Tumor-Suppressive Function of SLC5A8 in Mammary Gland and its Relevance to Breast

SLC5A8在乳腺中的抑癌功能及其与乳房的关系

• 批准号: 7615169
• 负责人: Muthusamy Thangaraju
• 金额: $ 26.35万
• 依托单位: AUGUSTA UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-17 至 2013-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7615169
• 关键词: Animal Model; Apoptosis; Apoptotic; Azacitidine; Biological Models; Breast; Breast Cancer Cell; Breast Cancer Treatment; Butyrates; CCAAT-Enhancer-Binding Proteins; Cancer cell line; Cell Death; Cell membrane; Cell physiology; Cells; Cessation of life; Colon; Colon Carcinoma; Combined Modality Therapy; DNA; DNA Methylation; DNA Methyltransferase; DNA Modification Methylases; DNMT3B gene; Data; Development; Dietary Fiber; Disease; Down-Regulation; Drug Delivery Systems; Epithelial Cells; Estrogen Antagonists; Estrogen Receptors; Estrogen Therapy; Estrogen receptor negative; Estrogen receptor positive; Event; Fermentation; Gene Activation; Genes; Genus Cola; Growth; Histone Deacetylase Inhibitor; Histone deacetylase inhibition; Histones; Human; Hypermethylation; Induction of Apoptosis; Knock-out; Knockout Mice; Laboratories; Lead; Link; MAPK Signaling Pathway Pathway; MCF7 cell; MDA MB 231; Mammary Neoplasms; Mammary Tumorigenesis; Mammary gland; Mediating; Membrane Transport Proteins; Methylation; Molecular; Mus; New Agents; Nude Mice; Oncogene Activation; Oncogenic; Patients; Play; Prevention; Process; Propionates; Proteins; Pyruvate; Pyruvates; Receptor Signaling; Recurrence; Research Design; Role; Secondary to; Signal Pathway; Signal Transduction; Small Interfering RNA; TP53 gene; Testing; Tetanus Helper Peptide; Therapeutic; Tissues; Transcription Coactivator; Transcription Repressor/Corepressor; Transferase; Transgenic Mice; Tumor Cell Line; Tumor Suppression; Tumor Suppressor Proteins; Volatile Fatty Acids; Whey Acidic Protein Staining Method; Xenograft Model; Xenograft procedure; apical membrane; base; cancer cell; cancer therapy; cell growth; design; effective therapy; homologous recombination; in vivo; inhibitor/antagonist; killings; loss of function; malignant breast neoplasm; metaplastic cell transformation; neoplastic cell; novel strategies; promoter; protein function; ras Oncogene; stable cell line; therapeutic development; tumor; tumor progression; tumorigenesis; tumorigenic; whey acidic proteins

DESCRIPTION (provided by applicant): The purpose of this project is to investigate the tumor-suppressive function of SLC5A8 in mammary gland and to evaluate its therapeutic potential in the treatment of breast cancer. SLC5A8 is a plasma membrane transporter originally identified as a tumor suppressor in colon, but neither the identity of its transport function nor how it elicits tumor suppression was known. Our recent studies have not only established the identity of the transport function of this protein but also the mechanism by which the transporter promotes tumor cell-specific apoptosis. SLC5A8 is a Na+coupled transporter for monocarboxylates (e.g., propionate, butyrate, lactate, pyruvate). Butyrate is a well known inhibitor of histone deacetylases (HDACs) and is generated in the colon by bacterial fermentation. HDAC inhibitors preferentially kill tumor cells. We have shown recently that pyruvate is also a potent HDAC inhibitor and that pyruvate and butyrate induce tumor cell-specific apoptosis in a SLC5A8-dependent manner. Thus, the ability of SLC5A8 to mediate the concentrative entry of the HDAC inhibitors pyruvate and/or butyrate into cells underlies the tumor-suppressive function of this transporter. SLC5A8 is expressed in normal mammary gland and the gene is silenced in breast cancer by DNA methylation. Exogenous expression of the transporter in mammary tumor cell lines leads to cell death in a pyruvate/butyrate-dependent manner. Methylation of SLC5A8 gene in mammary epithelial cells involves the DNA methyltransferase DNMT1; activation of the oncogene Ras plays a critical role in this process. Treatment of mammary tumor cells with DNA demethylating agents re-activates SLC5A8 expression. This phenomenon is seen in estrogen receptor (ER)-positive and in ER-negative cells. Importantly, re-expression of SLC5A8 leads to cell death both in ER-positive and ER-negative cells in the presence of pyruvate or butyrate. To achieve a better understanding of how breast cancer cells down-regulate SLC5A8 and how re-activation of the transporter expression leads to tumor cell-specific apoptosis and blockade of mammary tumorigenesis, we propose three aims. Aim 1 is to investigate the mechanism of down-regulation of SLC5A8 in breast cancer. Hypothesis: Methylation-associated silencing of SLC5A8 is secondary to the activation of Ras-associated MAPK signaling pathway. Aim 2 is to confirm the ability of SLC5A8 to block mammary tumorigenesis in vivo. Hypothesis: Re-activation of SLC5A8 in breast cancer or over-expression of SLC5A8 in normal mammary gland will effectively block mammary tumor formation. Aim 3 is to evaluate the therapeutic potential of SLC5A8 in ER-negative breast cancer. Hypothesis: Activation of SLC5A8 expression in ER-negative breast cancer will induce pyruvate/butyrate-mediated tumor cell-specific apoptosis. These studies will generate important and clinically/therapeutically relevant information which will aid in the development of novel strategies for the prevention and/or treatment of breast cancer. PUBLIC HEALTH RELEVANCE: The purpose of this project is to investigate the potential of a newly discovered tumor suppressor as a drug target for the treatment of breast cancer. This tumor suppressor is a plasma membrane transporter which mediates the entry of histone deacetylase (HDAC) inhibitors pyruvate and butyrate into cells. HDAC inhibition causes tumor cell-specific apoptosis and cell death. Breast cancer cells shut off the expression of the transporter to avoid this cell death. In the current project, we will test the hypothesis that re-activation of the expression of the transporter gene in breast cancer cells would induce tumor cell-specific apoptosis through transporter-mediated entry of pyruvate or butyrate. This mode of therapy may be effective not only for the estrogen receptor-positive breast cancer but also for the estrogen receptor-negative breast cancer.

