Research
Overexpression of DNA damage-induced 45 alpha gene contributes to esophageal squamous cell cancer by promoter hypomethylation
Journal of Experimental & Clinical Cancer Research 2012, 31:11 doi:10.1186/1756-9966-31-11
Published: 8 February 2012Abstract (provisional)
Background
Environmental factors-induced dysfunction of esophageal squamous epithelium, including genomic DNA impairment and apoptosis, play an important role in the pathogenesis of esophageal squamous cell cancer. DNA damage-induced 45alpha (GADD45alpha) has been found promoting DNA repair and removing methylation marker, Therefore, in this study we will investigate whether GADD45alpha expression is induced and its mechanism in esophageal squamous cell cancer.
Methods
Two human esophageal squamous cell lines (ESCC), ECA109 and KYSE510 were cultured in RPMI-1640 medium supplemented with 10% fetal bovine serum (FBS). Lipofectamine 2000 was used to transfect cells. mRNA level of GADD45alpha was measured by reverse transcription-quantitive PCR (RT-qPCR), protein level of GADD45alpha was detected by western blot. Global DNA methylation of tissue sample was detected by immunohistochemistry and promoter methylation was measured by bisulfite sequencing.
Results
GADD45a mRNA and protein levels were increased significantly in tumor tissue than that in adjacent normal tissue. Hypomethylation of global genomic DNA and GADD45alpha promoter were found in ESCC. The cell sensitivity to Cisplatin DDP was decreased significantly in Eca109 and Kyse510 cells, in which GADD45alpha expression was down-regulated by RNA interference (RNAi). In addition, silence of GADD45a expression in ESCC cells inhibited proliferation and promoted apoptosis.
Conclusion
Overexpression of GADD45alpha gene is due to DNA hypomethylation in ESCC. GADD45alpha may be a protective factor in DDP chemotherapy for esophageal squamous cell carcinoma.