2012-08-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/648560摘要：探討 Lin28b 影響神經母細胞瘤惡性度之機轉神經母細胞瘤是新生兒與幼童最常見的顱外腫瘤，起源於交感神經系統的前驅母細胞。神經母細胞瘤的臨床表癥與預後差異大，可從預後較好的自發性痊癒至預後極差的高惡性度腫瘤。過去已知發病年齡較高、特定染色體變化以及MYCN致癌基因座增幅等皆屬於與預後較差有關的因子。約25%的患者會出現基因座增幅的現象，並與疾病的進程相關：MYCN基因座增幅的患者，五年存活率僅達15%-35%。 MYCN(N-Myc)是維持胚胎幹細胞多能性與自我更新能力的重要因子，且在神經系統分化的過程中，MYCN的表現量必須下降，顯示MYCN調控早期分化的過程扮演重要角色。LIN28及其同源基因LIN28B可產生RNA結合蛋白，已知可抑制pre-let-7微核糖核酸的成熟。Lin28在線蟲至哺乳類動物多物種間高度保留，在哺乳動物的胚胎幹細胞時期，Lin28高度表現並維持幹細胞自我更新的能力。已有研究報告Lin28及Lin28b會表現在許多種類的癌症，並透過抑制let-7微核糖核酸而促進癌症發生的過程。Let-7微核糖核酸因可抑制許多致癌基因(包括MYCN與LIN28)，因而被認為具有抑癌功能。微核糖核酸125b是在神經細胞中高度表達的微核糖核酸，並在神經分化的過程中扮演重要角色。先前研究已指出，微核糖核酸125b是Lin28與Lin28b的負調控因子。此外，在神經母細胞瘤中高度表達微核糖核酸125b可促進細胞進行分化，顯示微核糖核酸125b對於神經母細胞瘤可能具有抑癌症的功能。在神經母細胞瘤的細胞中，Lin28b已證明是MYCN調控的下游分子，而微核糖核酸125b對於Lin28b則有負向調控的能力。然而在神經母細胞瘤中，Lin28b以及微核糖核酸125b/Lin28b調控路徑的角色仍不清楚。由以往文獻及我們在前驅細胞實驗中的測試結果，我們預期LIN28B是神經母細胞瘤的致癌基因，且微核糖核酸125b可能具有抑癌功能。為了解神經母細胞瘤發生的分子機轉與調控，我們提出三年期研究計畫，設定三個目標為：1.鑑定Lin28b於神經母細胞瘤發生的角色2.探討研究微核糖核酸125b/Lin28b調控路徑在神經母細胞瘤形成過程中的重要性3.研究Lin28b調控神經母細胞瘤產生的相關分子機轉在本計畫中，我們預計以體外實驗的方式探討Lin28b對於神經母細胞瘤癌症發生過程的影響，並藉由動物模型研究微核糖核酸125b/Lin28b調控路徑在神經母細胞瘤形成過程中的重要性。<br> Abstract: Investigating the molecular mechanisms implicated in the advanced tumorigenesis conferred by Lin28b in neuroblastomaNeuroblastoma is the most common extracranial solid tumor in infancy and childhood. It is a tumor originates from the primitive cells (pluripotent neuroblasts) of the sympathetic nervous system. The clinical presentations and prognosis vary in neuroblastomas, from spontaneous regression to aggressively malignant that refractory to intensive treatment. Numerous prognostic factors have been identified over the past decades. The unfavorable neuroblastoma is associated with older age at diagnosis and pseudo-diploid karyotypes, including 1p- or 11q-del, gain of 17q, and/or amplification of the MYCN proto-oncogene. MYCN gene is found amplified in ~25% of neuroblastomas and is associated with rapid tumor progression. DNA amplification of the MYCN is strongly associated with highly malignant behavior and poor prognosis accounting for only 15-35% of 5 year-survival. The presence of MYCN was essential for the maintenance of pluripotency and self-renewal capacity in murine embryonic stem cells (ESCs), and down-regulation of MYCN is needed for terminal differentiation of neurons. It is suggested that MYCN may play an important function in controlling early differentiation steps in some tissues including the nervous system.Lin28 and its homolog lin28b are the RNA-binding protein which represses maturation processes of pre-let-7 microRNAs. Lin28 is highly conserved throughout the species including mammalians. In early embryonic development of mammalians, Lin28 is ubiquitously expressed in embryonic stem cells for keeping self-renewal capacity. Previous studies showed that Lin28 and Lin28b were expressed in several types of cancers and promoted tumorigenesis through inhibiting biogenesis of let-7 microRNAs. Members of the let-7 family were known tumor suppressors for their ability to repress several oncogenes (including LIN28 itself and MYCN).MicroRNA-125b is enriched in neuron and plays important role during neuronal differentiation. Previous studies showed that the miR-125b was a negative regulator of Lin28 and Lin28b. Furthermore, overexpression of miR-125b promoted differentiation of neuroblastoma cells, suggesting that the miR-125b might have tumor suppressive effects on the tumorigenesis of neuroblastoma.Lin28b is the downstream target of MYCN in neuroblastoma cells and the miR-125b is the negative regulator of Lin28b. However, the role(s) of Lin28b and the miR-125b/Lin28b pathway in neuroblastoma have not been addressed. According to previous literatures and our preliminary data obtained from the neuroblastoma primary samples and cell lines, we proposed that the Lin28b might be oncogenic for neuroblastoma, and microRNA-125b has tumor suppressive effect on tumorigenesis. To study the molecular mechanisms and the controlling circuit underlying neuroblastoma formation, we raise a three-year project with three specific aims:1.To characterize the role(s) of Lin28b in promoting tumorigenesis of neuroblastoma2.To investigate miR-125b/Lin28b controlling pathway in neuroblastoma3.To elucidate the molecular mechanism(s) underlying advanced tumorigenesis regulated by Lin28b in neuroblastomaIn this project, we will investigate the effects of lin28b in tumorigenesis in neuroblastoma cell lines, and elucidate the importance of microRNA-125b/Lin28b regulatory pathways in neuroblastoma by genetically-modified animal models.神經母細胞瘤MYCNLin28b微核糖核酸125bneuroblastomaMYCNLin28bmicroRNA-125b