HCCS

Abstract: Hepatocellular carcinoma (HCC) is the major primary malignant tumor in the human liver, but the molecular changes leading to liver cell transformation remain largely unknown. The Wnt-β-catenin pathway is activated in colon cancers and some melanoma cell lines, but has not yet been investigated in HCC. We have examined the status of the β-catenin gene in different transgenic mouse lines of HCC obtained with the oncogenes c-myc or H-ras. Fifty percent of the hepatic tumors in these transgenic mice had activating somatic mutations within the β-catenin gene similar to those found in colon cancers and melanomas. These alterations in the β-catenin gene (point mutations or deletions) lead to a disregulation of the signaling function of β-catenin and thus to carcinogenesis. We then analyzed human HCCs and found similar mutations in eight of 31 (26%) human liver tumors tested and in HepG2 and HuH6 hepatoma cells. The mutations led to the accumulation of β-catenin in the nucleus. Thus alterations in the β-catenin gene frequently are selected for during liver tumorigenesis and suggest that disregulation of the Wnt-β-catenin pathway is a major event in the development of HCC in humans and mice.

Abstract: The Wnt signalling pathway is essential for development and organogenesis1,2,3. Wnt signalling stabilizes β-catenin, which accumulates in the cytoplasm, binds to T-cell factor (TCF; also known as lymphocyte enhancer-binding factor, LEF) and then upregulates downstream genes4,5,6. Mutations in CTNNB1 (encoding β-catenin) or APC (adenomatous polyposis coli) have been reported in human neoplasms including colon cancers and hepatocellular carcinomas7,8,9,10,11,12,13 (HCCs). Because HCCs tend to show accumulation of β-catenin more often than mutations in CTNNB1 , we looked for mutations in AXIN1, encoding a key factor for Wnt signalling, in 6 HCC cell lines and 100 primary HCCs. Among the 4 cell lines and 87 HCCs in which we did not detect CTNNB1 mutations, we identified AXIN1 mutations in 3 cell lines and 6 mutations in 5 of the primary HCCs. In cell lines containing mutations in either gene, we observed increased DNA binding of TCF associated with β-catenin in nuclei. Adenovirus mediated gene transfer of wild-type AXIN1 induced apoptosis in hepatocellular and colorectal cancer cells that had accumulated β-catenin as a consequence of either APC, CTNNB1 or AXIN1 mutation, suggesting that axin may be an effective therapeutic molecule for suppressing growth of hepatocellular and colorectal cancers.

Abstract: The CD95 (APO-1/Fas) system is an important mediator of T-cell cytotoxicity. We investigated this system in 22 hepatocellular carcinomas (HCCs) from patients. All HCCs had partially or completely lost the expression of the CD95 receptor constitutively expressed by normal liver cells and might thus evade CD95-mediated killing. We also considered a new mechanism of immune evasion, namely, the active destruction of T-lymphocytes by tumor cells expressing CD95 ligand (CD95L). CD95L messenger RNA and protein could be detected in the HCCs. In coculture experiments, HepG2 hepatoblastoma cells, expressing CD95L mRNA after treatment with cytostatic drugs, killed CD95+ Jurkat lymphocytes. Our data suggest that tumor cells can evade immune attack by down-regulation of the CD95 receptor and killing of lymphocytes through expression of CD95L.