involved in some of the most important signaling pathways in neuroblastoma. In this study, we found that di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) potently decreases N-MYC in MYCN-amplified and c-MYC in MYCN-nonamplified neuroblastoma cell lines. Furthermore, DpC succeeded in downregulating total EGFR and phosphorylation of its most prominent tyrosine residues through the involvement of NDRG1, a positive prognostic marker in neuroblastoma, which was markedly upregulated after thiosemicarbazone treatment. These findings could provide useful knowledge for the treatment of MYC-driven neuroblastomas that are unresponsive to conventional therapies.

Claudin-2 promotes colorectal cancer growth and metastasis by suppressing NDRG1 transcription

Colorectal cancer (CRC) is one of the most common malignant tumours, with multiple driving factors and biological transitions involved in its development. Claudin-2 (CLDN2), a well-defined component of cellular tight junction, has been indicated to associate with CRC progression. However, the function of CLDN2 and the underlying mechanism whereby the downstream signalling transduction is regulated in CRC remains largely unclear. In this study, we demonstrated that CLDN2 is upregulated in CRC samples and associated with poor survival. And CLDN2 depletion significantly promotes N-myc downstream-regulated gene 1 (NDRG1) transcription, leading to termination of the CRC growth and metastasis in vitro and in vivo. Mechanistically, this process promotes CLDN2/ZO1/ZONAB complex dissociation and ZONAB shuttle into nucleus to enrich in the promoter of NDRG1. Thus, this study reveals a novel CLDN2/ZO1/ZONAB-NDRG1 axis in CRC by regulating the expression of EMT-related genes and CDKIs, suggesting CLDN2 may serve as a promising target for CRC treatment.

The Metastasis Suppressor NDRG1 Directly Regulates Androgen Receptor Signaling in Prostate Cancer

N-myc-downregulated gene 1 (NDRG1) has potent anticancer effects and inhibits cell growth, survival, metastasis, and angiogenesis. Previous studies suggested that NDRG1 is linked to the androgen signaling network, but this mechanistic relationship is unclear. Considering the crucial role of the androgen receptor (AR) in prostate cancer (PCa) progression, here we examined for the first time the effect of NDRG1 on AR expression, activation, and downstream signaling in LNCaP, 22Rv1, and C4-2B PCa cell types. We demonstrate that NDRG1 effectively promotes interaction of AR with the chaperone HSP90, which in turn stabilizes the AR while decreasing its androgen-mediated activation. The expression of NDRG1 suppressed: (1) AR activation, as measured by p-AR^Ser213 and p-AR^Ser81; (2) expression of a major AR transcriptional target, prostate-specific antigen (PSA); and (3) AR transcriptional activity, probably via inhibiting the c-Jun-AR interaction by reducing c-Jun phosphorylation (p-c-Jun^Ser63). NDRG1 was also demonstrated to inhibit multiple key molecules involved in androgen-dependent and -independent signaling (namely EGFR, HER2, HER3, PI3K, STAT3, and NF-κB), which promote the development of castration-resistant prostate cancer. We also identified the cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) domain of NDRG1 as vital for inhibition of AR activity. Examining NDRG1 and p-NDRG1 in PCa patient specimens revealed a significant negative correlation between NDRG1 and PSA levels in prostatectomy patients that went on to develop metastasis. These results highlight a vital role for NDRG1 in androgen signaling and its potential as a key therapeutic target and biomarker in PCa.

Breaking the cycle: Targeting of NDRG1 to inhibit bi-directional oncogenic cross-talk between pancreatic cancer and stroma

Pancreatic cancer (PaCa) is characterized by dense stroma that hinders treatment efficacy, with pancreatic stellate cells (PSCs) being a major contributor to this stromal barrier and PaCa progression. Activated PSCs release hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-1) that induce PaCa proliferation, metastasis and resistance to chemotherapy. We demonstrate for the first time that the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), is a potent inhibitor of the PaCa-PSC cross-talk, leading to inhibition of HGF and IGF-1 signaling. NDRG1 also potently reduced the key driver of PaCa metastasis, namely GLI1, leading to reduced PSC-mediated cell migration. The novel clinically trialed anticancer agent, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which upregulates NDRG1, potently de-sensitized PaCa cells to ligands secreted by activated PSCs. DpC and NDRG1 also inhibited the PaCa-mediated activation of PSCs via inhibition of sonic hedgehog (SHH) signaling. In vivo, DpC markedly reduced PaCa tumor growth and metastasis more avidly than the standard chemotherapy for this disease, gemcitabine. Uniquely, DpC was selectively cytotoxic against PaCa cells, while "re-programming" PSCs to an inactive state, decreasing collagen deposition and desmoplasia. Thus, targeting NDRG1 can effectively break the oncogenic cycle of PaCa-PSC bi-directional cross-talk to overcome PaCa desmoplasia and improve therapeutic outcomes.

