乳腺癌在女性統計數據中是造成癌症死亡的第二大原因。在乳癌症的患者中，轉移與否與癌症的死亡率有非常大的關連性。迄今為止，還沒有可用於治療乳腺癌轉移的標靶療法。我們先前的研究表明，糖皮質激素（GCs）可通過誘導microRNA-708的表現因此抑制卵巢癌的遠端轉移。在此篇研究，我們深入探討糖皮質激素用於治療轉移性乳腺癌的潛力。我們觀察到microRNA-708啟動子區域在轉移性乳腺癌細胞中會透過DNA甲基化和組蛋白甲基化的方式導致表觀遺傳學的改變，進而抑制基因的表現。而共同給予糖皮質激素與DNA去甲基化劑─阿扎胞苷，可以顯著增加microRNA-708的表達，偕同抑制腫瘤的生長與轉移。總體而言，我們的數據揭示了使用糖皮質激素與表觀遺傳藥物抑制乳腺癌的進展和轉移的治療策略。

Breast cancer is the second leading cause of cancer death in women and cancer metastasis are responsible for almost 90% of breast cancer-related deaths. To date, there is no targeted therapy available in treating breast cancer metastasis. Previous study indicates that glucocorticoids (GCs) suppress cancer metastasis in ovarian cancer through induction of microRNA-708. Here we propose to investigate the therapeutic potential of GCs in treating metastatic breast cancer. We observe that microRNA-708 promoter region is epigenetically silenced by both DNA methylation and histone methylation among metastatic breast cancer cells. Co-treatment of GCs, together with DNA-demethylation agents, decitabine (5-aza-2'-deoxycytidine), significantly increases the expression of microRNA-708, leading to the synergistic suppression of tumor growth. Overall, our data reveal a potential strategy of using GCs together with the epigenetic drug to suppress breast cancer progression and metastasis.

摘要.....................................................i
Abstract................................................ii
致謝....................................................iii
Table of Contents.......................................iv
Table of Figures........................................vi
Introduction............................................1
1.1 Breast Cancer...................................1
1.1.1 Treatment options for metastatic breast cancer..3
1.2 Epigenetics.....................................4
1.3 MicroRNA........................................6
1.4 Decitabine......................................6
1.5 Dexamethasone...................................7
Motivation and aims.....................................8
Materials and Methods..................................10
3.1 Cell culture and transfection..................10
3.2 Western blot analysis..........................11
3.3 Quantitative real-time RT-PCR..................12
3.4 Mouse orthotropic metastasis model.............14
3.5 Bisulfite sequencing...........................15
3.6 Chromatin Immunoprecipitation assay............18
Results ...............................................23
4.1 MicroRNA-708 is downregulated in breast cancer.23
4.2 The promoter region of microRNA-708 highly methylated and associated with patient survival.......................23
4.3 Knockdown of EZH2 induces expression of microRNA-708..24
4.4 Knockdown of EZH2 increases methylation level in the promoter region of microRNA-708.................................25
4.5 The promoter region of microRNA-708 is bound to methylated H3K27 and H3K4 .......................................25
4.6 Co-treatment of DEX and Decitabine suppresses breast cancer metastasis in the mouse model..........................26
4.7 Co-treatment of DEX and Decitabine induce expression of microRNA-708 in mouse model..................................................27
Conclusion.............................................29
Discussion.............................................30
Reference..............................................41

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