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.
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.
Project description:The CD44hi compartment in human breast cancer is enriched in tumor-initiating cells, however the functional heterogeneity within this subpopulation remains poorly defined. From a human breast cancer cell line with a known bi-lineage phenotype we have isolated and cloned CD44hi populations that exhibited mesenchymal/Basal B and luminal/Basal A features, respectively:CD44+/CD24-,Basal B (G4, H6) cells and CD44hi/CD24lo epithelioid Basal A (A4, AB) cells. Seven replicates of A4, seven replicates of G4, three replicates of AB, three replicates of H6
Project description:The CD44hi compartment in human breast cancer is enriched in tumor-initiating cells, however the functional heterogeneity within this subpopulation remains poorly defined. From a human breast cancer cell line with a known bi-lineage phenotype we have isolated and cloned CD44hi populations that exhibited mesenchymal/Basal B and luminal/Basal A features, respectively:CD44+/CD24-,Basal B (G4, H6) cells and CD44hi/CD24lo epithelioid Basal A (A4, AB) cells.
Project description:Both EZH2 and NF-?B contribute to aggressive breast cancer, yet whether the two oncogenic factors have functional cross-talk in breast cancer is largely unknown. Here, we uncover an unexpected role of EZH2 in conferring the constitutive activation of NF-?B target gene expression in ER-negative basal-like breast cancer cells. This function of EZH2 is independent of its histone methyltransferase activity but requires the physical interaction with RelA/RelB to promote the expression of NF-?B targets. Intriguingly, EZH2 acts oppositely in repressing NF-?B targets in ER-positive luminal-like breast cancer cells by interacting with ER and directing repressive histone methylation. Thus, EZH2 function as a double-facet molecule in breast cancers, functioning either as a transcriptional activator or repressor of NF-?B targets, in a cell context-dependent manner. These findings reveals an additional mechanism by which EZH2 promotes breast cancer progression and also underscore the need for developing context-specific strategy for therapeutic targeting of EZH2 in breast cancers. 12 samples were analyzed including three replicates of siNC CTRL and siEZH2 CTRL.
Project description:The CD44hi compartment in human breast cancer is enriched in tumor-initiating cells, however the functional heterogeneity within this subpopulation remains poorly defined. From a human breast cancer cell line with a known bi-lineage phenotype we have isolated and cloned two CD44hi populations that exhibited mesenchymal/Basal B and luminal/Basal A features, respectively. Rather than CD44+/CD24-,Basal B (G4) cells, only CD44hi/CD24lo, epithelioid Basal A (A4) cells retained a tumor-initiating capacity in NOG mice, form mammospheres and exhibit resistance to standard chemotherapy. Microarray data obtained from Affymetrix Human Gene 1.0 ST Array Five replicates of A4 and 5 replicates of G4
Project description:Both EZH2 and NF-κB contribute to aggressive breast cancer, yet whether the two oncogenic factors have functional cross-talk in breast cancer is largely unknown. Here, we uncover an unexpected role of EZH2 in conferring the constitutive activation of NF-κB target gene expression in ER-negative basal-like breast cancer cells. This function of EZH2 is independent of its histone methyltransferase activity but requires the physical interaction with RelA/RelB to promote the expression of NF-κB targets. Intriguingly, EZH2 acts oppositely in repressing NF-κB targets in ER-positive luminal-like breast cancer cells by interacting with ER and directing repressive histone methylation. Thus, EZH2 function as a double-facet molecule in breast cancers, functioning either as a transcriptional activator or repressor of NF-κB targets, in a cell context-dependent manner. These findings reveals an additional mechanism by which EZH2 promotes breast cancer progression and also underscore the need for developing context-specific strategy for therapeutic targeting of EZH2 in breast cancers.
Project description:The CD44hi compartment in human breast cancer is enriched in tumor-initiating cells, however the functional heterogeneity within this subpopulation remains poorly defined. From a human breast cancer cell line with a known bi-lineage phenotype we have isolated and cloned two CD44hi populations that exhibited mesenchymal/Basal B and luminal/Basal A features, respectively. Rather than CD44+/CD24-,Basal B (G4) cells, only CD44hi/CD24lo, epithelioid Basal A (A4) cells retained a tumor-initiating capacity in NOG mice, form mammospheres and exhibit resistance to standard chemotherapy. Microarray data obtained from Affymetrix Human Gene 1.0 ST Array
Project description:The tumor suppressor LATS1, whose expression is often downregulated in human breast cancer, helps maintain luminal breast cancer cell identity by keeping basal-specific genes in a closed chromatin state, preventing their spurious activation. This is achieved via interaction of LATS1 with the NCOR1 nuclear corepressor and recruitment of HDAC1,driving histone H3K27 deacetylation near NCOR1-repressed “basal” genes. Consequently, decreased expression of LATS1 elevates the expression of such “basal” genes and promotes luminal-to-basal slippage.
Project description:The tumor suppressor LATS1, whose expression is often downregulated in human breast cancer, helps maintain luminal breast cancer cell identity by keeping basal-specific genes in a closed chromatin state, preventing their spurious activation. This is achieved via interaction of LATS1 with the NCOR1 nuclear corepressor and recruitment of HDAC1,driving histone H3K27 deacetylation near NCOR1-repressed “basal” genes. Consequently, decreased expression of LATS1 elevates the expression of such “basal” genes and promotes luminal-to-basal slippage.