Therapeutic perspective of thiosemicarbazones derivatives in inflammatory pathologies: A summary of in vitro/in vivo studies

Following induction of inflammation, the nuclear factor kappa B (NF-κB) in activated macrophages induces the transcription of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and cyclooxygenase (COX), an inflammatory enzyme implicated in the synthesis of prostaglandins (PGs). The latter are involved in the transition and the maintenance of chronic inflammation underling various chronic disorders that require treatment. Concerning this, many anti-inflammatory drugs are available to treat the inflammatory disorders, but their therapeutic use is associated with a variety of side effects. Therefore, the discovery of new safer and potential anti-inflammatory drugs is necessary. In this regard, thiosemicarbazones (TSC) compounds and their metals complexes attracted high interest due to their wide range of biological activities, interestingly, the anti-inflammatory activity. They are formed by the action of thiosemicarbazide on an aldehyde or ketone, and contain a sulfur atom in place of the oxygen atom. Their ability to form a stable complex with transition metal is known to enhances the biological activity and reduces the side effects of the parent compound. Thus, this review article describes the inflammatory response mediated by NF-κB-COX-PGs and summarizes the anti-inflammatory activity of different thiosemicarbazones derivatives synthesized in research area.

Crystal and solution structure of NDRG1, a membrane-binding protein linked to myelination and tumour suppression

N-myc downstream-regulated gene 1 (NDRG1) is a tumour suppressor involved in vesicular trafficking and stress response. NDRG1 participates in peripheral nerve myelination, and mutations in the NDRG1 gene lead to Charcot-Marie-Tooth neuropathy. The 43-kDa NDRG1 is considered as an inactive member of the α/β hydrolase superfamily. In addition to a central α/β hydrolase fold domain, NDRG1 consists of a short N terminus and a C-terminal region with three 10-residue repeats. We determined the crystal structure of the α/β hydrolase domain of human NDRG1 and characterised the structure and dynamics of full-length NDRG1. The structure of the α/β hydrolase domain resembles the canonical α/β hydrolase fold with a central β sheet surrounded by α helices. Small-angle X-ray scattering and CD spectroscopy indicated a variable conformation for the N- and C-terminal regions. NDRG1 binds to various types of lipid vesicles, and the conformation of the C-terminal region is modulated upon lipid interaction. Intriguingly, NDRG1 interacts with metal ions, such as nickel, but is prone to aggregation in their presence. Our results uncover the structural and dynamic features of NDRG1, as well as elucidate its interactions with metals and lipids, and encourage studies to identify a putative hydrolase activity of NDRG1. DATABASES: The coordinates and structure factors for the crystal structure of human NDRG1 were deposited to PDB (PDB ID: 6ZMM).

Reversing oncogenic transformation with iron chelation

Cancer cells accumulate iron to supplement their aberrant growth and metabolism. Depleting cells of iron by iron chelators has been shown to be selectively cytotoxic to cancer cells in vitro and in vivo. Iron chelators are effective at combating a range of cancers including those which are difficult to treat such as androgen insensitive prostate cancer and cancer stem cells. This review will evaluate the impact of iron chelation on cancer cell survival and the underlying mechanisms of action. A plethora of studies have shown iron chelators can reverse some of the major hallmarks and enabling characteristics of cancer. Iron chelators inhibit signalling pathways that drive proliferation, migration and metastasis as well as return tumour suppressive signalling. In addition to this, iron chelators stimulate apoptotic and ER stress signalling pathways inducing cell death even in cells lacking a functional p53 gene. Iron chelators can sensitise cancer cells to PARP inhibitors through mimicking BRCAness; a feature of cancers trademark genomic instability. Iron chelators target cancer cell metabolism, attenuating oxidative phosphorylation and glycolysis. Moreover, iron chelators may reverse the major characteristics of oncogenic transformation. Iron chelation therefore represent a promising selective mode of cancer therapy.

NDRG1 enhances the sensitivity of cetuximab by modulating EGFR trafficking in colorectal cancer

N-myc downstream-regulated gene 1 (NDRG1) is a key regulator that interacts with many classic tumor signaling pathways, including some molecules downstream of the epidermal growth factor receptor (EGFR). However, whether NDRG1 is involved in the mechanism of resistance to cetuximab (CTX), the first monoclonal antibody targeting the EGFR has not been reported. Here, we found that NDRG1 enhanced the sensitivity of CTX in colorectal cancer (CRC) cell lines. Afterwards, we determined the underlying mechanism of this phenomenon. We demonstrated that NDRG1 inhibited the expression of EGFR; blocked EGFR phosphorylation and reduced the EGFR distribution in the cell membrane, cytoplasm and nucleus. And then, NDRG1 suppressed the EGFR downstream signaling: RAS/RAF/ERK and PI3k/AKT/mTOR pathways. Moreover, we discovered that NDRG1 attenuated the endocytosis and degradation of EGFR induced by caveolin-1 (Cav1). Additionally, our findings were further observed in an animal model and human tissues. Our results represent a potentially significant discovery that explains the mechanisms of NDRG1 in CTX resistance. NDRG1 could be a promising biomarker to predict optimum responses to CTX, and a key target to enhance CTX activity in the treatment of metastatic CRC (mCRC).

