Inhibition of mTOR and HIF pathways diminishes chondro-osteogenesis and cell proliferation in chondroblastoma

Tumour Biol. 2013 Oct;34(5):3111-9. doi: 10.1007/s13277-013-0879-8. Epub 2013 Jun 13.

Abstract

Chondroblastoma (CBL) is a benign bone tumor occurring mostly in teenagers. Despite this, CBL can recur and metastasize after curettage, which may impede normal epiphysis. In search of a novel targeted therapy for CBL, we aimed at BMP-2, a factor critical for chondro-osteogenesis and chondrocyte proliferation. Two pathways upstream of BMP-2, the mTOR and HIF, were targeted with rapamycin (Rapa) and FM19G11 (FM), respectively. Using immunohistochemistry, we found BMP-2 was highly expressed in CBL tissues. CBL cells explanted and confirmed with higher BMP-2 level than normal cartilage. Protumorigenic effect of Rapa and FM on CBL cells were transduced via BMP-2. Combination of Rapa and FM conferred stronger inhibition of cell proliferation than either monotherapy and inhibited levels of chondro-osteogenic markers (Sox9, aggrecan, and type II collagen). To minimize the adverse effect of Rapa, we performed screening in essential amino acids and found leucine deprivation-sensitized CBL cells to Rapa. Combination treatment of low dose Rapa, FM, and leucine deprivation conferred compatible inhibitory effects on CBL cell proliferation, chondro-osteogenic potential, and tumorigenic capacity. We conclude that targeting BMP-2 using mTOR/HIF inhibition could potently curb the disease. Addition of low-leucine diet could lower the dose of rapamycin in chase for less toxicity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Antibiotics, Antineoplastic / pharmacology*
  • Benzamides / pharmacology*
  • Bone Morphogenetic Protein 2 / genetics
  • Bone Morphogenetic Protein 2 / metabolism
  • Cell Proliferation / drug effects*
  • Chondroblastoma / drug therapy*
  • Chondrogenesis / drug effects
  • Down-Regulation
  • Female
  • Gene Expression
  • Gene Knockdown Techniques
  • Humans
  • Hypoxia-Inducible Factor 1 / antagonists & inhibitors
  • Hypoxia-Inducible Factor 1 / metabolism
  • Leucine / metabolism
  • Male
  • Osteogenesis / drug effects
  • Sirolimus / pharmacology*
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / metabolism
  • Tissue Culture Techniques
  • Tumor Cells, Cultured / drug effects
  • Young Adult

Substances

  • Antibiotics, Antineoplastic
  • BMP2 protein, human
  • Benzamides
  • Bone Morphogenetic Protein 2
  • FM19G11
  • Hypoxia-Inducible Factor 1
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Leucine
  • Sirolimus