TARGETING β-CATENIN IN HEPATOCELLULAR CANCERS INDUCED BY CO-EXPRESSION OF MUTANT β-CATENIN AND K-RAS IN MICE

摘要

Recently we have shown that co-expression of hMet and mutant-β-catenin using sleeping beauty transposon/transposase leads to HCC in mice that represents around 10% of human HCC. In the current study, we investigate if Ras activation, which can occur downstream of Met signaling, is sufficient to cause HCC in association with mutant-β-catenin. We also tested therapeutic efficacy of targeting β-catenin in HCC model. We show that mutant-K-Ras (G12D), which leads to Ras activation, cooperates with β-catenin mutants (S33Y, S45Y) to yield HCC in mice. Affymetrix microarray shows >90% similarity in gene expression in mutant-K-Ras-β-catenin and Met-β-catenin HCC. K-Ras-β-catenin tumors showed upregulation of β-catenin targets like Glutamine Synthetase (GS), Lect2, Regucalcin and Cyclin-D1 and of K-Ras effectors including p-ERK, p-AKT, p-mTOR, p-EIF4E, p-4E-BP1 and p-S6 Ribosomal protein. Inclusion of dominant-negative TCF4 at the time of K-Ras-β-catenin injection prevented HCC and downstream β-catenin and Ras signaling. To address if targeting β-catenin has any benefit post-establishment of HCC, we administered K-Ras-β-catenin mice with EnCore lipid nanoparticle (LNP) loaded with a Dicer substrate siRNA targeting CTNNB1 (CTNNB1-LNP), scrambled sequence (Scr-LNP) or PBS for multiple cycles. A significant decrease in tumor burden was evident in CTNNB1-LNP group versus all controls, which was associated with dramatic decreases in β-catenin targets and some K-Ras effectors, leading to reduced tumor cell proliferation and viability. Intriguingly, in few mice, non-GS-positive tumors, which were evident as a small subset of overall tumor burden, were not affected by β-catenin suppression. In conclusion, we show that Ras activation downstream of c-Met is sufficient to induce clinically relevant HCC in cooperation with mutant β-catenin. β-Catenin suppression by a clinically relevant modality is effective in treatment of β-catenin-positive, GS-positive HCCs.