ZIP7-mediated intracellular zinc transport contributes to aberrant growth factor signaling in antihormone-resistant breast cancer Cells

Development of a live cell assay for the zinc transporter ZnT8

Zinc is an essential trace element that is involved in many biological processes and in cellular homeostasis. In pancreatic β-cells, zinc is crucial for the synthesis, processing, and secretion of insulin, which plays a key role in glucose homeostasis and which deficiency is the cause of diabetes. The accumulation of zinc in pancreatic cells is regulated by the solute carrier transporter SLC30A8 (or Zinc Transporter 8, ZnT8), which transports zinc from cytoplasm in intracellular vesicles. Allelic variants of SLC30A8 gene have been linked to diabetes. Given the physiological intracellular localization of SLC30A8 in pancreatic β-cells and the ubiquitous endogenous expression of other Zinc transporters in different cell lines that could be used as cellular model for SLC30A8 recombinant over-expression, it is challenging to develop a functional assay to measure SLC30A8 activity. To achieve this goal, we have firstly generated a HEK293 cell line stably overexpressing SLC30A8, where the over-expression favors the partial localization of SLC30A8 on the plasma membrane. Then, we used the combination of this cell model, commercial FluoZin-3 cell permeant zinc dye and live cell imaging approach to follow zinc flux across SLC30A8 over-expressed on plasma membrane, thus developing a novel functional imaging- based assay specific for SLC30A8. Our novel approach can be further explored and optimized, paving the way for future small molecule medium-throughput screening.

Modulation of Metal Homeostasis for Cancer Therapy

Metal ions such as iron, zinc, copper, manganese, and calcium are essential for normal cellular processes, including DNA synthesis, enzyme activity, cellular signaling, and oxidative stress regulation. When the balance of metal homeostasis is disrupted, it can lead to various pathological conditions, including cancer. Thus, understanding the role of metal homeostasis in cancer has led to the development of anti-tumor strategies that specifically target the metal imbalance. Up to now, diverse small molecule-based chelators, ionophores, metal complexes, and metal-based nanomaterials have been developed to restore the normal balance of metals or exploit the dysregulation for therapeutic purposes. They hold great promise in inhibiting tumor growth, preventing metastasis, and enhancing the effectiveness of existing cancer therapies. In this review, we aim to provide a comprehensive summary of the strategies employed to modulate the homeostasis of iron, zinc, copper, manganese, and calcium for cancer therapy. Their modulation mechanisms for metal homeostasis are succinctly described, and their recent applications in the field of cancer therapy are discussed. At the end, the limitations of these approaches are addressed, and potential avenues for future developments are explored.

ZIP transporters-regulated Zn2+ homeostasis: A novel determinant of human diseases

As an essential trace element for organisms, zinc participates in various physiological processes, such as RNA transcription, DNA replication, cell proliferation, and cell differentiation. The destruction of zinc homeostasis is associated with various diseases. Zinc homeostasis is controlled by the cooperative action of zinc transporter proteins that are responsible for the influx and efflux of zinc. Zinc transporter proteins are mainly categorized into two families: Zrt/Irt-like protein (SLC39A/ZIP) family and zinc transporter (SLC30A/ZNT) family. ZIP transporters contain 14 members, namely ZIP1-14, which can be further divided into four subfamilies. Currently, ZIP transporters-regulated zinc homeostasis is one of the research hotspots. Cumulative evidence suggests that ZIP transporters-regulated zinc homeostasis may cause physiological dysfunction and contribute to the onset and progression of diverse diseases, such as cancers, neurological diseases, and cardiovascular diseases. In this review, we initially discuss the structure and distribution of ZIP transporters. Furthermore, we comprehensively review the latest research progress of ZIP transporters-regulated zinc homeostasis in diseases, providing a new perspective into new therapeutic targets for treating related diseases.

The Zn2+ transporter ZIP7 enhances endoplasmic-reticulum-associated protein degradation and prevents neurodegeneration in Drosophila

Proteotoxic stress drives numerous degenerative diseases. Cells initially adapt to misfolded proteins by activating the unfolded protein response (UPR), including endoplasmic-reticulum-associated protein degradation (ERAD). However, persistent stress triggers apoptosis. Enhancing ERAD is a promising therapeutic approach for protein misfolding diseases. The ER-localized Zn2+ transporter ZIP7 is conserved from plants to humans and required for intestinal self-renewal, Notch signaling, cell motility, and survival. However, a unifying mechanism underlying these diverse phenotypes was unknown. In studying Drosophila border cell migration, we discovered that ZIP7-mediated Zn2+ transport enhances the obligatory deubiquitination of proteins by the Rpn11 Zn2+ metalloproteinase in the proteasome lid. In human cells, ZIP7 and Zn2+ are limiting for deubiquitination. In a Drosophila model of neurodegeneration caused by misfolded rhodopsin (Rh1), ZIP7 overexpression degrades misfolded Rh1 and rescues photoreceptor viability and fly vision. Thus, ZIP7-mediated Zn2+ transport is a previously unknown, rate-limiting step for ERAD in vivo with therapeutic potential in protein misfolding diseases.

Zinc homeostasis and redox alterations in obesity

Impairment of both cellular zinc and redox homeostasis is a feature of several chronic diseases, including obesity. A significant two-way interaction exists between redox metabolism and the relatively redox-inert zinc ion. Redox metabolism critically influences zinc homeostasis and controls its cellular availability for various cellular functions by regulating zinc exchange from/to zinc-binding proteins. Zinc can regulate redox metabolism and exhibits multiple pro-antioxidant properties. On the other hand, even minor disturbances in zinc status and zinc homeostasis affect systemic and cellular redox homeostasis. At the cellular level, zinc homeostasis is regulated by a multi-layered machinery consisting of zinc-binding molecules, zinc sensors, and two selective families of zinc transporters, the Zinc Transporter (ZnT) and Zrt, Irt-like protein (ZIP). In the present review, we summarize the current state of knowledge on the role of the mutual interaction between zinc and redox homeostasis in physiology and pathophysiology, pointing to the role of zinc in the alterations responsible for redox stress in obesity. Since zinc transporters primarily control zinc homeostasis, we describe how changes in the expression and activity of these zinc-regulating proteins are associated with obesity.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

From zinc homeostasis to disease progression: Unveiling the neurodegenerative puzzle

Zinc is a crucial trace element in the human body, playing a role in various physiological processes such as oxidative stress, neurotransmission, protein synthesis, and DNA repair. The zinc transporters (ZnTs) family members are responsible for exporting intracellular zinc, while Zrt- and Irt-like proteins (ZIPs) are involved in importing extracellular zinc. These processes are essential for maintaining cellular zinc homeostasis. Imbalances in zinc metabolism have been linked to the development of neurodegenerative diseases. Disruptions in zinc levels can impact the survival and activity of neurons, thereby contributing to the progression of neurodegenerative diseases through mechanisms like cell apoptosis regulation, protein phase separation, ferroptosis, oxidative stress, and neuroinflammation. Therefore, conducting a systematic review of the regulatory network of zinc and investigating the relationship between zinc dysmetabolism and neurodegenerative diseases can enhance our understanding of the pathogenesis of these diseases. Additionally, it may offer new insights and approaches for the treatment of neurodegenerative diseases.

Ligand-independent signaling and migration of breast cancer cells expressing membrane androgen receptor, ZIP9 (SLC39A9)

Zinc transporter ZIP9 is also a membrane androgen receptor that mediates androgen-dependent zinc and G-protein signaling to modulate tumorigenic responses in cancer cells. It is unclear whether unliganded ZIP9 causes similar responses. ZIP9 overexpression in MDA-MB-231 breast cancer cells (ZIP9 cells) increased zinc levels and cell migration/invasion which was mimicked with a zinc ionophore and attenuated with a zinc chelator, suggesting these tumorigenic responses are zinc-dependent. Expression of migration markers MYL9 and CYR61 was elevated in ZIP9 cells and further increased together with cell migration by forskolin treatment and blocked with H-89, indicating they are mediated through an AC/PKA pathway. Knockdown of ZIP9 expression in MDA-MB-468 cells decreased cell migration/invasion, migration markers and zinc levels, confirming similar roles of unliganded ZIP9 in another breast cancer cell line. Testosterone treatment further increased migration, biomarker expression and zinc in ZIP9 cells, suggesting it may act through similar pathways to induce tumorigenic responses.

