Indeed, recurrence was clinicopathologically associated with two host factors, serum albumin levels and HCV infection in our training cases (Table 1), suggesting that multicentric recurrence was dominant for the patients with chronic liver damages.18 Therefore, the assessment of noncancerous background tissue should reflect clinical outcomes that are not restricted to tumor progression.19, 20 BYL719 ic50 Our retrospective study indicated that the noncancerous gene expression of CYP1A2, CNDP1, and OAT was significantly associated with recurrence

(Table 1). The variable-selection procedure revealed the noncancerous CYP1A2 gene as the best predictive model for the recurrence of HCC, but not including the cancer-derived genes (Table 1).

Further prospective, multicenter study validated that noncancerous CYP1A2 expression was identified as a unique biomarker for the prediction of recurrence after the curative resection of early-stage HCC (Table 3). Using tissue microarrays, CYP1A2 showed significant negative correlation with the cumulative recurrence-free rates (Fig. 3). CYP1A2 is a major form of hepatic cytochorme P450 oxidative system, which is involved in drug metabolism and cholesterol synthesis.17 Decreased expression of hepatic CYP1A2 was known to be significantly correlated with fibrotic progression of hepatitis C patients21 and pathological progress of nonalcoholic Everolimus cell line fatty liver disease.22 Barker et al. reported previously that CYP1A2 was down-regulated dramatically by oxidative stress in hepatocytes, indicating CYP1A2 as a specific surrogate marker of hepatic oxidative damage.23 According to knockout mice analysis by Shertzer et al., oxidative stress was significantly elevated in the liver microsomes of CYP1A2-knockout mice, compared to those

of wild-type or CYP1A1-knockout mice.24 In this regard, CYP1A2 may be considered not only a biomarker of oxidative stress, but also an antioxidant enzyme. The other noncancerous candidates, CNDP1 medchemexpress and OAT, might also be associated with oxidative stress by the modulation of amino acids carnosine15 and ornithine.16 Oxidative stress is known to induce DNA damage, and accumulation of such genetic damage can eventually lead to hepatocarcinogenesis.25 To evaluate the biological pathways associated with CYP1A2 expression, we utilized GSEA on the gene-expression profiles of the noncancerous liver tissues.14 GSEA can directly analyze the changes of gene-expression levels as continuous variables.26 According to our GSEA assessment, the gene sets of peroxisome and oxidoreductase activity were significantly correlated with CYP1A2 expression levels (Fig. 4). The peroxisome is an organelle that participates not only in the generation of reactive oxygen species, but also in cell rescue from the damaging effects of such oxidative radicals.