B112

Cytoglobin-mediated epigenetic reprogramming of non-small cell lung carcinomas

George Xinarianos, Urszula Babiszkiewicz, Alexandros Daskalos, George Nikolaidis, Anastasia Filia, John Gosney, John Field, Triantafillos Liloglou

University of Liverpool, UK

Background

Cytoglobin is an intracellular globin whose function is not fully elucidated yet. We have previously shown a strong association between CYGB expression and hypermethylation in non-small cell lung carcinoma (NSCLC). Downregulation of CYGB in NSCLC was also associated with allelic imbalance (AI) and poor differentiation suggesting a critical involvement of CYGB in tumour behaviour. Our most recent collaborative study demonstrated that CYGB functions as a tumour suppressor gene affecting the cells malignant phenotype.

Method

mRNA levels of CYGB, UHRF1 and DNMT1 genes were assessed by qPCR and DNA methylation by Pyrosequencing in a set of 80 NSCLC tissues. We also examined DNA methylation at p16, TP73, RASSSF1 and hTERT promoters and L1.2 retrotransposable element and calculated hypermethylation index for each sample.

Results

CYGB expression was related to DNMT1 expression levels (Spearmans correlation, p=0.001). We also found a similar inverse relationship with UHRF1 (p=0.004). It was observed that CYGB expression levels correlated with the DNA methylation index (p16, p73, KCNH5, TERT, RASSF1 promoters) of the tumours demonstrating the lowest CYGB levels at the highest methylation indexes (Kruskal-Wallis, p= 1.210^-5). CYGB expression inversely correlates with the global DNA hypomethylation measured by L1.2 retrotransposable element methylation status (Spearmans p=2.310^-5).

Conclusion

Our data demonstrate that CYGB may be involved in regulating specific parts of the epigenetic machinery suggesting that CYGB may exert some of its tumour-suppressor functions through epigenetic reprogramming of the cancer cell by regulating the expression of specific key components of the epigenetic machinery.

Acknowledgments

This study was funded by the Roy Castle Lung Cancer Research Foundation.