Growth factor stimulated cell proliferation is accompanied by an elevated labile intracellular pool of zinc in 3T3 cells

Single nucleotide polymorphisms and Zn transport by ZIP11 shape functional phenotypes of HeLa cells

Zinc (Zn) is a vital micronutrient with essential roles in biological processes like enzyme function, gene expression, and cell signaling. Disruptions in the cellular regulation of Zn2+ ions often lead to pathological states. Mammalian Zn transporters, such as ZIP11, play a key role in homeostasis of this ion. ZIP11 resides predominately in the nucleus and Golgi apparatus. Our laboratory reported a function of ZIP11 in maintaining nuclear Zn levels in HeLa cervical cancer cells. Analyses of cervical and ovarian cancer patients' datasets identified four coding, single nucleotide polymorphisms (SNPs) in SLC39A11, the gene that encodes ZIP11, correlating with disease severity. We hypothesized that these SNPs might translate to functional changes in the ZIP11 protein by modifying access to substrate availability. We also proposed that a metal-binding site (MBS) in ZIP11 is crucial for transmembrane Zn2+ transport and required for maintenance of various pathogenic phenotypes observed in HeLa cells. Here, we investigated these claims by re-introducing single the SLC39A11 gene encoding for mutant residues associated with the SNPs, as well as MBS mutations into HeLa cells knocked down for the transporter. Some SNPs-encoding ZIP11 variants rescued Zn levels, proliferation, migration, and invasiveness of knockdown (KD) cells. Conversely, single MBS mutations mimicked the traits of KD cells, confirming the transporter's role in establishing and maintaining proliferative, migratory, and invasive traits. Overall, the intricate role of Zn in cellular dynamics and cancer progression underscores the significance of Zn transporters like ZIP11 in potential therapeutic interventions.

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.

Biotin-tagged fluorescent sensor to visualize ‘mobile’ Zn2+ in cancer cells

A biotin-tagged fluorescent sensor was developed to image Zn²⁺ in cancer cells specifically, which showed no entry to normal cells.

Fibroblast Growth Requires CT10 Regulator of Kinase (Crk) and Crk-like (CrkL)

CT10 regulator of kinase (Crk) and Crk-like (CrkL) are the cellular counterparts of the viral oncogene v-Crk Elevated levels of Crk and CrkL have been observed in many human cancers; inhibition of Crk and CrkL expression reduced the tumor-forming potential of cancer cell lines. Despite a close relationship between the Crk family proteins and tumorigenesis, how Crk and CrkL contribute to cell growth is unclear. We ablated endogenous Crk and CrkL from cultured fibroblasts carrying floxed alleles of Crk and CrkL by transfection with synthetic Cre mRNA (synCre). Loss of Crk and CrkL induced by synCre transfection blocked cell proliferation and caused shrinkage of the cytoplasm and the nucleus, formation of adherens junctions, and reduced cell motility. Ablation of Crk or CrkL alone conferred a much more modest reduction in cell proliferation. Reintroduction of CrkI, CrkII, or CrkL individually rescued cell proliferation in the absence of the endogenous Crk and CrkL, suggesting that Crk and CrkL play overlapping functions in regulating fibroblast growth. Serum and basic FGF induced phosphorylation of Akt, MAP kinases, and S6 kinase and Fos expression in the absence of Crk and CrkL, suggesting that cells lacking Crk and CrkL are capable of initiating major signal transduction pathways in response to extracellular stimuli. Furthermore, cell cycle and cell death analyses demonstrated that fibroblasts lacking Crk and CrkL become arrested at the G₁-S transition and undergo a modest apoptosis. Taken together, our results suggest that Crk and CrkL play essential overlapping roles in fibroblast growth.

Comparison of essential and toxic elements in esophagus, lung, mouth and urinary bladder male cancer patients with related to controls

There is a compelling evidence in support of negative associations between essential trace and toxic elements in different types of cancer. The aim of the present study was to investigate the relationship between carcinogenic (As, Cd, Ni) and anti-carcinogenic (Se, Zn) trace elements in scalp hair samples of different male cancerous patients (esophagus, lung, mouth, and urinary bladder). For comparative purposes, the scalp hair samples of healthy males of the same age group (ranged 35-65 years) as controls were analyzed. Both controls and patients have the same socioeconomic status, localities, dietary habits, and smoking locally made cigarette. The scalp hair samples were oxidized by 65% nitric acid: 30% hydrogen peroxide (2:1) ratio in microwave oven followed by atomic absorption spectrometry. The validity and accuracy of the methodology were checked using certified reference material of human hair BCR 397. The mean concentrations of As, Cd, and Ni were found to be significantly higher in scalp hair samples of patients having different cancers as compared to the controls, while reverse results were obtained in the case of Se and Zn levels (p < 0.01). The study revealed that the carcinogenic processes are significantly affecting the trace elements burden and mutual interaction of essential trace and toxic elements in the cancerous patients.

