Active efflux of Dasatinib from the brain limits efficacy against murine glioblastoma: broad implications for the clinical use of molecularly targeted agents.
The importance of the blood-brain barrier in preventing effective pharmacotherapy of glioblastoma has been controversial. The controversy stems from the fact that vascular endothelial cell tight junctions are disrupted in the tumor, allowing some systemic drug delivery. P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) efflux drugs from brain capillary endothelial cells into the blood. We tested the hypothesis that although the tight junctions are "leaky" in the core of glioblastomas, active efflux limits drug delivery to tumor-infiltrated normal brain and consequently, treatment efficacy. Malignant gliomas were induced by oncogene transfer into wild-type (WT) mice or mice deficient for Pgp and BCRP (knockout, KO). Glioma-bearing mice were orally dosed with dasatinib, a kinase inhibitor and dual BCRP/PgP substrate that is being currently tested in clinical trials. KO mice treated with dasatinib survived for twice as long as WT mice. Microdissection of the tumor core, invasive rim, and normal brain revealed 2- to 3-fold enhancement in dasatinib brain concentrations in KO mice relative to WT. Analysis of signaling showed that poor drug delivery correlated with the lack of inhibition of a dasatinib target, especially in normal brain. A majority of human glioma xenograft lines tested expressed BCRP or PgP and were sensitized to dasatinib by a dual BCRP/Pgp inhibitor, illustrating a second barrier to drug delivery intrinsic to the tumor itself. These data show that active efflux is a relevant obstacle to treating glioblastoma and provide a plausible mechanistic basis for the clinical failure of numerous drugs that are BCRP/Pgp substrates.
Corresponding Author: John Ohlfest, Department of Pediatrics, University of Minnesota, 420 Delaware St. SE, MMC 366, Minneapolis, MN 55455, USA.
Sagar
S
Agarwal
Rajendar K
RK
Mittapalli
David M
DM
Zellmer
Jose L
JL
Gallardo
Randy
R
Donelson
Charlie
C
Seiler
Stacy A
SA
Decker
Karen S
KS
Santacruz
Jenny L
JL
Pokorny
Jann N
JN
Sarkaria
William F
WF
Elmquist
John R
JR
Ohlfest
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism; D000166:Acridines / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D000069439:Dasatinib; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005909:Glioblastoma / Q000098:blood supply / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D058990:Molecular Targeted Therapy; D009857:Oncogenes; D010539:Permeability / Q000187:drug effects; D011743:Pyrimidines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use*; D015398:Signal Transduction / Q000187:drug effects; D016019:Survival Analysis; D044005:Tetrahydroisoquinolines / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D013844:Thiazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use*; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D014018:Tissue Distribution / Q000187:drug effects; D016896:Treatment Outcome; D023041:Xenograft Model Antitumor Assays
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C501412:Abcg2 protein, mouse; D000166:Acridines; D011743:Pyrimidines; D044005:Tetrahydroisoquinolines; D013844:Thiazoles; C083501:Elacridar; D000069439:Dasatinib