PARENT SESSION
1:30 PM to 3:30 PM
Sunday, April 21, 2002
Poster Session 5 Oxygenation of Tumors and Modification
Room: Nevada Exhibition Center

(P10-91) Inhibition of HIF-1 by ibuprofen under normoxia and hypoxia.

Palayoor, Sanjeewani^*,1, Tofilon, Philip¹, Coleman, C. Norman¹, ¹ Radiation Oncology Branch, NCI, National Institutes of Health, Bethesda, MD

ABSTRACT-
PC3, DU-145 and LNCaP human prostate cancer cells express HIF-1 (hypoxia-inducible factor) protein under normoxic condition. Cell density, growth factors, pH etc. are known to modulate HIF-1 protein levels under tissue culture conditions. We observed that HIF-1 protein levels deacreased by changing media and then increased over 24h. Ibuprofen inhibited the constitutive HIF-1 protein as well as the protein that accumulated following media change. A time course of inhibition of HIF-1 by ibuprofen showed that at 2mM concentration HIF-1 disappeared from cells within 30min. Although ibuprofen inhibited two HIF-1 target proteins, VEGF and GLUT-1, which were upregulated by hypoxia, inhibition of HIF-1 under normoxic condition did not result in the inhibition of basal VEGF in tissue culture media or inhibition of basal GLUT-1 protein in cell extracts. Under normoxic condition HIF-1 is rapidly degraded by ubiquitinylation and proteasomal degradation. Proteasomal inhibiter MG132 inhibited HIF-1 degradation and increased accumulation of HIF-1. Preincubation or simultaneous incubation with ibuprofen inhibited the increase in HIF-1 upregulation by MG132. When cells were pre-treated with MG132 and ibuprofen was added, HIF-1 was still inhibited but to a lower extent. These studies suggest that ibuprofen affects HIF-1 degradation and stabilization. Supported by DOD Prostate Cancer Grant DAMD 17-98-1-8605

KEYWORDS: HIF-1 , VEGF/GLUT-1, Normoxia/hypoxia, Proteasomal degradation