Novel Thiosemicarbazones Sensitize Pediatric Solid Tumor Cell-Types to Conventional Chemotherapeutics through Multiple Molecular Mechanisms

Simple Summary

Combination of chemotherapeutics for the treatment of childhood cancer can lead to the use of lower cytotoxic drug doses and better therapeutic tolerability (i.e., lower side effects) for patients. We discovered novel molecular targets of two lead thiosemicarbazone agents of the di-2-pyridylketone thiosemicarbazone class. These molecular targets include: cyclooxygenase, the DNA repair protein, O6-methylguanine DNA methyltransferase, mismatch repair proteins, and topoisomerase 2α. This research also identifies promising synergistic interactions of these thiosemicarbazones particularly with the standard chemotherapeutic, celecoxib.

Abstract

Combining low-dose chemotherapies is a strategy for designing less toxic and more potent childhood cancer treatments. We examined the effects of combining the novel thiosemicarbazones, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), or its analog, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), with the standard chemotherapies, celecoxib (CX), etoposide (ETO), or temozolomide (TMZ). These combinations were analyzed for synergism to inhibit proliferation of three pediatric tumor cell-types, namely osteosarcoma (Saos-2), medulloblastoma (Daoy) and neuroblastoma (SH-SY5Y). In terms of mechanistic dissection, this study discovered novel thiosemicarbazone targets not previously identified and which are important for considering possible drug combinations. In this case, DpC and Dp44mT caused: (1) up-regulation of a major protein target of CX, namely cyclooxygenase-2 (COX-2); (2) down-regulation of the DNA repair protein, O⁶-methylguanine DNA methyltransferase (MGMT), which is known to affect TMZ resistance; (3) down-regulation of mismatch repair (MMR) proteins, MSH2 and MSH6, in Daoy and SH-SY5Y cells; and (4) down-regulation in all three cell-types of the MMR repair protein, MLH1, and also topoisomerase 2α (Topo2α), the latter of which is an ETO target. While thiosemicarbazones up-regulate the metastasis suppressor, NDRG1, in adult cancers, it is demonstrated herein for the first time that they induce NDRG1 in all three pediatric tumor cell-types, validating its role as a potential target. In fact, siRNA studies indicated that NDRG1 was responsible for MGMT down-regulation that may prevent TMZ resistance. Examining the effects of combining thiosemicarbazones with CX, ETO, or TMZ, the most promising synergism was obtained using CX. Of interest, a positive relationship was observed between NDRG1 expression of the cell-type and the synergistic activity observed in the combination of thiosemicarbazones and CX. These studies identify novel thiosemicarbazone targets relevant to childhood cancer combination chemotherapy.

CYLD Promotes Apoptosis of Nasopharyngeal Carcinoma Cells by Regulating NDRG1

Purpose

Nasopharyngeal carcinoma (NPC) is among the most common malignancies derived from the epithelium of the nasopharynx. To date, the regulatory networks involved in NPC have not been fully identified. Previous studies revealed multiple loss-of-function mutations in NPC and specifically in cylindromatosis lysine 63 deubiquitinase (CYLD); however, the exact role of CYLD in NPC progression and its potential mechanism remains unclear.

Methods

We performed immunohistochemical (IHC) staining and real-time quantitative polymerase chain reaction (qPCR) to measure CYLD expression in NPC tissues, and Western blot was conducted to determine CYLD levels in NPC cell lines. Cell proliferation was detected by CCK8 assay and colony formation analysis, and apoptosis was determined by Annexin V/propidium iodide staining. Potential targets of CYLD were verified by co-immunoprecipitation and mass spectrometry. Xenograft assay was conducted to confirm the role of CYLD in vivo.

Results

We found that CYLD levels were significantly decreased in both NPC tissues and cell lines, and that CYLD overexpression inhibited NPC cell proliferation and promoted apoptosis. Additionally, we revealed that CYLD bound and upregulated N-Myc downstream regulated 1 (NDRG1), and that silencing NDRG1 abolished the tumor-suppressor effect of CYLD on NPC cells. Furthermore, CYLD suppressed tumor growth in xenograft mice models.

Conclusion

These results suggest CYLD as a tumor suppressor, potential biomarker for diagnosing NPC, and therapeutic target.

The Role of Extracellular Proteases in Tumor Progression and the Development of Innovative Metal Ion Chelators that Inhibit their Activity

The crucial role of extracellular proteases in cancer progression is well-known, especially in relation to the promotion of cell invasion through extracellular matrix remodeling. This also occurs by the ability of extracellular proteases to induce the shedding of transmembrane proteins at the plasma membrane surface or within extracellular vesicles. This process results in the regulation of key signaling pathways by the modulation of kinases, e.g., the epidermal growth factor receptor (EGFR). Considering their regulatory roles in cancer, therapeutics targeting various extracellular proteases have been discovered. These include the metal-binding agents di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) and di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which increase c-MET degradation by multiple mechanisms. Both the direct and indirect inhibition of protease expression and activity can be achieved through metal ion depletion. Considering direct mechanisms, chelators can bind zinc(II) that plays a catalytic role in enzyme activity. In terms of indirect mechanisms, Dp44mT and DpC potently suppress the expression of the kallikrein-related peptidase-a prostate-specific antigen-in prostate cancer cells. The mechanism of this activity involves promotion of the degradation of the androgen receptor. Additional suppressive mechanisms of Dp44mT and DpC on matrix metalloproteases (MMPs) relate to their ability to up-regulate the metastasis suppressors N-myc downstream regulated gene-1 (NDRG1) and NDRG2, which down-regulate MMPs that are crucial for cancer cell invasion.

