Metallothionein 3 Is a Hypoxia-Upregulated Oncogene Enhancing Cell Invasion and Tumorigenesis in Human Bladder Carcinoma Cells

Int J Mol Sci. 2019 Feb 23;20(4):980. doi: 10.3390/ijms20040980.

Abstract

Metallothioneins have been viewed as modulators in a number of biological regulations regarding cancerous development; however, the function of metallothionein 3 (MT3) in bladder cancer is unexplored. We determined the regulatory mechanisms and potential function of MT3 in bladder carcinoma cells. Real-Time Reverse Transcriptase-Polymerase Chain Reaction (RT-qPCR) assays revealed that TSGH-8301 cells expressed more MT3 levels than RT-4, HT1376, and T24 cells. Immunoblot and RT-qPCR assays showed that arsenic (AS₂O₃) treatments enhanced the gene expression of MT3. Hypoxia induced HIF-1α, HIF-2α, and MT3 expression; furthermore, HIF-2α-knockdown attenuated hypoxic activation on MT3 expression. Ectopic overexpression of MT3 increased cell proliferation, invasion, and tumorigenesis significantly in T24 and HT1376 cells in vitro and in vivo; however, MT3-knockdown in TSGH-8301 cells had the reverse effect. Moreover, knockdown of MT3 enhanced arsenic-induced apoptosis determined by the Annexin V-FITC apoptosis assay. MT3-overexpression downregulated the gene expressions of N-myc downstream regulated gene 1 (NDRG1), N-myc downstream regulated gene 2 (NDRG2), and the mammary serine protease inhibitor (MASPIN) in HT1376 and T24 cells, whereas MT3-knockdown in TSGH-8301 cells had the opposite effect. The experiments indicated that MT3 is an arsenic- and hypoxia-upregulated oncogene that promotes cell growth and invasion of bladder carcinoma cells via downregulation of NDRG1, NDRG2, and MASPIN expressions.

Keywords: MASPIN; NDRG1; bladder; hypoxia; metallothionein 3; tumorigenesis.

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Arsenic / pharmacology
  • Carcinogenesis / drug effects
  • Carcinogenesis / genetics*
  • Carcinogenesis / pathology
  • Cell Hypoxia / drug effects
  • Cell Hypoxia / genetics
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Down-Regulation / drug effects
  • Down-Regulation / genetics
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Knockdown Techniques
  • Humans
  • Metallothionein 3
  • N-Myc Proto-Oncogene Protein / metabolism
  • Neoplasm Invasiveness
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Oncogenes*
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism
  • Up-Regulation / drug effects
  • Up-Regulation / genetics*
  • Urinary Bladder Neoplasms / genetics*
  • Urinary Bladder Neoplasms / pathology*

Substances

  • MYCN protein, human
  • Metallothionein 3
  • N-Myc Proto-Oncogene Protein
  • Nerve Tissue Proteins
  • Tumor Suppressor Proteins
  • Arsenic