Regulation of miRNA in breast cancer

描述（由申请人提供）：选择性雌激素受体调节剂（SERM）他莫昔芬（TAM）是最广泛用于治疗和预防雌激素受体α (ER1)阳性乳腺癌的内分泌疗法。然而，约40%最初对tam敏感的肿瘤会产生内分泌/ tam抗性。这种获得性TAM耐药的机制尚不清楚，TAM反应的生物标志物可能有助于监测临床反应。MicroRNAs （miRNAs）是一类天然存在的非编码小RNA分子，参与调控mRNA的翻译和加工，通常通过结合靶mRNA的3'非翻译区，靶向待降解的mRNA转录物或阻断翻译。人类基因组中含有大约700个mirna。miRNA的异常表达模式最近与人类疾病有关，miRNA的差异表达与其他公认的乳腺癌分期和患者预后标志物一致，包括ER1和孕激素受体、肿瘤分期、阳性淋巴结数量和血管侵袭。利用NIH-R21机制，我们获得了初步数据，确定了MCF-7人乳腺癌细胞中由雌二醇（E2）以er1依赖的方式调控的miRNAs，并确定了通过E2下调miR-21而上调的下游靶基因。然而，到目前为止，还没有人研究过TAM对人类乳腺癌中miRNA表达模式的影响，只有2篇报道发现了MCF-7乳腺癌细胞中TAM耐药衍生物的miRNA表达模式。特异性目的1是鉴定抗雌激素敏感的MCF-7和T47D乳腺癌细胞中E2和4-羟基tam （4-OHT）差异调节的mirna。特异性目的2是鉴定抗雌激素/ TAM敏感与耐药乳腺癌细胞系和肿瘤异种移植物中的mirna及其靶基因。本研究验证了内分泌/TAM耐药与敏感乳腺癌细胞中miRNA表达失调的假设。特异性目的3是确定乳腺癌细胞系中E2调控和4-OHT调控的mirna是否在人类乳腺肿瘤中表现出异常表达，并与临床诊断措施和患者对他莫昔芬治疗的反应相关。该研究的总体目标是确定mirna的身份和基因靶点，这些mirna可能提供新的生物标志物，并为乳腺肿瘤获得内分泌/ tam抗性并成为侵袭性和转移性的机制提供新的见解。

DESCRIPTION (provided by applicant): The selective estrogen receptor modulator (SERM) tamoxifen (TAM) is the most widely used endocrine therapy for the treatment and prevention of estrogen receptor alpha (ER1) positive breast cancer. However, ~ 40% of initially TAM-sensitive tumors become endocrine/TAM-resistant. The mechanism behind such acquired TAM resistance is unknown and biomarkers of TAM-response may be useful to monitor clinical response. MicroRNAs (miRNAs) are a class of naturally-occurring, small, non-coding RNA molecules that are involved in regulating the translation and processing of mRNAs, usually by binding to the 3' untranslated region of target mRNAs and targeting the mRNA transcript to be degraded or by blocking translation. The human genome contains > 700 miRNAs. Aberrant patterns of miRNA expression have been recently implicated in human disease with miRNAs differentially expressed in concordance with other well-established markers of breast cancer stage and patient prognosis including ER1 and progesterone receptor, tumor stage, number of positive lymph nodes, and vascular invasion. Using the NIH-R21 mechanism, we obtained preliminary data identifying miRNAs regulated by estradiol (E2) in an ER1-dependent manner in MCF-7 human breast cancer cells and identified downstream target genes that were upregulated via E2 downregulation of miR-21. However, to date, no one has examined TAM affects the pattern of miRNA expression in human breast cancer and only 2 reports have identified miRNA expression patterns in TAM-resistant derivatives of MCF-7 breast cancer cells. Specific Aim 1 is to identify miRNAs that are differentially regulated by E2 and 4-hydroxyTAM (4-OHT) in antiestrogen- sensitive MCF-7 and T47D breast cancer cells. Specific Aim 2 is to identify miRNAs and their target genes in antiestrogen/ TAM- sensitive versus -resistant breast cancer cell lines and tumor xenografts. This Aim tests the hypothesis that miRNA expression is dysregulated in endocrine/TAM- resistant versus -sensitive breast cancer cells. Specific Aim 3 is to determine if the E2- regulated and 4-OHT- regulated miRNAs identified in breast cancer cell lines show aberrant expression in human breast tumors and correlate with clinical diagnostic measures and patient response to tamoxifen therapy. The overall goal of the proposed research is to determine the identity and gene targets of miRNAs that may provide novel biomarkers and new insights into the mechanisms by which breast tumors gain endocrine/TAM-resistance and become invasive and metastatic. PUBLIC HEALTH RELEVANCE: Aromatase inhibitor therapy is not useful for all ER1 positive breast cancer patients and the selective estrogen receptor modulator tamoxifen (TAM) remains the most widely used endocrine therapy for the treatment and prevention of estrogen receptor alpha (ER1) positive breast cancer. However, ~ 40% of initially TAM-sensitive tumors become endocrine/TAM-resistant. The mechanism behind such acquired TAM/endocrine resistance is unknown. The overall goal of the proposed research is to determine the identity and gene targets of miRNAs that may provide novel biomarkers and new insights into the mechanisms by which breast tumors gain endocrine/TAM-resistance and become invasive and metastatic.