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Epigenetics as a therapeutic target in breast cancer.

ABSTRACT: Epigenetics refers to alterations in gene expression due to modifications in histone acetylation and DNA methylation at the promoter regions of genes. Unlike genetic mutations, epigenetic alterations are not due to modifications in the gene primary nucleotide sequence. The importance of epigenetics in the initiation and progression of breast cancer has led many investigators to incorporate this novel and exciting field in breast cancer drug development. Several drugs that target epigenetic alterations, including inhibitors of histone deacetylase (HDAC) and DNA methyltransferase (DNMT), are currently approved for treatment of hematological malignancies and are available for clinical investigation in solid tumors. In this manuscript, we review the critical role of epigenetics in breast cancer including the potential for epigenetic alterations to serve as biomarkers determining breast cancer prognosis and response to therapy. We highlight initial promising results to date with use of epigenetic modifiers in patients with breast cancer and the ongoing challenges involved in the successful establishment of these agents for the treatment of breast cancer.

SUBMITTER: Connolly R

PROVIDER: S-EPMC3515719 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Epigenetics as a therapeutic target in breast cancer.

Connolly Roisin R Stearns Vered V

Journal of mammary gland biology and neoplasia 20120727 3-4

Epigenetics refers to alterations in gene expression due to modifications in histone acetylation and DNA methylation at the promoter regions of genes. Unlike genetic mutations, epigenetic alterations are not due to modifications in the gene primary nucleotide sequence. The importance of epigenetics in the initiation and progression of breast cancer has led many investigators to incorporate this novel and exciting field in breast cancer drug development. Several drugs that target epigenetic alter ...[more]

PMID: 22836913

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Project description:G-protein-coupled receptors (GPCRs, also called seven-transmembrane or heptahelical receptors) are a superfamily of cell surface receptor proteins that bind to many extracellular ligands and transmit signals to an intracellular guanine nucleotide-binding protein (G-protein). When a ligand binds, the receptor activates the attached G-protein by causing the exchange of Guanosine-5'-triphosphate (GTP) for guanosine diphosphate (GDP). They play a major role in many physiological functions, as well as in the pathology of many diseases, including cancer progression and metastasis. Only a few GPCR members have been exploited as targets for developing drugs with therapeutic benefit in cancer. Present review briefly summarizes the signaling pathways utilized by the EP (prostaglandin E receptor) family of GPCR, their physiological and pathological roles in carcinogenesis, with special emphasis on the roles of EP4 in breast cancer progression. We make a case for EP4 as a promising newer therapeutic target for treating breast cancer. We show that an aberrant over-expression of cyclooxygenase (COX)-2, which is an inflammation-associated enzyme, occurring in 40-50% of breast cancer patients leads to tumor progression and metastasis due to multiple cellular events resulting from an increased prostaglandin (PG) E2 production in the tumor milieu. They include inactivation of host anti-tumor immune cells, such as Natural Killer (NK) and T cells, increased immuno-suppressor function of tumor-associated macrophages, promotion of tumor cell migration, invasiveness and tumor-associated angiogenesis, due to upregulation of multiple angiogenic factors including Vascular Endothelial Growth Factor (VEGF)-A, increased lymphangiogenesis (due to upregulation of VEGF-C/D), and a stimulation of stem-like cell (SLC) phenotype in cancer cells. All of these events were primarily mediated by activation of the Prostaglandin (PG) E receptor EP4 on tumor or host cells. We show that selective EP4 antagonists (EP4A) could mitigate all of these events tested with cells in vitro as well as in vivo in syngeneic COX-2 expressing mammary cancer bearing mice or immune-deficient mice bearing COX-2 over-expressing human breast cancer xenografts. We suggest that EP4A can avoid thrombo-embolic side effects of long term use of COX-2 inhibitors by sparing cardio-protective roles of PGI2 via IP receptor activation or PGE2 via EP3 receptor activation. Furthermore, we identified two COX-2/EP4 induced oncogenic and SLC-stimulating microRNAs-miR526b and miR655, one of which (miR655) appears to be a potential blood biomarker in breast cancer patients for monitoring SLC-ablative therapies, such as with EP4A. We suggest that EP4A will likely produce the highest benefit in aggressive breast cancers, such as COX-2 expressing triple-negative breast cancers, when combined with other newer agents, such as inhibitors of programmed cell death (PD)-1 or PD-L1.

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Epigenetics as a therapeutic target in breast cancer.

Publications

Epigenetics as a therapeutic target in breast cancer.

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