Knockdown of Zinc Transporter ZIP5 by RNA Interference Inhibits Esophageal Cancer Growth In Vivo

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.

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.

Multifunctional role of zinc in human health: an update

Zinc is a multipurpose trace element for the human body, as it plays a crucial part in various physiological processes, such as cell growth and development, metabolism, cognitive, reproductive, and immune system function. Its significance in human health is widely acknowledged, and this has led the scientific community towards more research that aims to uncover all of its beneficial properties, especially when compared to other essential metal ions. One notable area where zinc has shown beneficial effects is in the prevention and treatment of various diseases, including cancer. This review aims to explain the involvement of zinc in specific health conditions such as cancer, coronavirus disease 2019 (COVID-19) and neurological disorders like Alzheimer's disease, as well as its impact on the gut microbiome.

Exposure to Di-(2-Ethylhexyl) phthalate drives ovarian dysfunction by inducing granulosa cell pyroptosis via the SLC39A5/NF-κB/NLRP3 axis

Endocrine-disrupting chemicals (EDCs) have been reported to affect populations by disrupting the human endocrine system. Di-(2-ethylhexyl) phthalate (DEHP) is an EDC that is present in various consumer products. Exposure to DEHP could contribute to reproductive system dysfunction, with subsequent adverse female reproductive outcomes. Granulosa cells (GCs) play essential roles in ovarian function and fertility. To further reveal the underlying mechanism by which DEHP impairs female fertility and affects the normal function of GCs, in vivo and in vitro experiments were performed. Transcript sequencing was used to identify genes that were differentially expressed in GCs after DEHP treatment. SLC39A5 was shown to be overexpressed in the DEHP group compared to the normal control group. DEHP treatment and overexpression of SLC39A5 activated NF-κB-related factors, followed by an increase in the transcript expression level of NLRP3. NLRP3 inflammasomes play crucial roles in pyroptosis by acting as sensors. Pyroptosis is a type of inflammation-related cell death associated with various diseases, including ovarian cancer and polycystic ovary syndrome. Activation of NF-κB contributed to the upregulation of pyroptosis in GCs, while pyroptosis factors were downregulated after the inhibition of NF-κB with JSH-23. The same phenomenon was also observed in a mouse model in which DEHP-treated mice had higher expression levels of NF-κB and pyroptosis markers in GCs. Moreover, this phenomenon could be partially reversed by the NF-κB inhibitor JSH-23. DEHP treatment also disrupted the normal expression of ovarian function-related genes and inhibited the proliferation of GCs. Reproductive system impairment was observed in mice exposed to DEHP. DEHP-treated mice had a lower body weight, smaller reproductive organs, fewer healthy follicles, and diminished ovarian reserve. Thus, DEHP contributes to ovarian dysfunction by inducing pyroptosis via the SLC39A5/NF-κB/NLRP3 axis in GCs.

SLC39A5 promotes lung adenocarcinoma cell proliferation by activating PI3K/AKT signaling

Lung cancer is the most common cancer and the primary cause of cancer-related deaths worldwide. Solute carrier family 39 member 5 (SLC39A5) regulates cellular zinc homeostasis and plays a vital role in several human cancers. However, the clinical significance and biological function of SLC39A5 in lung adenocarcinoma (LUAD) remain unclear. Hence, we sought to elucidate the role of SLC39A5 in LUAD pathophysiology in this study. The expression and clinical significance of SLC39A5 were evaluated using The Cancer Genome Atlas, the Gene Expression Omnibus, and tissue microarray data. We used the Cell Counting Kit-8, flow cytometry, western blotting, and quantitative reverse transcriptase-polymerase chain reaction analyses to determine the function of SLC39A5 in vitro. We also used a mouse xenograft model to evaluate the function of SLC39A5 in vivo. Our results indicate that SLC39A5 was upregulated in LUAD tissues compared with that in adjacent non-tumor lung tissues. SLC39A5 overexpression correlated with poor survival in patients with LUAD. SLC39A5 promoted LUAD cell proliferation by accelerating the G1-to-S phase transition and inhibiting apoptosis. SLC39A5 knockdown inhibited the tumorigenesis of LUAD cells in a nude mouse model of xenograft tumors. SLC39A5 promoted LUAD cell proliferation by activating the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling. SLC39A5 played an oncogenic role in LUAD by activating the PI3K/AKT signaling. Hence, SLC39A5 may serve as a novel prognostic biomarker and potential therapeutic target for LUAD.

