We previously identified BASP1 and SRD5A2 as novel hepatocellular carcinoma (HCC) methylation markers from among more than 10,000 screened genes. The present study aimed to improve the diagnostic potential of these genes. We compared the methylation status at distinct regions of the BASP1 and SRD5A2 genes using quantitative methylation-specific PCR, in 46 sets of HCC and corresponding non-tumor liver tissues. We also examined how their epigenetic status affected transcript levels in tissues and several hepatoma cell lines. We found that BASP1 and SRD5A2 loci were methylated in greater than 50% of the HCC tissues. Inverse correlations were identified between the methylation status and transcript levels in the tissues. Assessment of CpG island methylation rate of BASP1 and SRD5A2 resulted in different diagnostic powers for discriminating HCC even in the same CpG island. A combination analysis of BASP1 and SRD5A2 resulted in the optimum diagnostic performance (84.8% sensitivity and 91.3% specificity) with a maximal area under the receiver operating characteristic curve of 0.878. Even in patients with early HCC (well-differentiated, TNM stage I and small in diameter) and those negative for serum α-fetoprotein, combination analysis enabled an accurate diagnosis of HCC. In vitro analysis also showed that BASP1 and SRD5A2 transcripts were epigenetically regulated by methylation and acetylation. These results suggest that combined analysis of methylated BASP1 and SRD5A2 may prove useful in the accurate diagnosis of HCC, especially early HCC.

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