B104
UHRF1 overexpression correlates with hypermethylation in non-small cell lung cancer
Alexandros Daskalos1, Anastasia Filia1, George Nikolaidis1, George Xinarianos1, Vassilis Gorgoulis2, Athanassios Kotsinas2, John Field1, Triantafillos Liloglou1
1University of Liverpool, UK, 2Univeristy of Athens, Greece
Background
UHRF1 gene product binds hemimethylated DNA and recruits DNMT1, possessing a potentially critical role in DNA methylation maintenance. However, its relationship to DNA hypermethylation in human cancer is unclear. Here, we have investigated UHRF1 and DNMT1 expression and their association to DNA hypermethylation in primary non-small cell carcinomas.
Method
mRNA levels of UHRF1 and DNMT1 genes were assessed by qPCR and DNA methylation by Pyrosequencing in 116 lung tumours and 54 adjacent normal tissues. We also examined DNA methylation at p16, TP73, RASSSF1 and hTERT promoters and calculated hypermethylation index for each sample. Ki-67 immunhistochemistry provided the proliferation index information. In addition, we investigated the mRNA expression of UHRF1 and DNMT1 genes in lung cell lines in response to azacytidine and trichostatin A treatment.
Results
Tumour tissues demonstrated higher levels of UHRF1 (p= 1.710-9) and DNMT1 (p= 6.810-6) mRNA in comparison to their paired adjacent tissue. UHRF1 expression in tumour tissues correlated to that of DNMT1 (p<10-6) as well as the proliferation index (p=0.009). UHRF1 expression was higher in the group of tumours with hypermethylation index ≥1 (p<0.002) while no such relationship was true for DNMT1. Finally, we observed significant drop of UHRF1 and DNMT1 expression in cell lines following TSA treatment.
Conclusion
We demonstrate in primary human tumours the strong relationship between DNA hypermethylation and UHRF1 expression. Our data suggest that UHRF1 is a key epigenetic regulator in tumour pathogenesis probably by controlling the amount of DNMT1 recruited onto gene promoters.
Acknowledgments
This study was funded by the Roy Castle Lung Cancer Research Foundation.