Pharmacological targeting and the diverse functions of the metastasis suppressor, NDRG1, in cancer

N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that is regulated by hypoxia, metal ions including iron, the free radical nitric oxide (NO^.), and various stress stimuli. This intriguing molecule exhibits diverse functions in cancer, inhibiting epithelial-mesenchymal transition (EMT), cell migration and angiogenesis by modulation of a plethora of oncogenes via cellular signaling. Thus, pharmacological targeting of NDRG1 signaling in cancer is a promising therapeutic strategy. Of note, novel anti-tumor agents of the di-2-pyridylketone thiosemicarbazone series, which exert the "double punch" mechanism by binding metal ions to form redox-active complexes, have been demonstrated to markedly up-regulate NDRG1 expression in cancer cells. This review describes the mechanisms underlying NDRG1 modulation by the thiosemicarbazones and the diverse effects NDRG1 exerts in cancer. As a major induction mechanism, iron depletion appears critical, with NO^. also inducing NDRG1 through its ability to bind iron and generate dinitrosyl-dithiol iron complexes, which are then effluxed from cells. Apart from its potent anti-metastatic role, several studies have reported a pro-oncogenic role of NDRG1 in a number of cancer-types. Hence, it has been suggested that NDRG1 plays pleiotropic roles depending on the cancer-type. The molecular mechanism(s) underlying NDRG1 pleiotropy remain elusive, but are linked to differential regulation of WNT signaling and potentially differential interaction with the tumor suppressor, PTEN. This review discusses NDRG1 induction mechanisms by metal ions and NO^. and both the anti- and possible pro-oncogenic functions of NDRG1 in multiple cancer-types and compares the opposite effects this protein exerts on cancer progression.

Iron chelators in cancer therapy

Iron chelators have long been a target of interest as anticancer agents. Iron is an important cellular resource involved in cell replication, metabolism and growth. Iron metabolism is modulated in cancer cells reflecting their increased replicative demands. Originally, iron chelators were first developed for use in iron overload disorders, however, their potential as anticancer agents has been gaining increasing interest. This is due, in part, to the downstream effects of iron depletion such as the inhibition of proliferation through ribonucleotide reductase activity. Additionally, some chelators form redox active metal complexes with iron resulting in the production of reactive oxygen species and oxidative stress. Newer synthetic iron chelators such as Deferasirox, Triapine and di-2-pyridylketone-4,4,-dimethyl-3-thiosemicrbazone (Dp44mt) have improved pharmacokinetic properties over the older chelator Deferoxamine. This review examines and discusses the various iron chelators that have been trialled for cancer therapy including both preclinical and clinical studies. The successes and shortcomings of each of the chelators and their use in combination therapies are highlighted and future potential in the cancer therapy world is considered.

Unique targeting of androgen-dependent and -independent AR signaling in prostate cancer to overcome androgen resistance

The androgen receptor (AR) is a major driver of prostate cancer (PCa) and a key therapeutic target for AR inhibitors (ie, Enzalutamide). However, Enzalutamide only inhibits androgen-dependent AR signaling, enabling intrinsic AR activation via androgen-independent pathways, leading to aggressive castration-resistant PCa (CRPC). We investigated the ability of novel anti-cancer agents, Dp44mT and DpC, to overcome androgen resistance. The effect of Dp44mT and DpC on androgen-dependent and independent AR signaling was assessed in androgen-dependent and -independent PCa cells using 2D- and 3D-tissue culture. The clinically trialed DpC was then examined in vivo and compared to Enzalutamide. These agents uniquely promote AR proteasomal degradation and inhibit AR transcription in PCa cells via the upregulation of c-Jun, potently reducing the AR target, prostate-specific antigen (PSA). These agents also inhibited the activation of key molecules in both androgen-dependent and independent AR signaling (ie, EGFR, MAPK, PI3K), which promote CRPC. The clinically trialed DpC also significantly inhibited PCa tumor growth, AR, and PSA expression in vivo, being more potent than Enzalutamide. DpC is a promising candidate for a unique, structurally distinct generation of AR inhibitors that simultaneously target both androgen-dependent and independent arms of AR signaling. No other therapies exhibit such comprehensive and potent AR suppression, which is critical for overcoming the development of androgen resistance.

A novel antitumor dithiocarbamate compound inhibits the EGFR/AKT signaling pathway and induces apoptosis in esophageal cancer cells

