請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/28271
標題: | Methotrexate引發細胞週期中止及凋亡之研究 Investigation of Methotrexate-Induced Cell Cycle Arrest and Apoptosis |
作者: | Wen-Yu Huang 黃文郁 |
指導教授: | 陳青周(Ching-Chow Chen) |
關鍵字: | 細胞週期,抗癌藥,細胞凋亡, p53,Methotrexate,cell cycle,apoptosis,cancer, |
出版年 : | 2007 |
學位: | 碩士 |
摘要: | Methotrexate (MTX) 為dihydrofolate reductase (DHFR) 抑制劑,可抑制癌細胞之葉酸循環,干擾DNA合成所需之one carbon donor而中止細胞週期,促使細胞之凋亡。HDAC (histone deacetyltranferase) 可移去染色體組織蛋白 (histone) 之乙醯基,使DNA與組織蛋白緊密纏繞而抑制基因之表現,目前發現許多癌症皆會表現HDACs,降低抑癌基因(例如p53、p21、Rb等)之表現,因此HDACs抑制劑為發展抗癌藥物的新方向。
細胞受到UV、gamma-radiation或抗癌藥物造成DNA受損時,會啟動許多因子進行DNA之修補,p53即為重要因子之一。p53可在細胞受外界刺激下快速的受活化,透過轉譯後修飾作用增加其穩定性及活性,p53 N端之磷酸化,可減少受E3 ligase Mdm2之ubiquitination而分解,增加其蛋白之穩定性;p53之C端受乙醯化及磷酸化,則會增加p53與DNA之結合能力,因而增加其轉錄活性。p53下游所調控之基因與細胞週期、DNA修補或凋亡有關,例如活化p21可抑制cdk4造成細胞週期中止,活化Gadd45或CHK1會誘導DNA之修補,增加DR5、Fas、Bax和PUMA等基因表現會使細胞趨向凋亡,以上之作用皆可抑制不正常細胞之增生,因此p53是抑癌基因。臨床上發現之許多癌症,其p53有所突變,因此癌細胞之DNA因抗癌藥造成損傷時,細胞週期無法中止、也無法進行細胞凋亡,因而減低抗癌藥之細胞毒殺作用。 本論文發現,MTX處理A549肺腺癌細胞8小時,即可引發細胞凋亡及細胞週期中止於 S phase,此作用可能是透過活化p53而來;MTX增加p21之蛋白表現,可能透過某種激酶 (kinase) 磷酸化p53之Ser 15和Ser 392,再經由抑制HDAC活性增加p53轉譯後修飾之Lys 373/382乙醯化,因而增加p53之穩定性及活性。我們也發現A549細胞處理MTX四天會促使NF-kappaB之活化,有可能會增加癌細胞之抗藥性。 Methotrexate (MTX) is a dihydrofolate reductase inhibitor, and has been used in childhood acute leukemia for almost 60 years. MTX ceases intracellular folate metabolism, blocks purine and thymidylate synthesis and results in cell cycle arrest and apoptosis. Histone deacetylase (HDAC) removes the acetyl group from histone, makes chromatin structure more compact and silences genes. HDACs overexpression has been found in tumors thus inhibits tumor suppressor genes. HDAC inhibitors reactivate these tumor suppressor genes and could serve as potential anticancer drugs. p53 can be quickly activated upon different kinds of cellular stress and is responsible for the transcriptional activation of a series of proteins involved in cell cycle control, apoptosis, senescence and DNA repair. Post-translational modification of p53 plays a critical role in regulating its activity and stability. Once stabilized and activated, p53 serves as a tumor suppressor and prevents abnormal cell growth. Mutant p53 is frequently observed in many cancers and render them more resistant to genotoxic drugs. We found that, in A549 lung adenocarcinoma cells, MTX arrested cell cycle in S phase and promoted apoptosis after 8-hour treatment. This phenomenon might be caused by p53 activation. MTX induced p53 Ser 15 and Ser 392 phosphorylation, inhibits HDACs activity and promoted its acetylaion on Lys 373/382. NF-kB activation and its downstream gene ICAM-1 exprssion were seen after 4-day exposure to MTX, implying the possible occurrence of MTX resistance. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/28271 |
全文授權: | 有償授權 |
顯示於系所單位: | 藥理學科所 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-96-1.pdf 目前未授權公開取用 | 2.75 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。