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Cytoglobin is upregulated by tumour hypoxia and silenced by promoter hypermethylation in head and neck cancer.

Shaw RJ, Omar MM, Rokadiya S, Kogera FA, Lowe D, Hall GL, Woolgar JA, Homer J, Liloglou T, Field JK, Risk JM - Br. J. Cancer (2009)

Bottom Line: CYGB expression also showed a marked negative correlation with promoter methylation (P=0.018).Treatment with 5-aza-2-deoxycitidine dramatically increased CYGB expression in those cell lines with greater baseline promoter methylation.We conclude that the CYGB gene is regulated by both promoter methylation and tumour hypoxia in HNSCC and that increased expression of this gene correlates with clincopathological measures of a tumour's biological aggression.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics and Oncology Group, School of Dental Sciences, University of Liverpool, Liverpool, UK. Richard.shaw@liv.ac.uk

ABSTRACT

Background: Cytoglobin (Cygb) was first described in 2002 as an intracellular globin of unknown function. We have previously shown the downregulation of cytoglobin as a key event in a familial cancer syndrome of the upper aerodigestive tract.

Methods: Cytoglobin expression and promoter methylation were investigated in sporadic head and neck squamous cell carcinoma (HNSCC) using a cross-section of clinical samples. Additionally, the putative mechanisms of Cygb expression in cancer were explored by subjecting HNSCC cell lines to hypoxic culture conditions and 5-aza-2-deoxycitidine treatment.

Results: In clinically derived HNSCC samples, CYGB mRNA expression showed a striking correlation with tumour hypoxia (measured by HIF1A mRNA expression P=0.013) and consistent associations with histopathological measures of tumour aggression. CYGB expression also showed a marked negative correlation with promoter methylation (P=0.018). In the HNSCC cell lines cultured under hypoxic conditions, a trend of increasing expression of both CYGB and HIF1A with progressive hypoxia was observed. Treatment with 5-aza-2-deoxycitidine dramatically increased CYGB expression in those cell lines with greater baseline promoter methylation.

Conclusion: We conclude that the CYGB gene is regulated by both promoter methylation and tumour hypoxia in HNSCC and that increased expression of this gene correlates with clincopathological measures of a tumour's biological aggression.

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Related in: MedlinePlus

Upregulation of CYGB mRNA with hypoxia for six head and neck squamous cell carcinoma (HNSCC) cell lines and HeLa. Corresponding methylation data and expression data relative to the unmethylated HNSCC cell line, hn, are shown below the figure. Expression is shown relative to expression for each line in 21% O2. Unfilled bar, normoxia; pale bar, 6 h of hypoxia; dark bar, 24 h hypoxia. Bar charts indicate mean of five samples with error bars±1 s.e.
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fig3: Upregulation of CYGB mRNA with hypoxia for six head and neck squamous cell carcinoma (HNSCC) cell lines and HeLa. Corresponding methylation data and expression data relative to the unmethylated HNSCC cell line, hn, are shown below the figure. Expression is shown relative to expression for each line in 21% O2. Unfilled bar, normoxia; pale bar, 6 h of hypoxia; dark bar, 24 h hypoxia. Bar charts indicate mean of five samples with error bars±1 s.e.

Mentions: All the seven cell lines showed an increase in HIF1A expression (Figure 2) and a corresponding increase in CYGB expression (Figure 3) with longer incubation under anoxic conditions. It should be noted that the absolute levels of CYGB mRNA expression (relative to hn) for the cell lines 012, 019 and PE/CA-PJ15 were rather low, as were any incremental increases caused by hypoxia, and that all these cell lines had MtI>0.95. Consequently, the relevance of such minute fluctuations in actual expression might be questioned for these three cell lines. bhy, however, had higher basal levels of CYGB expression despite an MtI>0.75 and failed to increase CYGB expression in response to hypoxia. Thus, the trend was for increased CYGB expression with progressive hypoxia, although the effect was reduced by high baseline CYGB expression.


