Activated mammalian target of rapamycin pathway in the pathogenesis of tuberous sclerosis complex renal tumors

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Heidi L Kenerson1, Lauri D Aicher, Lawrence D True

  • 1Department of Surgery, University of Washington, Seattle 98195, USA.

Cancer Research
|October 18, 2002
PubMed

Insights

Tuberous sclerosis complex (TSC) involves tumors caused by TSC1/TSC2 gene disruption. This study shows mTOR pathway activation in TSC tumors, with rapamycin effectively reducing tumor growth in preclinical models.

Area of Science:

  • Oncology
  • Molecular Biology
  • Genetics

Background:

  • Tuberous sclerosis complex (TSC) is a genetic disorder characterized by tumor formation in multiple organs due to TSC1 or TSC2 gene mutations.
  • Recent research links TSC gene products to phosphoinositide 3-kinase (PI3K) signaling pathways.
  • Tuberin (TSC2 protein) phosphorylation by Akt releases its inhibition on p70S6K upon growth factor stimulation.

Purpose of the Study:

  • To investigate the role of the mammalian target of rapamycin (mTOR) pathway in TSC-associated renal pathology.
  • To evaluate the efficacy of mTOR inhibition using rapamycin in a preclinical model of TSC.

Main Methods:

  • Analysis of phosphorylated mTOR and its downstream effectors (p70S6K, S6 ribosomal protein, 4E-BP1, eIF4G) in primary tumors from TSC patients and the Eker rat model.
  • Short-term administration of rapamycin to Eker rats to assess tumor response.
  • Evaluation of apoptosis, cell proliferation, and levels of cyclin D1 and p27.

Main Results:

  • Elevated levels of phosphorylated mTOR and its effectors were observed in TSC tumors.
  • Rapamycin treatment in Eker rats led to significant tumor reduction, increased apoptosis, and decreased cell proliferation.
  • Surprisingly, rapamycin treatment did not significantly alter cyclin D1 and p27 levels.

Conclusions:

  • The mTOR pathway is aberrantly activated in TSC renal pathology.
  • Rapamycin demonstrates preclinical efficacy in treating TSC by inhibiting the mTOR pathway.
  • Further investigation into the specific mechanisms of rapamycin's effect on TSC tumor progression is warranted.

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