描述（由申请人提供）：本项目的目的是研究SLC 5A 8在乳腺中的肿瘤抑制功能，并评估其在乳腺癌治疗中的治疗潜力。SLC 5A 8是一种质膜转运蛋白，最初被鉴定为结肠中的肿瘤抑制因子，但其转运功能的身份及其如何促进肿瘤抑制尚不清楚。我们最近的研究不仅确定了这种蛋白的转运功能的身份，而且还确定了转运蛋白促进肿瘤细胞特异性凋亡的机制。SLC 5A 8是一种Na+偶联的单羧酸转运蛋白（例如，丙酸盐、丁酸盐、乳酸盐、丙酮酸盐）。丁酸盐是组蛋白脱乙酰酶（HDAC）的众所周知的抑制剂，并且通过细菌发酵在结肠中产生。HDAC抑制剂优先杀死肿瘤细胞。我们最近发现丙酮酸也是一种有效的HDAC抑制剂，丙酮酸和丁酸以SLC 5A 8依赖的方式诱导肿瘤细胞特异性凋亡。因此，SLC 5A 8介导HDAC抑制剂丙酮酸盐和/或丁酸盐集中进入细胞的能力是该转运蛋白的肿瘤抑制功能的基础。SLC 5A 8在正常乳腺组织中表达，在乳腺癌组织中通过DNA甲基化沉默。乳腺肿瘤细胞系中转运蛋白的外源性表达以丙酮酸/丁酸依赖性方式导致细胞死亡。乳腺上皮细胞中SLC 5A 8基因的甲基化涉及DNA甲基转移酶DNMT 1;癌基因Ras的激活在此过程中起关键作用。用DNA去甲基化剂处理乳腺肿瘤细胞会重新激活SLC 5A 8的表达。这种现象见于雌激素受体（ER）阳性和ER阴性细胞。重要的是，在丙酮酸盐或丁酸盐存在下，SLC 5A 8的再表达导致ER阳性和ER阴性细胞的细胞死亡。为了更好地理解乳腺癌细胞如何下调SLC 5A 8以及转运蛋白表达的重新激活如何导致肿瘤细胞特异性凋亡和乳腺肿瘤发生的阻断，我们提出了三个目标。目的1探讨乳腺癌中SLC 5A 8表达下调的机制。假设：SLC 5A 8的甲基化相关沉默继发于Ras相关MAPK信号通路的激活。目的2是证实SLC 5A 8在体内阻断乳腺肿瘤发生的能力。假设：乳腺癌中SLC 5A 8的重新激活或正常乳腺中SLC 5A 8的过表达将有效地阻断乳腺肿瘤的形成。目的3：评价SLC 5A 8在ER阴性乳腺癌中的治疗潜力。假设：ER阴性乳腺癌中SLC 5A 8表达的激活将诱导丙酮酸/丁酸介导的肿瘤细胞特异性凋亡。这些研究将产生重要的临床/治疗相关信息，有助于开发预防和/或治疗乳腺癌的新策略。 公共卫生相关性：本项目的目的是研究一种新发现的肿瘤抑制因子作为治疗乳腺癌的药物靶点的潜力。这种肿瘤抑制因子是一种质膜转运蛋白，介导组蛋白去乙酰化酶（HDAC）抑制剂丙酮酸和丁酸进入细胞。HDAC抑制导致肿瘤细胞特异性凋亡和细胞死亡。乳腺癌细胞关闭了转运蛋白的表达，以避免这种细胞死亡。在目前的项目中，我们将测试的假设，即在乳腺癌细胞中的转运蛋白基因的表达的重新激活将诱导肿瘤细胞特异性凋亡，通过转运蛋白介导的丙酮酸或丁酸的进入。这种治疗模式不仅对雌激素受体阳性乳腺癌有效，而且对雌激素受体阴性乳腺癌也有效。