Zinc Ions Modulate YY1 Activity: Relevance in Carcinogenesis

YY1 is widely recognized as an intrinsically disordered transcription factor that plays a role in development of many cancers. In most cases, its overexpression is correlated with tumor progression and unfavorable patient outcomes. Our latest research focusing on the role of zinc ions in modulating YY1's interaction with DNA demonstrated that zinc enhances the protein's multimeric state and affinity to its operator. In light of these findings, changes in protein concentration appear to be just one element relevant to modulating YY1-dependent processes. Thus, alterations in zinc ion concentration can directly and specifically impact the regulation of gene expression by YY1, in line with reports indicating a correlation between zinc ion levels and advancement of certain tumors. This review concentrates on other potential consequences of YY1 interaction with zinc ions that may act by altering charge distribution, conformational state distribution, or oligomerization to influence its interactions with molecular partners that can disrupt gene expression patterns.

NVS-ZP7-4 inhibits hepatocellular carcinoma tumorigenesis and promotes apoptosis via PI3K/AKT signaling

NVS-ZP7-4 was identified as a novel chemical reagent targeting the zinc input protein ZIP7, which accounts for the zinc surge from the apparatus to the cytoplasm. Since zinc dysregulation is related to multiple diseases, in this study, we aimed to identify the anti-tumor effects of NVS-ZP7-4 and explore the molecular mechanisms of NVS-ZP7-4 in hepatocellular carcinoma (HCC) progression. We found that NVS-ZP7-4 inhibited cell viability, caused cell cycle arrest, induced apoptosis, and inhibited the proliferation, migration, and invasion of HCCLM3 and Huh7 cells. We further investigated the inhibited activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway was involved in the antitumor effect of NVS-ZP7-4 in HCC. Furthermore, NVS-ZP7-4 inhibited HCC tumor growth in vivo. The present study demonstrated that NVS-ZP7-4 is a promising therapeutic target for HCC by regulating PI3K/AKT signaling.

Delineating Zinc Influx Mechanisms during Platelet Activation

Zinc (Zn2+) is released by platelets during a hemostatic response to injury. Extracellular zinc ([Zn2+]o) initiates platelet activation following influx into the platelet cytosol. However, the mechanisms that permit Zn2+ influx are unknown. Fluctuations in intracellular zinc ([Zn2+]i) were measured in fluozin-3-loaded platelets using fluorometry and flow cytometry. Platelet activation was assessed using light transmission aggregometry. The detection of phosphoproteins was performed by Western blotting. [Zn2+]o influx and subsequent platelet activation were abrogated by blocking the sodium/calcium exchanged, TRP channels, and ZIP7. Cation store depletion regulated Zn2+ influx. [Zn2+]o stimulation resulted in the phosphorylation of PKC substates, MLC, and β3 integrin. Platelet activation via GPVI or Zn2+ resulted in ZIP7 phosphorylation in a casein kinase 2-dependent manner and initiated elevations of [Zn2+]i that were sensitive to the inhibition of Orai1, ZIP7, or IP3R-mediated pathways. These data indicate that platelets detect and respond to changes in [Zn2+]o via influx into the cytosol through TRP channels and the NCX exchanger. Platelet activation results in the externalization of ZIP7, which further regulates Zn2+ influx. Increases in [Zn2+]i contribute to the activation of cation-dependent enzymes. Sensitivity of Zn2+ influx to thapsigargin indicates a store-operated pathway that we term store-operated Zn2+ entry (SOZE). These mechanisms may affect platelet behavior during thrombosis and hemostasis.

Rescue of proteotoxic stress and neurodegeneration by the Zn2+ transporter ZIP7

Proteotoxic stress drives numerous degenerative diseases. In response to misfolded proteins, cells adapt by activating the unfolded protein response (UPR), including endoplasmic reticulum-associated protein degradation (ERAD). However persistent stress triggers apoptosis. Enhancing ERAD is a promising therapeutic approach for protein misfolding diseases. From plants to humans, loss of the Zn2+ transporter ZIP7 causes ER stress, however the mechanism is unknown. Here we show that ZIP7 enhances ERAD and that cytosolic Zn2+ is limiting for deubiquitination of client proteins by the Rpn11 Zn2+ metalloproteinase as they enter the proteasome in Drosophila and human cells. ZIP7 overexpression rescues defective vision caused by misfolded rhodopsin in Drosophila. Thus ZIP7 overexpression may prevent diseases caused by proteotoxic stress, and existing ZIP inhibitors may be effective against proteasome-dependent cancers.

Comparison of Three Low-Molecular-Weight Fluorescent Probes for Measuring Free Zinc Levels in Cultured Mammary Cells

Free zinc is a critical regulator in signal transduction and affects many cellular processes relevant to cancer, including proliferation and cell death. Acting as a second messenger, altered free intracellular zinc has fundamental effects on regulating enzymes such as phosphatases and caspases. Therefore, the determination of free intracellular zinc levels is essential to assess its influence on the signaling processes involved in cancer development and progression. In this study, we compare three low-molecular-weight fluorescent probes, ZinPyr-1, TSQ, and FluoZin-3, for measuring free zinc in different mammary cell lines (MCF10A, MCF7, T47D, and MDA-MB-231). In summary, ZinPyr-1 is the most suitable probe for free Zn quantification. It responds well to calibration based on minimal fluorescence in the presence of the chelator TPEN (N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine) and maximal fluorescence by saturation with ZnSO₄, resulting in the detection of free intracellular zinc in breast cancer subtypes ranging from 0.62 nM to 1.25 nM. It also allows for measuring the zinc fluxes resulting from incubation with extracellular zinc, showing differences in the zinc uptake between the non-malignant MCF10A cell line and the other cell lines. Finally, ZinPyr-1 enables the monitoring of sub-cellular distributions by fluorescence microscopy. Altogether, these properties provide a basis for the further exploration of free zinc in order to realize its full potential as a possible biomarker or even therapeutic target in breast cancer.

A Systematic Study on Zinc-Related Metabolism in Breast Cancer

Breast cancer has become the most common cancer worldwide. Despite the major advances made in the past few decades in the treatment of breast cancer using a combination of chemotherapy, endocrine therapy, and immunotherapy, the genesis, treatment, recurrence, and metastasis of this disease continue to pose significant difficulties. New treatment approaches are therefore urgently required. Zinc is an important trace element that is involved in regulating various enzymatic, metabolic, and cellular processes in the human body. Several studies have shown that abnormal zinc homeostasis can lead to the onset and progression of various diseases, including breast cancer. This review highlights the role played by zinc transporters in pathogenesis, apoptosis, signal transduction, and potential clinical applications in breast cancer. Additionally, the translation of the clinical applications of zinc and associated molecules in breast cancer, as well as the recent developments in the zinc-related drug targets for breast cancer treatment, is discussed. These developments offer novel insights into understanding the concepts and approaches that could be used for the diagnosis and management of breast cancer.

Imaging zinc trafficking in vivo by positron emission tomography with zinc-62

Non-invasive imaging techniques to dynamically map whole-body trafficking of essential metals in vivo in health and diseases are needed. Despite 62Zn having appropriate physical properties for positron emission tomography (PET) imaging (half-life, 9.3 h; positron emission, 8.2%), its complex decay via 62Cu (half-life, 10 min; positron emission, 97%) has limited its use. We aimed to develop a method to extract 62Zn from a 62Zn/62Cu generator, and to investigate its use for in vivo imaging of zinc trafficking despite its complex decay. 62Zn prepared by proton irradiation of natural copper foil was used to construct a conventional 62Zn/62Cu generator. 62Zn was eluted using trisodium citrate and used for biological experiments, compared with 64Cu in similar buffer. PET/CT imaging and ex vivo tissue radioactivity measurements were performed following intravenous injection in healthy mice. [62Zn]Zn-citrate was readily eluted from the generator with citrate buffer. PET imaging with the eluate demonstrated biodistribution similar to previous observations with the shorter-lived 63Zn (half-life 38.5 min), with significant differences compared to [64Cu]Cu-citrate, notably in pancreas (>10-fold higher at 1 h post-injection). Between 4 and 24 h, 62Zn retention in liver, pancreas, and kidney declined over time, while brain uptake increased. Like 64Cu, 62Zn showed hepatobiliary excretion from liver to intestines, unaffected by fasting. Although it offers limited reliability of scanning before 1 h post-injection, 62Zn-PET allows investigation of zinc trafficking in vivo for >24 h and hence provides a useful new tool to investigate diseases where zinc homeostasis is disrupted in preclinical models and humans.

