Human hepatocellular carcinoma (HCC) appears to be strongly associated with apoptosis and its breakdown may be involved in the occurrence of HCC. Like the Fas/Fas-L system, the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) transduces apoptosis in a number of cancers; it is also a clinical candidate for cancer therapy. To examine its applicability in future therapy, the apoptotic pathway through TRAIL was investigated in HBV- and HCV-related HCC that have different mechanisms of hepatocarcinogenesis. Caspase-3 activity and the expression of four types of TRAIL receptor mRNAs were quantitated in tumor and contiguous non-tumor tissues obtained from 27 patients with HCC (HBV-related in 10; HCV-related in 17). The expression of caspase-3 and TRAIL receptors was also examined immunohistochemically. A significantly positive correlation was observed between caspase-3 activity and TRAIL-R1, -R2. Caspase-3 activity and TRAIL-R1, -R2 expression in tumor tissue were significantly lower than those in non-tumor tissue in HBV-related HCC. Some HCV-related HCC cases, however, demonstrated elevated caspase-3 activity and TRAIL-R1, -R2 expression in tumor tissue. HBV-related HCC demonstrated significantly suppressed caspase-3 activity, signifying apoptosis. Both TRAIL-R1 and -R2 showed coefficient correlation with caspase-3 activity, and were strongly associated with apoptosis in human HCC.

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