title: Targeting Notch Signaling and Autophagy Increases Cytotoxicity in Glioblastoma Neurospheres.
abstract: Glioblastomas are highly aggressive tumors that contain treatment resistant stem-like cells. Therapies targeting developmental pathways such as Notch eliminate many neoplastic glioma cells, including those with stem cell features, but their efficacy can be limited by various mechanisms. One potential avenue for chemotherapeutic resistance is the induction of autophagy, but little is known how it might modulate the response to Notch inhibitors. We used the γ-secretase inhibitor MRK003 to block Notch pathway activity in glioblastoma neurospheres and assessed its effects on autophagy. A dramatic, several fold increase of LC3B-II/LC3B-I autophagy marker was noted on western blots, along with the emergence of punctate LC3B immunostaining in cultured cells. By combining the late stage autophagy inhibitor chloroquine (CQ) with MRK003, a significant induction in apoptosis and reduction in growth was noted as compared to Notch inhibition alone. A similar beneficial effect on inhibition of cloogenicity in soft agar was seen using the combination treatment. These results demonstrated that pharmacological Notch blockade can induce protective autophagy in glioma neurospheres, resulting in chemoresistance, which can be abrogated by combination treatment with autophagy inhibitors.
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.|Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Natsumeda
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Maitani
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Miyahara
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Harpreet
authors.initials: H
authors.lastname: Kaur
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.|Department of Oncology, Tongji Hospital, Wuhan, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Chu
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.|Department of Neurosurgery, University Medical Center Düsseldorf, Düsseldorf, Germany.
authors.forename: Ulf D
authors.initials: UD
authors.lastname: Kahlert
authors.affiliation: Department of Pathology, Division of Neuropathology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Charles G
authors.initials: CG
authors.lastname: Eberhart
mesh_terms: D000962:Antimalarials / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology; D002738:Chloroquine / Q000494:pharmacology; D003114:Colony-Forming Units Assay; D003499:Cyclic S-Oxides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005909:Glioblastoma / Q000473:pathology; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D051880:Receptors, Notch / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013217:Starvation; D013830:Thiadiazoles / Q000494:pharmacology
chemical_list: D000962:Antimalarials; D003499:Cyclic S-Oxides; D004338:Drug Combinations; D019394:Ki-67 Antigen; C523799:MRK 003; D051880:Receptors, Notch; D013830:Thiadiazoles; D002738:Chloroquine
keywords: autophagy; chloroquine; combination treatment; gamma-secretase inhibitor; glioblastoma