Activation of beta-catenin pathway in human hepatocellular carcinoma negatively correlates to AFP and CD-44 expression

Background: Studies on HCC cell lines has recently highlighted connection between nuclear shift of b-catenin protein indicative of mutation and absent or weak AFP expression. Further, recent data indicate that HCCs associated with activation of the wnt pathway and downregulated AFP expression possess a better prognosis.

Aim: We wished to characterize b-catenin nuclear translocation in 37 human HCCs and surrounding liver samples and correlate to CD-44 and AFP expression.

Material and methods: 37 human HCC samples were examined by immunohistochemistry for b-catenin, AFP and CD-44 expression. 16 HCC samples were selected for relative quantification of AFP – real time RT-PCR using GAPDH as internal control.

Results: 8 of 37 (22%) HCC showed nuclear shift of b-catenin, and none of these tumors showed strong (++/+++) expression of AFP compared to 45% (13/29) of nuclear b-catenin negative HCCs. CD44 expression also negatively correlated to nuclear shift of b-catenin, 1/8 and 8/29 respectively. Real time RT-PCR performed on 7 samples with and 9 samples without nuclear accumulation of b-catenin showed 23.247 fold downregulation of AFP expression in nuclear b-catenin positive HCCs. The sequence analysis of these samples verified known mutations of EXON 3 (41 Thr-Ala; 37 Ser-Cys, 36 His-Thr, 32 Asp-Asn, 34 Gly-Val).

Conclusion: Our data suggest that activation of b-catenin pathway negatively correlates to AFP and CD44 expression in human HCC. The nuclear accumulation of b-catenin is associated with a markedly reduced mRNA and protein expression of AFP compared to HCCs with no activation of b-catenin pathway.

The project was supported by grants: Bio14/2001.