Induction of Macrophage Migration Inhibitory Factor by Lysophosphatidic Acid: Relevance to Tumor Growth and Angiogenesis

Int J Mol Med. 2003 Oct;12(4):633-41.

Abstract

Macrophage migration inhibitory factor (MIF) plays an important role not only in the immune system, but also in tumorigenesis. Lysophosphatidic acid (LPA), a unique lipid mediator, shares several biological functions with MIF, including promotion of tumor cell growth and associated angiogenesis. In this study, we investigated the signaling cross-talk between these two molecules during tumorigenesis and angiogenesis. We first examined the expression of MIF mRNA on a murine colon cancer cell line, colon 26, by LPA. We found that LPA enhanced the expression of MIF mRNA in a dose-dependent manner in vitro. In parallel, LPA stimulated cell growth and up-regulated the vascular endothelial growth factor (VEGF). These effects were dramatically blocked by 21 base double strand (ds) RNA specific for mouse MIF mRNA (RNAi). In vivo, colon 26 cells treated with MIF dsRNA were injected into the backs of mice. The size of tumor volumes became significantly smaller than that of controls. Angiogenesis examined by a Millipore chamber method was also suppressed by the MIF dsRNA. Next, we evaluated the signal transduction pathway relevant to the mitogen-activated protein kinase (MAPK) and Akt/PI3K pathways in response to LPA by RNAi. Ras activation and phosphorylation of Akt and ERK1/2 were strongly suppressed by the dsRNA. On the other hand, tyrosine phosphorylation was minimally changed by the treatment. Taken together, these results suggest that MIF could promote both tumor cell growth and angiogenesis induced by LPA via both the Ras-MAPK and Ras-Akt/PI3K signaling pathways.

MeSH terms

  • Animals
  • Cell Division
  • Cell Line, Tumor
  • Cyclin D1 / metabolism
  • DNA / metabolism
  • Dose-Response Relationship, Drug
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Immunoblotting
  • Lysophospholipids / metabolism*
  • Macrophage Migration-Inhibitory Factors / physiology*
  • Mice
  • Mice, Inbred BALB C
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / metabolism
  • Neovascularization, Pathologic*
  • Phosphorylation
  • RNA Interference
  • RNA, Double-Stranded / chemistry
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Time Factors
  • Transfection
  • Tyrosine / metabolism
  • Up-Regulation
  • Vascular Endothelial Growth Factor A / metabolism
  • ras Proteins / metabolism

Substances

  • Lysophospholipids
  • Macrophage Migration-Inhibitory Factors
  • RNA, Double-Stranded
  • RNA, Messenger
  • Vascular Endothelial Growth Factor A
  • Cyclin D1
  • Tyrosine
  • DNA
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • ras Proteins
  • lysophosphatidic acid