miR-454诱导人乳腺癌细胞增殖的分子机制

Previously, we identified that miR-454 was significantly overexpressed in breast cancer tissues compared to normal breast tissues, using a microRNA chip assay. The expression levels of miR-454 also strongly correlated with the clinical stage of breast cancer. Furthermore, our preliminary data showed that miR-454 induced the proliferation of breast cancer cells via promoting G1/S transitional entry. Moreover, integration of the results of bioinformatic analysis and biological experiments revealed that miR-454 downregulated the tumor suppressor PTEN by directly targeting its 3` untranslated region (3`-UTR) to enhance Akt kinase activity and repress the transcriptional activity of FOXO1, resulting in a pro-proliferative effect in breast cancer cells. These results suggest that miR-454 plays an important role in breast cancer tumorigenesis. Hence, in the current project, we aim to employ immuno-fluorence staining, miRNA in situ hybridization and luciferase reporter assays in both in vitro and in vivo systems and use clinical samples to further investigate the mechanism by which miR-454 induces proliferation, in order to provide new biomarkers and targets for the diagnosis and treatment of breast cancer.

前期采用MicroRNA芯片技术，我们发现miR-454在乳腺癌组织中表达明显增高并与乳腺癌恶性程度正相关。进一步预实验结果显示miR-454可通过促进细胞G1/S周期转换而诱导细胞增殖。生物信息学及生物学实验结果表明miR-454可直接抑制PTEN表达，增强AKT激酶活性，下调FOXO1的转录活性，从而调控细胞增殖，但具体机制尚待阐明。本项目将以过表达或抑制miR-454的细胞为模型，通过免疫荧光染色、原位杂交及荧光素酶报告基因分析等方法,研究miR-454促进细胞增殖的分子机制,探讨miR-454下调PTEN/激活AKT激酶活性/抑制FOXO1转录活性的信号通路的分子机制。并通过在体内肿瘤动物模型确定miR-454具有诱导肿瘤生长的功能。本研究将为miR-454通过直接调控PTEN/AKT/FOXO1信号通路而导致肿瘤发生发展的科学假设提供证据，并为乳腺癌的诊断治疗提供新的分子靶点。

乳腺癌是女性最高发的常见的恶性肿瘤之一，全世界每年发病率高达168万人，死亡人数约152万人，是一种严重影响妇女生命的恶性肿瘤. 尽管乳腺癌治疗方法的改进及多种新药物的应用已使乳腺癌患者存活率有所提高，但高复发率和死亡率仍使乳腺癌患者的生存依然面临着巨大的挑战。前期大量研究均已证实miRNA 在乳腺癌的发生发展中具有重大的生物学功能。我们研究发现：乳腺癌中下调的miR-495与乳腺癌患者预后显著附相关， 并可通过抑制Bmi-1原癌基因而抑制肿瘤的恶性增殖 (Medicine， 已发表). 同时我们研究发现miR-892b在乳腺癌中显著下降。 进一步研究显示miR-892b可抑制乳腺癌的恶性发展由于下调 TRAF2, TAK1, and TAB3而抑制NF-kB信号通路 (Cancer Research, 已接收)。 因此我们的研究为乳腺癌的恶性发展提供了新的分子机制。