微型核糖核酸miR-139在乳癌進程之角色探討

MicroRNA(miRNA)是一段長度約23個鹼基對的非編碼RNA分子，透過抑制基因轉譯，達到調節基因功能的目的。近年來，有許研究指出miRNA在腫瘤發展過程中，藉由調控細胞致癌基因和抑癌基因的表達，在癌症發展進程中扮演著極重要角色，本篇主旨在探討miR-139表現量的差異與乳癌預後之關聯。Chemokine receptor type 4 (CXCR4)為一細胞膜上之受體蛋白，被指出參與許多癌症的增生和侵襲轉移有密切關聯。本研究中，我們利用Targetsacn和microRNA.org網站上的生物資訊比對分析，預測CXCR4 基因可能為miR-139下游作用標的。接著，透過雙重冷光報導基因實驗(dual-luciferase reporter assay)和西方墨點法，證實miR-139會結合在CXCR4- 3'-UTR上，抑制CXCR4蛋白表現。進一步，持續表現(ecotopic expression) miR-139時，會抑制乳癌細胞的移動及侵襲能力。此外，於臨床檢體的分析中，我們針對66位乳癌患者的檢體以qPCR進行分析，相較於鄰近非腫瘤的乳房上皮細胞，miR-139在腫瘤細胞的表現量較低，且miR-139與乳癌惡化程度呈現負相關。

關鍵字

微型核糖核酸miR-139 ；乳癌

並列摘要

MicroRNAs (miRNAs) are a small non-coding RNAs (~23bps) regulating gene expression by inhibiting mRNA transcription or binding to the specific sequences of 3’-untanslated region (3’-UTR) of the target mRNAs to eventually suppress protein translation. Recently, several miRNAs have been reported to correlate with progression of tumor cells through affecting on the expression of oncogenes and/or tumor suppressor genes that lead to malignant transformation of tumors in different types of human cancer. Chemokine receptor type 4 (CXCR4), a chemokine receptor in the GPCR gene family, encodes a CXC chemokine receptor specific for stromal cell-derived factor-1 and is expressed by cells in the immune system and the central nervous system. In more recent, it has been reported that CXCR4 is overexpressed on several tumor cells, these CXCR4 positive tumor cells may exert pleiotropic effects in regulating processes essential to tumor metastasis through secretion of SDF-1. In this study, to unravel the molecular mechanism underlying CXCR4 signaling by which miRNAs affect breast cancer progression, a computational algorithm combining both miRNA target searching programs of TargetScan 5.1 (www.microrna.org) and microRNA.org was used to putatively predict the CXCR gene might be one of the downstream targets of the microRNA-139 (miR-139) Stepwise, dual-luciferase reporter assay and western blot, we validated that CXCR4 expression levels were reduced after transfection of the human breast cancer cell lines Hs578T and MDA-MB-231 with the precursors of the miR-139. Breast cancers cells whose miR-139 ecotopically expressed have effects on inhibition of migration and invasion. Furthermore, reduced tumor expression level of miR-139 in breast cancer tissue was associated with an unfavorable outcome, including late tumor stage and lymph node metastasis. In conclusion, these findings suggest a role for the miR-139 in inhibiting breast tumor invasiveness and metastasis, moreover, miR-139 downmodulates CXCR4 expression can serve as a novel therapeutic target for the treatment of breast cancer.

並列關鍵字

microRNA miR-139 ； breast cancer

參考文獻

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微型核糖核酸miR-139在乳癌進程之角色探討

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