Transcriptome analysis of mouse tumors driven by PIK3CA mutation variants
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE123519 | GEO | 2019/10/09
REPOSITORIES: GEO
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Project description: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.
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Project description:While growth factor-independent signaling and proliferation are well-established hallmarks of cancer, little is known regarding growth factor-independent changes in gene expression which occur downstream from oncogenes. The PI3K pathway is one of the most commonly misregulated signaling pathways in human cancers. Here, MCF10A cells expressing the two most common PI3K mutations, PIK3CA E545K and H1047R, were used to identify the repertoire of genes altered by oncogenic PI3K mutations following growth factor deprivation. This gene set most closely correlated with gene signatures from claudin-low and basal-like breast tumors, and categorical enrichment analyses suggested that NF-kB target genes were dramatically upregulated by these mutations. An IKKb inhibitor was used to identify the subset of PI3K-driven genes that is NF-kB dependent. Interestingly, virtually all of these NF-kB dependent genes were secreted proteins, suggesting a paracrine role for this gene set. Among these genes was IL-6, a cytokine frequently expressed in tumors which plays a critical role in generating a tumor-promoting microenvironment. Consistent with this, conditioned media from cells expressing the E545K or H1047R mutations led to increased STAT3 activation in recipient THP-1 monocytes or normal epithelial cells in a NF-kB and IL-6-dependent manner. Together, these data describe a PI3K-driven, NF-kB-dependent gene expression profile which may play a critical role in promoting a microenvironment amenable to tumor progression.
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