苯丁酸钠 苯丁酸钠是一个芳香族脂肪酸,在体内经过 -氧化作用变成苯乙酸盐。体外试验已证明苯丁酸钠和苯乙酸盐通过几种不同的机制能诱导细胞分化[2]。而苯丁酸钠是美国FDA认证的已用于临床上的用于治疗高氨血证的药物。有人认为苯丁酸钠是通过抑制组蛋白脱乙酰基酶来诱导肿瘤细胞分化抑制肿瘤细胞生长即改变染色质和基因表达来[3]。分化作用已被证明是通过诱导G1/G0 终末分化以及诱导与分化有关细胞周期调节关键点p21waf1/cip1 [4]。 已经有研究,旨在阐明分化药剂对患有进展性肿瘤的临床效果。Carducci et al [5] 认为在第一阶段病人所能耐受的最大剂量为120小时/21天静脉维持苯丁酸钠,此时血浆中的药物浓度大于体内发挥分子效应时的浓度[6]。第二阶段时的推荐剂量是410mg/Kg/天共21天。19个病人中有18个表现为前列腺癌特定抗原的急性增高,后者是苯丁酸钠诱导肿瘤的一个标志。一少部分病人表现为前列腺癌特定抗原的稳定状态,有一个病人表现为盆淋巴结的局部反应,继而出现了骨的转移灶。 Gilbert[4] 等评价了口服苯丁酸钠的随剂量增加而出现的治疗效应,认为27g/天的剂量较为合适(9g tid)。他的试验证明不间断地口服苯丁酸钠亦能取得发生生物效应的血浆浓度。在他的研究中尽管对于进展期肿瘤未见到反应,但的确有25%的病人病情稳定超过6个月。 Fisher[7]在他的研究中也见到了对某些高级别难治性星形细胞瘤苯丁酸钠治疗后出现的稳定阶段。由于苯丁酸钠的毒性不及传统的细胞毒性药物,所以联合治疗或许可以取得更好的效果。 Gore[8]最近评价了苯丁酸钠在急性骨髓性白血病和骨髓异常增值综合征中延长应用的效果。对分化剂来讲骨髓异常增值综合征是个能取得令人振奋的效果的疾病,因为临床上此类病人的骨髓中拥有大量异型分化的密集的细胞。理论上讲,分化剂可能使得恶性克隆转变为良性或灭亡。Gore[8]还证明长期应用苯丁酸钠对这类病人有良好的耐受(例如在14天中连续给7天或在28天中连续给21天)。对几例进展性的骨髓异常增值综合征苯丁酸钠还导致了临床症状的改善(两例病人治疗前必须依耐血小板输注治疗后都变成了不依耐者)。分子水平上的几个研究也增强了我们对苯丁酸钠作为分化剂的理解并揭示了在此途径上的几个潜在的分子学目标。 Witt, Schulze, Kanbach, Roth and Pekrun [9]评价了环境应激途径与丁酸盐结合治疗肿瘤的作用。丁酸盐是苯丁酸钠的组蛋白脱乙酰基酶抑制部分的衍生物。他们发现丁酸盐诱导的分化作用可以被p38应激激活酶的抑制剂所抑制。同时又证明环境应激和丁酸盐联合对体外的白血病细胞系能产生附加或协同的诱导作用。作者认为这些发现将对临床具有指导意义:既可利用应激通路上的其它分子目标如黄酮类[10],或者加用真正的环境诱导因素,例如放疗和化疗。 Goh et al. [11]证实苯丁酸钠减弱了三种癌肿相关基因的表达:凋亡对抗基因Bcl-XL,DNA修复蛋白酶caveolin-1和血管内皮生长因子,都是在临床上所能达到的苯丁酸钠药物浓度。有趣的是,DNA修复蛋白酶caveolin-1在前列腺癌中有很高的表达,并且与病人的恶性预后有关[12]。而且当苯丁酸钠与放疗联合应用在体外试验中的确诱导了前列腺癌细胞的凋亡。因而目前仍需要大量的证据来支持:苯丁酸钠与其它方法联合应用能更好的改善临床效果。 Matsui et al. [17]发现苯丁酸钠对急性粒细胞性白细胞的诱导分化作用在粒细胞-巨噬细胞集落刺激因子生长因子的附加下,对这个因子的抗体在体外阻止了分化。这些数据清晰的表明了其它特定谱系生长因子对分化来讲可能是很基本的,也指明了以后分化治疗试验应当考虑与生长因子联合应用进行。有趣的是,作者在采用其它的诱导分化剂后得到了同样的结果。