Leukocyte Cell Derived Chemotaxin 2 (LECT2) ELISA Kit (Human)

Activation of Wnt/beta-catenin signaling is frequent in human and rodent hepatocarcinogenesis. Although in mice the tumor-promoting activity of agonists of constitutive androstane receptor (CAR) occurs by selection of carcinogen-initiated cells harboring beta-catenin mutations, the molecular alterations leading to hepatocellular carcinoma (HCC) development by the CAR agonist 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene (TCP) in the absence of genotoxic injury are unknown. Here, we show that CAR activation per se induced HCC in mice and that 91% of them carried beta-catenin point mutations or large in-frame deletions/exon skipping targeting Ctnnb1 exon 3. Point mutations in HCCs induced by TCP alone displayed different nucleotide substitutions compared with those found in HCCs from mice pretreated with diethylnitrosamine. Moreover, unlike those occurring in HCCs from diethylnitrosamine TCP mice, they did not result in increased expression of beta-catenin target genes, such as Glul, Lgr5, Rgn, Lect2, Tbx3, Axing, and Ccnd1, or nuclear translocation of beta-catenin compared with the control liver. Remarkably, in the nontumoral Liver tissue, chronic CAR activation led to down-regulation of these genes and to a partial loss of glutamine synthetase-positive hepatocytes. These results show that, although chronic CAR activation per se induces HCCs carrying beta-catenin mutations, it concurrently down-regulates the Wnt/beta-catenin pathway in nontumoral liver. They also indicate that the relationship between CAR and beta-catenin may be profoundly different between normal and neoplastic hepatocytes.

Aim beta-catenin signaling is a major oncogenic pathway in hepatocellular carcinoma (HCC). Since beta-catenin phosphorylation by glycogen synthase kinase 3 beta (GSK3 beta) and casein kinase 1 epsilon (CK1 epsilon) results in its degradation, mutations affecting these phosphorylation sites cause beta-catenin stabilization. However, the relevance of missense mutations in non-phosphorylation sites in exon 3 remains unclear. The current study explores significance of such mutations in addition to addressing the clinical and biological implications of beta-catenin activation in human HCC. Methods Gene alteration in exon3 of CTNNB1, gene expression of beta-catenin targets such as glutamate synthetase (GS), axin2, lect2 and regucalcin (RGN), and protein expression of beta-catenin were examined in 125 human HCC tissues. Results Sixteen patients (12.8%) showed conventional missense mutations affecting codons 33, 37, 41, and 45. Fifteen additional patients (12.0%) had other missense mutations in codon 32, 34, and 35. Induction of exon3 mutation caused described beta-catenin target gene upregulation in HCC cell line. Interestingly, conventional and non-phosphorylation site mutations were equally associated with upregulation of beta-catenin target genes. Nuclear localization of beta-catenin was associated with poor overall survival (p = 0.0461). Of these patients with nuclear beta-catenin localization, loss of described beta-catenin target gene upregulation showed significant poorer overall survival than others (p = 0.0001). Conclusion This study suggests that both conventional and other missense mutations in exon 3 of CTNNB1 lead to beta-catenin activation in human HCC. Additionally, the mechanism of nuclear beta-catenin localization without upregulation of described beta-catenin target genes might be of clinical importance depending on distinct mechanism.