Identification of a Gene Panel Predictive of Triple-Negative Breast Cancer Response to Neoadjuvant Chemotherapy Employing Transcriptomic and Functional Validation

Triple-negative breast cancer (TNBC) patients exhibiting pathological complete response (pCR) have better clinical outcomes compared to those with residual disease (RD). Therefore, robust biomarkers that can predict pCR may help with triage and resource prioritization in patients with TNBC. Herein, we identified a gene panel predictive of RD and pCR in TNBC from the discovery (n = 90) treatment-naive tumor transcriptomic data. Eight RD-derived genes were identified as TNBC-essential genes, which were highly predicative of overall survival (OS) and relapse-free survival (RFS) in an additional cohort of basal breast cancer (n = 442). Mechanistically, targeted depletion of the eight genes reduced the proliferation potential of TNBC cell models, while most remarkable effects were for combined SLC39A7, TIMM13, BANF1, and MVD knockdown in conjunction with doxorubicin. Orthogonal partial least squares-discriminant analysis (OPLS-DA) and receiver operating characteristic curve (ROC) analyses revealed significant predictive power for the identified gene panels with an area under the curve (AUC) of 0.75 for the validation cohort (n = 50) to discriminate RD from pCR. Protein–Protein Interaction (PPI) network analysis of the pCR-derived gene signature identified an 87-immune gene signature highly predictive of pCR, which correlated with better OS, RFS, and distant-metastasis-free survival (DMFS) in an independent cohort of basal and, to a lesser extent, HER2+ breast cancer. Our data have identified gene signatures predicative of RD and pCR in TNBC with potential clinical implications.

Molecular Insights in Uterine Leiomyosarcoma: A Systematic Review

Uterine fibroids (UFs) are the most common benign tumors of female genital diseases, unlike uterine leiomyosarcoma (LMS), a rare and aggressive uterine cancer. This narrative review aims to discuss the biology and diagnosis of LMS and, at the same time, their differential diagnosis, in order to distinguish the biological and molecular origins. The authors performed a Medline and PubMed search for the years 1990–2022 using a combination of keywords on the topics to highlight the many genes and proteins involved in the pathogenesis of LMS. The mutation of these genes, in addition to the altered expression and functions of their enzymes, are potentially biomarkers of uterine LMS. Thus, the use of this molecular and protein information could favor differential diagnosis and personalized therapy based on the molecular characteristics of LMS tissue, leading to timely diagnoses and potential better outcomes for patients.

CK2 and the Hallmarks of Cancer

Cancer is a leading cause of death worldwide. Casein kinase 2 (CK2) is commonly dysregulated in cancer, impacting diverse molecular pathways. CK2 is a highly conserved serine/threonine kinase, constitutively active and ubiquitously expressed in eukaryotes. With over 500 known substrates and being estimated to be responsible for up to 10% of the human phosphoproteome, it is of significant importance. A broad spectrum of diverse types of cancer cells has been already shown to rely on disturbed CK2 levels for their survival. The hallmarks of cancer provide a rationale for understanding cancer’s common traits. They constitute the maintenance of proliferative signaling, evasion of growth suppressors, resisting cell death, enabling of replicative immortality, induction of angiogenesis, the activation of invasion and metastasis, as well as avoidance of immune destruction and dysregulation of cellular energetics. In this work, we have compiled evidence from the literature suggesting that CK2 modulates all hallmarks of cancer, thereby promoting oncogenesis and operating as a cancer driver by creating a cellular environment favorable to neoplasia.

The Role of Protein Kinase CK2 in Development and Disease Progression: A Critical Review

Protein kinase CK2 (CK2) is a ubiquitous holoenzyme involved in a wide array of developmental processes. The involvement of CK2 in events such as neurogenesis, cardiogenesis, skeletogenesis, and spermatogenesis is essential for the viability of almost all organisms, and its role has been conserved throughout evolution. Further into adulthood, CK2 continues to function as a key regulator of pathways affecting crucial processes such as osteogenesis, adipogenesis, chondrogenesis, neuron differentiation, and the immune response. Due to its vast role in a multitude of pathways, aberrant functioning of this kinase leads to embryonic lethality and numerous diseases and disorders, including cancer and neurological disorders. As a result, CK2 is a popular target for interventions aiming to treat the aforementioned diseases. Specifically, two CK2 inhibitors, namely CX-4945 and CIBG-300, are in the early stages of clinical testing and exhibit promise for treating cancer and other disorders. Further, other researchers around the world are focusing on CK2 to treat bone disorders. This review summarizes the current understanding of CK2 in development, the structure of CK2, the targets and signaling pathways of CK2, the implication of CK2 in disease progression, and the recent therapeutics developed to inhibit the dysregulation of CK2 function in various diseases.

Zinc and Breast Cancer Survival: A Prospective Cohort Study of Dietary Intake and Serum Levels

Zinc has been suggested to play a role in breast cancer progression; however, no previous study on zinc levels and the potential effect on breast cancer survival has been conducted. This study investigates recurrence-free survival (RFS), breast cancer-specific survival (BCSS) and overall survival (OS) in relation to zinc levels, in serum and diet, overall and stratified for phosphorus and selenium levels. The Malmö Diet and Cancer Study, a prospective population-based cohort in Sweden including 17,035 women, was used to identify breast cancer patients diagnosed in the period 1991–2013. Diet was assessed by a validated modified diet history method. A Cox regression analysis yielded hazard ratios (HRs) with 95% confidence intervals adjusted for potential confounders. Out of 1062 patients with invasive breast cancer, 268 recurrences, 205 breast cancer deaths and 228 deaths from other causes were recorded. No overall associations were seen between zinc and RFS, BCSS or OS. However, in women with a high phosphorus intake, a higher BCSS and OS were seen in zinc intake Q2 to Q4 versus Q1; the adjusted HR was 0.41 (0.23–0.73) and 0.64 (0.41–1.00), respectively. The results indicate that the combination of intermediate/high zinc intake and high phosphorus intake may lead to a better breast cancer survival.

Expression profiles of the genes associated with zinc homeostasis in normal and cancerous breast and prostate cells

Zn2+ dyshomeostasis is an intriguing phenomenon in breast and prostate cancers, with breast cancer cells exhibiting higher intracellular Zn2+ level compared to their corresponding normal epithelial cells, in contrast to the low Zn2+ level in prostate cancer cells. In order to gain molecular insights into the zinc homeostasis of breast and prostate cancer cells, this study profiled the expression of 28 genes, including 14 zinc importer genes (SLC39A1-14) which encode ZIP1-14 to transport Zn2+ into the cytoplasm, 10 zinc exporter genes (SLC30A1-10) which encode ZnT1-10 to transport Zn2+ out of the cytoplasm and 4 metallothionein genes (MT1B, MT1F, MT1X, MT2A) in breast (MCF10A, MCF-7, MDA-MB-231) and prostate (RWPE-1, PC3, DU145) cell lines in response to extracellular zinc exposures at a mild cytotoxic dosage and a benign dosage. The RNA samples were prepared at 0 min (T0), 30 min (T30) and 120 min (T120) in a time course with or without zinc exposure, which were used for profiling the baseline and dynamic gene expression. The up-regulation of MT genes was observed across the breast and prostate cancer cell lines. The expression landscape of SLC39A and SLC30A was revealed by the qRT-PCR data of this study, which sheds light on the divergence of intracellular Zn2+ levels for breast and prostate cancer cells. Taken together, the findings are valuable in unravelling the molecular intricacy of zinc homeostasis in breast and prostate cancer cells.

Zinc transporters ZIPT-2.4 and ZIPT-15 are required for normal C. elegans fecundity

PURPOSE

The requirement of zinc for the development and maturation of germ lines and reproductive systems is deeply conserved across evolution. The nematode Caenorhabditis elegans offers a tractable platform to study the complex system of distributing zinc to the germ line. We investigated several zinc importers to investigate how zinc transporters play a role in the reproductive system in nematodes, as well as establish a platform to study zinc transporter biology in germline and reproductive development.

METHODS

Previous high throughput transcriptional datasets as well as phylogenetic analysis identified several putative zinc transporters that have a function in reproduction in worms. Phenotypic analysis of CRISPR-generated knockouts and tags included characterization of offspring output, gonad development, and protein localization. Light and immunofluorescence microscopy allowed for visualization of physiological and molecular effects of zinc transporter mutations.

