Cadmium Induces Migration of Colon Cancer Cells: Roles of Reactive Oxygen Species, P38 and Cyclooxygenase-2

Cell Physiol Biochem. 2019;52(6):1517-1534. doi: 10.33594/000000106.

Abstract

Background/aims: Cadmium (Cd) is a heavy metal contaminant whose toxicity is associated with colorectal cancer (CRC). However, the underlying molecular mechanisms of Cd-induced CRC malignancy remain obscure.

Methods: A monolayer scratch assay was employed to assess the migration of HT-29 human adenocarcinoma cells. Luciferase reporter assay was used to determine cyclooxygenase-2 (COX-2) transcriptional activity, and Western blotting was used to detect p38 Mitogen Activated Protein Kinase (MAPK) and Akt phosphorylation as well as COX-2 expression. Prostaglandin E2 (PGE2) levels were measured using Enzyme Linked Immunosorbent Assay (ELISA) and reactive oxygen species (ROS) formation was assessed using dihydroethidium (DHE) stain.

Results: Here, we show that Cd potentiates the migratory capacity of HT-29 CRC cells. Cd caused a time-dependent increase in COX-2 expression. Celecoxib, a COX-2 selective inhibitor, significantly reduced Cd-induced migration. Cd also increased levels of ROS and phosphorylated p38. Importantly, Cd-induced COX-2 expression and migration were significantly abolished by N-Acetyl-Cysteine (NAC), a ROS scavenger, or SB202190, a specific p38 inhibitor. Furthermore, Cd-induced p38 phosphorylation was inhibited by NAC. Cd (100 nM) also increased PGE2 levels, which was abrogated by NAC, SB202190, or celecoxib. Exogenous PGE2 significantly potentiated cell migration. Cd caused a significant increase in Akt phosphorylation in a ROS-mediated pathway. Moreover, Cd-induced migration was significantly attenuated by LY294 002, a phosphatidylinositol-3-kinase inhibitor.

Conclusion: Taken together, our results suggest that exposure to low levels of Cd promotes a more migratory cancer phenotype in a ROS-p38-COX-2-PGE2 pathway as well as ROS-Akt pathway. Therefore, COX-2, PGE2 receptors or Akt represent potential targets in the treatment of CRC, particularly in patients exposed to Cd.

Keywords: COX-2; Cadmium; Colorectal cancer; Environmental pollution.

MeSH terms

  • Adenocarcinoma / chemically induced*
  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism
  • Adenocarcinoma / pathology
  • Cadmium / toxicity*
  • Cell Movement / drug effects
  • Colonic Neoplasms / chemically induced*
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism*
  • Enzyme Activation / drug effects
  • HT29 Cells
  • Humans
  • Reactive Oxygen Species / metabolism*
  • Transcriptional Activation / drug effects
  • p38 Mitogen-Activated Protein Kinases / metabolism*

Substances

  • Reactive Oxygen Species
  • Cadmium
  • Cyclooxygenase 2
  • p38 Mitogen-Activated Protein Kinases