title: Vertical targeting of the phosphatidylinositol-3 kinase pathway as a strategy for treating melanoma.
abstract: OBJECTIVE
  Melanoma is relatively resistant to chemotherapy; improved targeting of molecules critical for cell proliferation and survival are needed. Phosphatidylinositol-3 kinase (PI3K) is an important target in melanoma; however, activity of PI3K inhibitors (PI3KI) is limited. Our purpose was to assess mTOR as a cotarget for PI3K.
  
  
  METHODS
  Using a method of quantitative immunofluorescence to measure mTOR expression in a large melanoma cohort, we studied associations with PI3K subunits, p85 and p110α. We assessed addition of the mTOR inhibitor rapamycin to 2 PI3KIs, NVP-BKM120 and LY294002. We studied in vitro activity of a novel dual PI3K/mTOR inhibitor NVP-BEZ235 and activity of the combination of NVP-BEZ235 and the MAP/ERK kinase (MEK) inhibitor AZD6244.
  
  
  RESULTS
  Strong coexpression of mTOR and p110α was observed (ρ = 0.658; P < 0.0001). Less coexpression was seen with p85 (ρ = 0.239; P < 0.0001). Strong synergism was shown between rapamycin and both PI3KIs. Activity of both PI3KIs was similarly enhanced with all rapamycin concentrations used. The dual PI3K/mTOR inhibitor effectively inhibited viability in 23 melanoma cell lines (IC(50) values in the nanomolar range), regardless of B-Raf mutation status, with resultant reduction in clonogenicity and downregulation of pAkt and pP70S6K. Synergism was seen when combining NVP-BEZ235 and AZD6244, with resultant increases in poly(ADP-ribose) polymerase and caspase-2 cleavage.
  
  
  CONCLUSIONS
  mTOR and p110α are coexpressed in melanoma. Rapamycin concentrations as low as 1 nmol/L enhance activity of PI3KIs. The dual PI3K/mTOR inhibitor NVP-BEZ235 is highly active in melanoma cells in vitro, suggesting that concurrent PI3K and mTOR targeting in melanoma warrants further investigation, both alone and in combination with MEK inhibitors.
authors.affiliation: Department of Pathology, Yale University School of Medicine, Yale Cancer Center, New Haven, Connecticut 06510, USA.
authors.forename: Saadia A
authors.initials: SA
authors.lastname: Aziz
authors.forename: Lucia B
authors.initials: LB
authors.lastname: Jilaveanu
authors.forename: Christopher
authors.initials: C
authors.lastname: Zito
authors.forename: Robert L
authors.initials: RL
authors.lastname: Camp
authors.forename: David L
authors.initials: DL
authors.lastname: Rimm
authors.forename: Patricia
authors.initials: P
authors.lastname: Conrad
authors.forename: Harriet M
authors.initials: HM
authors.lastname: Kluger
mesh_terms: D001562:Benzimidazoles / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D045744:Cell Line, Tumor; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D008545:Melanoma / Q000188:drug therapy* / Q000378:metabolism; D058990:Molecular Targeted Therapy / Q000379:methods*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D011804:Quinolines / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D015398:Signal Transduction / Q000502:physiology; D012878:Skin Neoplasms / Q000188:drug therapy / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D046888:Tissue Array Analysis
chemical_list: C517975:AZD 6244; D001562:Benzimidazoles; D007093:Imidazoles; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011804:Quinolines; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; C531198:dactolisib