Dithiocarbamate has been reported to possess a potent antitumor efficacy against several types of cancer, such as ovarian cancer, breast cancer and hepatocellular carcinoma; however, only a few studies have investigated its inhibitory effect on esophageal cancer. Dipyridylhydrazone dithiocarbamate (DpdtC) is a novel dithiocarbamate derivative that was recently designed, synthesized and evaluated in our previous study. In the present study, the cell growth inhibition and apoptosis induced by DpdtC were measured using the CCK-8 and Annexin V-FITC/propidium iodide staining assays, respectively. Epidermal growth factor receptor (EGFR) signaling pathway and apoptosis related protein levels were examined by western blotting. In vivo effect of DpdtC was evaluated in nude mice bearing KYSE-450 ×enograft tumors. The aims of the present study were to further evaluate the antitumor effects of DpdtC on esophageal cancer cells (KYSE-150 and KYSE-450 cells), and to investigate its potential mechanism of action in vitro and in vivo. It was found that DpdtC significantly inhibited KYSE-150 and KYSE-450 cell proliferation by regulating the EGFR/AKT signaling pathway and inducing apoptosis. In addition, this effect was further identified in vivo; DpdtC inhibited the growth of the KYSE-450 esophageal cancer xenografts by regulating the EGFR/AKT signaling pathway. Furthermore, DpdtC did not affect the body weight in mice. Collectively, the present results suggested that DpdtC may be a promising antitumor drug candidate for the treatment of esophageal cancer.

Iron chelation inhibits mTORC1 signaling involving activation of AMPK and REDD1/Bnip3 pathways

The mammalian target of rapamycin (mTOR) functions as two complexes (mTORC1 and mTORC2), regulating cell growth and metabolism. Aberrant mTOR signaling occurs frequently in cancers, so mTOR has become an attractive target for cancer therapy. Iron chelators have emerged as promising anticancer agents. However, the mechanisms underlying the anticancer action of iron chelation are not fully understood. Particularly, reports on the effects of iron chelation on mTOR complexes are inconsistent or controversial. Here, we found that iron chelators consistently inhibited mTORC1 signaling, which was blocked by pretreatment with ferrous sulfate. Mechanistically, iron chelation-induced mTORC1 inhibition was not related to ROS induction, copper chelation, or PP2A activation. Instead, activation of AMPK pathway mainly and activation of both HIF-1/REDD1 and Bnip3 pathways partially contribute to iron chelation-induced mTORC1 inhibition. Our findings indicate that iron chelation inhibits mTORC1 via multiple pathways and iron is essential for mTORC1 activation.

Thiosemicarbazones as Potent Anticancer Agents and their Modes of Action

:

Thiosemicarbazones (TSCs) are a class of Schiff bases usually obtained by the condensation of thiosemicarbazide with a suitable aldehyde or ketone. TSCs have been the focus of chemists and biologists due to their wide range of pharmacological effects. One of the promising areas in which these excellent metal chelators are being developed is their use against cancer. TSCs have a wide clinical antitumor spectrum with efficacy in various tumor types such as leukemia, pancreatic cancer, breast cancer, non-small cell lung cancer, cervical cancer, prostate cancer and bladder cancer. To obtain better activity, different series of TSCs have been developed by modifying the heteroaromatic system in their molecules. These compounds possessed significant antineoplastic activity when the carbonyl attachment of the side chain was located at a position α to the ring nitrogen atom, whereas attachment of the side chain β or γ to the heterocyclic N atom resulted in inactive antitumor agents. In addition, replacement of the heterocyclic ring N with C also resulted in a biologically inactive compound suggesting that a conjugated N,N,S-tridentate donor set is essential for the biological activities of thiosemicarbazones. Several possible mechanisms have been implemented for the anticancer activity of thiosemicarbazones.

The metastasis suppressor, NDRG1, attenuates oncogenic TGF-β and NF-κB signaling to enhance membrane E-cadherin expression in pancreatic cancer cells

The metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), plays multifaceted roles in inhibiting oncogenic signaling and can suppress the epithelial mesenchymal transition (EMT), a key step in metastasis. In this investigation, NDRG1 inhibited the oncogenic effects of transforming growth factor-β (TGF-β) in PANC-1 pancreatic cancer cells, promoting expression and co-localization of E-cadherin and β-catenin at the cell membrane. A similar effect of NDRG1 at supporting E-cadherin and β-catenin co-localization at the cell membrane was also demonstrated for HT-29 colon and CFPAC-1 pancreatic cancer cells. The increase in E-cadherin in PANC-1 cells in response to NDRG1 was mediated by the reduction of three transcriptional repressors of E-cadherin, namely SNAIL, SLUG and ZEB1. To dissect the mechanisms how NDRG1 inhibits nuclear SNAIL, SLUG and ZEB1, we assessed involvement of the nuclear factor-κB (NF-κB) pathway, as its aberrant activation contributes to the EMT. Interestingly, NDRG1 comprehensively inhibited oncogenic NF-κB signaling at multiple sites in this pathway, suppressing NEMO, Iĸĸα and IĸBα expression, as well as reducing the activating phosphorylation of Iĸĸα/β and IĸBα. NDRG1 also reduced the levels, nuclear co-localization and DNA-binding activity of NF-κB p65. Further, Iĸĸα, which integrates NF-κB and TGF-β signaling to upregulate ZEB1, SNAIL and SLUG, was identified as an NDRG1 target. Considering this, therapies targeting NDRG1 could be a new strategy to inhibit metastasis, and as such, we examined novel anticancer agents, namely di-2-pyridylketone thiosemicarbazones, which upregulate NDRG1. These agents downregulated SNAIL, SLUG and ZEB1 in vitro and in vivo using a PANC-1 tumor xenograft model, demonstrating their marked potential.

