PDE5 inhibitors enhance tumor permeability and efficacy of chemotherapy in a rat brain tumor model

Brain Res. 2008 Sep 16;1230:290-302. doi: 10.1016/j.brainres.2008.06.122. Epub 2008 Jul 14.


The blood-brain tumor barrier (BTB) significantly limits delivery of therapeutic concentrations of chemotherapy to brain tumors. A novel approach to selectively increase drug delivery is pharmacologic modulation of signaling molecules that regulate BTB permeability, such as those in cGMP signaling. Here we show that oral administration of sildenafil (Viagra) and vardenafil (Levitra), inhibitors of cGMP-specific PDE5, selectively increased tumor capillary permeability in 9L gliosarcoma-bearing rats with no significant increase in normal brain capillaries. Tumor-bearing rats treated with the chemotherapy agent, adriamycin, in combination with vardenafil survived significantly longer than rats treated with adriamycin alone. The selective increase in tumor capillary permeability appears to be mediated by a selective increase in tumor cGMP levels and increased vesicular transport through tumor capillaries, and could be attenuated by iberiotoxin, a selective inhibitor for calcium-dependent potassium (K(Ca)) channels, that are effectors in cGMP signaling. The effect by sildenafil could be further increased by simultaneously using another BTB "opener", bradykinin. Collectively, this data demonstrates that oral administration of PDE5 inhibitors selectively increases BTB permeability and enhances anti-tumor efficacy for a chemotherapeutic agent. These findings have significant implications for improving delivery of anti-tumor agents to brain tumors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / therapeutic use*
  • Autoradiography
  • Blood Pressure / drug effects
  • Brain Chemistry / drug effects
  • Brain Neoplasms / drug therapy*
  • Brain Neoplasms / metabolism*
  • Brain Neoplasms / pathology
  • Capillaries / pathology
  • Capillary Permeability / drug effects
  • Cyclic GMP / blood
  • Cyclic GMP / metabolism
  • Female
  • Glioma / drug therapy*
  • Glioma / metabolism*
  • Glioma / pathology
  • Imidazoles / pharmacology
  • Microscopy, Electron, Transmission
  • Neovascularization, Pathologic / pathology
  • Phosphodiesterase 5 Inhibitors*
  • Phosphodiesterase Inhibitors / pharmacology*
  • Piperazines / pharmacology
  • Purines / pharmacology
  • Rats
  • Rats, Inbred F344
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sildenafil Citrate
  • Sucrose / metabolism
  • Sulfones / pharmacology
  • Survival Analysis
  • Tight Junctions / drug effects
  • Tight Junctions / ultrastructure
  • Triazines / pharmacology
  • Vardenafil Dihydrochloride


  • Antineoplastic Agents
  • Imidazoles
  • Phosphodiesterase 5 Inhibitors
  • Phosphodiesterase Inhibitors
  • Piperazines
  • Purines
  • Sulfones
  • Triazines
  • Sucrose
  • Vardenafil Dihydrochloride
  • Sildenafil Citrate
  • Cyclic GMP