RESULTS

Disruption of two zinc transporters, ZIPT-2.4 and ZIPT-15, was shown to lead to defects in reproductive output. A mutation in zipt-2.4 has subtle effects on reproduction, while a mutation in zipt-15 has a clear impact on gonad and germline development that translates into a more pronounced defect in fecundity. Both transporters have germline expression, as well as additional expression in other cell types.

CONCLUSIONS

Two ZIP-family zinc transporter orthologs of human ZIP6/10 and ZIP1/2/3 proteins are important for full reproductive fecundity and participate in development of the gonad. Notably, these zinc transporters are present in gut and reproductive tissues in addition to the germ line, consistent with a complex zinc trafficking network important for reproductive success.

G, Kathryn M. T. The importance of targeting signalling mechanisms of the SLC39A family of zinc transporters to inhibit endocrine resistant breast cancer

Aim:

Zinc is a key secondary messenger that can regulate multiple signalling pathways within cancer cells, thus its levels need to be strictly controlled. The Zrt, Irt-like protein (ZIP, SLC39A) family of zinc transporters increase cytosolic zinc from either extracellular or intracellular stores. This study examines the relevance of zinc transporters ZIP7 and ZIP6 as therapeutic targets in tamoxifen resistant (TAMR) breast cancer.

Methods:

A series of in vitro assays, including immunohistochemistry, immunofluorescence, flow cytometry, and western blotting were used to evaluate levels and activity of ZIP7 and ZIP6 in models of TAMR and sensitive (MCF-7) breast cancer. Analyses of these transporters in the clinical setting were performed using publicly available online resources: Gene Expression Profiling Interactive Analysis (GEPIA)2 and Kaplan-Meier Plotter (KmPlot).

Results:

Both total and activated levels of ZIP7 were significantly elevated in TAMR cells versus responsive MCF-7 cells. This was accompanied by an associated increase in free cytoplasmic zinc leading to amplification of downstream signals. Consistent with our proposed model, activated ZIP6 levels correlated with mitotic cells, which could be efficiently inhibited through use of our anti-ZIP6 monoclonal antibody. Mitotic inhibition translated to impaired proliferation in both models, with TAMR cells displaying increased sensitivity. Analysis of matched tumour and normal breast samples from patients revealed significant increases in both ZIP7 and ZIP6 in tumours, as well as family member ZIP4. Kaplan-Meier analysis revealed that high ZIP7 levels correlated with decreased overall and relapse-free survival (RFS) of patients, including patient groups who had received systemic endocrine therapy or tamoxifen only. In contrast, high ZIP6 levels were significantly linked to improved overall and RFS in all patients, as well as RFS in patients that received systemic endocrine therapy.

Conclusions:

TAMR cells displayed increased activity of both ZIP7 and ZIP6 transporters compared to anti-hormone responsive cells, suggesting their potential as novel therapeutic targets following development of resistant disease.

Zinc transporters as potential therapeutic targets: An updated review

Zinc is an essential trace element that plays important roles in the regulation of various physiological responses in the body. Zinc deficiency is known to cause various health problems, including dysgeusia, skin disorders, and immune disorders. Therefore, the maintenance of healthy zinc content in the body is critical to our healthy life. Zinc homeostasis is tightly controlled by two of the solute carrier protein families SLC30A and SLC39A, called zinc transporters. In the last decade, research on zinc biology has made dramatic progress based on the physiological and functional analysis of zinc transporters in the fields of molecular biology, human genetics, and drug discovery. In particular, since the association between zinc transporters and human diseases was recently reported using human genetics and gene knockout mouse studies, zinc and zinc signals controlled by zinc transporters have been considered useful therapeutic targets. In this review, we introduce the importance of zinc homeostasis based on the findings of zinc transporter functions and their signals in relation to human diseases.

Investigations on Zinc Isotope Fractionation in Breast Cancer Tissue Using in vitro Cell Culture Uptake-Efflux Experiments

Zinc (Zn) accumulates in breast cancer tumors compared to adjacent healthy tissue. Clinical samples of breast cancer tissue show light Zn isotopic compositions (δ66Zn) relative to healthy tissue. The underlying mechanisms causing such effects are unknown. To investigate if the isotopic discrimination observed for in vivo breast cancer tissue samples can be reproduced in vitro, we report isotopic data for Zn uptake-efflux experiments using a human breast cancer cell line. MDA-MB-231 cell line was used as a model for triple receptor negative breast cancer. We determined Zn isotope fractionation for Zn cell uptake (Δ66Znuptake) and cell efflux (Δ66Znefflux) using a drip-flow reactor to enable comparison with the in vivo environment. The MDA-MB-231 cell line analyses show Zn isotopic fractionations in an opposite direction to those observed for in vivo breast cancer tissue. Uptake of isotopically heavy Zn (Δ66Znuptake = +0.23 ± 0.05‰) is consistent with transport via Zn transporters (ZIPs), which have histidine-rich binding sites. Zinc excreted during efflux is isotopically lighter than Zn taken up by the cells (Δ66Znefflux = -0.35 ± 0.06‰). The difference in Zn isotope fractionation observed between in vitro MDA-MB-231 cell line experiments and in vivo breast tissues might be due to differences in Zn transporter levels or intercellular Zn storage (endoplasmic reticulum and/or Zn specific vesicles); stromal cells, such as fibroblasts and immune cells. Although, additional experiments using other human breast cancer cell lines (e.g., MCF-7, BT-20) with varying Zn protein characteristics are required, the results highlight differences between in vitro and in vivo Zn isotope fractionation.

The role of zinc transporter proteins as predictive and prognostic biomarkers of hepatocellular cancer

Identification of the key processes involved in the tumor progression, malignancy and the molecular factors which are responsible for the transition of the cirrhotic cells to the tumor cells, contribute to the detection of biomarkers for diagnosis of hepatocellular carcinoma (HCC) at an early stage. According to clinical data, HCC is mostly characterized by a significant decrease in zinc levels. It is strongly implied that zinc deficiency is the major event required in the early stages of tumor formation and development of malignancy. Due to this reason, the definition of the molecular players which have a role in zinc homeostasis and cellular zinc level could give us a clue about the transition state of the cirrhosis to hepatic tumor formation. Despite the well-known implications of zinc in the development of HCCthe correlation of the expression of zinc transporter proteins with tumor progression and malignancy remain largely unknown. In the present study, we evaluated in detail the relationship of zinc deficiency on the prognosis of early HCC patients. In this study, we aimed to test the potential zinc transporters which contribute tothe transformation of cirrhosis to HCCand the progression of HCC. Among the 24 zinc transporter proteins, the proteins to be examined were chosen by using Gene Expression Profiling Interactive Analysis (GEPIA) webpage and RNA-seq analysis using TCGA database. ZIP14 and ZIP5 transporters were found as common differentially expressed genes from both bioinformatic analyses. ZnT1, ZnT7 and ZIP7 transporters have been associated with tumor progression. Relative abundance of ZnT1, ZIP5 and ZIP14 protein level was determined by immunohistochemistry (IHC) in surgically resected liver specimens from 16 HCC patients at different stages. IHC staining intensity was analyzed by using ImageJ software and scored with the histological scoring (H-score) method. The staining of ZnT1 was significantly higher in Grade III comparing to Grade II and Grade I. On the contrary, ZIP14 staining decreased almost 10-foldcomparing to Grade Iand Grade II. ZIP5 staining was detected almost 2-fold higher in cirrhosis than HCC. But ZnT1 staining was observed almost 3-fold lower in cirrhosis comparing to HCC. Intracellular free zinc level was measured by flow cytometry in Hep40 and Snu398 cells using FluoZin-3 dye. The intracellular free zinc level was almost 9-fold decreased in poor differentiated Snu398 HCC cells comparing to well differentiated Hep40 HCC cells.This report establishes for the first time the correlation between the expression pattern of ZIP14, ZnT1 and ZIP5 and significant zinc deficiency which occurs concurrently with the advancing of malignancy. Our results provide new molecular insight into ZnT1, ZIP14 and ZIP5 mediated regulation of cellular zinc homeostasis and indicate that zinc transporters might be important factors and events in HCC malignancy, which can lead to the development of early biomarkers.

