The iron chelators Dp44mT and DFO inhibit TGF-β-induced epithelial-mesenchymal transition via up-regulation of N-Myc downstream-regulated gene 1 (NDRG1)

NDRG1 enhances the sensitivity to Cetuximab by promoting Stat1 ubiquitylation in colorectal cancer

INTRODUCTION

Cetuximab (CTX) is an effective targeted drug for the treatment of metastatic colorectal cancer, but it is effective only in patients with wild-type KRAS genes. Even in this subset of patients, the sensitivity of CTX in patients with right hemi-colon cancer is much lower than that in patients with left hemi-colon cancer. This significantly limits its clinical application. Therefore, further elucidation of the underlying molecular mechanisms is needed. N-myc downstream-regulated gene 1 (NDRG1) plays an important role in solid tumor invasion and metastasis, but whether it can influence CTX sensitivity has not been thoroughly investigated.

OBJECTIVE

Our study aimed to identify a novel mechanism by which NDRG1 affects CTX sensitivity.

METHODS

Through mass spectrometry analysis of our previously constructed CTX-resistant RKO and HCT116 cells, we found that the signal transducer and activator of transcription-1 (Stat1) might be a potential target of NDRG1. By knocking out NDRG1 or/and Stat1 genes, we then applied the loss-of-function experiments to explore the regulatory relationship between NDRG1 and Stat1 and their roles in the cell cycle, epithelial-mesenchymal transition (EMT), and the sensitivity to CTX in these two colorectal cancer (CRC) cells. Finally, we used the nude-mouse transplanted tumor model and human CRC samples to verify the expression of NDRG1 and Stat1 and their impact on CTX sensitivity in vivo.

RESULTS

Stat1 was upregulated in CTX-resistant cells, whereas NDRG1 was downregulated. Mechanically, NDRG1 was inversely correlated with Stat1 expression. It suppressed CRC cell proliferation, migration, and invasion, and promoted apoptosis and epithelial-mesenchymal transition (EMT) by inhibiting Stat1. In addition, NDRG1 directly interacted with Stat1 and promoted Smurf1-induced Stat1 ubiquitination. Importantly, this novel NDRG1-dependent regulatory loop also enhanced CTX sensitivity both in vitro and in vivo.

CONCLUSION

Our study revealed that NDRG1 enhanced the sensitivity to Cetuximab by inhibiting Stat1 expression and promoting its ubiquitination in colorectal cancer, elucidating NDRG1 might be a potential therapeutic target for refractory CTX-resistant CRC tumors. But its clinical value still needs to be validated in a larger sample size as well as a different genetic background.

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.

NDRG1 acts as an oncogene in triple-negative breast cancer and its loss sensitizes cells to mitochondrial iron chelation

Multiple studies indicate that iron chelators enhance their anti-cancer properties by inducing NDRG1, a known tumor and metastasis suppressor. However, the exact role of NDRG1 remains controversial, as newer studies have shown that NDRG1 can also act as an oncogene. Our group recently introduced mitochondrially targeted iron chelators deferoxamine (mitoDFO) and deferasirox (mitoDFX) as effective anti-cancer agents. In this study, we evaluated the ability of these modified chelators to induce NDRG1 and the role of NDRG1 in breast cancer. We demonstrated that both compounds specifically increase NDRG1 without inducing other NDRG family members. We have documented that the effect of mitochondrially targeted chelators is at least partially mediated by GSK3α/β, leading to phosphorylation of NDRG1 at Thr346 and to a lesser extent on Ser330. Loss of NDRG1 increases cell death induced by mitoDFX. Notably, MDA-MB-231 cells lacking NDRG1 exhibit reduced extracellular acidification rate and grow slower than parental cells, while the opposite is true for ER+ MCF7 cells. Moreover, overexpression of full-length NDRG1 and the N-terminally truncated isoform (59112) significantly reduced sensitivity towards mitoDFX in ER+ cells. Furthermore, cells overexpressing full-length NDRG1 exhibited a significantly accelerated tumor formation, while its N-terminally truncated isoforms showed significantly impaired capacity to form tumors. Thus, overexpression of full-length NDRG1 promotes tumor growth in highly aggressive triple-negative breast cancer.

Identification of proteins related to SIS3 by iTRAQ and PRM-based comparative proteomic analysis in cisplatin-induced acute kidney injury

Background

Cisplatin is a commonly used nephrotoxic drug and can cause acute kidney injury (AKI). In the present study, isobaric tags for relative and absolute quantification (iTRAQ) and parallel reaction monitoring (PRM)-based comparative proteomics were used to analyze differentially expressed proteins (DEPs) to determine the key molecular mechanism in mice with cisplatin-induced AKI in the presence or absence of SIS3, a specific p-smad3 inhibitor, intervention.

Methods

The cisplatin-induced AKI mouse model was established and treated with SIS3. We used iTRAQ to search for DEPs, PRM to verify key DEPs and combined Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) for bioinformatics analysis. We then assessed lipid deposition, malondialdehyde (MDA) and reactive oxygen species (ROS) and detected the expression of SREBF1, SCD1, CPT1A, PPARα and NDRG1 in vitro.

Results

Proteomic analysis showed that the identified DEPs were mainly enriched in energy metabolism pathways, especially in lipid metabolism. When SIS3 was applied to inhibit the phosphorylation of Smad3, the expression of NDRG1 and fatty acid oxidation key proteins CPT1A and PPARα increased, the expression of lipid synthesis related proteins SREBF1 and SCD1 decreased and the production of lipid droplets, MDA and ROS decreased.

Conclusion

SIS3 alleviates oxidative stress, reduces lipid accumulation and promotes fatty acid oxidation through NDRG1 in cisplatin-induced AKI. Our study provides a new candidate protein for elucidating the molecular mechanisms of fatty acid metabolism disorders in cisplatin-induced acute kidney injury.

Hypoxia-inducible factor 3α1 increases epithelial-to-mesenchymal transition and iron uptake to drive colorectal cancer liver metastasis

BACKGROUND/OBJECTIVES

Hypoxia-inducible factor (HIF)-3α1's role in colorectal cancer (CRC) cells, especially its effects on epithelial-mesenchymal transition (EMT), zinc finger E-box binding homeobox 2 (ZEB2) gene expression, and iron metabolism, remains largely unstudied. This research sought to elucidate these relationships.

METHODS

RNA-seq was conducted to investigate the impact of HIF-3α1 overexpression in CRC cells. Dual-luciferase reporter assays assessed the direct targeting of ZEB2 by HIF-3α1. Scratch assays measured changes in cell migration following HIF-3α1 overexpression and ZEB2 knockdown. The effects of HIF-3α1 overexpression on colon tumour growth and liver metastasis were examined in vivo. Iron chelation was used to explore the role of iron metabolism in HIF-3α1-mediated EMT and tumour growth.

