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EZH2 directs breast cancer progression through the modulation of epithelial cellular plasticity [RNA-Seq]

ABSTRACT: Breast cancer remains a leading cause of death among women, encompassing diverse molecular subtypes with distinct clinical outcomes. The HER2+ subtype is particularly aggressive, with many patients eventually developing resistance to HER2-targeted therapies, underscoring the urgent need for alternative treatment strategies. Enhancer of Zeste Homolog 2 (EZH2), the catalytic subunit of Polycomb Repressive Complex 2, represses the expression of genetic programs crucial for differentiation, control of proliferation, and apoptosis through histone H3 lysine 27 trimethylation (H3K27me3). To investigate the role of EZH2 in HER2+ tumor progression, we crossed a genetically engineered mouse model (GEMM) of HER2-driven breast cancer with a conditional Ezh2 knockout strain. The results showed that Ezh2 is essential for accelerating tumor initiation and metastatic dissemination in HER2-driven breast cancer. Combined bulk and single cell RNA sequencing analyses revealed a significant downregulation of basal cell populations in the absence of Ezh2, characterized by the loss of Tp63 expression, and an upregulation of luminal progenitor cell populations, driven by crucial transcription factors such as Esr1, thereby driving luminal lineage commitment. Further, inhibition of EZH2 in vitro resulted in increased expression of ER in HER2+ human breast cancer cell lines and rendered them susceptible to tamoxifen. Altogether, these findings demonstrate that EZH2 dictates breast cancer plasticity through control of cellular identity and provides rationale for combining EZH2 inhibitors with endocrine therapies to improve outcomes in HER2+ breast cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE303503 | GEO | 2025/11/07

REPOSITORIES: GEO

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EZH2 directs breast cancer progression through the modulation of epithelial cellular plasticity

Project description:Breast cancer remains a leading cause of death among women, encompassing diverse molecular subtypes with distinct clinical outcomes. The HER2+ subtype is particularly aggressive, with many patients eventually developing resistance to HER2-targeted therapies, underscoring the urgent need for alternative treatment strategies. Enhancer of Zeste Homolog 2 (EZH2), the catalytic subunit of Polycomb Repressive Complex 2, represses the expression of genetic programs crucial for differentiation, control of proliferation, and apoptosis through histone H3 lysine 27 trimethylation (H3K27me3). To investigate the role of EZH2 in HER2+ tumor progression, we crossed a genetically engineered mouse model (GEMM) of HER2-driven breast cancer with a conditional Ezh2 knockout strain. The results showed that Ezh2 is essential for accelerating tumor initiation and metastatic dissemination in HER2-driven breast cancer. Combined bulk and single cell RNA sequencing analyses revealed a significant downregulation of basal cell populations in the absence of Ezh2, characterized by the loss of Tp63 expression, and an upregulation of luminal progenitor cell populations, driven by crucial transcription factors such as Esr1, thereby driving luminal lineage commitment. Further, inhibition of EZH2 in vitro resulted in increased expression of ER in HER2+ human breast cancer cell lines and rendered them susceptible to tamoxifen. Altogether, these findings demonstrate that EZH2 dictates breast cancer plasticity through control of cellular identity and provides rationale for combining EZH2 inhibitors with endocrine therapies to improve outcomes in HER2+ breast cancer.

2025-10-28 | GSE303527 | GEO

EZH2 directs breast cancer progression through the modulation of epithelial cellular plasticity [ChIP-Seq]

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Mutant PI3K cooperates with HER2 to promote mammary tumor formation and induces trastuzumab resistance in vivo

Project description:HER2 (ERBB2) gene amplification and PIK3CA mutations often co-occur in breast cancer, and aberrant activation of the PI3K pathway has been implicated in resistance to HER2-directed therapies. We have created a mouse model of HER2-overexpressing (HER2+), PIK3CAH1047R-mutant breast cancer. Mice expressing both human HER2 and mutant PIK3CA in their mammary glands developed tumors with a significantly shorter latency compared to mice expressing either oncogene alone. By microarray analysis, HER2-driven tumors clustered with the luminal subtype, whereas HER2+PIK3CA and PIK3CA-driven tumors were associated with the claudin-low breast cancer subtype. In accordance, PIK3CA and HER2+PIK3CA tumors expressed elevated levels of EMT and stem cell markers, and cells from HER2+PIK3CA tumors more efficiently formed mammospheres, providing further evidence that activated PIK3CA may enrich for cancer stem cells. Finally, HER2+PIK3CA tumors are resistant to the HER2 antibody trastuzumab; resistance is partially reversed by the addition of a PI3K inhibitor. Taken together, these studies suggest that the co-expression of HER2 and PI3KH1047R in the mouse mammary gland accelerates the formation of aggressive, trastuzumab-resistant tumors. referenceXsample