The zinc transporter ZIP7 (Slc39a7) controls myocardial reperfusion injury by regulating mitophagy

Whereas elimination of damaged mitochondria by mitophagy is proposed to be cardioprotective, the regulation of mitophagy at reperfusion and the underlying mechanism remain elusive. Since mitochondrial Zn²⁺ may control mitophagy by regulating mitochondrial membrane potential (MMP), we hypothesized that the zinc transporter ZIP7 that controls Zn²⁺ levels within mitochondria would contribute to reperfusion injury by regulating mitophagy. Mouse hearts were subjected to ischemia/reperfusion in vivo. Mitophagy was evaluated by detecting mitoLC3II, mito-Keima, and mitoQC. ROS were measured with DHE and mitoB. Infarct size was measured with TTC staining. The cardiac-specific ZIP7 conditional knockout mice (ZIP7 cKO) were generated by adopting the CRISPR/Cas9 system. Human heart samples were obtained from donors and recipients of heart transplant surgeries. KO or cKO of ZIP7 increased mitophagy under physiological conditions. Mitophagy was not activated at the early stage of reperfusion in mouse hearts. ZIP7 is upregulated at reperfusion and ZIP7 cKO enhanced mitophagy upon reperfusion. cKO of ZIP7 led to mitochondrial depolarization by increasing mitochondrial Zn²⁺ and, accumulation of PINK1 and Parkin in mitochondria, suggesting that the decrease in mitochondrial Zn²⁺ in response to ZIP7 upregulation resulting in mitochondrial hyperpolarization may impede PINK1 and Parkin accumulation in mitochondria. Notably, ZIP7 is markedly upregulated in cardiac mitochondria from patients with heart failure (HF), whereas mitochondrial PINK1 accumulation and mitophagy were suppressed. Furthermore, ZIP7 cKO reduced mitochondrial ROS generation and myocardial infarction via a PINK1-dependet manner, whereas overexpression of ZIP7 exacerbated myocardial infarction. Our findings identify upregulation of ZIP7 leading to suppression of mitophagy as a critical feature of myocardial reperfusion injury. A timely suppression of cardiac ZIP7 upregulation or inactivation of ZIP7 is essential for the treatment of reperfusion injury.

Zinc Signaling in the Mammary Gland: For Better and for Worse

Zinc (Zn²⁺) plays an essential role in epithelial physiology. Among its many effects, most prominent is its action to accelerate cell proliferation, thereby modulating wound healing. It also mediates affects in the gastrointestinal system, in the testes, and in secretory organs, including the pancreas, salivary, and prostate glands. On the cellular level, Zn²⁺ is involved in protein folding, DNA, and RNA synthesis, and in the function of numerous enzymes. In the mammary gland, Zn²⁺ accumulation in maternal milk is essential for supporting infant growth during the neonatal period. Importantly, Zn²⁺ signaling also has direct roles in controlling mammary gland development or, alternatively, involution. During breast cancer progression, accumulation or redistribution of Zn²⁺ occurs in the mammary gland, with aberrant Zn²⁺ signaling observed in the malignant cells. Here, we review the current understanding of the role of in Zn²⁺ the mammary gland, and the proteins controlling cellular Zn²⁺ homeostasis and signaling, including Zn²⁺ transporters and the Gq-coupled Zn²⁺ sensing receptor, ZnR/GPR39. Significant advances in our understanding of Zn²⁺ signaling in the normal mammary gland as well as in the context of breast cancer provides new avenues for identification of specific targets for breast cancer therapy.

Expression profiles of SLC39A/ZIP7, ZIP8 and ZIP14 in response to exercise-induced skeletal muscle damage

BACKGROUND

Zinc transporters are thought to facilitate the mobilization of zinc (Zn) and the role of Zn as a signaling mediator during cellular events. Little is known about the response of Zn movement and zinc transporters during muscle proliferation and differentiation processes after damage.

METHODS

After rats were subjected to one 90-min session of downhill running to cause muscle damage, the gastrocnemius muscles were harvested to assess the expression of zinc transporters SLC39A/ZIP7, ZIP8, ZIP14 and myogenic regulatory factors at the 0 h, 6 h, 12 h, 1 d, 2 d, 3 d, 1 w and 2 w time points after exercise.

RESULTS

SLC39A/ZIP7, ZIP8 and ZIP14 had translocated to different compartments of the cell following damage, and they exhibited differential expression profiles after eccentric exercise. The results regarding the myogenetic regulators showed that nf-κb was upregulated 2 d after exercise, and STAT3 and Akt1 mRNA levels were mostly expressed 2 w after exercise. The upregulation of phosphatidylinositol 3-kinase, catalytic subunit gamma (pik3cg), erk1 and erk2 mostly occurred at the early stage (6 h or 12 h) after exercise. In addition, we found that zip7, zip8 and zip14 expression was moderately correlated with certain markers of muscle regeneration.

CONCLUSION

The zinc transporters SLC39A/ZIP7, ZIP8 and ZIP14 have differential expression profiles upon eccentric exercise, and they might regulate muscle proliferation or differentiation processes through different cellular pathways after exercise-induced muscle damage.

Zinc Favors Triple-Negative Breast Cancer's Microenvironment Modulation and Cell Plasticity

Triple-negative breast cancer (TNBC) tends to metastasize to the brain, a step that worsens the patient’s prognosis. The specific hallmarks that determine successful metastasis are motility and invasion, microenvironment modulation, plasticity, and colonization. Zinc, an essential trace element, has been shown to be involved in all of these processes. In this work, we focus our attention on the potential role of zinc during TNBC metastasis. We used MDA-MB-BrM2 (BrM2) cells, a brain metastasis model derived from the parental TNBC cell line MDA-MB-231. Our studies show that BrM2 cells had double the zinc content of MDA-MB-231 cells. Moreover, exploring different metastatic hallmarks, we found that the zinc concentration is especially important in the microenvironment modulation of brain metastatic cells, enhancing the expression of SerpinB2. Furthermore, we show that zinc promotes the tumorigenic capacity of breast cancer stem cells. In addition, by causing a disturbance in MDA-MB-231 zinc homeostasis by overexpressing the Zip4 transporter, we were able to increase tumorigenicity. Nevertheless, this strategy did not completely recapitulate the BrM2 metastatic phenotype. Altogether, our work suggests that zinc plays an important role in the transformative steps that tumoral cells take to acquire tumorigenic potential and niche specificity.

SLC39A10 Upregulation Predicts Poor Prognosis, Promotes Proliferation and Migration, and Correlates with Immune Infiltration in Hepatocellular Carcinoma

Background

Recent evidence has shown that Solute Carrier Family 39 Member 10 (SLC39A10) promoted tumor progression in several cancer types. The study intended to explore the expression and function of SLC39A10 in hepatocellular carcinoma (HCC).

Methods

Multiple bioinformatics analyses were used to evaluate SLC39A10 expression and potential role in HCC. Quantitative real-time polymerase chain reaction and immunohistochemistry were used to confirm SLC39A10 expression. Intro studies were performed to assess the effects of SLC39A10 on HCC cells proliferation and migration. Furthermore, flow cytometry was conducted to identify its specific function in apoptosis of HCC.

Results

SLC39A10 was significantly over-expressed in HCC samples from both bioinformatic databases and our cohort. Survival analyses suggested patients with high expression of SLC39A10 had poor overall survival and disease-free survival (P-value <0.01). Further, the expression of SLC39A10 was positively correlated with tumor-infiltrating lymphocytes and some immune checkpoints like CTLA4, TIM3 and TGFB1. In HCC cell lines, SLC39A10 knockdown inhibited cells proliferation and migration, but promoted apoptosis.

Conclusion

An increased SLC39A10 expression was found and served as an unfavorable indicator of survival in HCC. Further studies suggested SLC39A10 promotes tumor aggressiveness and may provide a novel target for HCC therapy.