RESULTS

HIF-3α1 overexpression induced EMT and upregulated ZEB2 expression, enhancing cancer cell migration. ZEB2 knockdown reduced mesenchymal markers and cell migration. HIF-3α1 promoted colon tumour growth and liver metastasis, increased transferrin receptor (TFRC) expression and cellular iron levels, and downregulated HIF-1α, HIF-2α, and NDRG1. Iron chelation mitigated HIF-3α1-mediated EMT, tumour growth, and survival.

CONCLUSIONS

HIF-3α1 plays a critical role in colon cancer progression by promoting EMT, iron accumulation, and metastasis through ZEB2 and TFRC regulation, suggesting potential therapeutic targets in CRC.

Iron metabolism: backfire of cancer cell stemness and therapeutic modalities

Cancer stem cells (CSCs), with their ability of self-renewal, unlimited proliferation, and multi-directional differentiation, contribute to tumorigenesis, metastasis, recurrence, and resistance to conventional therapy and immunotherapy. Eliminating CSCs has long been thought to prevent tumorigenesis. Although known to negatively impact tumor prognosis, research revealed the unexpected role of iron metabolism as a key regulator of CSCs. This review explores recent advances in iron metabolism in CSCs, conventional cancer therapies targeting iron biochemistry, therapeutic resistance in these cells, and potential treatment options that could overcome them. These findings provide important insights into therapeutic modalities against intractable cancers.

NDRGs in Breast Cancer: A Review and In Silico Analysis

The N-myc downstream regulated gene family (NDRGs) includes four members: NDRG1, NDRG2, NDRG3, and NDRG4. These members exhibit 53-65% amino acid identity. The role of NDRGs in tumor growth and metastasis appears to be tumor- and context-dependent. While many studies have reported that these family members have tumor suppressive roles, recent studies have demonstrated that NDRGs, particularly NDRG1 and NDRG2, function as oncogenes, promoting tumor growth and metastasis. Additionally, NDRGs are involved in regulating different signaling pathways and exhibit diverse cellular functions in breast cancers. In this review, we comprehensively outline the oncogenic and tumor suppressor roles of the NDRG family members in breast cancer, examining evidence from in vitro and in vivo breast cancer models as well as tumor tissues from breast cancer patients. We also present analyses of publicly available genomic and transcriptomic data from multiple independent cohorts of breast cancer patients.

Ferroptosis mediates airway epithelial E-cadherin dysfunction in LPS-induced acute lung injury

BACKGROUND

Loss of E-cadherin in the airway epithelial cells is a critical contributor to the development of ALI/ARDS. Yet the underlying mechanisms are largely unknown. Increasing evidences have revealed the significance of ferroptosis in the pathophysiological process of ALI/ARDS. The aim of this study was to investigate the role of ferroptosis in dysregulation of airway epithelial E-cadherin in ALI/ARDS.

METHODS

BALB/c mice were subjected to intratracheal instillation of lipopolysaccharide (LPS) to establish an ALI model. Two inhibitors of ferroptosis, liproxstatin-1 (Lip-1, at the dose of 10 mg/kg and 30 mg/kg) and ferrostatin-1 (Fer-1, at the dose of 1 mg/kg and 5 mg/kg), were respectively given to the mice through intraperitoneal injection after LPS challenge. The expression of ferroptotic markers, full-length E-cadherin and soluble E-cadherin (sE-cadherin) were both detected.

RESULTS

LPS exposure dramatically down-regulated pulmonary expression of E-cadherin in mice, with profound loss of membrane E-cadherin in the airway epithelial cells and increased secretion of sE-cadherin in the airway lumen. At the same time, we found that the mitochondrial of airway epithelial cells in LPS-exposed mice exhibited significant morphological alterations that are hallmark features of ferroptosis, with smaller volume and increased membrane density. Other makers of ferroptosis were also detected, including increased cytoplasmic levels of iron and lipid peroxidates (MDA), as well as decreased GPX4 expression. 30 mg/kg of Lip-1 not only showed potent protective effects against the LPS-induced injury, inflammation, edema of the lung in those mice, but also rescued airway epithelial E-cadherin expression and decreased the release of sE-cadherin through inhibiting ferroptosis. While no noticeable changes induced by LPS were observed in mice treated with Lip-1 at 10 mg/kg nor Fer-1 at 1 mg/kg or 5 mg/kg.

CONCLUSIONS

Taken together, these data demonstrated that ferroptosis mediates airway epithelial E-cadherin dysfunction in LPS-induced ALI.

Steric Blockade of Oxy-Myoglobin Oxidation by Thiosemicarbazones: Structure-Activity Relationships of the Novel PPP4pT Series

The di-2-pyridylketone thiosemicarbazones demonstrated marked anticancer efficacy, prompting progression of DpC to clinical trials. However, DpC induced deleterious oxy-myoglobin oxidation, stifling development. To address this, novel substituted phenyl thiosemicarbazone (PPP4pT) analogues and their Fe(III), Cu(II), and Zn(II) complexes were prepared. The PPP4pT analogues demonstrated potent antiproliferative activity (IC50: 0.009-0.066 μM), with the 1:1 Cu:L complexes showing the greatest efficacy. Substitutions leading to decreased redox potential of the PPP4pT:Cu(II) complexes were associated with higher antiproliferative activity, while increasing potential correlated with increased redox activity. Surprisingly, there was no correlation between redox activity and antiproliferative efficacy. The PPP4pT:Fe(III) complexes attenuated oxy-myoglobin oxidation significantly more than the clinically trialed thiosemicarbazones, Triapine, COTI-2, and DpC, or earlier thiosemicarbazone series. Incorporation of phenyl- and styryl-substituents led to steric blockade, preventing approach of the PPP4pT:Fe(III) complexes to the heme plane and its oxidation. The 1:1 Cu(II):PPP4pT complexes were inert to transmetalation and did not induce oxy-myoglobin oxidation.

