The rate of DNA methylation [(gene sample/Alu-C4 sample)/(gene SssI-treated sample/Alu-C4 SssI-treated sample) × 100] in the APC gene promoter was also revealed to be significantly higher in the HCC tissues compared with the adjacent non-cancerous tissues (paired t-test, P=0.0003; Fig. 1B). Here, C4A is linked to hepatocellular carcinoma.