Synergistic effects of methylnaltrexone with 5-fluorouracil and bevacizumab on inhibition of vascular endothelial growth factor-induced angiogenesis.

Abstract

Many patients with cancer receive combinations of drug treatments that include 5-fluorouracil (5-FU) and bevacizumab. Therapeutic doses of 5-FU are often associated with unwanted side effects, and bevacizumab is costly. Therefore, we explored potential agents that can reduce the therapeutic concentration of these drugs. Our data indicate that methylnaltrexone (MNTX), a peripheral antagonist of the mu-opioid receptor, exerts a synergistic effect with 5-FU and bevacizumab on inhibition of vascular endothelial growth factor (VEGF)-induced human pulmonary microvascular endothelial cell (EC) proliferation and migration, two key components in cancer-associated angiogenesis. MNTX inhibited EC proliferation with an IC(50) of approximately 100 nmol/L. Adding 100 nmol/L MNTX to EC shifted the IC(50) of 5-FU from approximately 5 micromol/L to approximately 7 nmol/L. Further, adding 50 ng/mL MNTX shifted the IC(50) of bevacizumab on inhibition of EC migration from approximately 25 to approximately 6 ng/mL. These synergistic effects were not observed with naltrexone, a tertiary mu-opioid receptor antagonist. On a mechanistic level, we observed that treatment of human EC with MNTX, but not naltrexone, increased receptor protein tyrosine phosphatase mu activity, which was independent of mu-opioid receptor expression. Silencing receptor protein tyrosine phosphatase mu expression (small interfering RNA) in human EC inhibited both synergy between MNTX and bevacizumab or 5-FU and increased VEGF-induced tyrosine phosphorylation of Src and p190 RhoGAP with enhanced activation of Akt and the actin cytoskeletal regulatory protein, RhoA, whereas silencing Src, Akt, or RhoA blocked VEGF-induced angiogenic events. Therefore, addition of MNTX could potentially lower the therapeutic doses of 5-FU and bevacizumab, which could improve index.

• Authors: Patrick A Singleton, Joe G N Garcia, Jonathan Moss
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 7 Issue 6 Pg. 1669-79 (Jun 2008) ISSN: 1535-7163 [Print] United States
• PMID: 18566238 (Publication Type: Journal Article)

Chemical References

• ARHGAP35 protein, human
• Antibodies, Monoclonal
• Antibodies, Monoclonal, Humanized
• Guanine Nucleotide Exchange Factors
• Quaternary Ammonium Compounds
• Repressor Proteins
• Vascular Endothelial Growth Factor A
• methylnaltrexone
• Bevacizumab
• Naltrexone
• Proto-Oncogene Proteins pp60(c-src)
• Proto-Oncogene Proteins c-akt
• Receptor-Like Protein Tyrosine Phosphatases, Class 2
• rhoA GTP-Binding Protein
• Fluorouracil

Topics

• Antibodies, Monoclonal (pharmacology)
• Antibodies, Monoclonal, Humanized
• Bevacizumab
• Cell Movement (drug effects)
• Cell Proliferation (drug effects)
• Cells, Cultured
• Drug Synergism
• Endothelial Cells (cytology, drug effects, enzymology)
• Enzyme Activation (drug effects)
• Fluorouracil (pharmacology)
• Guanine Nucleotide Exchange Factors (metabolism)
• Humans
• Models, Biological
• Naltrexone (analogs & derivatives, pharmacology)
• Neovascularization, Physiologic (drug effects)
• Proto-Oncogene Proteins c-akt (metabolism)
• Proto-Oncogene Proteins pp60(c-src) (antagonists & inhibitors)
• Quaternary Ammonium Compounds (pharmacology)
• Receptor-Like Protein Tyrosine Phosphatases, Class 2 (metabolism)
• Repressor Proteins (metabolism)
• Vascular Endothelial Growth Factor A (pharmacology)
• rhoA GTP-Binding Protein (metabolism)