Molecular interaction of metastasis suppressor genes and tumor microenvironment in breast cancer

Breast cancer (BC) is a leading cause of cancer-related deaths in women worldwide where the process of metastasis is a major contributor to the mortality associated with this disease. Metastasis suppressor genes are a group of genes that play a crucial role in preventing or inhibiting the spread of cancer cells. They suppress the metastasis process by inhibiting colonization and by inducing dormancy. These genes function by regulating various cellular processes in the tumor microenvironment (TME), such as cell adhesion, invasion, migration, and angiogenesis. Dysregulation of metastasis suppressor genes can lead to the acquisition of an invasive and metastatic phenotype and lead to poor prognostic outcomes. The components of the TME generally play a necessary in the metastasis progression of tumor cells. This review has identified and elaborated on the role of a few metastatic suppressors associated with the TME that have been shown to inhibit metastasis in BC by different mechanisms, such as blocking certain cell signaling molecules involved in cancer cell migration, invasion, enhancing immune surveillance of cancer cells, and promoting the formation of a protective extracellular matrix (ECM). Understanding the interaction of metastatic suppressor genes and the components of TME has important implications for the development of novel therapeutic strategies to target the metastatic cascade. Targeting these genes or their downstream signaling pathways offers a promising approach to inhibiting the spread of cancer cells and improves patient outcomes.

Advances in understanding and treating diabetic kidney disease: focus on tubulointerstitial inflammation mechanisms

Diabetic kidney disease (DKD) is a serious complication of diabetes that can lead to end-stage kidney disease. Despite its significant impact, most research has concentrated on the glomerulus, with little attention paid to the tubulointerstitial region, which accounts for the majority of the kidney volume. DKD's tubulointerstitial lesions are characterized by inflammation, fibrosis, and loss of kidney function, and recent studies indicate that these lesions may occur earlier than glomerular lesions. Evidence has shown that inflammatory mechanisms in the tubulointerstitium play a critical role in the development and progression of these lesions. Apart from the renin-angiotensin-aldosterone blockade, Sodium-Glucose Linked Transporter-2(SGLT-2) inhibitors and new types of mineralocorticoid receptor antagonists have emerged as effective ways to treat DKD. Moreover, researchers have proposed potential targeted therapies, such as inhibiting pro-inflammatory cytokines and modulating T cells and macrophages, among others. These therapies have demonstrated promising results in preclinical studies and clinical trials, suggesting their potential to treat DKD-induced tubulointerstitial lesions effectively. Understanding the immune-inflammatory mechanisms underlying DKD-induced tubulointerstitial lesions and developing targeted therapies could significantly improve the treatment and management of DKD. This review summarizes the latest advances in this field, highlighting the importance of focusing on tubulointerstitial inflammation mechanisms to improve DKD outcomes.

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.

Six-transmembrane epithelial antigen of prostate 3 (STEAP3) is a potential prognostic biomarker in clear cell renal cell carcinoma that correlates with M2 macrophage infiltration and epithelial-mesenchymal

BACKGROUND

The six-transmembrane epithelial antigen of the prostate 3 (STEAP3) is a metalloreductase, which is essential for iron uptake. Existing literature has shown that STEAP3 may perform an important role in the onset and progression of tumors. Nonetheless, a complete pan-cancer investigation of the prognostic significance and immune properties of STEAP3 is currently unavailable.

AIMS

As part of our investigation into the possible functions of STEAP3 in malignancies, we conducted a comprehensive analysis to examine the prognostic value and immune features of STEAP3 in human pan-cancer.

METHODS AND RESULTS

R and Cytoscape programs were applied to analyze and visualize the data. The expression of STEAP3 in both cell lines and tissues was measured utilizing a variety of approaches. Using the shRNA knockdown technique, we tested the viability of the A498 and 786-O cell lines and validated their functions. Both CCK-8 and transwell assays were conducted to estimate cell proliferation and invasion. The expression of STEAP3 was substantially elevated and was shown to be linked to prognosis in the majority of malignancies, notably in clear cell renal cell carcinoma (ccRCC). In addition, the expression of STEAP3 was shown to have a strong correlation with immune infiltrates, which in turn triggered the recruitment and polarization of M2 macrophages in ccRCC. The protein STEAP3 shows promise as a predictor of responses to immune-checkpoint blockade (ICB) therapy. Positive links between STEAP3 and the epithelial-mesenchymal transition (EMT), the p53 pathway, and the immune-associated pathways were also found in the enrichment analysis. Our results illustrated that the STEAP3 expression level was substantially elevated in ccRCC tissues and suggested that it could stimulate EMT in ccRCC by downregulating CDH1.

CONCLUSION

In a diverse range of cancers, STEAP3 might serve as a biomarker for determining the prognosis as well as a predictor of immunotherapy responsiveness. STEAP3 is a novel biological marker for determining prognosis, and it also performs a remarkable function in the promotion of tumor growth in ccRCC by enhancing invasion and EMT, as well as by triggering the recruitment and polarization of M2 macrophages.

Novel Iron Chelator SK4 Drives Cytotoxicity through Inhibiting Mitochondrial Metabolism in Ovarian and Triple Negative Breast Cancer Cell Lines

Anti-cancer therapy by iron chelation has been shown to inhibit many cellular processes including DNA replication, mitochondrial metabolism and oncogenic signalling pathways (e.g., EGFR). Iron chelator SK4 represents a double pronged approach towards treating cancer. SK4 enters through LAT1, a commonly overexpressed amino acid transporter in tumours, thus targeting iron addiction and LAT1 overexpression. The aim of this study was to characterise the mode of action of SK4 through proteomics, metabolomics, lipidomics and seahorse real-time analysis in ovarian cell line SKOV3 and triple negative breast cancer cell line MDA MB 231. Pathway enrichment of proteomics data showed an overrepresentation of metabolism related pathways. Metabolic change after SK4 exposure have been confirmed in investigations of changes in basal and maximal mitochondrial respiration using seahorse real-time analysis of mitochondrial metabolism. Metabolomics also showed an increase in AMP and glucose-1-phosphate. Interestingly, our lipidomics data show a decrease in phospholipid synthesis in the SKOV3 cells which is in contrast with previous data which showed an upregulation of ceramide driven apoptosis. In summary, our data highlight impairment of energy metabolism as a mechanism of action underlying SK4 apoptosis, but also suggest a potential role of ceramide induction in the phenotypic outcome of the cell model.

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.

