Hypoxia-Independent Downregulation of Hypoxia-Inducible Factor 1 Targets by Androgen Deprivation Therapy in Prostate Cancer

Journal Article · Fri Nov 15 04:00:00 EST 2013 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/J.IJROBP.2013.07.023· OSTI ID:22267946

Ragnum, Harald Bull ^[1]; Røe, Kathrine ^[1]; Holm, Ruth; Vlatkovic, Ljiljana ^[2]; Nesland, Jahn Marthin ^[2]; Aarnes, Eva-Katrine ^[1]; Ree, Anne Hansen ^[3]; Flatmark, Kjersti ^[4]; Seierstad, Therese ^[5]; Lilleby, Wolfgang ^[6]; Lyng, Heidi ^[1]

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1. Department of Radiation Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway)
2. Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway)
3. Division of Medicine, Department of Oncology, Akershus University Hospital, Lørenskog (Norway)
4. Department of Tumor Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway)
5. Department of Radiology and Nuclear Medicine, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway)
6. Department of Oncology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway)

Purpose: We explored changes in hypoxia-inducible factor 1 (HIF1) signaling during androgen deprivation therapy (ADT) of androgen-sensitive prostate cancer xenografts under conditions in which no significant change in immunostaining of the hypoxia marker pimonidazole had occurred. Methods and Materials: Gene expression profiles of volume-matched androgen-exposed and androgen-deprived CWR22 xenografts, with similar pimonidazole-positive fractions, were compared. Direct targets of androgen receptor (AR) and HIF1 transcription factors were identified among the differentially expressed genes by using published lists. Biological processes affected by ADT were determined by gene ontology analysis. HIF1α protein expression in xenografts and biopsy samples from 35 patients receiving neoadjuvant ADT was assessed by immunohistochemistry. Results: A total of 1344 genes showed more than 2-fold change in expression by ADT, including 35 downregulated and 5 upregulated HIF1 targets. Six genes were shared HIF1 and AR targets, and their downregulation was confirmed with quantitative RT-PCR. Significant suppression of the biological processes proliferation, metabolism, and stress response in androgen-deprived xenografts was found, consistent with tumor regression. Nineteen downregulated HIF1 targets were involved in those significant biological processes, most of them in metabolism. Four of these were shared AR and HIF1 targets, including genes encoding the regulatory glycolytic proteins HK2, PFKFB3, and SLC2A1. Most of the downregulated HIF1 targets were induced by hypoxia in androgen-responsive prostate cancer cell lines, confirming their role as hypoxia-responsive HIF1 targets in prostate cancer. Downregulation of HIF1 targets was consistent with the absence of HIF1α protein in xenografts and downregulation in patients by ADT (P<.001). Conclusions: AR repression by ADT may lead to downregulation of HIF1 signaling independently of hypoxic fraction, and this may contribute to tumor regression. HIF1α expression is probably not a useful hypoxia biomarker during ADT in prostate cancer.

• OSTI ID: 22267946
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 4 Vol. 87; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ANDROGENS
ANOXIA
BIOLOGICAL MARKERS
GENES
METABOLISM
NEOPLASMS
PROSTATE
THERAPY