NDRG1 suppresses basal and hypoxia-induced autophagy at both the initiation and degradation stages and sensitizes pancreatic cancer cells to lysosomal membrane permeabilization

BACKGROUND

N-myc downstream regulated gene 1 (NDRG1) is an established stress-response protein. This study investigated the effects of NDRG1 on autophagic degradation and how this can be therapeutically exploited.

METHODS

Cell culture, western analysis, confocal microscopy, acridine orange staining, cholesterol determination, cellular proliferation assessment and combination index (CI) estimation.

RESULTS

NDRG1 expression suppressed autophagic degradation and autolysosome formation, measured by increased p62 expression and reduced co-localization between the well-characterized, autophagosomal and lysosomal markers, LC3 and LAMP2, respectively. NDRG1 elicited autophagic suppression at the initiation stage of autophagy. The NDRG1-inducer and anti-cancer agent, di-2-pyridylketone 4,4,-dimethyl-3-thiosemicarbazone (Dp44mT), was able to induce lysosomal membrane permeabilization (LMP). Over-expression of NDRG1 further sensitized cells to LMP mediated by both Dp44mT, or the redox active Dp44mT‑copper complex. This sensitization may be mediated via a decrease in cholesterol levels upon NDRG1 expression, as cholesterol stabilizes lysosomal membranes. However, the effect of NDRG1 on cholesterol appeared independent of the key energy homeostasis sensor, 5' AMP-activated protein kinase (AMPK), whose activation was significantly (p < 0.001) reduced by NDRG1. Finally, Dp44mT synergistically potentiated the anti-proliferative activity of Gemcitabine that activates autophagy. In fact, Dp44mT and Gemcitabine (Combination Index (CI): 0.38 ± 0.07) demonstrated higher synergism versus the autophagy inhibitor, Bafilomycin A1 and Gemcitabine (CI: 0.64 ± 0.19).

CONCLUSIONS AND GENERAL SIGNIFICANCE

Collectively, this study demonstrated a dual-inhibitory mechanism of NDRG1 on autophagic activity, and that NDRG1 expression sensitized cells to Dp44mT-induced LMP. Considering the ability of Dp44mT to inhibit autophagy, studies demonstrated the potential of combination therapy for cancer treatment of Dp44mT with Gemcitabine.

Altered Iron Metabolism and Impact in Cancer Biology, Metastasis, and Immunology

Iron is an essential nutrient that plays a complex role in cancer biology. Iron metabolism must be tightly controlled within cells. Whilst fundamental to many cellular processes and required for cell survival, excess labile iron is toxic to cells. Increased iron metabolism is associated with malignant transformation, cancer progression, drug resistance and immune evasion. Depleting intracellular iron stores, either with the use of iron chelating agents or mimicking endogenous regulation mechanisms, such as microRNAs, present attractive therapeutic opportunities, some of which are currently under clinical investigation. Alternatively, iron overload can result in a form of regulated cell death, ferroptosis, which can be activated in cancer cells presenting an alternative anti-cancer strategy. This review focuses on alterations in iron metabolism that enable cancer cells to meet metabolic demands required during different stages of tumorigenesis in relation to metastasis and immune response. The strength of current evidence is considered, gaps in knowledge are highlighted and controversies relating to the role of iron and therapeutic targeting potential are discussed. The key question we address within this review is whether iron modulation represents a useful approach for treating metastatic disease and whether it could be employed in combination with existing targeted drugs and immune-based therapies to enhance their efficacy.

Dp44mT, an iron chelator, suppresses growth and induces apoptosis via RORA-mediated NDRG2-IL6/JAK2/STAT3 signaling in glioma

PURPOSE

The iron-chelating agent di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) has been found to inhibit cell growth and to induce apoptosis in several human cancers. However, its effects and mechanism of action in glioma are unknown.

METHODS

Human glioma cell line LN229 and patient-derived glioma stem cells GSC-42 were applied for both in vitro and in vivo xenograft nude mouse experiments. The anti-tumor effects of Dp44mT were assessed using MTS, EdU, TUNEL, Western blotting, qRT-PCR, luciferase reporter, chromatin immunoprecipitation and immunohistochemical assays.

RESULTS

We found that Dp44mT can upregulate the expression of the anti-oncogene N-myc downstream-regulated gene (NDRG)2 by directly binding to and activating the RAR-related orphan receptor (ROR)A. In addition, we found that NDRG2 overexpression suppressed inflammation via activation of interleukin (IL)-6/Janus kinase (JAK)2/signal transducer and activator of transcription (STAT)3 signaling.

CONCLUSIONS

Our data indicate that Dp44mT may serve as an effective drug for the treatment of glioma by targeting RORA and enhancing NDRG2-mediated IL-6/JAK2/STAT3 signaling.