The role of the NDRG1 in the pathogenesis and treatment of breast cancer

Breast cancer (BC) is the leading cause of cancer death in women. This disease is heterogeneous, with clinical subtypes being estrogen receptor-α (ER-α) positive, having human epidermal growth factor receptor 2 (HER2) overexpression, or being triple-negative for ER-α, progesterone receptor, and HER2 (TNBC). The ER-α positive and HER2 overexpressing tumors can be treated with agents targeting these proteins, including tamoxifen and pertuzumab, respectively. Despite these treatments, resistance and metastasis are problematic, while TNBC is challenging to treat due to the lack of suitable targets. Many studies examining BC and other tumors indicate a role for N-myc downstream-regulated gene-1 (NDRG1) as a metastasis suppressor. The ability of NDRG1 to inhibit metastasis is due, in part, to the inhibition of the initial step in metastasis, namely the epithelial-to-mesenchymal transition. Paradoxically, there are also reports of NDRG1 playing a pro-oncogenic role in BC pathogenesis. The oncogenic effects of NDRG1 in BC have been reported to relate to lipid metabolism or the mTOR signaling pathway. The molecular mechanism(s) of how NDRG1 regulates the activity of multiple signaling pathways remains unclear. Therapeutic strategies that up-regulate NDRG1 have been developed and include agents of the di-2-pyridylketone thiosemicarbazone class. These compounds target oncogenic drivers in BC cells, suppressing the expression of multiple key hormone receptors including ER-α, progesterone receptor, androgen receptor, and prolactin receptor, and can also overcome tamoxifen resistance. Considering the varying role of NDRG1 in BC pathogenesis, further studies are required to examine what subset of BC patients would benefit from pharmacopeia that up-regulate NDRG1.

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.

A Review of the Regulatory Mechanisms of N-Myc on Cell Cycle

Neuroblastoma has obvious heterogeneity. It is one of the few undifferentiated malignant tumors that can spontaneously degenerate into completely benign tumors. However, for its high-risk type, even with various intensive treatment options, the prognosis is still unsatisfactory. At the same time, a large number of research data show that the abnormal amplification and high-level expression of the MYCN gene are positively correlated with the malignant progression, poor prognosis, and mortality of neuroblastoma. In this context, this article explores the role of the N-Myc, MYCN gene expression product on its target genes related to the cell cycle and reveals its regulatory network in promoting tumor proliferation and malignant progression. We hope it can provide ideas and direction for the research and development of drugs targeting N-Myc and its downstream target genes.

Ferroportin depletes iron needed for cell cycle progression in head and neck squamous cell carcinoma

Introduction

Ferroportin (FPN), the only identified eukaryotic iron efflux channel, plays an important role in iron homeostasis and is downregulated in many cancers. To determine if iron related pathways are important for Head and Neck Squamous Cell Carcinoma (HNSCC) progression and proliferation, we utilize a model of FPN over-expression to simulate iron depletion and probe associated molecular pathways.

Methods

The state of iron related proteins and ferroptosis sensitivity was assessed in a panel of metastatic HNSCC cell lines. Stable, inducible expression of FPN was confirmed in the metastatic HNSCC lines HN12 and JHU-022 as well as the non-transformed normal oral keratinocyte (NOK) cell line and the effect of FPN mediated iron depletion was assessed in these cell lines.

Results

HNSCC cells are sensitive to iron chelation and ferroptosis, but the non-transformed NOK cell line is not. We found that FPN expression inhibits HNSCC cell proliferation and colony formation but NOK cells are unaffected. Inhibition of cell proliferation is rescued by the addition of hepcidin. Decreases in proliferation are due to the disruption of iron homeostasis via loss of labile iron caused by elevated FPN levels. This in turn protects HNSCC cells from ferroptotic cell death. Expression of FPN induces DNA damage, activates p21, and reduces levels of cyclin proteins thereby inhibiting cell cycle progression of HNSCC cells, arresting cells in the S-phase. Induction of FPN severely inhibits Edu incorporation and increased β-galactosidase activity, indicating cells have entered senescence. Finally, in an oral orthotopic mouse xenograft model, FPN induction yields a significant decrease in tumor growth.

Conclusions

Our results indicate that iron plays a role in HNSCC cell proliferation and growth and is important for cell cycle progression. Iron based interventional strategies such as ferroptosis or iron chelation may have potential therapeutic benefits in advanced HNSCC.

Role of Ferroptosis in Regulating the Epithelial-Mesenchymal Transition in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a chronic interstitial lung disease whose pathogenesis involves a complex interaction of cell types and signaling pathways. Lung epithelial cells responding to repeated injury experience persistent inflammation and sustained epithelial-mesenchymal transition (EMT). The persistence of EMT-induced signals generates extracellular matrix accumulation, thereby causing fibrosis. Ferroptosis is a newly characterized iron-dependent non-apoptotic regulated cell death. Increased iron accumulation can increase iron-induced oxidant damage in alveolar epithelial cells. Studies have demonstrated that iron steady states and oxidation steady states play an important role in the iron death regulation of EMT. This review summarizes the role of ferroptosis in regulating EMT in pulmonary fibrosis, aiming to provide a new idea for the prevention and treatment of this disease.

TGFβ Governs the Pleiotropic Activity of NDRG1 in Triple-Negative Breast Cancer Progression

In triple-negative breast cancer (TNBC), the pleiotropic NDRG1 (N-Myc downstream regulated gene 1) promotes progression and worse survival, yet contradictory results were documented, and the mechanisms remain unknown. Phosphorylation and localization could drive NDRG1 pleiotropy, nonetheless, their role in TNBC progression and clinical outcome was not investigated. We found enhanced p-NDRG1 (Thr346) by TGFβ1 and explored whether it drives NDRG1 pleiotropy and TNBC progression. In tissue microarrays of 81 TNBC patients, we identified that staining and localization of NDRG1 and p-NDRG1 (Thr346) are biomarkers and risk factors associated with shorter overall survival. We found that TGFβ1 leads NDRG1, downstream of GSK3β, and upstream of NF-κB, to differentially regulate migration, invasion, epithelial-mesenchymal transition, tumor initiation, and maintenance of different populations of cancer stem cells (CSCs), depending on the progression stage of tumor cells, and the combination of TGFβ and GSK3β inhibitors impaired CSCs. The present study revealed the striking importance to assess both total NDRG1 and p-NDRG1 (Thr346) positiveness and subcellular localization to evaluate patient prognosis and their stratification. NDRG1 pleiotropy is driven by TGFβ to differentially promote metastasis and/or maintenance of CSCs at different stages of tumor progression, which could be abrogated by the inhibition of TGFβ and GSK3β.

Olfactomedin 4 produces dysplasia but suppresses metastasis of colon cancer

Development of colorectal cancer (CRC) is regulated by a series of genetic and microenvironmental alterations. Olfactomedin 4 (OLFM4) is a secreted glycoprotein that is highly expressed in the gastrointestinal tract and modulates inflammation. However, the role of OLFM4 in CRC is uncertain. Here we aimed to explore the function of OLFM4 in CRC in vivo and in vitro. The mRNA expression of OLFM4 was up-regulated in precursor lesions with dysplasia or ulcerative colitis but was reduced in CRC. OLFM4 neutralizing antibody suppressed inflammation-mediated early-stage CRC formation in an AOM/DSS colitis-associated cancer model. OLFM4 knockdown cells exhibited increased cell proliferation and motility in vitro and in vivo. Ablation of OLFM4 increased tumor growth and metastasis in xenograft experiments. In addition, OLFM4 knockdown cells showed elevated expression of colon cancer stem cell markers including CD133, resulting in increased metastasis via epithelial-mesenchymal transition signaling. This study demonstrated that OLFM4 regulates inflammation and cancer progression differently; ablation of OLFM4 promotes cancer metastasis via stemness and epithelial-mesenchymal transition. These results suggest a new route for controlling cancer progression and metastasis.