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Mutant PI3K cooperates with HER2 to promote mammary tumor formation and induces trastuzumab resistance in vivo

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Ezh2 promotes mammary tumor initiation through epigenetic regulation of the Wnt and mTORC1 signaling pathways (ChIP-Seq)

Project description:The regulation of gene expression through histone post-translational modifications plays a crucial role in breast cancer progression. However, the molecular mechanisms underlying the contribution of histone modification to tumor initiation remain unclear. To gain a deeper understanding of the role of the histone modifier Enhancer of Zeste homology 2 (Ezh2) in the early stages of mammary tumor progression, we employed an inducible mammary organoid system bearing conditional Ezh2 alleles that faithfully recapitulates key events of Luminal B breast cancer initiation. We showed that the loss of Ezh2 severely impairs oncogene-induced organoid growth, with Ezh2-deficient organoids maintaining a polarized epithelial phenotype. Transcriptomic profiling showed that Ezh2-deficient mammary epithelial cells upregulated the expression of negative regulators of Wnt signaling and downregulated genes involved in mTORC1 (mechanistic target of rapamycin complex 1) signaling. We identified Sfrp1, a Wnt signaling suppressor, as an Ezh2 target gene that is de-repressed and expressed in Ezh2-deficient epithelium. Furthermore, an analysis of breast cancer data revealed that Sfrp1 expression was associated with favorable clinical outcomes in Luminal B breast cancer patients. Finally, we confirmed that targeting Ezh2 impairs mTORC1 activity through an indirect mechanism that upregulates the expression of the tumour suppressor Pten. These findings indicate that Ezh2 integrates the mTORC1 and Wnt signaling pathways during early mammary tumor progression, arguing that inhibiting Ezh2 or therapeutically targeting Ezh2-dependent programs could be beneficial for the treatment of early-stage Luminal B breast cancer.

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Ezh2 promotes mammary tumor initiation through the epigenetic regulation of the Wnt and mTORC1 signaling pathways (RNA-Seq)

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EZH2 promotes a bi-lineage identity in basal-like breast cancer cells

Project description:The mechanisms regulating breast cancer differentiation state are poorly understood. Of particular interest are molecular regulators controlling the highly aggressive and poorly differentiated traits of basal-like breast carcinomas. Here we show that the Polycomb factor EZH2 maintains the differentiation state of basal-like breast cancer cells, and promotes the expression of progenitor-associated and basal-lineage genes. Specifically, EZH2 regulates the composition of basal-like breast cancer cell populations by promoting a M-bM-^@M-^\bi-lineageM-bM-^@M-^] differentiation state, in which cells co-express basal- and luminal-lineage markers. We show that human basal-like breast cancers contain a subpopulation of bi-lineage cells, and that EZH2-deficient cells give rise to tumors with a decreased proportion of such cells. Bi-lineage cells express genes that are active in normal luminal progenitors, and possess increased colony formation capacity, consistent with a primitive differentiation state. We found that GATA3, a driver of luminal differentiation, performs a function opposite to EZH2, acting to suppress bi-lineage identity and luminal progenitor gene expression. GATA3 levels increase upon EZH2 silencing, leading to the observed decrease in bi-lineage cell numbers. Our findings reveal a novel role for EZH2 in controlling basal-like breast cancer differentiation state and intra-tumoral cell composition. Total of four treatments (HCC70 cells stably expressing shEZH2, shEED, or EZH2 cDNA, and MDA-MB-468 cells stably expressing shEZH2) were done in duplicates, each with its own control.

