Published on

  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  1. 1. mTOR: a new pathway to target in oncology Madlaina Breuleux, PhD Novartis Phrma AG Basel, Switzerland
  2. 2. The mTOR pathway and cancer • A high molecular weight serine-threonine kinase • Senses and responds to cellular nutrient and energy levels • Influences protein translation regulating G1 progression, S-phase entry, and ultimately cell growth and proliferation • Functions downstream of the PI3 kinase / AKT pathway, which is often deregulated in human cancer • mTOR pathway deregulation causes loss of growth control in cancer mTOR (mammalian “Target Of Rapamycin”):
  3. 3. mTOR: A central controller of tumor cell growth
  4. 4. mTOR: A controller of angiogenic processes
  5. 5. RAD001 (Everolimus): An oral mTOR pathway inhibitor • Broad antiproliferative and antitumor properties Model of RAD001 binding to intracellular receptor (FKBP-12) to form complex inhibiting mTOR pathway Inhibits the mTOR pathway • Sensor of physiological signals • “Downstream“ of PI3K / AKT pathway • RAD001 activity associated with overactivation of the PTEN / PI3K / AKT pathway Inhibits tumor cell growth • Delays G1/S phase progression • Sensitises tumor cells to targeted and chemotherapeutic agents • Anti-angiogenic properties • Direct and indirect activity • Phase IB/II clinical trials in oncology
  6. 6. p-AKT levels correlate with RAD001 sensitivity
  7. 7. RAD001: Broad in vivo antitumor activity
  8. 8. mTOR inhibition decreases angiogenesis • mTOR regulates HIF-1α and HIF-2α expression (transcription factors mediating hypoxia-induced gene expression) • HIF-1α/2α are normally degraded by VHL protein • HIF-1 and HIF-2 condition the tumor to adapt to growth under hypoxic conditions and promote angiogenesis and metastasis HIF = hypoxia-inducible factor; VHL = von Hippel-Lindau protein.
  9. 9. Evidence of antiangiogenic activity • Tumor xenograft–bearing mice: single 5 mg/kg oral dose – RAD001 plasma levels never exceed the in vitro IC50 for HCT116 (colon) or KB-31 (epidermoid) tumor cells – However, both HCT116 and KB-31 xenografts are sensitive to RAD001 in vivo at this dose – RAD001 levels exceed the in vitro IC50 for VEGF- or FGF-stimulated human umbilical vein endothelial cultures (HUVECs) • RAD001 inhibits tumor cell VEGF production in vitro and decreases tumor and plasma VEGF levels in animal models • RAD001 selectively inhibits VEGF-dependent angiogenic response in vivo, and reduces microvessel density in tumors derived from sensitive or resistant cell lines • These data suggest an antiangiogenic effect against tumors
  10. 10. RAD001 reduces microvessel density (B16/BL6) Vehicle Controls RAD001 Significant reduction in microvessel density following RAD001 treatment in primary tumor and cranial lymphnode metastases (shown)
  11. 11. RAD001: Combination potential • Chemotherapeutics – DNA-damaging agents (i.e. cisplatin, temozolomide) – Topoisomerase inhibitors (i.e. doxorubicin) – MT active agents (i.e. Taxol) • Targeted therapeutics – ErbB inhibitors (i.e. AEE788; trastuzumab) – Estrogen antagonists - aromatase inhibitors (i.e. letrozole) – BCR-ABL, Kit inhibitors (i.e. imatinib) – VEGFR inhibitors (i.e. PTK787) – IGF-1R inhibitors (i.e. AEW541) • Radiotherapy Although RAD001 has antiproliferative activity as a monotherapy, its potential may be better realized in combination with other therapeutic agents
  12. 12. Combinations with cisplatin (in RAD001-sensitive H596 NSCLC xenografts) * P < 0.05 versus controls by the Dunnett test. Combinations of RAD001 and low-dose cisplatin elicit a more potent antitumor effect than either agent alone (also in model derived from resistant line) Tumor Volumes Body Weights
  13. 13. Cisplatin combinations: Potentiate cell death (A549 cells: cell death with sub-optimal cisplatin concentrations) * Significant fold induction with P < 0.05, t-tests; two-way ANOVA indicates highly significant interaction between RAD001 and cisplatin P < 0.001.
  14. 14. Cell death is dependent on p53 status * Significant fold induction with P < 0.05, t-tests.
  15. 15. The p53/p21 response Beuvink et al. Cell. 2005;120:747-759. • DNA damage (i.e cisplatin treatment) activates p53. • In the presence of extensive DNA damage, p53 initiates a cell death program. • In the presence of sub-optimal DNA damage, p53 induces p21 expression, a cell cycle inhibitor, allows DNA repair (and cell survival). • RAD001 inhibits p21 expression forcing tumor cell death even at suboptimal cisplatin concentrations (non-lethal DNA damage)
  16. 16. Rationale for combination with letrozole • Akt activation predicts a worse outcome for breast cancer patients treated with endocrine therapy. • Activated Akt mediates resistance to antiestrogen therapy (related to HER2 overexpression). • mTOR inhibition restores responses to tamoxifen in breast cancer models with high levels of Akt activity. • Synergistic in vitro and in vivo effects have been seen with combined antiestrogen therapy and mTOR inhibition.
  17. 17. Inhibition of estrogen-induced proliferation (aromatase-expressing MCF7 cells) Highly significant interactions ( p < 0.001; two-way ANOVA) Synergistic effects (isobologram analysis) Also in aromatase-expressing T47D cells
  18. 18. Potential RADIANT Trials Decreased cell viability as compared to single agents (YOPRO:  p < 0.01; two-way ANOVA). Defined as apoptosis (TUNEL:  p < 0.05; Friedman Test). Also in aromatase-expressing T47D cells TUNEL YOPRO
  19. 19. Summary • mTOR acts as a central regulator of tumor cell growth and survival, and activation of the PI3K/AKT pathway may predict tumor response to mTOR inhibition. • RAD001 exhibits a broad antitumor activity, and inhibits elements of the angiogenic process. • Combination therapy targeting mTOR and other targets/processes deregulated in human cancer may provide enhanced anticancer activity. Targeting deregulated pathways has been a successful clinical strategy in cancer.