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.

The Ni(II)-Binding Activity of the Intrinsically Disordered Region of Human NDRG1, a Protein Involved in Cancer Development

Nickel exposure is associated with tumors of the respiratory tract such as lung and nasal cancers, acting through still-uncharacterized mechanisms. Understanding the molecular basis of nickel-induced carcinogenesis requires unraveling the mode and the effects of Ni(II) binding to its intracellular targets. A possible Ni(II)-binding protein and a potential focus for cancer treatment is hNDRG1, a protein induced by Ni(II) through the hypoxia response pathway, whose expression correlates with higher cancer aggressiveness and resistance to chemotherapy in lung tissue. The protein sequence contains a unique C-terminal sequence of 83 residues (hNDRG1*C), featuring a three-times-repeated decapeptide, involved in metal binding, lipid interaction and post-translational phosphorylation. In the present work, the biochemical and biophysical characterization of unmodified hNDRG1*C was performed. Bioinformatic analysis assigned it to the family of the intrinsically disordered regions and the absence of secondary and tertiary structure was experimentally proven by circular dichroism and NMR. Isothermal titration calorimetry revealed the occurrence of a Ni(II)-binding event with micromolar affinity. Detailed information on the Ni(II)-binding site and on the residues involved was obtained in an extensive NMR study, revealing an octahedral paramagnetic metal coordination that does not cause any major change of the protein backbone, which is coherent with CD analysis. hNDRG1*C was found in a monomeric form by light-scattering experiments, while the full-length hNDRG1 monomer was found in equilibrium between the dimer and tetramer, both in solution and in human cell lines. The results are the first essential step for understanding the cellular function of hNDRG1*C at the molecular level, with potential future applications to clarify its role and the role of Ni(II) in cancer development.

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.

Thiosemicarbazones Can Act Synergistically with Anthracyclines to Downregulate CHEK1 Expression and Induce DNA Damage in Cell Lines Derived from Pediatric Solid Tumors

Anticancer therapy by anthracyclines often leads to the development of multidrug resistance (MDR), with subsequent treatment failure. Thiosemicarbazones have been previously suggested as suitable anthracycline partners due to their ability to overcome drug resistance through dual Pgp-dependent cytotoxicity-inducing effects. Here, we focused on combining anthracyclines (doxorubicin, daunorubicin, and mitoxantrone) and two thiosemicarbazones (DpC and Dp44mT) for treating cell types derived from the most frequent pediatric solid tumors. Our results showed synergistic effects for all combinations of treatments in all tested cell types. Nevertheless, further experiments revealed that this synergism was independent of Pgp expression but rather resulted from impaired DNA repair control leading to cell death via mitotic catastrophe. The downregulation of checkpoint kinase 1 (CHEK1) expression by thiosemicarbazones and the ability of both types of agents to induce double-strand breaks in DNA may explain the Pgp-independent synergism between anthracyclines and thiosemicarbazones. Moreover, the concomitant application of these agents was found to be the most efficient approach, achieving the strongest synergistic effect with lower concentrations of these drugs. Overall, our study identified a new mechanism that offers an avenue for combining thiosemicarbazones with anthracyclines to treat tumors regardless the Pgp status.

BACH1 Expression Is Promoted by Tank Binding Kinase 1 (TBK1) in Pancreatic Cancer Cells to Increase Iron and Reduce the Expression of E-Cadherin

BTB and CNC homology 1 (BACH1) represses the expression of genes involved in the metabolism of iron, heme and reactive oxygen species and promotes metastasis of various cancers including pancreatic ductal adenocarcinoma (PDAC). However, it is not clear how BACH1 is regulated in PDAC cells. Knockdown of Tank binding kinase 1 (TBK1) led to reductions of BACH1 mRNA and protein amounts in AsPC−1 human PDAC cells. Gene expression analysis of PDAC cells with knockdown of TBK1 or BACH1 suggested the involvement of TBK1 and BACH1 in the regulation of iron homeostasis. Ferritin mRNA and proteins were both increased upon BACH1 knockdown in AsPC−1 cells. Flow cytometry analysis showed that AsPC−1 cells with BACH1 knockout or knockdown contained lower labile iron than control cells, suggesting that BACH1 increased labile iron by repressing the expression of ferritin genes. We further found that the expression of E-cadherin was upregulated upon the chelation of intracellular iron content. These results suggest that the TBK1-BACH1 pathway promotes cancer cell metastasis by increasing labile iron within cells.

Expression and clinicopathological significance of glucocorticoid receptor, SGK1, and NDRG1 in hormone-naïve prostate carcinoma

Glucocorticoid receptor (GR) has been implicated in prostate carcinoma growth and progression. Glucocorticoid receptor beta (GRβ) acts as an inhibitor of GR; however, its function is not well understood. Serum- and glucocorticoid-regulated kinase 1 (SGK1) is a GR-responsive gene that phosphorylates N-myc downstream-regulated gene 1 (NDRG1) and is involved in cancer growth and invasion. However, the expression of GR, GRβ, SGK1, and NDRG1 in prostate cancer and their relationship with clinicopathological and functional significance remain unknown. The association between the status of GR, GRβ, SGK1, and NDRG1 immunoreactivity and clinicopathological variables was analyzed in patients with prostate carcinoma to explore their clinical significance. In prostate carcinoma cases, the relative abundance of GR and NDRG1 immunoreactivity was inversely and significantly associated with the primary tumor stage (pT), while GR immunoreactivity was inversely and significantly associated with the Ki-67 score. The relative expression status of NDRG1 was significantly associated with that of GR. However, no significant correlation was observed between any of the clinicopathological parameters and GRβ and SGK1 expression. Our findings indicate that GR and NDRG1 expression status is correlated with clinicopathological features in patients with prostate cancer.

