title: Augmenting tumor sensitivity to topotecan by transient hypoxia.
abstract: We examined how the effect of topotecan is modulated by transient hypoxia in three different tumor lines, Lewis lung carcinoma (LLC), U87 human glioblastoma and DMS273 human small cell lung cancer. Four groups of tumor bearing mice were treated with saline or a single dose of topotecan, immediately followed by 6-h or 72-h exposure to a hypoxic environment (10% O(2)) or normal air. Topotecan + hypoxia resulted in significantly greater suppression of tumor growth than normoxic topotecan or hypoxia alone. Correspondingly, the sensitivity of LLC cells to topotecan in a clonogenic survival assay was significantly higher under hypoxia. This effect of hypoxia was not a general phenomenon, since the tumor growth inhibitory effect of the alkylating agent cisplatin was not changed by hypoxic environment. In a parallel series of in vitro experiments, cell cultures were exposed to hypoxia (0.1% or 0.7% O(2)) in a hypoxic chamber or normoxia for 24 h. We found a dose-dependent downregulation of HIF-1alpha by topotecan (30-270 nM). The hypoxic upregulation of Glucose transporter-1 and VEGF secretion to the culture medium was inhibited by the addition of topotecan, while doses up to 270 nM had no effect on VEGF under normoxia. VEGF protein levels in tumors were also reduced by topotecan. These data show that the effect of topotecan is increased by transient hypoxia, and this may be a direct effect on the ability of cells to survive under hypoxia as well as an antiangiogenic effect, mediated through the HIF-1 inhibitory effect of topotecan.
authors.affiliation: Laboratory of Experimental Oncology, Department of Molecular Pathology, University of Copenhagen, Denmark. eva@pai.ku.dk
authors.forename: Eva L
authors.initials: EL
authors.lastname: Lund
authors.forename: Lasse T
authors.initials: LT
authors.lastname: Hansen
authors.forename: Paul E G
authors.initials: PE
authors.lastname: Kristjansen
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018827:Carcinoma, Lewis Lung / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D018288:Carcinoma, Small Cell / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D016543:Central Nervous System Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D005909:Glioblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051272:Glucose Transporter Type 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D019772:Topotecan / Q000494:pharmacology*; D047368:Tumor Burden / Q000187:drug effects*; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D051272:Glucose Transporter Type 1; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C495678:Slc2a1 protein, mouse; D042461:Vascular Endothelial Growth Factor A; D019772:Topotecan