Phosphoproteomics Analysis Reveals a Pivotal Mechanism Related to Amino Acid Signals in Goat Fetal Fibroblast

In addition to serving as the building blocks for protein synthesis, amino acids serve as critical signaling molecules in cells. However, the mechanism through which amino acid signals are sensed in cells is not yet fully understood. This study examined differences in the phosphorylation levels of proteins in response to amino acid signals in Cashmere goat fetal fibroblasts (GFb). Amino acid deficiency was found to induce autophagy and attenuate mammalian/mechanistic target of rapamycin complex (mTORC1)/Unc-51-like autophagy activating kinase 1 (ULK1) signaling in GFb cells. A total of 144 phosphosites on 102 proteins positively associated with amino acid signaling were screened using phosphorylation-based proteomics analysis. The mitogen-activated protein kinase (MAPK) signaling pathway was found to play a potentially important role in the interaction network involved in the response to amino acid signals, according to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and MAPK1/3 may serve as a central hub for the entire network. Motif analysis identified three master motifs, xxx_S_Pxx, xxx_S_xxE, and xxx_S_xDx, which were centered on those phosphosites at which phosphorylation was positively regulated by amino acid signaling. Additionally, the phosphorylation levels of three membrane proteins, the zinc transporter SLC39A7, the sodium-dependent neutral amino acid transporters SLC1A5 and SLC38A7, and three translation initiation factors, eukaryotic initiation factor (eIF)5B, eIF4G, and eIF3C, were positively regulated by amino acid signals. These pivotal proteins were added to currently known signaling pathways to generate a novel model of the network pathways associated with amino acid signals. Finally, the phosphorylation levels of threonine 203 and tyrosine 205 on MAPK3 in response to amino acid signals were examined by western blot analysis, and the results were consistent with the data from the phosphoproteomics analysis. The findings of this study provide new evidence and insights into the precise mechanism through which amino acid signals are sensed and conducted in Cashmere goat fetal fibroblasts.

Identification of Somatic Genetic Alterations Using Whole-Exome Sequencing of Uterine Leiomyosarcoma Tumors

Background

The genomic abnormalities associated with uterine leiomyosarcoma (uLMS) have not been fully elucidated to date.

Objective

To understand the pathogenesis of uLMS and to identify driver mutations and potential therapeutic targets in uLMS.

Methods

Three matched tumor-constitutional DNA pairs from patients with recurrent uLMS were subjected to whole-exome capture and next-generation sequencing. The role of the selected gene SHARPIN in uLMS was analyzed by the CCK-8 assay and colony formation assay after specific siRNA knockdown.

Results

We identified four genes with somatic SNVs, namely, SLC39A7, GPR19, ZNF717, and TP53, that could be driver mutations. We observed that 30.7% (4/13) of patients with uLMS had TP53 mutations as analyzed by direct sequencing. Analysis of somatic copy number variants (CNVs) showed regions of chromosomal gain at 1q21-23, 19p13, 17q21, and 17q25, whereas regions of chromosomal loss were observed at 2q35, 2q37, 1p36, 10q26, 6p22, 8q24, 11p15, 11q12, and 9p21. The SHARPIN gene was amplified in two patients and mutated in another (SHARPIN: NM_030974: exon2: c.G264C, p.E88D). Amplification of the SHARPIN gene was associated with shorter PFS and OS in soft tissue sarcoma, as shown by TCGA database analysis. Knockdown of SHARPIN expression was observed to decrease cell growth and colony formation in uterine sarcoma cell lines.

Conclusions

Exome sequencing revealed mutational heterogeneity of uLMS. The SHARPIN gene was amplified in uLMS and could be a candidate oncogene.

SLC39A7 promotes malignant behaviors in glioma via the TNF-α-mediated NF-κB signaling pathway

Purpose: Several studies have indicated that SLC39A7 plays an important role in tumor progression; however, little is known about the function and mechanism of SLC39A7 in glioma. In this study, we aimed to explore the role of SLC39A7 in glioma development. Patients and methods: Bioinformatic analysis was used to predict the role of SLC39A7 in glioma. Cell viability and Edu assays were used to detect the proliferation of glioma cells. A transwell assay was used to measure the invasion and migration of glioma cells. Western blotting, qPCR and ELISA were used to detect the expression of all molecules. Results: SLC39A7 was found to be highly expressed in high-grade glioma patients with a poor prognosis. Our results indicated that SLC39A7 significantly promoted the proliferation, invasion and migration of glioma cells. Furthermore, SLC39A7 promoted tumorigenesis in orthotopic models. We determined that SLC39A7 promotes the malignant behaviors of glioma by activating the TNF-α-mediated NF-κB signaling pathway. Conclusion: Our study revealed that SLC39A7 promotes the proliferation, invasion and migration of glioma cells via the TNF-α-mediated NF-κB signaling pathway, which provides potential targets for glioma therapy.

Aberrant Expression of ZIP and ZnT Zinc Transporters in UROtsa Cells Transformed to Malignant Cells by Cadmium

Maintenance of zinc homeostasis is pivotal to the regulation of cell growth, differentiation, apoptosis, and defense mechanisms. In mammalian cells, control of cellular zinc homeostasis is through zinc uptake, zinc secretion, and zinc compartmentalization, mediated by metal transporters of the Zrt-/Irt-like protein (ZIP) family and the Cation Diffusion Facilitators (CDF) or ZnT family. We quantified transcript levels of ZIP and ZnT zinc transporters expressed by non-tumorigenic UROtsa cells and compared with those expressed by UROtsa clones that were experimentally transformed to cancer cells by prolonged exposure to cadmium (Cd). Although expression of the ZIP8 gene in parent UROtsa cells was lower than ZIP14 (0.1 vs. 83 transcripts per 1000 β-actin transcripts), an increased expression of ZIP8 concurrent with a reduction in expression of one or two zinc influx transporters, namely ZIP1, ZIP2, and ZIP3, were seen in six out of seven transformed UROtsa clones. Aberrant expression of the Golgi zinc transporters ZIP7, ZnT5, ZnT6, and ZnT7 were also observed. One transformed clone showed distinctively increased expression of ZIP6, ZIP10, ZIP14, and ZnT1, with a diminished ZIP8 expression. These data suggest intracellular zinc dysregulation and aberrant zinc homeostasis both in the cytosol and in the Golgi in the transformed UROtsa clones. These results provide evidence for zinc dysregulation in transformed UROtsa cells that may contribute in part to their malignancy and/or muscle invasiveness.

SLC39A7, regulated by miR-139-5p, induces cell proliferation, migration and inhibits apoptosis in gastric cancer via Akt/mTOR signaling pathway

As a zinc transporter, SLC39A7 (zip7) is vital in intestinal epithelial self-renewal, and recent studies suggested that SLC39A7 was related to cancer progression. Whereas, little is known about the role of SLC39A7 in gastric cancer (GC). In the present study, qRT-PCR analysis demonstrated that SLC39A7 mRNA level was increased in both GC tissues and cell lines. Overexpressing SLC39A7 boosted cell proliferation and migration, while inhibited apoptosis in GC. It was also found that si-SLC39A7 suppressed Akt/mTOR pathway and activation of Akt/mTOR pathway reversed the effects of si-SLC39A7 on GC development. Through prediction website, we found that SLC39A7 was directly regulated by miR-139-5p. miR-139-5p mimic had adverse effects on SLC39A7 expression and influence in the GC cell proliferation, migration and apoptosis by Akt/mTOR signaling pathway, while miR-139-5p inhibitor showed opposite effects. To conclude, our studies showed that SLC39A7 was negatively regulated by miR-139-5p. Besides, SLC39A7 positively regulated GC development through Akt/mTOR signaling pathway. These results indicate that SLC39A7 may be a candidate target gene for GC treatment.

Evaluation of the prognostic values of solute carrier (SLC) family 39 genes for patients with lung adenocarcinoma

BACKGROUND

Lung cancer is the first fatality rate of cancer-related death worldwide. This study aimed to evaluate the solute carrier family 39 (SLC39A) genes as biological markers associated with the prognosis of lung adenocarcinoma (LUAD).

METHODS AND MATERIALS

MRNA expression of SLC39A genes in non-small cell lung cancer (NSCLC) was analyzed using UCSC database. We investigated the overall survival (OS) of SLC39A genes in patients with NSCLC as the only prognostic indicator using the Kaplan-Meier plotter. CERES score obtained from the Project Achilles was used to perform the survival analysis. Crystal violet-glutaraldehyde solution staining and CCK-8 assay were used to determine colony formation and cell viability, respectively.

RESULTS

For patients with lung squamous cell carcinoma, only high expression of SLC39A3, SLC39A4 and SLC39A7 have significant affections to the prognosis. But for patients with LUAD, 11 out of 14 SLC39A genes were significantly associated with prognostic values. Additional analysis indicated that SLC39A7 played an essential role for cell survival of LUAD. Furthermore, SLC39A7 high expression in LUAD was associated with current smoking.