Thiosemicarbazones reprogram pancreatic cancer bidirectional oncogenic signaling between cancer cells and stellate cells to suppress desmoplasia

Standard treatments have shown dismal activity against pancreatic cancer (PC), due in part to the development of a dense stroma (desmoplasia). This perspective discusses the development of the di-2-pyridylketone thiosemicarbazones that overcomes bidirectional oncogenic signaling between PC cells and pancreatic stellate cells (PSCs), which is critical for desmoplasia development. This activity is induced by the up-regulation of the metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), which inhibits oncogenic signaling via HGF, IGF-1 and Sonic Hedgehog pathway. More recent studies have deciphered additional pathways including those mediated by Wnt and tenascin C that are secreted by PSCs to activate β-catenin and YAP/TAZ signaling in PC cells. Suppression of bidirectional signaling between cell types presents a unique therapeutic opportunity.

Clinical Diagnostic and Prognostic Potential of NDRG1 and NDRG2 in Hepatocellular Carcinoma Patients

Background

Primary liver cancer is still the most common lethal malignancy. The N-myc downstream-regulated gene family (NDRG1–4) is a group of multifunctional proteins associated with carcinogenesis. However, systematic evaluation of the diagnostic and prognostic values of NDRG1 or NDRG2 expression in liver cancer is poorly investigated.

Method

The gene expression matrix of liver hepatocellular carcinoma (LIHC) was comprehensively analyzed by the “limma” and “Dseq2” R packages. The Gene Ontology (GO) and Gene Set Enrichment Analysis (GSEA) were used to identify the biological functional differences. A single-sample GSEA (ssGSEA) was conducted to quantify the extent of immune cell infiltration. Finally, the clinical and prognostic information of LIHC patients was systematically investigated using Kaplan–Meier analysis and logistic and Cox regression analysis.

Results

Compared with normal tissues, NDRG1 expression was higher, whereas NDRG2 expression was lower in tumor tissues (P <0.001). The area under the receiver operator characteristic curve (AUROC) of NDRG1 and NDRG2 for LIHC was 0.715 and 0.799, respectively. Kaplan–Meier analysis revealed that NDRG1 and NDRG2 were independent clinical prognostic biomarkers for the overall survival (OS, P = 0.001 and 2.9e−06), progression-free interval (PFI, P = 0.028 and 0.005) and disease-specific survival (DSS, P = 0.027 and P <0.001). The C-indexes and calibration plots of the nomogram suggest that NDRG1 and NDRG2 have an effective predictive performance for OS (C-index: 0.676), DSS (C-index: 0.741) and PFI (C-index: 0.630) of liver cancer patients. The mutation rate of NDRG1 in liver cancer reached up to 14%, and DNA methylation levels of NDRG1 and NDRG2 promoters correlated significantly with clinical prognosis.

Conclusions

The mRNA expression and DNA methylation of NDRG superfamily members have the potential for LIHC diagnosis and prognosis via integrative analysis from multiple cohorts.

A Tumor Suppressor Gene, N-myc Downstream-Regulated Gene 1 (NDRG1), in Gliomas and Glioblastomas

The development of potent and selective therapeutic approaches to glioblastoma (GBM) requires the identification of molecular pathways that critically regulate the survival and proliferation of GBM. Glioblastoma stem-like cells (GSCs) possess stem-cell-like properties, self-renewal, and differentiation into multiple neural cell lineages. From a clinical point of view, GSCs have been reported to resist radiation and chemotherapy. GSCs are influenced by the microenvironment, especially the hypoxic condition. N-myc downstream-regulated gene 1 (NDRG1) is a tumor suppressor with the potential to suppress the proliferation, invasion, and migration of cancer cells. Previous studies have reported that deregulated expression of NDRG1 affects tumor growth and clinical outcomes of patients with GBM. This literature review aimed to clarify the critical role of NDRG1 in tumorigenesis and acquirement of resistance for anti-GBM therapies, further to discussing the possibility and efficacy of NDRG1 as a novel target of treatment for GBM. The present review was conducted by searching the PubMed and Scopus databases. The search was conducted in February 2022. We review current knowledge on the regulation and signaling of NDRG1 in neuro-oncology. Finally, the role of NDRG1 in GBM and potential clinical applications are discussed.

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.

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.

Alterations of Ion Homeostasis in Cancer Metastasis: Implications for Treatment

We have previously reported that metastases from all malignancies are characterized by a core program of gene expression that suppresses extracellular matrix interactions, induces vascularization/tissue remodeling, activates the oxidative metabolism, and alters ion homeostasis. Among these features, the least elucidated component is ion homeostasis. Here we review the literature with the goal to infer a better mechanistic understanding of the progression-associated ionic alterations and identify the most promising drugs for treatment. Cancer metastasis is accompanied by skewing in calcium, zinc, copper, potassium, sodium and chloride homeostasis. Membrane potential changes and water uptake through Aquaporins may also play roles. Drug candidates to reverse these alterations are at various stages of testing, with some having entered clinical trials. Challenges to their utilization comprise differences among tumor types and the involvement of multiple ions in each case. Further, adverse effects may become a concern, as channel blockers, chelators, or supplemented ions will affect healthy and transformed cells alike.

Immunosuppressive mesenchymal stem cells aggregates incorporating hydrogel microspheres promote an in vitro invasion of cancer cells

Introduction

The objective of this study is to design a co-culture system of cancer cells and three-dimensional (3D) mesenchymal stem cells (MSC) aggregates for the in vitro evaluation of cancer invasion.

Methods

First, the MSC of an immunosuppressive phenotype (MSC2) were prepared by the MSC stimulation of polyriboinosinic polyribocytidylic acid. By simple mixing MSC2 and gelatin hydrogel microspheres (GM) in a U-bottomed well of 96 well plates which had been pre-coated with poly (vinyl alcohol), 3D MSC2 aggregates incorporating GM were obtained. The amount of chemokine (C–C motif) ligand 5 (CCL5) secreted from the MSC2 aggregates incorporating GM. Finally, an invasion assay was performed to evaluate the cancer invasion rate by co-cultured cancer cells and the 3D MSC2 incorporating GM.

Results

The amount of CCL5 secreted for the 3D MSC2 aggregates incorporating GM was significantly higher than that of two-dimensional (2D) MSC, 2D MSC2, and 3D MSC aggregates incorporating GM. When MDA-MB-231 human breast cancer cells were co-cultured with the 3D MSC2 aggregates incorporating GM, the invasion rate of cancer cells was significantly high compared with that of 2D MSC or 2D MSC2 and 3D MSC aggregates incorporating GM. In addition, high secretion of matrix metalloproteinase-2 was observed for the 3D MSC2 aggregates/cancer cells system.

Conclusions

It is concluded that the co-culture system of 3D MSC2 aggregates incorporating GM and cancer cells is promising to evaluate the invasion of cancer cells in vitro.

•

This invasion model is an important tool for anti-cancer drug screening.

