Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer

Yonghua Zhu, David T. Denhardt, Hongbin Cao, Patrick D. Sutphin, Albert C. Koong, Amato J. Giaccia, Quynh Thu Le

Research output: Contribution to journalArticle

62 Citations (Scopus)

Abstract

Osteopontin (OPN) is a secreted phosphoglycoprotein that has been linked to tumor progression and survival in several solid tumors, including head and neck cancers. Previous studies showed that OPN expression is induced by tumor hypoxia, and its plasma levels can serve as a surrogate marker for tumor hypoxia and treatment outcome in head and neck cancer patients. In this study, we investigate the transcriptional mechanism by which hypoxia enhances OPN expression. We found that OPN is induced in head and neck squamous cell carcinoma (HNSCC) cell lines and in NIH3T3 cells by hypoxia at both mRNA and protein levels in a time-dependent manner. Actinomycin D chase experiments showed that hypoxic induction of OPN was not due to increased mRNA stability. Deletion analyses of the mouse OPN promoter regions indicated that a ras-activated enhancer (RAE) located at -731 to -712 relative to the transcription start site was essential for hypoxia-enhanced OPN transcription. Using electrophoretic mobility shift assays with the RAE DNA sequence, we found that hypoxia induced sequence-specific DNA-binding complexes. Furthermore, hypoxia and ras exposure resulted in an additive induction of OPN protein and mRNA levels that appeared to be mediated by the RAE. Induction of OPN through the RAE element by hypoxia is mediated by an Akt-kinase signaled pathway as decreasing Akt levels with dominant negative constructs resulted in inhibition of OPN induction by hypoxia. Taken together, these results have identified a new hypoxia responsive transcriptional enhancer that is regulated by Akt signaling.

Original languageEnglish (US)
Pages (from-to)6555-6563
Number of pages9
JournalOncogene
Volume24
Issue number43
DOIs
StatePublished - Sep 29 2005

Fingerprint

NIH 3T3 Cells
Osteopontin
Up-Regulation
Head and Neck Neoplasms
Hypoxia
Cell Hypoxia
Messenger RNA
Transcription Initiation Site
RNA Stability
Dactinomycin
Electrophoretic Mobility Shift Assay
Genetic Promoter Regions
Neoplasms
Proteins
Phosphotransferases
Biomarkers
Cell Line

Keywords

  • Akt
  • Hypoxia
  • Osteopontin
  • ras
  • Regulation

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research
  • Genetics

Cite this

Zhu, Y., Denhardt, D. T., Cao, H., Sutphin, P. D., Koong, A. C., Giaccia, A. J., & Le, Q. T. (2005). Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer. Oncogene, 24(43), 6555-6563. https://doi.org/10.1038/sj.onc.1208800

Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer. / Zhu, Yonghua; Denhardt, David T.; Cao, Hongbin; Sutphin, Patrick D.; Koong, Albert C.; Giaccia, Amato J.; Le, Quynh Thu.

In: Oncogene, Vol. 24, No. 43, 29.09.2005, p. 6555-6563.

Research output: Contribution to journalArticle

Zhu, Y, Denhardt, DT, Cao, H, Sutphin, PD, Koong, AC, Giaccia, AJ & Le, QT 2005, 'Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer', Oncogene, vol. 24, no. 43, pp. 6555-6563. https://doi.org/10.1038/sj.onc.1208800
Zhu, Yonghua ; Denhardt, David T. ; Cao, Hongbin ; Sutphin, Patrick D. ; Koong, Albert C. ; Giaccia, Amato J. ; Le, Quynh Thu. / Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer. In: Oncogene. 2005 ; Vol. 24, No. 43. pp. 6555-6563.
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