HLA-B and carcinoma of esophagus: Because hydralazine can be considered as a weak DNA methylation inhibitor and it has been reported that 5-aza-2'-deoxycytidine does demethylate the HLA-B promoter in the KYSE esophageal carcinoma cell line, we searched the expression of HLA-A, -B and -C genes and the promoter methylation status in several cell lines.