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

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE173963 | GEO | 2021/05/06

REPOSITORIES: GEO

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Project description:Breast cancer is the most frequent cancer in women and consists of heterogeneous types of tumours that are classified into different histological and molecular subtypes1-3. Pik3ca and p53 are the two most frequently mutated genes and are associated with different types of human breast cancers4. The cellular origin and the mechanisms leading to Pik3ca-induced tumour heterogeneity remain unknown. Here, we used a genetic approach in mice to define the cellular origin of Pik3ca-derived tumours and its impact on tumour heterogeneity. Surprisingly, oncogenic Pik3ca-H1047R expression at physiological levels5 in basal cells (BCs) using K5CREERT2 induced the formation of luminal ER+PR+ tumours, while its expression in luminal cells (LCs) using K8CREERT2 gave rise to luminal ER+PR+ tumours or basal-like ER-PR- tumours. Concomitant deletion of p53 and expression of Pik3ca-H1047R accelerated tumour development and induced more aggressive mammary tumours. Interestingly, expression of Pik3ca-H1047R in unipotent BCs gave rise to luminal-like cells, while its expression in unipotent LCs gave rise to basal-like cells before progressing into invasive tumours. Transcriptional profiling of cells that have undergone cell fate transition upon Pik3ca-H1047R expression in unipotent progenitors demonstrate a profound oncogene-induced reprogramming of these newly formed cells and identified gene signatures, characteristic of the different cell fate switches that occur upon Pik3ca-H1047R expression in BC and LCs, which correlated with the cell of origin, tumour type and different clinical outcomes. Altogether our study identifies the cellular origin of Pik3ca-induced tumours and reveals that oncogenic Pik3ca-H1047R activates a multipotent genetic program in normally lineage-restricted populations at the early stage of tumour initiation, setting the stage for future intratumoural heterogeneity. These results have important implications for our understanding of the mechanisms controlling tumour heterogeneity and the development of new strategies to block PIK3CA breast cancer initiation. Luminal and basal cells, or tumour cells, from mice in which expression of PIK3CA-H1047R and YFP (and in some conditions loss of p53) was targeted in basal cells using K5CREERT2 or in luminal cells using K8CREERT2 were FACS isolated and RNA was extracted before being hybridized Affymetrix microarrays.

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

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