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See detailIdentification of cyclooxygenase-2 as a major actor of the transcriptomic adaptation of endothelial and tumor cells to cyclic hypoxia: effect on angiogenesis and metastases.
Daneau; Boidot; MARTINIVE, Philippe ULg et al

in Clinical Cancer Research : An Official Journal of the American Association for Cancer Research (2010), 16(2), 410-419

Purpose: Cyclic hypoxia in tumors originates from heterogeneities in RBC flux and influences not only tumor cells but also endothelial cells lining tumor blood vessels. Whether pO2 fluctuations ... [more ▼]

Purpose: Cyclic hypoxia in tumors originates from heterogeneities in RBC flux and influences not only tumor cells but also endothelial cells lining tumor blood vessels. Whether pO2 fluctuations, particularly transient reoxygenation periods, alter the well-known hypoxia-inducible factor (HIF)–dependent gene program is largely unknown. Experimental Design: We compared the transcriptomic profiles of endothelial and tumor cells exposed to cyclic hypoxia versus continuous hypoxia to uncover a possible differential effect on angiogenesis and metastases. Results: Microarray analyses identified early genes that were selectively induced by cyclic hypoxia in endothelial cells. Among them, we focused on PTGS2 because the observed increase in mRNA expression led to a significant increase in the expression and activity of cyclooxygenase-2 (COX-2; the protein product of PTGS2). HIF-1α was shown to be stabilized by cyclic hypoxia (despite reoxygenation periods) and to favor COX-2 induction as validated by the use of echinomycin and HIF-1α targeting small interfering RNA. Using a specific COX-2 inhibitor and a dedicated COX-2 targeting small interfering RNA, we documented that COX-2 accounted for the higher endothelial cell survival and angiogenic potential conferred by cyclic hypoxia. Cyclic hypoxia also led to a preferential COX-2 induction in tumor cells and, contrary to continuous hypoxia, fostered a higher metastatic take of prechallenged tumor cells. Conclusions: Our study documents that PTGS2/COX-2 is part of a cyclic hypoxia gene signature and largely accounts for the unique phenotype of endothelial and tumor cells exposed to fluctuations in pO2, thereby offering new perspectives for the clustering of tumors expressing COX-2 together with other cyclic hypoxia-responsive genes. Clin Cancer Res; 16(2); 410–9 [less ▲]

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See detailMechanism of reoxygenation after antiangiogenic therapy using SU5416 and its importance for guiding combined antitumor therapy
ANSIAUX, Réginald; BAUDELET, Christine; JORDAN, Bénédicte et al

in Cancer Research (2006), 66(19), 9698704

Emerging preclinical studies support the concept of a transient "normalization" of tumor vasculature during the early stage of antiangiogenic treatment, with possible beneficial effects on associated ... [more ▼]

Emerging preclinical studies support the concept of a transient "normalization" of tumor vasculature during the early stage of antiangiogenic treatment, with possible beneficial effects on associated radiotherapy or chemotherapy. One key issue in this area of research is to determine whether this feature is common to all antiangiogenic drugs and whether the phenomenon occurs in all types of tumors. In the present study, we characterized the evolution of the tumor oxygenation (in transplantable liver tumor and FSAII tumor models) after administration of SU5416, an antagonist of the vascular endothelial growth factor receptor. SU5416 induced an early increase in tumor oxygenation [measured by electronic paramagnetic resonance (EPR)], which did not correlate with remodeling of the tumor vasculature (assessed by CD31 labeling using immunohistochemistry) or with tumor perfusion (measured by dynamic contrast enhanced-magnetic resonance imaging). Inhibition of mitochondrial respiration (measured by EPR) was responsible for this early reoxygenation. Consistent with these unique findings in the tumor microenvironment, we found that SU5416 potentiated tumor response to radiotherapy but not to chemotherapy. In addition to the fact that the characterization of the tumor oxygenation is essential to enable correct application of combined therapies, our results show that the long-term inhibition of oxygen consumption is a potential novel target in this class of compounds. [less ▲]

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See detailCharacterization of the tumor micro-environment after administration of glucocorticoids to understand their radiosensitization effect
Crokart; Jordan; Baudelet et al

Poster (2004, November 26)

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