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Mesenchymal stem cells of an immunosuppressive phenotype (MSC2) were obtained.

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3D MSC2 aggregates incorporating gelatin hydrogel microspheres were prepared.

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3D MSC2 aggregates promoted the invasion rate of cancer cells.

Lack of CFTR alters the ferret pancreatic ductal epithelial secretome and cellular proteome: Implications for exocrine/endocrine signaling

BACKGROUND

Cystic fibrosis (CF) related diabetes is the most common comorbidity for CF patients and associated with islet dysfunction. Exocrine pancreas remodeling in CF alters the microenvironment in which islets reside. Since CFTR is mainly expressed in pancreatic ductal epithelium, we hypothesized altered CF ductal secretions could impact islet function through paracrine signals.

METHOD

We evaluated the secretome and cellular proteome of polarized WT and CF ferret ductal epithelia using quantitative ratiometric mass spectrometry. Differentially secreted proteins (DSPs) or expressed cellular proteins were used to mine pathways, upstream regulators and the CFTR interactome to map candidate CF-associated alterations in ductal signaling and phenotype. Candidate DSPs were evaluated for their in vivo pancreatic expression patterns and their functional impact on islet hormone secretion.

RESULTS

The secretome and cellular proteome of CF ductal epithelia was significantly altered relative to WT and implicated dysregulated TGFβ, WNT, and BMP signaling pathways. Cognate receptors of DSPs from CF epithelia were equally distributed among endocrine, exocrine, and stromal pancreatic cell types. IGFBP7 was a downregulated DSP in CF ductal epithelia in vitro and exhibited reduced CF ductal expression in vivo. IGFBP7 also altered WT islet insulin secretion in response to glucose. Many CFTR-associated proteins, including SLC9A3R1, were differentially expressed in the CF cellular proteome. Upstream regulators of the differential CF ductal proteome included TGFβ, PDX1, AKT/PTEN, and INSR signaling. Data is available via ProteomeXchange with identifier PXD025126.

CONCLUSION

These findings provide a proteomic roadmap for elucidating disturbances in autocrine and paracrine signals from CF pancreatic ducts and how they may alter islet function and maintenance.

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.

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.

HDAC inhibition induces EMT and alterations in cellular iron homeostasis to augment ferroptosis sensitivity in SW13 cells

Epithelial-to-mesenchymal transition (EMT) is an essential mechanism for development and wound healing, but in cancer it also mediates the progression and spread of aggressive tumors while increasing therapeutic resistance. Adoption of a mesenchymal state is also associated with increased iron uptake, but the relationship between EMT and the key regulators of cellular iron metabolism remains undefined. In this regard, the human adrenal cortical carcinoma SW13 cell line represents an invaluable research model as HDAC inhibitor treatment can convert them from an epithelial-like (SW13-) cell type to a mesenchymal-like (SW13+) subtype. In this study we establish SW13 cells as a model for exploring the link between iron and EMT. Increased iron accumulation following HDAC inhibitor mediated EMT is associated with decreased expression of the iron export protein ferroportin, enhanced ROS production, and reduced expression of antioxidant response genes. As availability of redox active iron and loss of lipid peroxide repair capacity are hallmarks of ferroptosis, a form of iron-mediated cell death, we next examined whether HDAC inhibitor treatment could augment ferroptosis sensitivity. Indeed, HDAC inhibitor treatment synergistically increased cell death following induction of ferroptosis. The exact mechanisms by which HDAC inhibition facilitates cell death following ferroptosis induction requires further study. As several HDAC inhibitors are already in use clinically for the treatment of certain cancer types, the findings from these studies have immediate implications for improving iron-targeted chemotherapeutic strategies.

The Relationship of Glutathione-S-Transferase and Multi-Drug Resistance-Related Protein 1 in Nitric Oxide (NO) Transport and Storage

Nitric oxide is a diatomic gas that has traditionally been viewed, particularly in the context of chemical fields, as a toxic, pungent gas that is the product of ammonia oxidation. However, nitric oxide has been associated with many biological roles including cell signaling, macrophage cytotoxicity, and vasodilation. More recently, a model for nitric oxide trafficking has been proposed where nitric oxide is regulated in the form of dinitrosyl-dithiol-iron-complexes, which are much less toxic and have a significantly greater half-life than free nitric oxide. Our laboratory has previously examined this hypothesis in tumor cells and has demonstrated that dinitrosyl-dithiol-iron-complexes are transported and stored by multi-drug resistance-related protein 1 and glutathione-S-transferase P1. A crystal structure of a dinitrosyl-dithiol-iron complex with glutathione-S-transferase P1 has been solved that demonstrates that a tyrosine residue in glutathione-S-transferase P1 is responsible for binding dinitrosyl-dithiol-iron-complexes. Considering the roles of nitric oxide in vasodilation and many other processes, a physiological model of nitric oxide transport and storage would be valuable in understanding nitric oxide physiology and pathophysiology.

Innovative therapies for neuroblastoma: The surprisingly potent role of iron chelation in up-regulating metastasis and tumor suppressors and down-regulating the key oncogene, N-myc

Iron is an indispensable requirement for essential biological processes in cancer cells. Due to the greater proliferation of neoplastic cells, their demand for iron is considerably higher relative to normal cells, making them highly susceptible to iron depletion. Understanding this sensitive relationship led to research exploring the effect of iron chelation therapy for cancer treatment. The classical iron-binding ligand, desferrioxamine (DFO), has demonstrated effective anti-proliferative activity against many cancer-types, particularly neuroblastoma tumors, and has the surprising activity of down-regulating the potent oncogene, N-myc, which is a major oncogenic driver in neuroblastoma. Even more significant is the ability of DFO to simultaneously up-regulate the potent metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), which plays a plethora of roles in suppressing a variety of oncogenic signaling pathways. However, DFO suffers the disadvantage of demonstrating poor membrane permeability and short plasma half-life, requiring administration by prolonged subcutaneous or intravenous infusions. Considering this, the specifically designed di-2-pyridylketone thiosemicarbazone (DpT) series of metal-binding ligands was developed in our laboratory. The lead agent from the first generation DpT series, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), showed exceptional anti-cancer properties compared to DFO. However, it exhibited cardiotoxicity in mouse models at higher dosages. Therefore, a second generation of agents was developed with the lead compound being di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) that progressed to Phase I clinical trials. Importantly, DpC showed better anti-proliferative activity than Dp44mT and no cardiotoxicity, demonstrating effective anti-cancer activity against neuroblastoma tumors in vivo.

