Effect of Radiation and Ibuprofen on Normoxic Renal Carcinoma Cells Overexpressing Hypoxia-Inducible Factors by Loss of von Hippel–Lindau Tumor Suppressor Gene Function

Palayoor, Sanjeewani T.; Burgos, Melissa; Shoaibi, Azadeh; Tofilon, Philip J.; Coleman, C. Norman

doi:10.1158/1078-0432.ccr-04-0005

Cited by 20 publications

(25 citation statements)

References 42 publications

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“…[1][2][3][4] Although HIF-1a level is good indicator of poor outcome in clinical data, evidence of the role of HIF-1a in hypoxia-related radiation and drug resistance is inconsistent because of different oxygen concentration and cell lines used in experiments. [5][6][7][8][9][10] HIF-1 knockdownmediated radiation or drug sensitization under normoxia produced negative results in some studies since HIF-1 was expected to play minor roles in the presence of O 2 . Cells with normal or suppressed HIF-1 status were not indicated as the major part of therapy barrier under normoxia.…”

Section: Introductionmentioning

confidence: 99%

Effects of lentivirus-mediated HIF-1α knockdown on hypoxia-related cisplatin resistance and their dependence on p53 status in fibrosarcoma cells

Hao

Song

et al. 2008

Cancer Gene Ther

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Therapy targeting hypoxia-inducible factor-1 (HIF-1) to reverse the hypoxia-related drug resistance has received much interest. Despite a close interaction between HIF-1 and p53 and that p53 mutation is seen in 450% of tumors, whether HIF-1 silencing by targeted therapy depends on tumor p53 status remains unknown. Two isogenic fibrosarcoma cells HT1080 (wild-type p53) and HT1080-6TG (mutant p53) were transduced with HIF-1a-specific RNAi lentiviral vectors and selected with blasticidin. Real-time PCR and western blot analysis of HIF-1a mRNA and protein respectively validated the silencing effects. Cells were first preconditioned under hypoxia (0.5% O 2 ) for 4 h and then co-treated with cisplatin for another 24 h. MTT was used for assessment of chemosensitivity to cisplatin. Moreover, annexin V and propidium iodide staining was detected on flow cytometry for analysis of cisplatin-induced apoptosis. Furthermore, changes of some Bcl-2 family members were detected on western blotting. Exposure to hypoxia significantly increased resistance to cisplatin than exposure to normoxia. HIF-1a knockdown could reverse hypoxia-related resistance to cisplatin and apoptotic resistance only in HT1080 cells, but had little effect on HT1080-6TG cells. With HIF-1a knockdown, Bid expression was higher in HT1080 than in HT1080-6TG under hypoxia. In summary, HIF-1 targeted therapy to reverse hypoxia-related cisplatin resistance depends on normal p53 status. Changes of Bid expression levels under hypoxia might contribute in part to the differential response to HIF-1a silencing in cells with different p53 status.

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Section: Introductionmentioning

confidence: 99%

Effects of lentivirus-mediated HIF-1α knockdown on hypoxia-related cisplatin resistance and their dependence on p53 status in fibrosarcoma cells

Hao

Song

et al. 2008

Cancer Gene Ther

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“…A study by Ugurel and coworkers suggests that angiogenic factors like VEGF are useful predictive serum markers for survival (22). On the other hand, the measurement of angiogenic factors in serum can be of interest for the evaluation of the effects of antiangiogenic treatments (13) and particularly those targeting HIF-1␣ (24). It is known that the cellular half-life of HIF-1␣ is very short (17).…”

Section: Resultsmentioning

confidence: 99%

“…Nonquantitative Western blotting analysis is the sole technique which can be used in such conditions. Experimental studies into HIF-1␣ are currently expanding (13), and targeted therapies directed specifically to HIF-1␣ are being developed (19,25). There is thus a need, in preclinical pharmacological studies, to measure more precisely the level of HIF-1␣ expression as a function of the dose and/or time of antiangiogenic treatments in tumor cells.…”

mentioning

confidence: 99%

Enzyme-Linked Immunosorbent Assay for Pharmacological Studies Targeting Hypoxia-Inducible Factor 1α