Cytoglobin is upregulated by tumour hypoxia and silenced by promoter hypermethylation in head and neck cancer.

Shaw RJ, Omar MM, Rokadiya S, Kogera FA, Lowe D, Hall GL, Woolgar JA, Homer J, Liloglou T, Field JK, Risk JM - Br. J. Cancer (2009)

Upregulation of CYGB mRNA with hypoxia for six head and neck squamous cell carcinoma (HNSCC) cell lines and HeLa. Corresponding methylation data and expression data relative to the unmethylated HNSCC cell line, hn, are shown below the figure. Expression is shown relative to expression for each line in 21% O2. Unfilled bar, normoxia; pale bar, 6 h of hypoxia; dark bar, 24 h hypoxia. Bar charts indicate mean of five samples with error bars±1 s.e.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2713706&req=5

fig3: Upregulation of CYGB mRNA with hypoxia for six head and neck squamous cell carcinoma (HNSCC) cell lines and HeLa. Corresponding methylation data and expression data relative to the unmethylated HNSCC cell line, hn, are shown below the figure. Expression is shown relative to expression for each line in 21% O2. Unfilled bar, normoxia; pale bar, 6 h of hypoxia; dark bar, 24 h hypoxia. Bar charts indicate mean of five samples with error bars±1 s.e.
Mentions: All the seven cell lines showed an increase in HIF1A expression (Figure 2) and a corresponding increase in CYGB expression (Figure 3) with longer incubation under anoxic conditions. It should be noted that the absolute levels of CYGB mRNA expression (relative to hn) for the cell lines 012, 019 and PE/CA-PJ15 were rather low, as were any incremental increases caused by hypoxia, and that all these cell lines had MtI>0.95. Consequently, the relevance of such minute fluctuations in actual expression might be questioned for these three cell lines. bhy, however, had higher basal levels of CYGB expression despite an MtI>0.75 and failed to increase CYGB expression in response to hypoxia. Thus, the trend was for increased CYGB expression with progressive hypoxia, although the effect was reduced by high baseline CYGB expression.

Bottom Line: CYGB expression also showed a marked negative correlation with promoter methylation (P=0.018).Treatment with 5-aza-2-deoxycitidine dramatically increased CYGB expression in those cell lines with greater baseline promoter methylation.We conclude that the CYGB gene is regulated by both promoter methylation and tumour hypoxia in HNSCC and that increased expression of this gene correlates with clincopathological measures of a tumour's biological aggression.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics and Oncology Group, School of Dental Sciences, University of Liverpool, Liverpool, UK. Richard.shaw@liv.ac.uk

ABSTRACT

Background: Cytoglobin (Cygb) was first described in 2002 as an intracellular globin of unknown function. We have previously shown the downregulation of cytoglobin as a key event in a familial cancer syndrome of the upper aerodigestive tract.

Methods: Cytoglobin expression and promoter methylation were investigated in sporadic head and neck squamous cell carcinoma (HNSCC) using a cross-section of clinical samples. Additionally, the putative mechanisms of Cygb expression in cancer were explored by subjecting HNSCC cell lines to hypoxic culture conditions and 5-aza-2-deoxycitidine treatment.

Results: In clinically derived HNSCC samples, CYGB mRNA expression showed a striking correlation with tumour hypoxia (measured by HIF1A mRNA expression P=0.013) and consistent associations with histopathological measures of tumour aggression. CYGB expression also showed a marked negative correlation with promoter methylation (P=0.018). In the HNSCC cell lines cultured under hypoxic conditions, a trend of increasing expression of both CYGB and HIF1A with progressive hypoxia was observed. Treatment with 5-aza-2-deoxycitidine dramatically increased CYGB expression in those cell lines with greater baseline promoter methylation.

Conclusion: We conclude that the CYGB gene is regulated by both promoter methylation and tumour hypoxia in HNSCC and that increased expression of this gene correlates with clincopathological measures of a tumour's biological aggression.

Show MeSH
Related in: MedlinePlus