Thiosemicarbazones suppress expression of the c-Met oncogene by mechanisms involving lysosomal degradation and intracellular shedding

Considering the role of proto-oncogene c-Met (c-Met) in oncogenesis, we examined the effects of the metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), and two NDRG1-inducing thiosemicarbazone-based agents, Dp44mT and DpC, on c-Met expression in DU145 and Huh7 cells. NDRG1 silencing without Dp44mT and DpC up-regulated c-Met expression, demonstrating that NDRG1 modulates c-Met levels. Dp44mT and DpC up-regulated NDRG1 by an iron-dependent mechanism and decreased c-Met levels, c-Met phosphorylation, and phosphorylation of its downstream effector, GRB2-associated binding protein 1 (GAB1). However, incubation with Dp44mT and DpC after NDRG1 silencing or silencing of the receptor tyrosine kinase inhibitor, mitogen-inducible gene 6 (MIG6), decreased c-Met and its phosphorylation, suggesting NDRG1- and MIG6-independent mechanism(s). Lysosomal inhibitors rescued the Dp44mT- and DpC-mediated c-Met down-regulation in DU145 cells. Confocal microscopy revealed that lysosomotropic agents and the thiosemicarbazones significantly increased co-localization between c-Met and lysosomal-associated membrane protein 2 (LAMP2). Moreover, generation of c-Met C-terminal fragment (CTF) and its intracellular domain (ICD) suggested metalloprotease-mediated cleavage. In fact, Dp44mT increased c-Met CTF while decreasing the ICD. Dp44mT and a γ-secretase inhibitor increased cellular c-Met CTF levels, suggesting that Dp44mT induces c-Met CTF levels by increasing metalloprotease activity. The broad metalloprotease inhibitors, EDTA and batimastat, partially prevented Dp44mT-mediated down-regulation of c-Met. In contrast, the ADAM inhibitor, TIMP metallopeptidase inhibitor 3 (TIMP-3), had no such effect, suggesting c-Met cleavage by another metalloprotease. Notably, Dp44mT did not induce extracellular c-Met shedding that could decrease c-Met levels. In summary, the thiosemicarbazones Dp44mT and DpC effectively inhibit oncogenic c-Met through lysosomal degradation and metalloprotease-mediated cleavage.

E6AP Promotes a Metastatic Phenotype in Prostate Cancer

Although primary prostate cancer is largely curable, progression to metastatic disease is associated with very poor prognosis. E6AP is an E3 ubiquitin ligase and a transcriptional co-factor involved in normal prostate development. E6AP drives prostate cancer when overexpressed. Our study exposed a role for E6AP in the promotion of metastatic phenotype in prostate cells. We revealed that elevated levels of E6AP in primary prostate cancer correlate with regional metastasis and demonstrated that E6AP promotes acquisition of mesenchymal features, migration potential, and ability for anchorage-independent growth. We identified the metastasis suppressor NDRG1 as a target of E6AP and showed it is key in E6AP induction of mesenchymal phenotype. We showed that treatment of prostate cancer cells with pharmacological agents upregulated NDRG1 expression suppressed E6AP-induced cell migration. We propose that the E6AP-NDRG1 axis is an attractive therapeutic target for the treatment of E6AP-driven metastatic prostate cancer.

•

Elevated E6AP levels in primary PC in men correlate with regional metastasis

•

Elevated E6AP levels promote mesenchymal features and migration potential

•

E6AP promotes a metastatic phenotype by reducing NDRG1 expression levels

•

Pharmacological upregulation of NDRG1 suppresses E6AP-induced cell migration

Migration and Invasion Enhancer 1 Is an NF-ĸB-Inducing Gene Enhancing the Cell Proliferation and Invasion Ability of Human Prostate Carcinoma Cells In Vitro and In Vivo

Migration and invasion enhancer 1 (MIEN1) is a membrane-anchored protein and exists in various cancerous tissues. However, the roles of MIEN1 in prostate cancer have not yet been clearly addressed. We determined the expression, biological functions, and regulatory mechanisms of MIEN1 in the prostate. The results of immunohistochemical analysis indicated that MIEN1 was expressed specifically in epithelial cells and significantly higher in adenocarcinoma as compared to in normal tissues. MIEN1 enhanced in vitro cell proliferation, invasion, and in vivo tumorigenesis. Meanwhile, MIEN1 attenuated cisplatin-induced apoptosis in PC-3 cells. Overexpression of NF-ĸB-inducing kinase (NIK) enhanced MIEN1 expression, while overexpression of NF-ĸB inhibitor α (IĸBα) blocked MIEN1 expression in PC-3 cells. In prostate carcinoma cells, MIEN1 provoked Akt phosphorylation; moreover, MIEN1 downregulated N-myc downstream regulated 1 (NDRG1) but upregulated interleukin-6 (IL-6) gene expression. MK2206, an Akt inhibitor, impeded the modulation of MIEN1 on NDRG1 and IL-6 expressions. Our studies suggest that MIEN1 is an NF-ĸB downstream oncogene in the human prostate. Accordingly, the modulation of Akt signaling in the gene expressions of NDRG1 and IL-6 may account for the functions of MIEN1 in cell proliferation, invasion, and tumorigenesis in prostate carcinoma cells.

Targeted drug combination therapy design based on driver genes

Targeted therapies against cancer types with more than one driver gene hold bright but elusive promise, since approved drugs are not available for all driver mutations and monotherapies often result in resistance. Targeting multiple driver genes in different pathways at the same time may provide an impact extensive enough to fight resistance. Our goal was to find synergistic drug combinations based on the availability of targeted drugs and their biological activity profiles and created an associated compound library based on driver gene-related protein targets. In this study, we would like to show that driver gene pattern based customized combination therapies are more effective than monotherapies on six cell lines and patient-derived primary cell cultures.

