Abstract
Our previous results demonstrated that the apolipoprotein A-I (apoA-I) mimetic peptides L-4F and L-5F inhibit vascular endothelial growth factor production and tumor angiogenesis. The present study was designed to test whether apoA-I mimetic peptides inhibit the expression and activity of hypoxia-inducible factor-1α (HIF-1α), which plays a critical role in the production of angiogenic factors and angiogenesis. Immunohistochemistry staining was used to examine the expression of HIF-1α in tumor tissues. Immunoblotting, real-time polymerase chain reaction, immunofluorescence, and luciferase activity assays were used to determine the expression and activity of HIF-1α in human ovarian cancer cell lines. Immunohistochemistry staining demonstrated that L-4F treatment dramatically decreased HIF-1α expression in mouse ovarian tumor tissues. L-4F inhibited the expression and activity of HIF-1α induced by low oxygen concentration, cobalt chloride (CoCl2, a hypoxia-mimic compound), lysophosphatidic acid, and insulin in two human ovarian cancer cell lines, OV2008 and CAOV-3. L-4F had no effect on the insulin-induced phosphorylation of Akt, but inhibited the activation of extracellular signal-regulated kinase and p70s6 kinase, leading to the inhibition of HIF-1α synthesis. Pretreatment with L-4F dramatically accelerated the proteasome-dependent protein degradation of HIF-1α in both insulin- and CoCl2-treated cells. The inhibitory effect of L-4F on HIF-1α expression is in part mediated by the reactive oxygen species-scavenging effect of L-4F. ApoA-I mimetic peptides inhibit the expression and activity of HIF-1α in both in vivo and in vitro models, suggesting the inhibition of HIF-1α may be a critical mechanism responsible for the suppression of tumor progression by apoA-I mimetic peptides.
Footnotes
This work was supported by funds from the Women's Endowment, the Carl and Roberta Deutsch Family Foundation, the Joan English Fund for Women's Cancer Research, a VA Merit I Award (to R.F.-E.), the Ovarian Cancer Coalition, the Helen Beller Foundation, the Wendy Stark Foundation, the Sue and Mel Geleibter Family Foundation, Kelly Day, the National Institutes of Health National Heart, Lung, and Blood Institute [Grants HL-30568, HL-082823], and the Laubisch and M. K. Gray funds at the University of California, Los Angeles.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
ABBREVIATIONS:
- apoA-I
- apolipoprotein A-I
- HIF-1
- hypoxia-inducible factor-1
- CoCl2
- cobalt chloride
- LPA
- lysophosphatidic acid
- ROS
- reactive oxygen species
- VEGF
- vascular endothelial growth factor
- CHX
- cycloheximide
- DAPI
- 4,6-diamidino-2-phenylindole
- DCFH-DA
- dichlorofluorescein diacetate
- ERK
- extracellular signal-regulated kinase
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- HRE
- hypoxia response element
- PCR
- polymerase chain reaction
- PBS
- phosphate-buffered saline
- RT
- reverse transcription
- sc-4F
- scrambled 4F
- SOD
- superoxide dismutase
- MG-132
- N-(benzyloxycarbonyl)leucinylleucinylleucinal-Z-Leu-Leu-Leu-al.
- Received January 31, 2012.
- Accepted April 24, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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