CONCLUSIONS

Our findings indicated that SLC39A groups were significantly associated with prognosis of LUAD. The SLC39A7 gene was significantly linked with survival and growth of LUAD cells.

Zinc transporters and their functional integration in mammalian cells

Zinc is a ubiquitous biological metal in all living organisms. The spatiotemporal zinc dynamics in cells provide crucial cellular signaling opportunities, but also challenges for intracellular zinc homeostasis with broad disease implications. Zinc transporters play a central role in regulating cellular zinc balance and subcellular zinc distributions. The discoveries of two complementary families of mammalian zinc transporters (ZnTs and ZIPs) in the mid-1990s spurred much speculation on their metal selectivity and cellular functions. After two decades of research, we have arrived at a biochemical description of zinc transport. However, in vitro functions are fundamentally different from those in living cells, where mammalian zinc transporters are directed to specific subcellular locations, engaged in dedicated macromolecular machineries, and connected with diverse cellular processes. Hence, the molecular functions of individual zinc transporters are reshaped and deeply integrated in cells to promote the utilization of zinc chemistry to perform enzymatic reactions, tune cellular responsiveness to pathophysiologic signals, and safeguard cellular homeostasis. At present, the underlying mechanisms driving the functional integration of mammalian zinc transporters are largely unknown. This knowledge gap has motivated a shift of the research focus from in vitro studies of purified zinc transporters to in cell studies of mammalian zinc transporters in the context of their subcellular locations and protein interactions. In this review, we will outline how knowledge of zinc transporters has been accumulated from in-test-tube to in-cell studies, highlighting new insights and paradigm shifts in our understanding of the molecular and cellular basis of mammalian zinc transporter functions.

Increase of the Intracellular Zinc Concentration Leads to an Activation and Internalisation of the Epidermal Growth Factor Receptor in A549 Cells

(1) Background: Zinc is suggested to play a major role in epidermal growth factor (EGF)-induced cell regeneration and proliferation. To deepen the knowledge on the underlying mechanisms zinc’s effects on the epidermal growth factor receptor (EGFR) activation and its endocytosis was investigated in the alveolar carcinoma cell line A549. (2) Methods: An increase of intracellular zinc was generated by adding zinc extracellularly compared to the intracellular release of zinc from zinc-binding proteins by stimulation with a nitric oxide donor. Zinc-initiated EGFR phosphorylation was checked by Western blotting and receptor endocytosis assays were performed by using flow cytometry. (3) Results: Besides a dose-dependent EGFR phosphorylation, a dose- and time dependent significant receptor internalisation was initiated by both types of zinc increases. In addition, both increased intracellular zinc levels further promoted EGF-induced EGFR phosphorylation and internalisation. (4) Conclusion: This report confirms a transactivating effect of zinc on the EGFR for A549 cells and is the first describing an influence of zinc on the EGFR endocytosis. The transferability of the fine-tuning of EGFR-induced signalling by zinc needs to be verified in vivo, but the presented data underline that zinc might be helpful during treatment of disturbed regeneration and tissue repair.

Toward unzipping the ZIP metal transporters: structure, evolution, and implications on drug discovery against cancer

The Zrt-/Irt-like protein (ZIP) family consists of divalent metal transporters, ubiquitous in all kingdoms of life. Since the discovery of the first ZIPs in the 1990s, the ZIP family has been expanding to contain tens of thousands of members playing key roles in uptake and homeostasis of life-essential trace elements, primarily zinc, iron and manganese. Some family members are also responsible for toxic metal (particularly cadmium) absorption and distribution. Their central roles in trace element biology, and implications in many human diseases, including cancers, have elicited interest across multiple disciplines for potential applications in biomedicine, agriculture and environmental protection. In this review and perspective, selected areas under rapid progress in the last several years, including structural biology, evolution, and drug discovery against cancers, are summarised and commented. Future research to address the most prominent issues associated with transport and regulation mechanisms are also discussed.

The Role of Zinc and Copper in Gynecological Malignancies

Zinc (Zn) and copper (Cu) are essential microelements, which take part in cellular metabolism, feature in enzymatic systems, and regulate enzyme activity. Homeostasis of these micronutrients is tightly regulated by multiple compensatory mechanisms that balance their concentrations including transporters, importers, and metallothioneins. An altered intake of only one of these trace elements may cause an imbalance in their levels and result in their competition for absorption. Relatively low levels of zinc and increased levels of copper may result in an increased level of oxidative stress and impair the antioxidant properties of multiple enzymes. Altered levels of trace elements were discovered in various pathologies including immunological, degenerative, and inflammatory diseases. Moreover, due to the role of Zn and Cu in oxidative stress and chronic inflammation, they were found to influence cancerogenesis. We review the roles of zinc and copper and their mechanisms in tumor growth, metastasis potential, microenvironment remodeling, and drug resistance. We highlight their role as potential biomarkers for cancer diagnosis, treatment, and prognosis, concentrating on their impact on gynecological malignancies.

The role of labile Zn2+ and Zn2+-transporters in the pathophysiology of mitochondria dysfunction in cardiomyocytes

An important energy supplier of cardiomyocytes is mitochondria, similar to other mammalian cells. Studies have demonstrated that any defect in the normal processes controlled by mitochondria can lead to abnormal ROS production, thereby high oxidative stress as well as lack of ATP. Taken into consideration, the relationship between mitochondrial dysfunction and overproduction of ROS as well as the relation between increased ROS and high-level release of intracellular labile Zn²⁺, those bring into consideration the importance of the events related with those stimuli in cardiomyocytes responsible from cellular Zn²⁺-homeostasis and responsible Zn²⁺-transporters associated with the Zn²⁺-homeostasis and Zn²⁺-signaling. Zn²⁺-signaling, controlled by cellular Zn²⁺-homeostatic mechanisms, is regulated with intracellular labile Zn²⁺ levels, which are controlled, especially, with the two Zn²⁺-transporter families; ZIPs and ZnTs. Our experimental studies in mammalian cardiomyocytes and human heart tissue showed that Zn²⁺-transporters localizes to mitochondria besides sarco(endo)plasmic reticulum and Golgi under physiological condition. The protein levels as well as functions of those transporters can re-distribute under pathological conditions, therefore, they can interplay among organelles in cardiomyocytes to adjust a proper intracellular labile Zn²⁺ level. In the present review, we aimed to summarize the already known Zn²⁺-transporters localize to mitochondria and function to stabilize not only the cellular Zn²⁺ level but also cellular oxidative stress status. In conclusion, one can propose that a detailed understanding of cellular Zn²⁺-homeostasis and Zn²⁺-signaling through mitochondria may emphasize the importance of new mitochondria-targeting agents for prevention and/or therapy of cardiovascular dysfunction in humans.

Zinc Modulates Several Transcription-Factor Regulated Pathways in Mouse Skeletal Muscle Cells

Zinc is an essential metal ion involved in many biological processes. Studies have shown that zinc can activate several molecules in the insulin signalling pathway and the concomitant uptake of glucose in skeletal muscle cells. However, there is limited information on other potential pathways that zinc can activate in skeletal muscle. Accordingly, this study aimed to identify other zinc-activating pathways in skeletal muscle cells to further delineate the role of this metal ion in cellular processes. Mouse C2C12 skeletal muscle cells were treated with insulin (10 nM), zinc (20 µM), and the zinc chelator TPEN (various concentrations) over 60 min. Western blots were performed for the zinc-activation of pAkt, pErk, and pCreb. A Cignal 45-Reporter Array that targets 45 signalling pathways was utilised to test the ability of zinc to activate pathways that have not yet been described. Zinc and insulin activated pAkt over 60 min as expected. Moreover, the treatment of C2C12 skeletal muscle cells with TPEN reduced the ability of zinc to activate pAkt and pErk. Zinc also activated several associated novel transcription factor pathways including Nrf1/Nrf2, ATF6, CREB, EGR1, STAT1, AP-1, PPAR, and TCF/LEF, and pCREB protein over 120 min of zinc treatment. These studies have shown that zinc’s activity extends beyond that of insulin signalling and plays a role in modulating novel transcription factor activated pathways. Further studies to determine the exact role of zinc in the activation of transcription factor pathways will provide novel insights into this metal ion actions.