2012-09-21 | E-GEOD-36939 | biostudies-arrayexpress

Next Generation Sequencing Transcriptomes of breast cancer

Project description:We performed high throughput transcriptome of breast cancer and normal tissues, identifying lincRNA associated molecular subtype with powerful capacity to distinct breast cancer population and predict prognosis. We also identified subtype-specific lincRNAs that may be a useful complement to intrinsic molecular subtype classification when divergence emerges among pathologists.Paired-end transcriptome sequencing were carried out on a cohort of 33 breast tissues from 11 groups including five breast cancer subtypes including luminal A (LA), luminal B (HER2 negative)(LB, HER2-), luminal B (HER2 positive) (LB, HER2+), HER2 and tripple negative breast cancer (TNB), adjacent noncancerous breast tissue (ANT, three samples for each subtype) and the complete normal breast tissues (three samples)

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Treatment effects of trastuzumab and TDM-1 in a murine model of breast cancer brain metastasis

Project description:Background: Central nervous system (CNS) metastases represent a major problem in the treatment of HER2-positive breast cancer due to the disappointing efficacy of HER2-targeted therapies in the brain microenvironment. The antibody-drug conjugate ado-trastuzumab emtansine (T-DM1) has shown efficacy in trastuzumab-resistant systemic breast cancer. Here, we tested the hypothesis that T-DM1 could overcome trastuzumab resistance in preclinical models of brain metastases. Methods: We treated mice bearing BT474 or MDA-MB-361 tumors in the CNS (N=9-11 per group), or cancer cells grown in organotypic brain slice cultures with trastuzumab or T-DM1 at equivalent or equipotent doses. Using intravital imaging, molecular techniques and histological analysis we determined tumor growth, mouse survival, cancer cell apoptosis and proliferation, tumor drug distribution, and HER2 signaling. All statistical tests were two-sided. Results: T-DM1 significantly delayed the growth of HER2-positive breast cancer brain metastases compared to trastuzumab. These findings were consistent between HER2-driven and PI3K-driven tumors. The activity of T-DM1 resulted in a striking survival benefit (median survival for BT474 tumors: 28d for trastuzumab vs 112d for T-DM1, HR=6.2, 95% CI=6.1 to 85.84; P<.001). No difference in drug distribution and HER2-signaling was revealed between the two groups. However, T-DM1 led to a significant increase in tumor cell apoptosis (One-way ANOVA for ApopTag, p<.001), which was associated with mitotic catastrophe. Conclusions: T-DM1 can overcome resistance to trastuzumab therapy in HER2-driven and PI3K-driven breast cancer brain lesions due to the cytotoxicity of the DM1 component. Clinical investigation of T-DM1 for patients with CNS metastases from HER2-positive breast cancer is warranted. Comparison of trastuzumab (n=4) and TDM-1 (n=4) treated BT-474 human breast carcinoma cells growing in murine brain

2015-11-09 | E-GEOD-69042 | biostudies-arrayexpress

EZH2 promotes a bi-lineage identity in basal-like breast cancer cells

Project description:The mechanisms regulating breast cancer differentiation state are poorly understood. Of particular interest are molecular regulators controlling the highly aggressive and poorly differentiated traits of basal-like breast carcinomas. Here we show that the Polycomb factor EZH2 maintains the differentiation state of basal-like breast cancer cells, and promotes the expression of progenitor-associated and basal-lineage genes. Specifically, EZH2 regulates the composition of basal-like breast cancer cell populations by promoting a “bi-lineage” differentiation state, in which cells co-express basal- and luminal-lineage markers. We show that human basal-like breast cancers contain a subpopulation of bi-lineage cells, and that EZH2-deficient cells give rise to tumors with a decreased proportion of such cells. Bi-lineage cells express genes that are active in normal luminal progenitors, and possess increased colony formation capacity, consistent with a primitive differentiation state. We found that GATA3, a driver of luminal differentiation, performs a function opposite to EZH2, acting to suppress bi-lineage identity and luminal progenitor gene expression. GATA3 levels increase upon EZH2 silencing, leading to the observed decrease in bi-lineage cell numbers. Our findings reveal a novel role for EZH2 in controlling basal-like breast cancer differentiation state and intra-tumoral cell composition.

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