PNAS:癌症复发的关键酶:ADAR1

2012-12-26 PNAS 生物通 佚名

  慢性粒细胞性白血病CML是一种血液和骨髓癌,其患病率正在逐年增加。日前,加州大学圣迭戈分校医学院的研究人员发现,在促进干细胞恶意增殖和CML发展的重编程过程中存在着一种关键的酶。这一发现提前发表在十二月二十四日美国国家科学院院刊PNAS杂志的网站上。   美国目前有七万人患有CML,预计到2050年这一数字将稳定增长到约181000人。CML是BCR-ABL基因突变引起的,但科学家尚还不清楚

  慢性粒细胞性白血病CML是一种血液和骨髓癌,其患病率正在逐年增加。日前,加州大学圣迭戈分校医学院的研究人员发现,在促进干细胞恶意增殖和CML发展的重编程过程中存在着一种关键的酶。这一发现提前发表在十二月二十四日美国国家科学院院刊PNAS杂志的网站上。

  美国目前有七万人患有CML,预计到2050年这一数字将稳定增长到约181000人。CML是BCR-ABL基因突变引起的,但科学家尚还不清楚这一突变发生的原因。尽管人们开发出了酪氨酸激酶抑制剂等新治疗方法,CML等白血病仍旧令人头疼。因为癌症干细胞能够逃避药物的破坏作用并最终再生,这种干细胞的自我更新会导致疾病复发和癌转移。

  长期以来,炎症一直被认为与癌症发生有关,现在加州大学圣迭戈分校医学副教授Catriona H. M. Jamieson博士及其同事发现,炎症会增加腺苷脱氨酶ADAR1的活性。  

    ADAR1负责在胚胎发生过程中帮助血细胞发育,随后ADAR1的表达就会被关闭,而病毒感染会使ADAR1启动来保护正常造血干细胞免受攻击。然而,在白血病干细胞中ADAR1的过表达会使RNA错误剪切增多,从而增强癌症干细胞的自我更新能力及其对治疗的抵抗力。

  Jamieson及其同事曾在此前的研究中,阐明了RNA错误剪切及其不稳定性的后果。“人们通常认为在癌症中DNA是不稳定的,不过在这种情况下,是RNA的剪切对癌症干细胞的抗性和增殖产生了真正的影响。”

  研究人员指出上述RNA剪切事件发生在人类和其他灵长类特有的序列中,这一发现不仅再次证明炎症是癌症抗性和癌症复发的驱动因素,也为未来的癌症治疗提供了新的靶标。

  “我们可以用小分子抑制剂来特异性地靶标ADAR1,这一策略已经在其他情况下有效使用过了,” Jamieson说。“如果我们能够阻断白血病干细胞使用ADAR1的能力,或者能够抑制这一通路,也许我们就能将这些干细胞导入正轨阻止它们恶性增殖。”

  CML这种癌症是由血液形成干细胞的BCR-ABL基因发生突变引起的,这种突变会导致白细胞及其前体异常扩增。这种癌症发展缓慢,往往到了癌晚期才得以确诊,这时癌细胞急剧增加因此也被称为急变期blast crisis。这种癌症确诊时的中位数年龄是66岁,其发病率随着年龄增长而增加。尽管在BCR-ABL酪氨酸激酶抑制剂疗法出现后,CML治疗有了巨大的进步,但一旦治疗中断大多数患者的CML都会复发,这种情况有部分是因为休眠的癌症干细胞对治疗产生抵抗。这项研究发现的新机制,将有望帮助人们克服癌症干细胞的抵抗,开发阻止癌症复发和发展的新治疗策略。



Abstract
Cellular behavior is sustained by genetic programs that are progressively disrupted in pathological conditions—notably, cancer. High-throughput gene expression profiling has been used to infer statistical models describing these cellular programs, and development is now needed to guide orientated modulation of these systems. Here we develop a regression-based model to reverse-engineer a temporal genetic program, based on relevant patterns of gene expression after cell stimulation. This method integrates the temporal dimension of biological rewiring of genetic programs and enables the prediction of the effect of targeted gene disruption at the system level. We tested the performance accuracy of this model on synthetic data before reverse-engineering the response of primary cancer cells to a proliferative (protumorigenic) stimulation in a multistate leukemia biological model (i.e., chronic lymphocytic leukemia). To validate the ability of our method to predict the effects of gene modulation on the global program, we performed an intervention experiment on a targeted gene. Comparison of the predicted and observed gene expression changes demonstrates the possibility of predicting the effects of a perturbation in a gene regulatory network, a first step toward an orientated intervention in a cancer cell genetic program.
    

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    2013-04-23 drwjr
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    2012-12-28 般若傻瓜
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