Cadmium Increases HIF-1 and VEGF Expression Through ROS, ERK, and AKT Signaling Pathways and Induces Malignant Transformation of Human Bronchial Epithelial Cells

Toxicol Sci. 2012 Jan;125(1):10-9. doi: 10.1093/toxsci/kfr256. Epub 2011 Oct 9.

Abstract

Cadmium is categorized as a human carcinogen especially involved in lung cancers. Angiogenesis is considered a fundamental requirement for tumorigenesis, but the mechanisms underlying the tumor angiogenesis induced by cadmium are poorly understood. Using in vitro and in vivo models, we investigated the angiogenic mechanisms of cadmium in human bronchial epithelial cells and tumor formation. Our results demonstrated that cadmium (CdCl(2)) activated extracellular signal-regulated kinases (ERK) and AKT signaling and elevated the expression of a key downstream proangiogenic molecule hypoxia-inducible factor-1 (HIF-1) in immortalized human lung epithelial BEAS-2B cells. Cadmium also induced reactive oxygen species (ROS) production, which could be inhibited by ROS scavengers, catalase and diphenyleneiodonium chloride. Inhibition of ROS generation also attenuated ERK, AKT, p70S6K1 activation, and HIF-1α expression. Similar results were obtained in normal human bronchial epithelial (NHBE) cells, showing that cadmium induced HIF-1 expression via ROS/ERK/AKT signaling pathway. Furthermore, cadmium induced vascular endothelial growth factor expression and transcriptional activation through ROS, ERK, and AKT pathways. Finally, cadmium transformed human bronchial epithelial cells in culture; the transformed cells induced tube formation in vitro, angiogenesis on chicken chorioallantoic membrane, and formed tumors in nude mice. Taken together, the results of this study provide explanation for the role and molecular mechanisms of cadmium in promoting angiogenesis in lung epithelial cells and malignant transformation and will be helpful for improved occupational protection, prevention, as well as chemotherapy of human lung cancers caused by heavy metal cadmium.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Blotting, Western
  • Bronchi / blood supply
  • Bronchi / pathology*
  • Cadmium / toxicity*
  • Cell Culture Techniques
  • Cell Line
  • Cell Transformation, Neoplastic / chemically induced*
  • Chick Embryo
  • Chorioallantoic Membrane / blood supply
  • Chorioallantoic Membrane / drug effects
  • Dose-Response Relationship, Drug
  • Epithelial Cells / drug effects*
  • Epithelial Cells / enzymology
  • Epithelial Cells / metabolism
  • Epithelial Cells / pathology
  • Female
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / biosynthesis*
  • MAP Kinase Signaling System / drug effects*
  • Mice
  • Microscopy, Fluorescence
  • Neoplasm Transplantation
  • Neovascularization, Pathologic / chemically induced*
  • Neovascularization, Pathologic / enzymology
  • Neovascularization, Pathologic / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Reactive Oxygen Species / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors
  • Vascular Endothelial Growth Factor A / biosynthesis*

Substances

  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Reactive Oxygen Species
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A
  • Cadmium
  • Proto-Oncogene Proteins c-akt