例如羟基脲和苔藓抑素1。苔藓抑素1是个新的分化剂,其机理未明。 目前有许多临床前期的证据表明在应用甲基转换酶抑制剂(如氮胞苷)阻止甲基化,一般都能与苯丁酸钠等对肿瘤细胞的诱导分化作用有协同作用[18]。有趣的是,氮胞苷作为一种诱导分化剂最近被发现对骨髓异常增值综合征的病人有益。氮胞苷是一种核苷类似物,它参与甲基化新合成的DNA并在体外试验中参与诱导分化[19]。对191例患有骨髓异常增值综合征的病人随机应用氮胞苷治疗后发现,有60%的病人有反应,另有白细胞过多症的转变和死亡的延长,且有总体存活时间的延长[20]。对同一人群的进一步的研究表明,与单纯应用支持疗法的相对照,应用氮胞苷后,病人的生存质量都有明显提高[21]。 目前已有关于联合苯丁酸钠和氮胞苷用于血液或非血液系统的肿瘤的研究。这些研究以骨髓异常增值综合征为对象[22,23,24],并在二期临床效果中观察到了初步的效果。11个患有血液系统恶性疾病的病人中有2个有明显的改善,组织病检发现了组蛋白脱乙酰基酶的抑制。目前这些研究虽然很初步,但效果良好,一旦药物剂量和测定方法得到确定,则病人造福于病人。其它核苷类似物可能与氮胞苷有同样的作用机制。 1998年Engelhard HH等[29]发现,苯丁酸钠可以对胶质瘤细胞的增值、形态学、迁移、侵袭及原癌基因(c-myc)和尿激酶表达产生剂量依赖性的抑制作用。 苯丁酸钠抑制胶质瘤细胞增殖的可能的机制 耗竭谷胺 降低TGF-β-2的表达 抑制蛋白的异戊间二烯化 增加第一类主要组织相容性复合体抗原的表达 改变DNA甲基化模式 上调TGF-α和分化通道 诱导凋亡 2002年9月Baker MJ等[30]对一例44岁病人实施了苯丁酸钠口服治疗。治疗前病人有四年病程,病理活检间变星形细胞瘤,在进行了正规的PCV化疗和放疗后,病人病情仍旧进展,且出现多中心生长。并在进行了4周期的BCNU/Cisplatinum顺铂化疗后仍未控制,且肿瘤通过胼胝体长向对侧。病人随即接受苯丁酸钠口服治疗,剂量从18g/日逐渐递减到4.5g/日坚持4年后病人肿瘤消失,恢复正常工作。
目前还有一些非丁酸盐类的组蛋白脱乙酰基酶抑制剂需要提及。
丙戊酸盐
一直被用来治疗癫痫和躁郁症,已被证明其通过一种与治疗双相行精神障碍不同的途径来直接抑制组蛋白脱乙酰基酶[13]。丙戊酸盐已在临床上应用很长时间,在很大剂量范围内能被良好耐受,临床的常用剂量很容易能达到体外试验时抑制组蛋白脱乙酰基酶的浓度,尽管相当一部分的该药与血浆蛋白结合,因而作为一种没有活性的组蛋白脱乙酰基酶抑制剂而存在。Göttlicher et al. [14]的体外试验业已证明丙戊酸盐不仅抑制了组蛋白脱乙酰基酶的活性而且能诱导分化结肠癌,乳腺癌和畸胎癌细胞系,还有在动物体内试验中显著减小了肿瘤生长和转移灶形成。他们还证明了丙戊酸盐能诱导生红细胞的祖细胞的分化以及急性早幼粒细胞性白血病人的白细胞过多症冲击。这些肯定了几年前证明的丙戊酸盐在胶质瘤细胞系的初步的抗肿瘤作用[15]。Cinatl et al. [16]证明了丙戊酸盐对髓母细胞瘤的诱导能力。在这个研究中,经过丙戊酸盐诱导分化后的肿瘤细胞失去了穿透内皮细胞的能力,从而减小了转移的发生率。所有这些作用在丙戊酸盐与 -干扰素联合应用时都被增强。由于丙戊酸盐在临床上很容易得到,并且易于检测其血药浓度,毒性反应小,因而它完全可以代替苯丁酸钠进行诱导分化肿瘤的试验治疗。
Valproic acid induces polarization, neuronal-like differentiation of a subpopulation of C6 glioma cells and selectively regulates transgene expression.
