mTOR and MEK1/2 inhibition differentially modulate tumor growth and the immune microenvironment in syngeneic models of oral cavity cancer

Oncotarget. 2015 Nov 3;6(34):36400-17. doi: 10.18632/oncotarget.5063.


We investigated the effects of mTOR and MEK1/2 inhibition on tumor growth and the tumor microenvironment in immunogenic and poorly immunogenic models of murine oral cancer. In vitro, rapamycin and PD901 inhibited signaling through expected downstream targets, but only PD901 reduced viability and altered function of MOC cells. Following transplantation of MOC cells into immune-competent mice, effects on both cancer and infiltrating immune cells were characterized following rapamycin and/or PD901 treatment for 21 days. In vivo, both rapamycin and PD901 inhibition reduced primary growth of established MOC tumors on treatment. Following withdrawal of PD901, rapid rebound of tumor growth limited survival, whereas durable tumor control was observed following rapamycin treatment in immunogenic MOC1 tumors despite more robust inhibition of oncogenic signaling by PD901. Characterization of the immune microenvironment revealed diminished infiltration and activation of antigen-specific CD8+ T-cells and other immune cells following PD901 but not rapamycin in immunogenic tumors. Subsequent in vitro T-cell assays validated robust inhibition of T-cell expansion and activation following MEK inhibition compared to mTOR inhibition. CD8 cell depletion abrogated rapamycin-induced primary tumor growth inhibition in MOC1 mice. These data have critical implications in the design of combination targeted and immune therapies in oral cancer.

Keywords: animal models of cancer; head and neck/oral cancers; immunomodulation; inflammation and tumor development; signal transduction pathways.

Publication types

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

MeSH terms

  • Animals
  • Female
  • MAP Kinase Kinase 1 / antagonists & inhibitors*
  • MAP Kinase Kinase 1 / metabolism
  • MAP Kinase Kinase 2 / antagonists & inhibitors*
  • MAP Kinase Kinase 2 / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mouth Neoplasms / drug therapy*
  • Mouth Neoplasms / enzymology
  • Mouth Neoplasms / metabolism
  • Protein Kinase Inhibitors / pharmacology*
  • Signal Transduction / drug effects
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • TOR Serine-Threonine Kinases / metabolism
  • Tumor Microenvironment


  • Protein Kinase Inhibitors
  • mTOR protein, mouse
  • TOR Serine-Threonine Kinases
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • Map2k1 protein, mouse
  • Map2k2 protein, mouse
  • Sirolimus