title: PI3K-mTOR Pathway Inhibition Exhibits Efficacy Against High-grade Glioma in Clinically Relevant Mouse Models.
abstract: Purpose:The PI3K-AKT-mTOR signaling pathway is frequently activated in glioblastoma and offers several druggable targets. However, clinical efficacy of PI3K/mTOR inhibitors in glioblastoma has not yet been demonstrated. Insufficient drug delivery may limit the efficacy of PI3K/mTOR inhibitors against glioblastoma. The presence of the efflux transporters ABCB1/Abcb1 (P-glycoprotein, MDR1) and ABCG2/Abcg2 (BCRP) at the blood-brain barrier (BBB) restricts the brain penetration of many drugs.Experimental Design:We usedin vitrodrug transport assays and performed pharmacokinetic/pharmacodynamic studies in wild-type and ABC-transporter knockout mice. The efficacy of PI3K-mTOR inhibition was established using orthotopic allograft and genetically engineered spontaneous glioblastoma mouse models.Results:The mTOR inhibitors rapamycin and AZD8055 are substrates of ABCB1, whereas the dual PI3K/mTOR inhibitor NVP-BEZ235 and the PI3K inhibitor ZSTK474 are not. Moreover, ABCG2 transports NVP-BEZ235 and AZD8055, but not ZSTK474 or rapamycin. Concordantly,Abcb1a/b-/-;Abcg2-/-mice revealed increased brain penetration of rapamycin (13-fold), AZD8055 (7.7-fold), and NVP-BEZ235 (4.5-fold), but not ZSTK474 relative to WT mice. Importantly, ABC transporters limited rapamycin brain penetration to subtherapeutic levels, while the reduction in NVP-BEZ235 brain penetration did not prevent target inhibition. NVP-BEZ235 and ZSTK474 demonstrated antitumor efficacy with improved survival against U87 orthotopic gliomas, although the effect of ZSTK474 was more pronounced. Finally, ZSTK474 prolonged overall survival in Cre-LoxP conditional transgenicPten;p16Ink4a/p19Arf;K-Rasv12;LucRmice, mainly by delaying tumor onset.Conclusions:PI3K/mTOR inhibitors with weak affinities for ABC transporters can achieve target inhibition in brain (tumors), but have modest single-agent efficacy and combinations with (BBB penetrable) inhibitors of other activated pathways may be required.Clin Cancer Res; 23(5); 1286-98. ©2016 AACR.
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands.
authors.forename: Fan
authors.initials: F
authors.lastname: Lin
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands.
authors.forename: Mark C
authors.initials: MC
authors.lastname: de Gooijer
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands.
authors.forename: Diana
authors.initials: D
authors.lastname: Hanekamp
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands.
authors.forename: Gayathri
authors.initials: G
authors.lastname: Chandrasekaran
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands.
authors.forename: Levi C M
authors.initials: LC
authors.lastname: Buil
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands.
authors.forename: Nishita
authors.initials: N
authors.lastname: Thota
authors.affiliation: Department of Pharmacy and Pharmacology, The Netherlands Cancer Institute/Slotervaart Hospital, Amsterdam, the Netherlands.
authors.forename: Rolf W
authors.initials: RW
authors.lastname: Sparidans
authors.affiliation: Department of Pharmacy and Pharmacology, The Netherlands Cancer Institute/Slotervaart Hospital, Amsterdam, the Netherlands.|Faculty of Science, Department of Pharmaceutical Sciences, Division of Pharmacoepidemiology & Clinical Pharmacology, Utrecht University, Utrecht, the Netherlands.
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
authors.affiliation: Neuro-oncology Research Group, Departments of Neurosurgery and Pediatric Oncology/Hematology, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, the Netherlands.|Molecular Neurogenetics Unit, Departments of Neurology and Radiology, Massachusetts General Hospital, and Neuroscience Program, Harvard Medical School, Boston, Massachusetts.
authors.forename: Tom
authors.initials: T
authors.lastname: Würdinger
authors.affiliation: Department of Bio-Pharmacology/Mouse Cancer Clinic, The Netherlands Cancer Institute (Antoni van Leeuwenhoek Hospital), Amsterdam, the Netherlands. o.v.tellingen@nki.nl.
authors.forename: Olaf
authors.initials: O
authors.lastname: van Tellingen
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2 / Q000235:genetics*; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects; D005260:Female; D005910:Glioma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage; D051379:Mice; D018345:Mice, Knockout; D009025:Morpholines / Q000008:administration & dosage; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011804:Quinolines / Q000008:administration & dosage; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000008:administration & dosage; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics*; D014227:Triazines / Q000008:administration & dosage
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D007093:Imidazoles; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011804:Quinolines; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D014227:Triazines; C501412:Abcg2 protein, mouse; C510150:ZSTK474; C546624:(5-(2,4-bis((3S)-3-methylmorpholin-4-yl)pyrido(2,3-d)pyrimidin-7-yl)-2-methoxyphenyl)methanol; C546842:MTOR protein, human; C531198:dactolisib