Abstract
Aberrant activation of the PI3K/AKT/mTOR and Ras/Mitogen-Activated Protein Kinase pathways is a hepatocarcinogenesis hallmark. In a subset of hepatocellular carcinomas (HCC), PI3K/AKT/mTOR signaling dysregulation depends on PIK3CA mutations, while RAS/MAPK activation is partly attributed to promoter methylation of the tumor suppressor RASSF1A. To evaluate a possible co-carcinogenic effect of PIK3CA activation and RASSF1A knockout, plasmids expressing oncogenic forms of PIK3CA (E545K or H1047R mutants) were delivered to the liver of RASSF1A knockout and wildtype mice by hydrodynamic tail vein injection combined with Sleeping Beauty–mediated somatic integration. Transfection of either PIK3CA E545K or H1047R mutants sufficed to induce hepatocellular carcinomas in mice irrespective of RASSF1A mutational background. The related tumors displayed a lipogenic phenotype with upregulation of Fatty acid synthase and Stearoyl-CoA desaturase-1 (SCD1). Galectin-1, which was commonly upregulated in preneoplastic lesions and tumors, emerged as a regulator of SCD1. Co-inhibitory treatment with PIK3CA inhibitors and the Galectin-1 inhibitor OTX-008 resulted in synergistic cytotoxicity in human HCC cell lines, suggesting novel therapeutic venues.
Graphical Abstract Hydrodynamic tail vein injection of Phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutant forms E545K and H1047R induces stepwise hepatocarcinogenesis in mice, independent of Ras association domain-containing protein 1 (RASSF1A) status. Gene expression analyses revealed an early increase in Galectin-1, which regulates the lipogenic enzyme Stearoyl-CoA desaturase-1 (SCD1). PIK3CA- and Galectin1 inhibitors act synergistically, pointing at novel therapeutic strategies.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- ACAC
- Acetyl-CoA carboxylase 1
- ACLY
- ATP citrate synthase
- CK7
- cytokeratin 7
- COX2
- Prostaglandin-endoperoxide synthase 2
- CPS1
- carbamoyl phosphate synthetase I
- EOB
- excess over the Bliss score
- EMT
- epithelial-mesenchymal-transition
- EV
- empty vector
- FASN
- Fatty acid synthase
- FBXW7
- F-box and WD repeat domain-containing 7
- Gal-1
- Galectin-1
- Gal-3
- Galectin-3
- Gpc3
- Glypican-3
- GSEA
- Gene Set Enrichment Analyses
- HCC
- hepatocellular carcinoma
- JAK2
- Janus-Kinase 2
- KO
- knockout
- MAPK
- Ras/Mitogen Activated Protein Kinase
- myrAKT
- AKT with myristoylation sequence
- PI3K
- phosphoinositide 3-kinase
- PIK3CA
- Phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha
- PIP2
- phosphatidylinositol (4,5)-bisphosphate
- PIP3
- phosphatidylinositol (3,4,5)-trisphosphate
- PPARγ
- peroxisome proliferator-activated receptor gamma
- RASSF1A
- Ras association domain-containing protein 1
- SCD1
- Stearoyl-CoA desaturase-1
- SGK3
- serum/glucocorticoid regulated kinase family member 3
- STAT3
- Signal transducer and activator of transcription 3
- WT
- wildtype
- YAP
- yes-associated protein 1
- ZIP4
- Zrt-Irt-like protein 4