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 dysregulation in cancers and its potential as a therapeutic target

Zinc is an essential element and serves as a structural or catalytic component in many proteins. Two families of transporters are involved in maintaining cellular zinc homeostasis: the ZIP (SLC39A) family that facilitates zinc influx into the cytoplasm, and the ZnT (SLC30A) family that facilitates zinc efflux from the cytoplasm. Zinc dyshomeostasis caused by the dysfunction of zinc transporters can contribute to the initiation or progression of various cancers, including prostate cancer, breast cancer, and pancreatic cancer. In addition, intracellular zinc fluctuations lead to the disturbance of certain signaling pathways involved in the malignant properties of cancer cells. This review briefly summarizes our current understanding of zinc dyshomeostasis in cancer, and discusses the potential roles of zinc or zinc transporters in cancer therapy.

A Brief Overview from the Physiological and Detrimental Roles of Zinc Homeostasis via Zinc Transporters in the Heart

Zinc (mostly as free/labile Zn²⁺) is an essential structural constituent of many proteins, including enzymes in cellular signaling pathways via functioning as an important signaling molecule in mammalian cells. In cardiomyocytes at resting condition, intracellular labile Zn²⁺ concentration ([Zn²⁺]_i) is in the nanomolar range, whereas it can increase dramatically under pathological conditions, including hyperglycemia, but the mechanisms that affect its subcellular redistribution is not clear. Therefore, overall, very little is known about the precise mechanisms controlling the intracellular distribution of labile Zn²⁺, particularly via Zn²⁺ transporters during cardiac function under both physiological and pathophysiological conditions. Literature data demonstrated that [Zn²⁺]_i homeostasis in mammalian cells is primarily coordinated by Zn²⁺ transporters classified as ZnTs (SLC30A) and ZIPs (SLC39A). To identify the molecular mechanisms of diverse functions of labile Zn²⁺ in the heart, the recent studies focused on the discovery of subcellular localization of these Zn²⁺ transporters in parallel to the discovery of novel physiological functions of [Zn²⁺]_i in cardiomyocytes. The present review summarizes the current understanding of the role of [Zn²⁺]_i changes in cardiomyocytes under pathological conditions, and under high [Zn²⁺]_i and how Zn²⁺ transporters are important for its subcellular redistribution. The emerging importance and the promise of some Zn²⁺ transporters for targeted cardiac therapy against pathological stimuli are also provided. Taken together, the review clearly outlines cellular control of cytosolic Zn²⁺ signaling by Zn²⁺ transporters, the role of Zn²⁺ transporters in heart function under hyperglycemia, the role of Zn²⁺ under increased oxidative stress and ER stress, and their roles in cancer are discussed.

Long noncoding RNA TSLNC8 suppresses cell proliferation and metastasis and promotes cell apoptosis in human glioma

Glioma is among the most common primary brain tumors and one of the most aggressive and lethal forms of human cancer. Long noncoding RNAs (lncRNAs) have demonstrated great importance in the development and progression of cancer. The present study aimed to investigate the role of the novel tumor suppressive lncRNA on Chromosome 8p12 (TSLNC8), in cell proliferation, metastasis and apoptosis in human glioma. It was initially reported that the relative transcript levels of TSLNC8 were significantly decreased in human glioma tissues and cultured glioma cells, as evidenced by RT‑qPCR. Among clinical variables, the expression of TSLNC8 was negatively associated with tumor size, distant metastasis, and tumor, node and metastasis stage. MTT assay demonstrated that overexpression of TSLNC8 in glioma cell lines U25‑MG and SWO38 decreased, whereas knockdown of TSLNC8 in glioma cells SHG‑44 and BT325 increased the cell proliferative rate over 5 consecutive days. Additionally, cell metastasis was inhibited in U251 and SWO38 cells when cells were transfected with TSLNC8‑expressing plasmid as observed via Transwell and wound‑healing assays. Furthermore, cell apoptotic rate was upregulated in TSLNC8 plasmid‑treated U251 and SWO38 cells, and inhibited by siRNA against TSLNC8 in SHG‑44 and BT325 cells by cell apoptotic assay. The relative activities of caspase‑3 and caspase‑9 were increased by TSLNC8 overexpression and decreased by TSLNC depletion; however, the activity of caspase‑8 remained unchanged. The results of the present study demonstrated the inhibitory effects of TSLNC8 in human glioma, which may contribute to advancement in the diagnosis and treatment of patients with glioma in clinic.

