NTera-2 (NT2) 細胞是取自人類畸胎瘤的細胞株，在前人研究中發現利用視網酸 (retinoic acid) 處理細胞後可誘導細胞分化為類似神經的NT2N細胞，這些由NT2分化的神經細胞擁有神經突並且表現一些成熟神經的特定物質，包含了N-cadherin、neurofilment和神經傳導物質等，所以NT2細胞株可以做為人類神經分化研究的模式系統。
酪胺酸磷酸化是多種細胞膜上接受器將訊息傳入胞內的基本機制，藉由酪胺酸磷酸化 (tyrosine phosphorylation) 所引導的訊息傳遞系統調控了細胞增生、分化及移動。Genistein，是一種大豆萃取出的異黃酮，在前人的研究中已發現genistein是酪胺酸激酶 (tyrosine kinase) 的抑制劑，genistein可以減弱由生長因子刺激所引起的正常細胞及腫瘤細胞增生現象。在一些研究也證實了genistein可以做為某些腫瘤細胞最終分化的誘發劑，而且抑制了酪胺酸激酶Src或上皮生長因子接受器及拓樸異構酶Ⅱ (topoisomeraseⅡ) 的作用，所以Genistein對於細胞有多重影響。
本實驗利用了NT2細胞株來探討genistein對於細胞增生及神經分化的影響，結果發現10μg/ml濃度的genistein處理幾天後NT2細胞形成類神經突結構，並且增加了胞外訊息調控激酶 (ERK) 的活性，此外genistein有抑制細胞增生現象，隨著genistein 濃度增高抑制現象也明顯增強。在蛋白質方面genistein誘發了週期素依賴型激酶 (CDK) 抑制蛋白P21的表現，並減少了細胞內增殖細胞核抗原蛋白 (PCNA) 的量，這些現象顯示了genistein影響了一些分子機制而使細胞增生速率降低。另外本實驗也發現genistein可以誘導NT2細胞分化為神經細胞，經由genistein處理20天後NT2細胞確實表現了許多成熟神經的特定蛋白質，包含了NF-L、NF-M和N-cadherin等。利用免疫螢光染色法觀察也可發現genistein處理30及60天後NT2細胞除了型態上有很明顯的變化外，神經的特定蛋白質亦可被偵測到，綜合本實驗數據顯示酪胺酸磷酸化的蛋白質在人類神經分化中扮演重要調控角色，而酪胺酸激酶的活性在NT2細胞形成神經突的過程是扮演負調控的角色並且直接或間接的影響神經的型態變化。

NTera-2 (NT2) cells are an embryonic carcinoma cell line derived from a human teratocarcinoma that responds to retinoic acid (RA) by differentiating into neuron-like NT2N cells in vitro. The NT2-derived terminally differentiated neurons , which have neuritic processes and expression neuronal marks including N-cadherin, neurofilaments, neurotransmitters and glutamate receptors. The NT2/D1 cell line is a novel model system for investigating molecular events during human neuronal differentiation.
Tyrosine phosphorylation provides a basic mechanism by which a variety of cellular receptors transmit their responses to growth factors ，signal transduction cascades that are driven by tyrosine phosphorylation regulate cell proliferation, differentiation , and migration. Genistein, a soybean-derived isoflavone, is a protein tyrosine kinase (PTK) inhibitor that attenuates growth factor- stimulated proliferation of both normal and cancer cells. Genistein is an inducer of terminal differentiation in human tumor cells and can inhibite the activity of certain tyrosine kinases such as Src and the epidermal growth factor receptor and inhibition of topoisomeraseⅡ, so Genistein has multiple intracellular effects.
To investigate the effects of genistein on cell proliferation and neuronal differentiation of NTera-2 cell cultures were used and the activation of MAPK was examined. Following 10μg/ml genistein treatment several days, NT2 cells formed neurite-like structures and increased the activity of extracellular signal-regulated kinase (ERK), a member of mitogen-activated protein kinase (MAPK). Genistein has a potent and dose-dependent inhibitory effect on NT2 cell proliferation. The data has shown that Western blotting indicates that genistein induces the cyclin dependent kinase (CDK) inhibitor p21 expression and reduces the level of proliferlating cell nuclear antigen (PCNA) protein. Here we present evidence first that genistein induces neuronal differentiation of NT2 cells. Long-term exposures of NT2 cells to genistein for twenty days, NT2 cells express several terminal differentiation markers including neurofilament light chain (NF-L)﹑neurofilament middle chain (NF-M) and N-cadherin, also indicating its inductive function.
On the other hand, the immunocytochemistry data have showe that the neuronal specific markers can be detected after genistein treatment for 30 days or 60 days. Taken together, the results suggest that tyrosine phosphorylated proteins play an important role in regulating the neuronal differentiation of human NT2 cells and the protein tyrosine kinase activity in NT2 cells negatively regulates neurite outgrowth and directly or indirectly affects neuronal morphology.

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