PIK3CA-dependent hepatocarcinogenesis. A microarray comparing PIK3CA E545K and H1047R injected mice compared to age matched controls.

Gene expression microarray analyses of PIK3CA H1047R and E545K induced preneoplastic lesions and tumors compared to age matched controls. Plasmids expressing oncogenic forms of PIK3CA (H1047R or E545K mutants) were delivered to the mouse liver by tail vein hydrodynamic injection combined with Sleeping Beauty–mediated somatic integration (SBT-HTVI). Resulting preneoplastic and neoplastic lesions were subjected to gene expression microarray analysis. The putative PIK3CA target gene Galectin1 (Gal1) was further characterized by in vitro studies. Transfection of either PIK3CA E545K or H1047R mutants via SBT-HTVI was sufficient to induce hepatocellular carcinomas in mice. A stepwise hepatocarcinogenesis from singular pericentral lipid-rich preneoplastic hepatocytes to clusters, expansive preneoplastic lesions, and HCCs was observed. In PIK3CA H1047R injected mice, HCCs were detected in the 12 months injection group, while PIK3CA E545K injections resulted in tumor occurrence as early as 3 months after SB-HTVI. Histologically, a predominant lipid-rich phenotype characterized all tumorigenesis stages, as confirmed by Sudan III staining and electron microscopy. Immunohistochemically, preneoplastic lesions and tumors displayed high levels of the lipid master regulators Fatty acid synthase and Stearoyl-CoA desaturase-1. Gal1 was commonly overexpressed in PIK3CA-driven preneoplastic and neoplastic liver lesions by gene expression microarray analysis compared with age-matched controls. 4 x PIK3CA H1047R preneoplasia 3 months vs 5 x empty vector control 3 months; 5 x PIK3CA E545K preneoplasia 3 months vs 5 x empty vector control 3 months; 5 x PIK3CA E545K tumor 5 months vs 5 x empty vector control 5 months; 5 x empty vector control 6 months versus 5 x empty vector control 3 months; 2 x PIK3CA H1047R 6 and 12 months versus 5 x empty vector control 6 months