Regulation of miRNA in breast cancer

说明(申请人提供)：选择性雌激素受体调节剂他莫昔芬()是治疗和预防雌激素受体α1阳性乳腺癌最广泛使用的内分泌疗法。然而，在最初对敏感的肿瘤中，约有40%对内分泌/具有耐药性。这种获得性耐药背后的机制尚不清楚，反应的生物标志物可能有助于监测临床反应。MicroRNAs(MiRNAs)是一类自然存在的、小的、非编码的RNA分子，参与调节mRNAs的翻译和加工，通常通过与靶mRNAs的3‘非翻译区结合，靶向被降解的mRNA转录物或通过阻断翻译来参与。人类基因组包含700个miRNAs。MiRNA表达的异常模式最近被认为与人类疾病有关，miRNA的差异表达与其他公认的乳腺癌分期和患者预后的标志物一致，包括ER1和孕激素受体、肿瘤分期、阳性淋巴结数和血管侵犯。利用NIH-R21机制，我们获得了初步的数据，鉴定了雌激素(E2)以ER1依赖的方式调节MCF-7人乳腺癌细胞中的miRNAs，并鉴定了通过E2下调miR-21上调的下游靶基因。然而，到目前为止，还没有人研究对乳腺癌miRNA表达模式的影响，只有2篇报告确定了耐药的乳腺癌MCF7细胞的miRNA表达模式。具体目的1是确定在抗雌激素敏感的MCF-7和T47D乳腺癌细胞中，受E2和4-羟基TAM(4-OHT)差异调控的miRNAs。特异目的2是鉴定抗雌激素/敏感与耐药乳腺癌细胞系和肿瘤异种移植瘤中的miRNA及其靶基因。这一目的验证了这样的假设，即在内分泌/耐药与敏感的乳腺癌细胞中，miRNA的表达存在失调。具体目的3是确定在乳腺癌细胞系中发现的由E2调节和4-OHT调节的miRNAs是否在人类乳腺肿瘤中显示异常表达，并与临床诊断措施和患者对他莫昔芬治疗的反应相关。这项研究的总体目标是确定miRNAs的身份和基因靶点，从而为乳腺癌获得内分泌/耐药并成为侵袭和转移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.