Objectives: In this study, the regulation of cytoglobin in OSCC was studied.
Methods: 38 snap frozen oral or oropharyngeal squamous cell carcinoma (OSCC) tumour and paired normal specimens were obtained at surgery. DNA was bisulphite treated and the methylation status of 4 individual CpG sites within the CYGB promoter determined by pyrosequencing. Real time RT-PCR was used to measure CYGB expression. HIF1-α expression was used as a representative biomarker of tumour hypoxia. These data were correlated with clinico-pathological data. Seven oral cancer cell lines were cultured under differing ambient O2 concentrations to investigate the dynamic effects of hypoxia.
Results: CYGB down-regulation was observed in 19/38 tumours and was concurrent with promoter methylation (P=0.018). CYGB up-regulation was associated with HIF1-α over-expression (P=0.004) and these tumours had significantly higher pTNM stage and showed greater mandibular invasion, ECS, tumour depth, lymph node metastases and Anneroth score, and had worse survival (p<0.05). In the cell culture study, a trend of increasing expression of both CYGB and HIF1-α expression with progressive hypoxia was observed.
Conclusion: CYGB mRNA expression in OSCC is variable but appears to be regulated by promoter methylation and the cellular mechanisms of tumour hypoxia. CYGB up-regulation correlated with clinco-pathological measures of a tumour's biological aggression. Furthermore, tumour hypoxia is highly prognostic and correlated with radiosensitivity. These observations prompt further investigation into the role of CYGB in the hypoxia pathway and the correlation of clinical response of OSCC to radiotherapy. Acknowledgements: RJS was supported by a Royal College of Surgeons Research Fellowship. This research was supported by grants from the British Association of Oral and Maxillofacial Surgeons.