Nucleostemin基因在白血病病人之表現

Nucleostemin expression in leukemia patients

蔡慧珍(Hui-Jen Tsai)

指導教授 ： 林勝豐

高雄醫學大學/醫學院/醫學研究所/碩士(2005年)

摘要

Nucleostemin是一種新發現的蛋白質，McKay和Tasi發現它存在於老鼠中樞神經幹細胞、胚胎幹細胞以及三種人類癌細胞株並且坐落於核仁上。Nucleostemin的降調控發現是nucleostemin是存在於細胞分化的早期階段。Nucleostemin過度表現或是缺失會使得老鼠中樞細胞及轉型細胞的細胞增生減少。此外nucleostemin發現是與p53形成ㄧ蛋白質複合體，並且nucleostemin對細胞之增生產生影響是介由p53之作用，在缺乏p53的實驗組中發現nucleostemin之缺失對細胞之增生無明顯影響。Nucleostemin也可以在成鼠含有c-kit+/lin-表現的骨髓細胞中發現，但在顆粒球與淋巴球中則沒有。它特別的地方是和中樞神經幹細胞與癌細胞的細胞循環之進行(cell cycle progression)有關。在SJ Lui的研究中發現nucleostemin它也表現在人類胃癌及肝癌細胞中。由於上述的一連串研究發現，nucleostemin 表現於較原始的幹細胞及癌症細胞，以及異常表現的nucleostemin會造成細胞增生之減少，而白血病細胞尤其是急性白血病具有和造血幹細胞許多相似之特徵，尤其是在自我更新複製的能力上和造血幹細胞是很類似的，所以我們推測Nucleostemin亦在血液癌症細胞中表現，同時它可能在血液癌症細胞的增生上扮演一定之角色。基於上述之假設，我們想要研究nucleostemin在白血病病人的表現情形，我們使用一般正常人的周邊血液作為控制組，以白血病病人的骨髓細胞作為實驗組，來確認Nucleostemin在白血病病人的表現。我們利用real time 定量RT-PCR來分析Nucleostemin的表現量，發現在正常人，急性骨髓性白血病，慢性骨髓性白血病病人，及K562, Jurkat這兩株血液癌症細胞株都有Nucleostemin的表現，由西方點墨法也證實其蛋白質之表現，在即時定量RT-PCR實驗中發現nucleostemin在正常人的周邊血液之表現量比急性及慢性骨髓性白血病病人骨髓細胞的表現量增加，而急性骨髓性白血病和慢性骨髓性白血病的nucleostemin表現量是沒有差別的。我們得到的結論是在本研究中，Nucleostemin同時表現在一般人的已分化白血球與白血病病人的骨髓幹細胞中，而在急性骨髓性白血病和慢性骨髓性白血病病人的nucleostemin其表現量要比正常人nucleostemin的表現量減少，nucleostemin之存在和表現量之多寡對白血病之生成是否直接相關或是經由其他與細胞增生調控之路徑來影響白血病之生成或其疾病進展則有待進一步的探討。

關鍵字

白血病 ； 西方點墨法分析 ； 即時定量RT-PCR ； 幹細胞 ； Nucleostemin

並列摘要

Nucleostemin is a novel protein found in the nucleoli of CNS stem cells, embryonic stem cells of rat and three cancer cell lines of human by McKay and Tsai. Down regulation of nucleostemin was found in the early stage of cell differentiation. Overexpression or depletion of nucleostemin reduces cell proliferation in CNS stem cells and transformed cells of rats. Nucleostemin forms a protein complex with p53 and its effect on cell proliferation is mediated by p53. Mutational studies of nucleostemin cause decreased cell proliferation only in p53(+) cell line, but not in p53 null cell line. Nucleostemin was also found in c-kit+/lin- bone marrow cells but not in granulocytes and lineage-committed B lymphocytes from adult rat. Nucleostemin expression was also found in gastric and liver cancers of human by SJ Liu. Among hematologic malignancies, acute myelogenous leukemia is typically a disease of stem/progenitor cell origin. The leukemic cell share many characteristics with normal hematopoietic stem cells including the ability to renewal. We hypothesize that nucleostemin is expressed in cancer cells of malignancies and possesses a role in the proliferation of cancer cells, including hematologic malignancy. To determine the expression of nucleostemin in leukemia patients, we examined bone marrow from leukemia patients, peripheral blood from normal population by real time quantitative reverse transcription-polymerase chain reaction and western blot analysis for the expression of nucleostemin. There were nucleostemin expression in normal population, acute myeloid leukemia, chronic myeloid leukemia and two hematopoietic cell lines, including K562 and Jurkat. The expression of nucleostemin is decreased in leukemia patients compared with normal population. There is no significant difference of nucleostemin expression in both acute myeloid leukemia and chronic myeloid leukemia patients. Western blot shows expression of nucleostemin in each group. Conclusively nucleostemin is expressed in differentiated leukocytes of normal population and stem cell, blasts-enriched BM of leukemia patients in our study. Whether presence of nucleostemin or altered expression of nucleostemin in leukemia patients cause effect in the pathogenesis of leukemia or associate with the clinical course in leukemia patients? Dose nucleostemin play its role in the regulation of leukemic cell proliferation like a gene regulator, not independently? Further investigations are needed to identify these problems.

並列關鍵字

western blot analysis ； leukemia ； stem cells ； Nucleostemin ； real-time quantitative reverse transcription-pol

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