Met‐β‐catenin induced hepatocellular cancer requires Ras but not Akt or Stat3 signaling

We have previously shown that co‐expression of hMet and mutant‐β‐catenin (S33Y or S45Y) using sleeping beauty transposon/transposase via hydrodynamic tail vein injection (SB‐HTVI) leads to HCC in mice referred to as Met‐b‐catenin model, which represented 11% of human HCC. Since Met signaling can activate downstream signaling including Ras, AKT/PI3K and STAT3, we next wanted to address if all these downstream components are equally or differentially required to lead to Met‐b‐catenin HCC. Recently, we replaced Met with G12D‐Kras to activate Ras/MAPK/Erk signaling and co‐expressed with mutant b‐catenin, which showed >90% gene expression similarity to Met‐b‐catenin HCC. Here, in leiu of Met, we co‐delivered mutant‐β‐catenin (S45Y/S33Y) with either myr‐AKT or H1047R‐PIK3CA or STAT3 via SB‐HTVI. Tumorigenesis was monitored at different stages after injection and molecular analysis was performed. Co‐injection of H1047R‐PIK3CA and S45Y/S33Y‐β‐catenin or myr‐ AKT and S45Y‐β‐catenin showed a notably slower tumor development as compared to Met‐b‐catenin or Kras‐b‐catenin model, taking >15 weeks post injection to develop appreciable tumor burden seen in the other 2 models at around 8 weeks. In fact, it took about 16 weeks and 22 weeks to induce comparable tumors for AKT‐S33Y‐β‐catenin group, and H1047R‐PIK3CA‐S33Y‐β‐catenin group, respectively. Co‐expression of active AKT/PI3K with mutant‐b‐catenin led to HCC displaying lipid accumulation in tumor cells. Co‐delivery of STAT3 and mutant‐catenin induced none or few small tumor nodules even around 34‐weeks post injection. There was evidence of increased p‐ERK, p‐AKT, and mTORC1/mTORC2 and downstream signaling including p‐EIF4E, p‐4E‐BP1 and p‐S6 Ribosomal protein as well as β‐catenin targets GS and CCND1 in AKT/PI3K‐b‐catenin. In conclusion, Ras signaling appears to be the most important downstream effector of Met signaling which cooperates with mutant β‐catenin for HCC development, while AKT/PI3K are of lesser relevance, and STAT3 of least relevance. These findings will have implications in biology as well as therapeutics for these subsets of human HCC as use of inhibitors of appropriate downstream effectors of Met may be more efficacious and with lesser off‐target effects than Met inhibition by itself in the Met‐b‐catenin HCC. Support or Funding Information This work was supported by NIH grants R01CA204586 to S.P.M