Project description:Perturbations in histone modifications alter transcription and promote carcinogenesis. Breast cancers frequently overexpress the histone methyltransferase EZH2, the catalytic subunit of Polycomb Repressor Complex 2 (PRC2). However, the mechanisms driving EZH2 overexpression are obscure and elucidating the role of PRC2 in breast cancer, which is highly heterogeneous, is challenging given its context-dependent oncogenic and tumor suppressive functions. Here, using genetically engineered mouse, PDX and cell line models, we show that the tyrosine kinase c-Src links energy sufficiency with PRC2 subunit overexpression via control of mRNA translation. In breast cancers initiated by the oncogene ErbB2, c-Src stimulates mitochondrial ATP production to suppress energy stress and permit sustained activation of the mammalian/mechanistic target of rapamycin complex 1 (mTORC1), which increases the translation of mRNAs encoding the PRC2 subunits Ezh2 and Suz12. We show that Ezh2 overexpression and activity are pivotal in ErbB2-mediated mammary tumorigenesis. These results reveal the hitherto unknown c-Src/mTORC1/PRC2 axis, which is essential for ErbB2-driven carcinogenesis.
Project description:Perturbations in histone modifications alter transcription and promote carcinogenesis. Breast cancers frequently overexpress the histone methyltransferase EZH2, the catalytic subunit of Polycomb Repressor Complex 2 (PRC2). However, the mechanisms driving EZH2 overexpression are obscure and elucidating the role of PRC2 in breast cancer, which is highly heterogeneous, is challenging given its context-dependent oncogenic and tumor suppressive functions. Here, using genetically engineered mouse, PDX and cell line models, we show that the tyrosine kinase c-Src links energy sufficiency with PRC2 subunit overexpression via control of mRNA translation. In breast cancers initiated by the oncogene ErbB2, c-Src stimulates mitochondrial ATP production to suppress energy stress and permit sustained activation of the mammalian/mechanistic target of rapamycin complex 1 (mTORC1), which increases the translation of mRNAs encoding the PRC2 subunits Ezh2 and Suz12. We show that Ezh2 overexpression and activity are pivotal in ErbB2-mediated mammary tumorigenesis. These results reveal the hitherto unknown c-Src/mTORC1/PRC2 axis, which is essential for ErbB2-driven carcinogenesis.
Project description:Perturbations in histone modifications alter transcription and promote carcinogenesis. Breast cancers frequently overexpress the histone methyltransferase EZH2, the catalytic subunit of Polycomb Repressor Complex 2 (PRC2). However, the mechanisms driving EZH2 overexpression are obscure and elucidating the role of PRC2 in breast cancer, which is highly heterogeneous, is challenging given its context-dependent oncogenic and tumor suppressive functions. Here, using genetically engineered mouse, PDX and cell line models, we show that the tyrosine kinase c-Src links energy sufficiency with PRC2 subunit overexpression via control of mRNA translation. In breast cancers initiated by the oncogene ErbB2, c-Src stimulates mitochondrial ATP production to suppress energy stress and permit sustained activation of the mammalian/mechanistic target of rapamycin complex 1 (mTORC1), which increases the translation of mRNAs encoding the PRC2 subunits Ezh2 and Suz12. We show that Ezh2 overexpression and activity are pivotal in ErbB2-mediated mammary tumorigenesis. These results reveal the hitherto unknown c-Src/mTORC1/PRC2 axis, which is essential for ErbB2-driven carcinogenesis.
Project description:To identify genes that may facilitate early steps of ErbB2/Neu-mediated mammary tumorigenesis, we performed comparative microarray analysis of 5- and 10-week bitransgenic mammary glands (LHxMMTV-neu) in triplicate. Keywords: transgenic mouse, erbB2, MMTV-neu, HER2, mammary tumor, breast cancer
Project description:To identify early events of erbB2-induced mammary tumorigenesis, we compared datasets from 14 genechip experiments including MMTV-neu tumors, preneoplastic neu mammary gland (adjacent neu), and age-matched, wild-type control mammary glands
Project description:Previously we have demonstrated that inactivation of retinoic acid receptor beta (Rarb) in the mouse results in a protective effect against ErbB2-induced mammary gland tumorigenesis although Rarb has been reported as a tumor suppressor before. In the current study, we further confirmed that ablation of Rarb has a very similar impact on Wnt1-induced mammary gland tumorigenesis as those on ErbB2-induced mammary gland tumorigenesis. Nevertheless, the mechanisms by which Rarb confers its effects on tumor progression is quite different although both involving in tumor microenvironment (TME) remodeling. In the Wnt1 tumors, ectopic wnt1 produced by malignant luminal cells activates nearby stromal cells by a paracrine manner. In return, the stromal cells secreted IGF1 to regulate the growth of tumor cells. There is a need of Rarb expression in this interaction. Deletion of Rarb inhibits both wnt1/β-catenin signaling and IGF1/Akt axis in the myoepithelial tumor cells which results in the suppression of epithelial-mesenchymal transition (EMT) in these tumors. Since wnt1 tumors resemble basal-like breast cancer with a poor clinical prognosis in which EMT is one of the most important way for tumor cells to survive against standard treatment and to go to metastasis, we propose that (1) the stromal gene expression signature of Rarb ablation in wnt1 tumors could have some clinical value in predicting the breast cancer outcome; and (2) Rarb antagonist might be a potential therapeutic strategy in EMT-driven aggressive cancers such as basal-like breast cancer. Laser capture microdissection (LCM) was performed to separate the mammary tumor samples into epithelial cell compartment and stromal cell compartment. Transcriptional profiling of the two compartments were investigated by microarray analysis.
