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）是治疗和预防雌激素受体α（ER 1）阳性乳腺癌的最广泛使用的内分泌疗法。然而，约40%最初对TAM敏感的肿瘤变得内分泌/TAM耐药。这种获得性TAM耐药性背后的机制尚不清楚，TAM反应的生物标志物可能有助于监测临床反应。MicroRNA（miRNAs）是一类天然存在的小的非编码RNA分子，其通常通过结合靶mRNA的3'非翻译区并靶向待降解的mRNA转录物或通过阻断翻译来参与调节mRNA的翻译和加工。人类基因组包含超过700个miRNAs。最近发现miRNA表达的异常模式与人类疾病有关，其中miRNA的差异表达与乳腺癌分期和患者预后的其他公认标志物一致，包括ER 1和孕酮受体、肿瘤分期、阳性淋巴结数量和血管浸润。使用NIH-R21机制，我们获得了鉴定MCF-7人乳腺癌细胞中雌二醇（E2）以ER 1依赖性方式调控的miRNA的初步数据，并鉴定了通过E2下调miR-21而上调的下游靶基因。然而，迄今为止，还没有人研究过TAM对人乳腺癌中miRNA表达模式的影响，只有2篇报道鉴定了MCF-7乳腺癌细胞的TAM耐药衍生物中的miRNA表达模式。具体目的1是鉴定在抗雌激素敏感的MCF-7和T47 D乳腺癌细胞中由E2和4-羟基TAM（4-OHT）差异调节的miRNA。具体目标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miRNAs及其靶基因。本研究旨在验证miRNA在内分泌/TAM耐药与敏感乳腺癌细胞中表达失调的假设。具体目标3是确定在乳腺癌细胞系中鉴定的E2调节的和4-OHT调节的miRNA是否在人乳腺肿瘤中显示异常表达，并且与临床诊断措施和患者对他莫昔芬治疗的反应相关。拟议研究的总体目标是确定miRNA的身份和基因靶点，这些miRNA可能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生物标志物和新的见解。 公共卫生相关性：芳香化酶抑制剂疗法并不适用于所有ER 1阳性乳腺癌患者，并且选择性雌激素受体调节剂他莫昔芬（TAM）仍然是用于治疗和预防雌激素受体α（ER 1）阳性乳腺癌的最广泛使用的内分泌疗法。然而，约40%最初对TAM敏感的肿瘤变得内分泌/TAM耐药。这种获得性TAM/内分泌抗性背后的机制尚不清楚。拟议研究的总体目标是确定miRNA的身份和基因靶点，这些miRNA可能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生物标志物和新的见解。

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.