The Oncogenic Signaling Disruptor, NDRG1: Molecular and Cellular Mechanisms of Activity

NDRG1 is an oncogenic signaling disruptor that plays a key role in multiple cancers, including aggressive pancreatic tumors. Recent studies have indicated a role for NDRG1 in the inhibition of multiple tyrosine kinases, including EGFR, c-Met, HER2 and HER3, etc. The mechanism of activity of NDRG1 remains unclear, but to impart some of its functions, NDRG1 binds directly to key effector molecules that play roles in tumor suppression, e.g., MIG6. More recent studies indicate that NDRG1s-inducing drugs, such as novel di-2-pyridylketone thiosemicarbazones, not only inhibit tumor growth and metastasis but also fibrous desmoplasia, which leads to chemotherapeutic resistance. The Casitas B-lineage lymphoma (c-Cbl) protein may be regulated by NDRG1, and is a crucial E3 ligase that regulates various protein tyrosine and receptor tyrosine kinases, primarily via ubiquitination. The c-Cbl protein can act as a tumor suppressor by promoting the degradation of receptor tyrosine kinases. In contrast, c-Cbl can also promote tumor development by acting as a docking protein to mediate the oncogenic c-Met/Crk/JNK and PI3K/AKT pathways. This review hypothesizes that NDRG1 could inhibit the oncogenic function of c-Cbl, which may be another mechanism of its tumor-suppressive effects.

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.

Epithelial-to-Mesenchymal Transition in the Light of Plasticity and Hybrid E/M States

Epithelial-to-mesenchymal transition (EMT) is a cellular program which leads to cells losing epithelial features, including cell polarity, cell-cell adhesion and attachment to the basement membrane, while gaining mesenchymal characteristics, such as invasive properties and stemness. This program is involved in embryogenesis, wound healing and cancer progression. Over the years, the role of EMT in cancer progression has been heavily debated, and the requirement of this process in metastasis even has been disputed. In this review, we discuss previous discrepancies in the light of recent findings on EMT, plasticity and hybrid E/M states. Moreover, we highlight various tumor microenvironmental cues and cell intrinsic signaling pathways that induce and sustain EMT programs, plasticity and hybrid E/M states. Lastly, we discuss how recent findings on plasticity, especially on those that enable cells to switch between hybrid E/M states, have changed our understanding on the role of EMT in cancer metastasis, stemness and therapy resistance.

NDRG1 regulates Filopodia-induced Colorectal Cancer invasiveness via modulating CDC42 activity

N-myc downstream regulated gene-1 (NDRG1) has been identified as a putative metastasis suppressor gene and proved to be a key player in cancer spreading and proliferation in our previous work. However, the effects of NDRG1 on tumor invasion and the mechanisms behind it are rarely understood. Here we provided in silico evidence that NDRG1 plays a crucial role in actin reorganization in colorectal cancer (CRC). Through in vitro experiments, we next observed filopodia formation was altered in NDRG1-modified cell lines, while cell division cycle-42 (CDC42) displayed excessive activation in NDRG1-silenced cells. Mechanistically, NDRG1 loss disrupts the binding between RhoGDIα and CDC42 and triggers the activation of CDC42 and the downstream cascades PAK1/Cofilin, thereby promotes the formation of filopodia and invasiveness of CRC. The knockdown of NDRG1 led to enhanced dissemination of CRC cells in vivo and correlates with active CDC42 expression. Using clinical sample analysis, we found an elevated level of active CDC42 in patients with advanced T stage, and it was negatively related to NDRG1 expression. In sum, these results uncover a mechanism utilized by NDRG1 to regulate CDC42 activity in coordinating cytoskeleton reorganization, which was crucial in cancer invasion.

Cystic proliferation of germline stem cells is necessary to reproductive success and normal mating behavior in medaka

The production of an adequate number of gametes is necessary for normal reproduction, for which the regulation of proliferation from early gonadal development to adulthood is key in both sexes. Cystic proliferation of germline stem cells is an especially important step prior to the beginning of meiosis; however, the molecular regulators of this proliferation remain elusive in vertebrates. Here, we report that ndrg1b is an important regulator of cystic proliferation in medaka. We generated mutants of ndrg1b that led to a disruption of cystic proliferation of germ cells. This loss of cystic proliferation was observed from embryogenic to adult stages, impacting the success of gamete production and reproductive parameters such as spawning and fertilization. Interestingly, the depletion of cystic proliferation also impacted male sexual behavior, with a decrease of mating vigor. These data illustrate why it is also necessary to consider gamete production capacity in order to analyze reproductive behavior.

Siderophores for medical applications: Imaging, sensors, and therapeutics

Siderophores are low-molecular-weight chelators produced by microorganisms to scavenge iron from the environment and deliver it to cells via specific receptors. Tremendous researches on the molecular basis of siderophore regulation, synthesis, secretion, and uptake have inspired their diverse applications in the medical field. Replacing iron with radionuclides in siderophores, such as the most prominent Ga-68 for positron emission tomography (PET), carves out ways for targeted imaging of infectious diseases and cancers. Additionally, the high affinity of siderophores for metal ions or microorganisms makes them a potent detecting moiety in sensors that can be used for diagnosis. As for therapeutics, the notable Trojan horse-inspired siderophore-antibiotic conjugates demonstrate enhanced toxicity against multi-drug resistant (MDR) pathogens. Besides, siderophores can tackle iron overload diseases and, when combined with moieties such as hydrogels and nanoparticles, a wide spectrum of iron-induced diseases and even cancers. In this review, we briefly outline the related mechanisms, before summarizing the siderophore-based applications in imaging, sensors, and therapeutics.

Identification of Gene Signatures and Expression Patterns During Epithelial-to-Mesenchymal Transition From Single-Cell Expression Atlas

Cancer, which refers to abnormal cell proliferative diseases with systematic pathogenic potential, is one of the leading threats to human health. The final causes for patients’ deaths are usually cancer recurrence, metastasis, and drug resistance against continuing therapy. Epithelial-to-mesenchymal transition (EMT), which is the transformation of tumor cells (TCs), is a prerequisite for pathogenic cancer recurrence, metastasis, and drug resistance. Conventional biomarkers can only define and recognize large tissues with obvious EMT markers but cannot accurately monitor detailed EMT processes. In this study, a systematic workflow was established integrating effective feature selection, multiple machine learning models [Random forest (RF), Support vector machine (SVM)], rule learning, and functional enrichment analyses to find new biomarkers and their functional implications for distinguishing single-cell isolated TCs with unique epithelial or mesenchymal markers using public single-cell expression profiling. Our discovered signatures may provide an effective and precise transcriptomic reference to monitor EMT progression at the single-cell level and contribute to the exploration of detailed tumorigenesis mechanisms during EMT.

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.