Formento

Berra

Ferruà

et al. 2005

Clin Vaccine Immunol

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Hypoxia-inducible factor 1 (HIF-1) activates the transcription of a wide range of genes related to oxygen delivery and metabolic adaptation under hypoxic (low-oxygen) conditions. HIF-1 is, in fact, a heterodimer of two subunits, HIF-1␣ and HIF-1␤. The only analytical methods available for measuring HIF-1␣ levels in tumors are immunohistochemistry and Western blotting. Immunohistochemistry has the advantage of allowing the identification and direct examination of HIF-1␣-expressing cells, but has the intrinsic limitation, as for Western blotting, of being nonquantitative. We developed and validated an enzyme-linked immunosorbent assay (ELISA) approach to measure HIF-1␣ levels in cultured tumor cell lines in vitro. HIF-1␣ was expressed in thirteen tumor cell lines grown under hypoxic conditions; however, the levels differed strongly between cell lines. These data point to intrinsic differences between cell lines for the induction of HIF-1␣ under hypoxic conditions. The ELISA developed in the present study is thus an interesting alternative to other analytical methods used to measure HIF-1␣ protein levels and should be useful in preclinical pharmacological studies targeting HIF-1␣.

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“…A clinical study of radiation treatment for head and neck cancer reported that levels of both HIF1α and HIF2α correlated with radiation resistance [9]. However, in experiments by Palayoor et al [16], transfection of VHL into RCC cells lacking this gene did not alter radiation sensitivity, despite leading to an increase in protein levels for both HIF1α and HIF2α. One possible reason for the difference in the present results and that obtained by Palayoor et al may be due to the pleiomorphic effects of VHL on gene expression.…”

Section: Discussionmentioning

confidence: 98%

Hypoxia‐inducible factor‐2α: effect on radiation sensitivity and differential regulation by an mTOR inhibitor

Bhatt

Landis²,

Zimmer

et al. 2008

BJU International

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OBJECTIVE-To determine the role of hypoxia-inducible factor-2α (HIF2α) on the sensitivity of renal cell carcinoma (RCC) cell lines to ionizing radiation and to determine if the mTOR antagonist, rapamycin, could decrease HIF2α protein levels.MATERIALS AND METHODS-Cell lines expressing stable short-hairpin RNAs (shRNAs) encoding HIF2α shRNAs or an empty vector were transfected with a hypoxia responsive element (HRE)-driven firefly luciferase reporter gene. Two separate paired cell lines were assayed for their response to increasing doses of ionizing radiation. Proliferation and cell cycle kinetics were compared for cell lines expressing HIF2α shRNAs and empty vectors. The effect of an mTOR antagonist, rapamycin on HIF1α and HIF2α proteins levels was also assessed. RESULTS-We confirmed that the 786-O RCC lines with stably integrated shRNAs againstHIF2α had decreased activation of a plasmid with a HRE-driven firefly luciferase reporter gene. Lines from two separate cell clones with decreased HIF2α levels showed a significant increase in radiation sensitivity and an increase in G2 cell cycle arrest. Rapamycin, while effective in decreasing HIF1α protein levels, did not affect HIF2α levels in either of the RCC cell lines.CONCLUSIONS-These results show that decreasing levels of HIF2α leads to an increased sensitivity to ionizing radiation. This finding may explain in part, the known resistance of RCC to radiation therapy. Although mTOR antagonists are approved for the treatment of RCC, these agents do not decrease HIF2α levels and therefore might not be effective in enhancing the radiosensitivity of these tumours.

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Effect of Radiation and Ibuprofen on Normoxic Renal Carcinoma Cells Overexpressing Hypoxia-Inducible Factors by Loss of von Hippel–Lindau Tumor Suppressor Gene Function

Cited by 20 publications

References 42 publications

Effects of lentivirus-mediated HIF-1α knockdown on hypoxia-related cisplatin resistance and their dependence on p53 status in fibrosarcoma cells

Effects of lentivirus-mediated HIF-1α knockdown on hypoxia-related cisplatin resistance and their dependence on p53 status in fibrosarcoma cells

Enzyme-Linked Immunosorbent Assay for Pharmacological Studies Targeting Hypoxia-Inducible Factor 1α

Hypoxia‐inducible factor‐2α: effect on radiation sensitivity and differential regulation by an mTOR inhibitor

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