Novel mechanism of aberrant ZIP4 expression with zinc supplementation in oral tumorigenesis.
Zrt-Irt-like protein 4 (ZIP4) is critical molecule for proper mammalian development and releasing zinc from vesicular compartments. Recent studies suggested that ZIP4 plays an important role of tumor progression in pancreatic, prostate, and hepatocellular cancers, however, little is known about the detail mechanism of ZIP4 in their cancers. In the present study, we examined the possibility of ZIP4 as a new molecular target for oral squamous cell carcinoma (OSCC). We evaluated ZIP4 expression in OSCC-derived cell lines and primary OSCC samples by quantitative RT-PCR, immunoblotting, and immunohistochemistry (IHC). We also analyzed the clinical correlation between ZIP4 status and clinical behaviors in patients with OSCC. In addition, ZIP4 knockdown cells (shZIP4 cells) and ZnCl2 treatment were used for functional experiments, including cellular proliferation assay, zinc uptake assay, and cell-cycle analysis. ZIP4 mRNA and protein were up-regulated significantly in OSCCs compared with normal counterparts in vitro and in vivo. IHC showed that ZIP4 expression in the primary OSCC was positively correlated with primary tumoral size. The shZIP4 cells showed decrease accumulation of intercellular zinc and decreased cellular growth by cell-cycle arrest at the G1 phase, resulting from up-regulation of cyclin-dependent kinase inhibitors and down-regulation of cyclins and cyclin-dependent kinases. Since cellular growth of OSCC cells after treatment with zinc was significantly greater than control cells, we speculated that intercellular ZnCl2 accumulation is an important factor for cellular growth. Consistent with our hypothesis, not only decreased zinc uptake by ZIP4 knockdown but also chelating agent, N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), showed inhibitory effects of cellular proliferation. Therefore, our data provide evidence for an essential role of ZIP4 and intracellular zinc for tumoral growth in OSCC, suggesting that zinc uptake might be a potential therapeutic targeting event for OSCCs.
['Ishida|Sho|S|', 'Kasamatsu|Atsushi|A|', 'Endo-Sakamoto|Yosuke|Y|', 'Nakashima|Dai|D|', 'Koide|Nao|N|', 'Takahara|Toshikazu|T|', 'Shimizu|Toshihiro|T|', 'Iyoda|Manabu|M|', 'Shiiba|Masashi|M|', 'Tanzawa|Hideki|H|', 'Uzawa|Katsuhiro|K|']
D063646:Carcinogenesis D002294:Carcinoma, Squamous Cell D027682:Cation Transport Proteins D002453:Cell Cycle D045744:Cell Line, Tumor D049109:Cell Proliferation D002614:Chelating Agents D002712:Chlorides D019587:Dietary Supplements D018450:Disease Progression D004305:Dose-Response Relationship, Drug D005029:Ethylenediamines D015972:Gene Expression Regulation, Neoplastic D006801:Humans D007150:Immunohistochemistry D009062:Mouth Neoplasms D034741:RNA, Small Interfering D015032:Zinc D017967:Zinc Compounds
ZIP4 expression Zinc ZRT- and IRT-like protein 4