Zinc-dependent changes in oxidative and endoplasmic reticulum stress during cardiomyocyte hypoxia/reoxygenation

Myocardial zinc dyshomeostasis is associated with caspase-3 activation, ErbB2 degradation and apoptosis during hypoxia/reoxygenation. Zinc pyrithione replenishes intracellular zinc, suppresses caspase-3, augments ErbB2 levels and improves cell survival. We hypothesize that zinc is capable of modulating redox and endoplasmic reticulum (ER) stress in the setting of cardiomyocyte hypoxia-reoxygenation. Hypoxia/reoxygenation lowered intracellular zinc, increased ER as well as oxidative stress in H9c2 cells, both of which were effectively attenuated by zinc supplementation. Silencing of gp91phox attenuated oxidative and ER stress, decreased caspase-3 activation and improved cell survival. Mimicking the oxidative insult using 50 μM H2O2 increased the caspase-3 activity that correlated with decreased ErbB2 levels, concomitant with augmented ER stress. N-acetyl cysteine (NAC) administration completely suppressed ER stress as well as caspase-3 activity. Zinc depletion using TPEN also resulted in lowered ErbB2 and increased apoptosis, along with NOX2 mRNA upregulation, increased oxidative and ER stress. Repletion with zinc suppressed NOX2 mRNA, lowered oxidative as well as ER stress and decreased cell death. These results suggest that zinc dyshomeostasis, along with oxidative stress contribute to the unfolded protein response during myocardial H/R and that zinc replenishment corrects zinc homeostasis, alleviates associated stress and improves cardiomyocyte survival.

Galvanization of Protein-Protein Interactions in a Dynamic Zinc Interactome

The presence of Zn²⁺ at protein-protein interfaces modulates complex function, stability, and introduces structural flexibility/complexity, chemical selectivity, and reversibility driven in a Zn²⁺-dependent manner. Recent studies have demonstrated that dynamically changing Zn²⁺ affects numerous cellular processes, including protein-protein communication and protein complex assembly. How Zn²⁺-involved protein-protein interactions (ZPPIs) are formed and dissociate and how their stability and reactivity are driven in a zinc interactome remain poorly understood, mostly due to experimental obstacles. Here, we review recent research advances on the role of Zn²⁺ in the formation of interprotein sites, their architecture, function, and stability. Moreover, we underline the importance of zinc networks in intersystemic communication and highlight bioinformatic and experimental challenges required for the identification and investigation of ZPPIs.

Zinc distribution within breast cancer tissue of different intrinsic subtypes

PURPOSE

To show feasibility of laser ablation inductively coupled mass spectrometry (LA-ICPMS) for analysis of zinc content and concentration in breast cancer tissue and to correlate this with validated prognostic and predictive markers, i.e. histological grading and expression of steroid receptors (estrogen receptor, ER; progesterone receptor, PR) and human epidermal growth-factor receptor 2 (Her2).

METHODS

28 samples of human invasive ductal breast cancer tissue were subclassified into groups of four different intrinsic subtypes according to the expression of ER, PR and Her2 by immunohistological staining and then analyzed for zinc content and distribution by LA-ICPMS applying a calibration technique based on spiked polyacrylamide gels. A correlation of zinc concentration with histological grading and molecular subtypes was analyzed.

RESULTS

Consistent with results of a pilot-study LA-ICPMS was feasible to show zinc accumulation in cancerous tissue, even more adjacent healthy stroma was with proportional increase of zinc. Zinc levels were most elevated in triple-positive (TPBC) and in triple-negative (TNB) breast cancers.

CONCLUSION

LA-ICPMS was feasible to confirm a connection between zinc and grade of malignancy; furthermore, focusing on a correlation of zinc and intrinsic breast cancer subtypes, LA-ICPMS depicted an upwards trend of zinc for "high-risk-cancers" with highest levels in Her2-positive and in triple-negative (TNBC) disease. The currently uncommon alliance of clinicians and analytical chemists in basic research is most promising to exploit the full potential of diagnostic accuracy in the efforts to solve the enigma of breast cancer initiation and course of disease.

Analysis of the prognostic significance of solute carrier (SLC) family 39 genes in breast cancer

BACKGROUND

Breast cancer (BC) is the most common malignancy in females and remains a main cause of cancer-associated death worldwide. The solute carrier (SLC) groups of membrane transport proteins, which control the influx of zinc, participate in ranging of physiological processes and may provide novel therapeutic targets of cancers. However, the prognostic values of individual SLC family 39 (SLC39A) genes in patients with BC are not clarified.

MATERIALS AND METHODS

The mRNA expression of SLC family 39 genes in BC was evaluated by using the UALCAN database. The prognostic values of overall survival (OS) of SLC family 39 genes in patients with BC were investigated by Kaplan-Meier plotter. The survival analysis of cells was determined by Project Achilles.

RESULTS

The analytic results suggested that SLC39A1, SLC39A3, SLC39A4, SLC39A5, SLC39A6, SLC39A7, SLC39A9, SLC39A10, SLC39A11 and SLC39A13 were significantly up-regulated in BC tissues compared with normal breast tissues. However, SLC39A8 and SLC39A14 were expressed higher in normal tissues than in BC tissues. High expression of SLC39A2, SLC39A3, SLC39A4, SLC39A5, SLC39A7, SLC39A12 and SLC39A13 was significantly associated with worse OS in patients with BC. In contrast, high mRNA levels of SLC39A6 and SLC39A14 indicated favorable OS. Through subgroup analysis, all abnormal expressed SLC family members were correlated with prognoses of patients with specific BC. Moreover, SLC39A7 was associated with proliferation and cloning of BC.

CONCLUSIONS

Our results suggested that SLC family 39 members were promising prognostic biomarkers of BC. The SLC39A7 played a key role in growth and survival of BC cells.

The ZIP6/ZIP10 heteromer is essential for the zinc-mediated trigger of mitosis

Zinc has been known to be essential for cell division for over 40 years but the molecular pathways involved remain elusive. Cellular zinc import across biological membranes necessitates the help of zinc transporters such as the SLC39A family of ZIP transporters. We have discovered a molecular process that explains why zinc is required for cell division, involving two highly regulated zinc transporters, as a heteromer of ZIP6 and ZIP10, providing the means of cellular zinc entry at a specific time of the cell cycle that initiates a pathway resulting in the onset of mitosis. Crucially, when the zinc influx across this heteromer is blocked by ZIP6 or ZIP10 specific antibodies, there is no evidence of mitosis, confirming the requirement for zinc influx as a trigger of mitosis. The zinc that influxes into cells to trigger mitosis additionally changes the phosphorylation state of STAT3 converting it from a transcription factor to a protein that complexes with this heteromer and pS³⁸Stathmin, the form allowing microtubule rearrangement as required in mitosis. This discovery now explains the specific cellular role of ZIP6 and ZIP10 and how they have special importance in the mitosis process compared to other ZIP transporter family members. This finding offers new therapeutic opportunities for inhibition of cell division in the many proliferative diseases that exist, such as cancer.

Why and how to investigate the role of protein phosphorylation in ZIP and ZnT zinc transporter activity and regulation

Zinc is required for the regulation of proliferation, metabolism, and cell signaling. It is an intracellular second messenger, and the cellular level of ionic, mobile zinc is strictly controlled by zinc transporters. In mammals, zinc homeostasis is primarily regulated by ZIP and ZnT zinc transporters. The importance of these transporters is underscored by the list of diseases resulting from changes in transporter expression and activity. However, despite numerous structural studies of the transporters revealing both zinc binding sites and motifs important for transporter function, the exact molecular mechanisms regulating ZIP and ZnT activities are still not clear. For example, protein phosphorylation was found to regulate ZIP7 activity resulting in the release of Zn2+ from intracellular stores leading to phosphorylation of tyrosine kinases and activation of signaling pathways. In addition, sequence analyses predict all 24 human zinc transporters to be phosphorylated suggesting that protein phosphorylation is important for regulation of transporter function. This review describes how zinc transporters are implicated in a number of important human diseases. It summarizes the current knowledge regarding ZIP and ZnT transporter structures and points to how protein phosphorylation seems to be important for the regulation of zinc transporter activity. The review addresses the need to investigate the role of protein phosphorylation in zinc transporter function and regulation, and argues for a pressing need to introduce quantitative phosphoproteomics to specifically target zinc transporters and proteins involved in zinc signaling. Finally, different quantitative phosphoproteomic strategies are suggested.