Site-specific hypomethylation of the c-myc oncogene in human hepatocellular carcinoma

In order to examine the effect of alteration in methylation of the c-myc gene on hepatocarcinogenesis, the extent of methylation of the c-myc gene was examined in 24 tissues of hepatocellular carcinoma (HCC), 24 adjacent non-tumor liver tissues from the same patients and 16 control liver tissues by the use of restriction endonucleases. The following results were obtained. (1) The c-myc gene from HCC tissue tended to be hypomethylated in comparison with that in non-tumor liver tissue from the same patient. (2) The c-myc gene from non-tumor liver tissue was hypomethylated to various degrees in comparison with that in control liver tissues. (3) The CCGG site in the third exon of the c-myc gene tended to be more extensively hypomethylated in HCC tissues than in non-tumor and control liver tissues. These results suggest that hypomethylation of the c-myc gene may occur to various degrees before the appearance of HCC, and may be associated with hepatocarcinogenesis. Moreover, the hypomethylation in the third exon of the c-myc gene is probably important for the development of HCC.