title: Combined temozolomide and sunitinib treatment leads to better tumour control but increased vascular resistance in O6-methylguanine methyltransferase-methylated gliomas.
abstract: BACKGROUND
  Combined antiangiogenic and cytotoxic treatment represents an appealing treatment approach for malignant glioma. In this study we characterised the antitumoural and microvascular consequences of sunitinib (Su) and temozolomide (TMZ) therapy and verified the ideal treatment protocol, with special focus on a potential therapeutic window for combined scheduling.
  
  
  METHODS
  O(6)-Methylguanine methyltransferase (MGMT) status was analysed by pyrosequencing. Tumour growth of subcutaneous xenografts was assessed under different treatment protocols (TMZ, SU, SU followed by TMZ, TMZ followed by SU, combined TMZ/SU). Intravital microscopy (dorsal skinfold chamber model) assessed microvascular consequences. Immunohistochemistry included tumour and endothelial cell proliferation, apoptosis and vascular pericyte coverage. Real-time polymerase chain reaction (RT-PCR) analysed the expression of angiogenesis-related pathways in response to therapy.
  
  
  RESULTS
  Combined TMZ/SU resulted in significantly reduced tumour growth compared to either monotreatment (TMZ: 106 ± 13 mm(3); SU: 114 ± 53 mm(3); TMZ/SU: 34 ± 7 mm(3)) by additional antiangiogenic effects and synergistic induction of apoptosis versus TMZ monotreatment. Sequential treatment protocols did not show additive antitumour responses. TMZ/SU aggravated vascular resistance mechanisms characterised by significantly higher blood flow rate (TMZ: 74 ± 34 μl/s; SU: 164 ± 36 μl/s; TMZ/SU: 254 ± 95 μl/s), reduced permeability (TMZ: 1.05 ± 0.02; SU: 0.99 ± 0.07; TMZ/SU: 0.89 ± 0.05) and recovery of pericyte-endothelial interactions (TMZ: 89 ± 7%; SU: 67 ± 9%, TMZ/SU:80 ± 10%) versus either monotreatment. Vascular resistance was paralleled by an increase in Ang-1 and Tie-2 and by the downregulation of Dll4.
  
  
  CONCLUSIONS
  Sequential application of TMZ and SU in the angiogenic window does not add antitumour efficacy to monotherapy. Simultaneous application yields beneficial tumour control due to additive antiangiogenic and proapoptotic effects. Combined treatment may aggravate pericyte-mediated vascular resistance mechanisms by altering Ang-1-Tie-2 and Dll4/Notch pathways.
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Czabanka
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Bruenner
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Parmaksiz
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Broggini
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Topalovic
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: S H
authors.initials: SH
authors.lastname: Bayerl
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Auf
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Kremenetskaia
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Nieminen
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Talence, France; Université de Bordeaux, Talence, France.
authors.forename: A
authors.initials: A
authors.lastname: Jabouille
authors.affiliation: Center for Stroke Research, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Mueller
authors.affiliation: Department of Neurology, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Harms
authors.affiliation: Center for Stroke Research, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Harms
authors.affiliation: Department of Neuropathology, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Koch
authors.affiliation: Department of Neuropathology, Universitätsmedizin Charité, Berlin, Germany.
authors.forename: F L
authors.initials: FL
authors.lastname: Heppner
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Charité, Berlin, Germany. Electronic address: peter.vajkoczy@charite.de.
authors.forename: P
authors.initials: P
authors.lastname: Vajkoczy
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation / Q000502:physiology; D004273:DNA, Neoplasm / Q000378:metabolism; D003606:Dacarbazine / Q000008:administration & dosage / Q000031:analogs & derivatives; D005910:Glioma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D064593:Heterografts; D006801:Humans; D007211:Indoles / Q000008:administration & dosage; D008297:Male; D051379:Mice; D008819:Mice, Nude; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000378:metabolism*; D011758:Pyrroles / Q000008:administration & dosage; D000077210:Sunitinib; D000077204:Temozolomide; D014407:Tumor Cells, Cultured; D014655:Vascular Resistance / Q000187:drug effects*
chemical_list: D020533:Angiogenesis Inhibitors; D004273:DNA, Neoplasm; D007211:Indoles; D011758:Pyrroles; D003606:Dacarbazine; D019853:O(6)-Methylguanine-DNA Methyltransferase; D000077210:Sunitinib; D000077204:Temozolomide