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Microarray expression profiling data for Trp53-null mammary epithelial cells and tumors from a mouse model with a K8+ luminal cell origin

ABSTRACT: Mammary epithelium is hierarchically organized, with multipotent basal mammary stem cells (MaSCs) producing both luminal and basal cells during development or upon transplantation. Recent studies suggested that most breast cancers might originate from luminal cells, and oncogenic events, such as ectopic expression of PIK3CAH1047R, could induce multipotency in committed luminal cells. p53 is the most commonly mutated gene in human breast cancer; in particular, its inactivating mutations are found in most triple-negative breast cancers, raising a question as to whether p53-loss plays a key role in acquisition of MaSC-like properties by luminal cells. By in situ lineage tracing, we found that induced loss of p53 in Keratin 8 (K8)+ luminal cells led to their clonal expansion, in part due to increased proliferation, but did not directly affect their luminal identity. Expansion of luminal cells, in particular oestrogen receptor-positive luminal cells, was observed 3-4 weeks after induced p53-loss, which was accompanied by increased expression of cell cycle genes and downregulation of genes related to immune microenvironment, p53 downstream pathway and apoptosis control. All induced mice eventually developed mammary tumours with 9qA1 (Yap1) amplification and/or 6qA2 (Met) amplification. The resulting tumours exhibited a MaSC-like expression signature and most closely resembled Claudin-Low breast cancer. Overall, these data suggest that although p53 does not directly control the luminal fate, its loss facilitates acquisition of MaSC-like properties by luminal cells and predisposes them to development of mammary tumours with loss of luminal identity. Our data also suggest that Claudin-Low breast cancer can originate from luminal cells, possibly upon transition through a basal-like state.

ORGANISM(S): Mus musculus

PROVIDER: GSE77496 | GEO | 2016/12/20

SECONDARY ACCESSION(S): PRJNA310637

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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Microarray expression profiling data for Trp53-null mammary epithelial cells and tumors from a mouse model with a K8+ luminal cell origin

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