ZIP4 Promotes Pancreatic Cancer Progression by Repressing ZO-1 and Claudin-1 through a ZEB1-Dependent Transcriptional Mechanism

Purpose: ZIP4 is overexpressed in human pancreatic cancer and promotes tumor growth. However, little is known about the role of ZIP4 in advanced stages of this dismal neoplasm. Our goal is to study the underlying mechanism and define a novel signaling pathway controlled by ZIP4-modulating pancreatic tumor metastasis.Experimental Design: The expression of ZIP4, ZO-1, claudin-1, and ZEB1 in human pancreatic cancer tissues, genetically engineered mouse model, xenograft tumor model, and pancreatic cancer cell lines were examined, and the correlations between ZIP4 and those markers were also analyzed. Functional analysis of ZO-1, claudin-1, and ZEB1 was investigated in pancreatic cancer cell lines and orthotopic xenografts.Results: Genetic inactivation of ZIP4 inhibited migration and invasion in pancreatic cancer and increased the expression of ZO-1 and claudin-1. Conversely, overexpression of ZIP4 promoted migration and invasion and increased the expression of ZEB1 and downregulation of the aforementioned epithelial genes. ZIP4 downregulation of ZO-1 and claudin-1 requires the transcriptional repressor ZEB1. Further analysis demonstrated that ZIP4-mediated repression of ZO-1 and claudin-1 leads to upregulation of their targets FAK and Paxillin. Silencing of ZIP4 caused reduced phosphorylation of FAK and Paxillin, which was rescued by simultaneous blocking of ZO-1 or claudin-1. Clinically, we demonstrated that ZIP4 positively correlates with the levels of ZEB1 and inversely associates with the expression of ZO-1 and claudin-1.Conclusions: These findings suggest a novel pathway activated by ZIP4-controlling pancreatic cancer invasiveness and metastasis, which could serve as a new therapeutic target for this devastating disease. Clin Cancer Res; 24(13); 3186-96. ©2018 AACR.

Quantification of STAT3 and VEGF expression for molecular diagnosis of lymph node metastasis in breast cancer

BACKGROUND

Axillary lymph node metastasis is associated with increased risk of regional recurrence, distant metastasis, and poor survival in breast malignant neoplasm. Expression of signal transducer and activator of transcription 3 (STAT3) is significantly associated with tumor formation, migration, and invasion in various cancers. In addition, vascular endothelial growth factor (VEGF) expression could promote angiogenesis and increase the risk of tumorigenesis. To determine correlations among STAT3 expression, VEGF, and clinicopathological data on lymph node involvement in breast cancer patients after surgery.

METHODS

The mRNA expression levels of STAT3 and VEGFs were measured in 45 breast invasive ductal carcinoma tissues, 45 peritumoral tissues, and 45 adjacent nontumor tissues by real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR). Postoperative pathological examination revealed explicit axillary lymph node involvement in all patients.

RESULTS

Average mRNA levels of STAT3 and VEGFs were the highest in breast invasive ductal carcinoma tissues, followed by peritumoral tissues. High expression of STAT3 showed significant positive correlation with high axillary lymph node involvement and progesterone receptor (PR), VEGF-C, VEGF-D, and vascular endothelial growth factor receptor (VEGFR)-3 expression. The expression levels of STAT3, VEGF-C, and VEGFR-3 were significantly higher in the tumor tissues of patients with axillary lymph node metastasis than in those of patients without the metastasis. Expression levels of VEGF-C and VEGFR-3 were also significantly higher in peritumoral tissues of patients with axillary lymph node metastasis. Positive correlations were found between STAT3 and VEGF-C/-D mRNA levels.

CONCLUSION

These data suggest that STAT3/VEGF-C/VEGFR-3 signaling pathway plays an important role in carcinogenesis and lymph-angiogenesis. Our findings suggest that STAT3 may be a potential molecular biomarker for predicting the involvement of axillary lymph nodes in breast cancer, and therapies targeting STAT3 may be important for preventing breast cancer metastasis.