P70S6K and Elf4E dual inhibition is essential to control bladder tumor growth and progression in orthotopic mouse non-muscle invasive bladder tumor model

J Korean Med Sci. 2015 Mar;30(3):308-16. doi: 10.3346/jkms.2015.30.3.308. Epub 2015 Feb 16.

Abstract

We investigated how the dual inhibition of the molecular mechanism of the mammalian target of the rapamycin (mTOR) downstreams, P70S6 kinase (P70S6K) and eukaryotic initiation factor 4E (eIF4E), can lead to a suppression of the proliferation and progression of urothelial carcinoma (UC) in an orthotopic mouse non-muscle invasive bladder tumor (NMIBT) model. A KU-7-luc cell intravesically instilled orthotopic mouse NMIBC model was monitored using bioluminescence imaging (BLI) in vivo by interfering with different molecular components using rapamycin and siRNA technology. We then analyzed the effects on molecular activation status, cell growth, proliferation, and progression. A high concentration of rapamycin (10 µM) blocked both P70S6K and elF4E phosphorylation and inhibited cell proliferation in the KU-7-luc cells. It also reduced cell viability and proliferation more than the transfection of siRNA against p70S6K or elF4E. The groups with dual p70S6K and elF4E siRNA, and rapamycin reduced tumor volume and lamina propria invasion more than the groups with p70S6K or elF4E siRNA instillation, although all groups reduced photon density compared to the control. These findings suggest that both the mTOR pathway downstream of eIF4E and p70S6K can be successfully inhibited by high dose rapamycin only, and p70S6K and Elf4E dual inhibition is essential to control bladder tumor growth and progression.

Keywords: Mouse Orthotopic Model; Urinary Bladder Neoplasms; mTOR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Proliferation / drug effects
  • Cell Proliferation / genetics
  • Cell Survival / drug effects
  • Disease Progression
  • Eukaryotic Initiation Factor-4E / antagonists & inhibitors*
  • Eukaryotic Initiation Factor-4E / genetics
  • Female
  • Mice
  • Mice, Nude
  • Mucous Membrane / pathology
  • Phosphorylation / drug effects
  • RNA Interference
  • RNA, Small Interfering
  • Ribosomal Protein S6 Kinases, 70-kDa / antagonists & inhibitors*
  • Ribosomal Protein S6 Kinases, 70-kDa / genetics
  • Signal Transduction / drug effects
  • Sirolimus / pharmacology*
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • TOR Serine-Threonine Kinases / metabolism
  • Urinary Bladder Neoplasms / genetics
  • Urinary Bladder Neoplasms / pathology*
  • Urothelium / pathology

Substances

  • Eukaryotic Initiation Factor-4E
  • RNA, Small Interfering
  • eIF4E protein, mouse
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Sirolimus