We tested 55–102 drug combinations targeting driver genes and driver pathways for each cell line and found 25–85% of these combinations highly synergistic. Blocking 2–5 cancer pathways using only 2–3 targeted drugs was sufficient to reach high rates of tumor cell eradication at remarkably low concentrations.

Our results demonstrate that the efficiency of cancer treatment may be significantly improved by combining drugs against multiple tumor specific drivers.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

Ironing out the role of the cyclin-dependent kinase inhibitor, p21 in cancer: Novel iron chelating agents to target p21 expression and activity

Iron (Fe) has become an important target for the development of anti-cancer therapeutics with a number of Fe chelators entering human clinical trials for advanced and resistant cancer. An important aspect of the activity of these compounds is their multiple molecular targets, including those that play roles in arresting the cell cycle, such as the cyclin-dependent kinase inhibitor, p21. At present, the exact mechanism by which Fe chelators regulate p21 expression remains unclear. However, recent studies indicate the ability of chelators to up-regulate p21 at the mRNA level was dependent on the chelator and cell-type investigated. Analysis of the p21 promoter identified that the Sp1-3-binding site played a significant role in the activation of p21 transcription by Fe chelators. Furthermore, there was increased Sp1/ER-α and Sp1/c-Jun complex formation in melanoma cells, suggesting these complexes were involved in p21 promoter activation. Elucidating the mechanisms involved in the regulation of p21 expression in response to Fe chelator treatment in neoplastic cells will further clarify how these agents achieve their anti-tumor activity. It will also enhance our understanding of the complex roles p21 may play in neoplastic cells and lead to the development of more effective and specific anti-cancer therapies.

The metastasis suppressor NDRG1 down-regulates the epidermal growth factor receptor via a lysosomal mechanism by up-regulating mitogen-inducible gene 6

The metastasis suppressor, N-Myc downstream-regulated gene-1 (NDRG1) inhibits a plethora of oncogenic signaling pathways by down-regulating the epidermal growth factor receptor (EGFR). Herein, we examined the mechanism involved in NDRG1-mediated EGFR down-regulation. NDRG1 overexpression potently increased the levels of mitogen-inducible gene 6 (MIG6), which inhibits EGFR and facilitates its lysosomal processing and degradation. Conversely, silencing NDRG1 in multiple human cancer cell types decreased MIG6 expression, demonstrating the regulatory role of NDRG1. Further, NDRG1 overexpression facilitated MIG6-EGFR association in the cytoplasm, possibly explaining the significantly (p <0.001) increased half-life of MIG6 from 1.6 ± 0.2 h under control conditions to 7.9 ± 0.4 h after NDRG1 overexpression. The increased MIG6 levels enhanced EGFR co-localization with the late endosome/lysosomal marker, lysosomal-associated membrane protein 2 (LAMP2). An increase in EGFR levels after MIG6 silencing was particularly apparent when NDRG1 was overexpressed, suggesting a role for MIG6 in NDRG1-mediated down-regulation of EGFR. Silencing phosphatase and tensin homolog (PTEN), which facilitates early to late endosome maturation, decreased MIG6, and also increased EGFR levels in both the presence and absence of NDRG1 overexpression. These results suggest a role for PTEN in regulating MIG6 expression. Anti-tumor drugs of the di-2-pyridylketone thiosemicarbazone class that activate NDRG1 expression also potently increased MIG6 and induced its cytosolic co-localization with NDRG1. This was accompanied by a decrease in activated and total EGFR levels and its redistribution to late endosomes/lysosomes. In conclusion, NDRG1 promotes EGFR down-regulation through the EGFR inhibitor MIG6, which leads to late endosomal/lysosomal processing of EGFR.

Up-regulation of the kinase gene SGK1 by progesterone activates the AP-1-NDRG1 axis in both PR-positive and -negative breast cancer cells

Preoperative progesterone intervention has been shown to confer a survival benefit to breast cancer patients independently of their progesterone receptor (PR) status. This observation raises the question how progesterone affects the outcome of PR-negative cancer. Here, using microarray and RNA-Seq-based gene expression profiling and ChIP-Seq analyses of breast cancer cells, we observed that the serum- and glucocorticoid-regulated kinase gene (SGK1) and the tumor metastasis-suppressor gene N-Myc downstream regulated gene 1 (NDRG1) are up-regulated and that the microRNAs miR-29a and miR-101-1 targeting the 3'-UTR of SGK1 are down-regulated in response to progesterone. We further demonstrate a dual-phase transcriptional and post-transcriptional regulation of SGK1 in response to progesterone, leading to an up-regulation of NDRG1 that is mediated by a set of genes regulated by the transcription factor AP-1. We found that NDRG1, in turn, inactivates a set of kinases, impeding the invasion and migration of breast cancer cells. In summary, we propose a model for the mode of action of progesterone in breast cancer. This model helps decipher the molecular basis of observations in a randomized clinical trial of the effect of progesterone on breast cancer and has therefore the potential to improve the prognosis of breast cancer patients receiving preoperative progesterone treatment.