Zinc and cancer: implications for LIV-1 in breast cancer

Zinc is a trace mineral which is vital for the functioning of numerous cellular processes, is critical for growth, and may play an important role in cancer etiology and outcome. The intracellular levels of this mineral are regulated through the coordinated expression of zinc transporters, which modulate both zinc influx as well as efflux. LIV-1 (ZIP6) was first described in 1988 as an estrogen regulated gene with later work suggesting a role for this transporter in cancer growth and metastasis. Despite evidence of its potential utility as a target gene for cancer prognosis and treatment, LIV-1 has received relatively little attention, with only three prior reviews being published on this topic. Herein, the physiological effects of zinc are reviewed in light of this mineral’s role in cancer growth with specific attention being given to LIV-1 and the potential importance of this transporter to breast cancer etiology.

Increased abundance of labile intracellular zinc during cell proliferation was due to increased retention of extracellular zinc in 3T3 cells

Platelet-derived growth factor (PDGF)-, epidermal growth factor (EGF)- and insulin-like growth factor I (IGF-I)-stimulated cell proliferation in 3T3 cells was accompanied by increased abundance of labile intracellular pool of zinc (LIPZ). However, the origin and regulation of this cell proliferation-associated increase in the abundance of LIPZ are unknown. Cellular zinc homeostasis involves zinc transporters and metallothionein. The objectives of this study were to determine whether cell proliferation-associated increase in the abundance of LIPZ was a result of an increased zinc uptake and to assess the involvement of zinc transporters and metallothionein in this cell proliferation-associated increase in the abundance of LIPZ in 3T3 fibroblasts. Zinc transporters assessed included both zinc importer (Zip1) and zinc exporters (ZnT1, ZnT2 and ZnT4). Growth factors increased the abundance of LIPZ while total cellular zinc concentration remained unaffected, demonstrating that LIPZ was responsive to the increased needs for zinc during growth factor-stimulated cell proliferation. Growth factors also increased net zinc retention as indicated by higher 65zinc radioactivity and elevated mRNA levels of Zip1, ZnT1 and ZnT4. Although zinc is essential to cell proliferation, excessive cellular zinc accumulation causes cytotoxicity. Collectively, these observations suggest that increase in the abundance of LIPZ during growth factor-stimulated cell proliferation was due to increased net retention of extracellular zinc, which was apparently achieved through a coordinated up-regulation of the expression of transporters involved in both zinc influx and efflux to ensure adequate supply of zinc to sustain cell proliferation, yet to prevent potential zinc cytotoxicity in 3T3 cells.

Role of metallothionein in regulating the abundance of histochemically reactive zinc in rat tissues

The objectives of this study were (i) to investigate the modulating effects of zinc nutrition on histochemically reactive zinc in the rat intestine and liver and (ii) to assess the relationship between histochemically reactive zinc and metallothionein-bound zinc in these tissues under varying zinc nutrition. Male Wistar rats were fed a zinc-deficient (3 mg zinc/kg), adequate-zinc (30 mg zinc/kg, ad libitum or pair-fed), or zinc-supplemented (155 mg zinc/kg) diet for 2 or 6 weeks. Plasma N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide-reactive zinc reflected dietary zinc intake. Abundance of the intestine histochemically reactive zinc was correlated with dietary zinc intake after 2 weeks of dietary treatment. Dietary zinc intake had no effect on the abundance of the intestine histochemically reactive zinc after 6 weeks of dietary treatment and the hepatic histochemically reactive zinc after both 2 and 6 weeks of dietary treatment. This lack of effect of dietary zinc intake on the abundance of histochemically reactive zinc was associated with a higher level of metallothionein. The molecular-mass distribution profile revealed that N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide-reactive zinc and metallothionein-bound zinc represented two different, but interrelated, pools of zinc. Overall, these results suggested that the abundance of histochemically reactive zinc was homeostatically regulated, which was partially achieved through the regulation of metallothionein levels in rats.