Benítez JA, Arregui L, Cabrera G, Segovia J.
Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico 07360, D.F.
Glioblastoma is the most frequent primary brain tumor, and for which standard therapies have not significantly increased the survival of patients. Recently, chromatin alterations have been linked to the pathogenesis of cancer, and drugs that modify chromatin structure, such as inhibitors of histone deacetylases (iHDAC), are now considered as a valuable strategy for the treatment of cancer. For instance, valproic acid (VPA), an iHDAC srcly used for the treatment of bipolar disorders and epilepsy, is now being used in cancer therapy. In this work we show that VPA induces morphological changes in astrocytoma C6 cells, which are associated with inhibition of cell proliferation, growth arrest, decreased cell migration, cell death and histone 4 hyper acetylation. VPA-treated cells extended processes with characteristics similar to the structure of a growth cone, and we also observed both a down-regulation of glial protein markers and increased expression of a neuronal specific protein after VPA treatment. Finally, there is an increase in the expression of a reporter transgene driven by a neuronal-specific promoter and a decrease of gene expression using a glial specific promoter in VPA-treated cells. These results indicate that VPA induces a specific differentiation of C6 cells toward a neuronal-like phenotype. The present data highlight the importance of epigenetic phenomena in the development and differentiation of the nervous system.
是一种类黄酮,它的抗癌作用已在很多肿瘤细胞系中得到确认。Kim KW等的体外试验和体内试验均证实:水飞蓟素抑制了脑胶质瘤的生长,可以作为一种潜在的抗恶性胶质瘤制剂。 Silibinin Inhibits Glioma Cell Proliferation via Ca(2+)/ROS/MAPK-Dependent Mechanism In Vitro and Glioma Tumor Growth In Vivo Kim KW, Choi CH, Kim TH, Kwon CH, Woo JS, Kim YK. Neurochem Res. 2009 Mar 5 Department of Neurosurgery, College of Medicine, Pusan National University, Pusan, 602-739, Korea. Anticancer activity of silibinin, a flavonoid, has been demonstrated in various cancer cell types. However, the underlying mechanism and in vivo efficacy in glioma were not elucidated. The present study was undertaken to determine the effect of silibinin on glioma cell proliferation in vitro and to examine whether silibinin inhibits tumor growth in vivo. Silibinin resulted in inhibition of proliferation in a dose- and time-dependent manner, which was largely attributed to cell death. Silibinin induced a transient increase in intracellular Ca(2+) followed by an increase in reactive oxygen species (ROS) generation. The silibinin-induced cell death was prevented by EGTA, calpain inhibitor and antioxidants (N-acetylcysteine and Trolox). Western blot analysis showed that silibinin also induced ROS-dependent activation of extracellular signal-regulated kinase, p38 kinase, and c-Jun N-terminal kinase. Inhibitors of these kinases prevented the silibinin-induced cell death. Silibinin caused caspase activation and the silibinin-induced cell death was prevented by caspase inhibitors. Glioma cell migration was also decreased by silibinin treatment. Oral administration of silibinin in animals with subcutaneous U87MG glioma cells reduced tumor volume. Subsequent tumor tissue analysis showed a decrease in Ki-67 positive cells, an increase in TUNEL-positive cells, and caspase activation. These results indicate that silibinin induces a caspase-dependent cell death via Ca(2+)/ROS/MAPK-mediated pathway in vitro and inhibits glioma growth in vivo. These data suggest that silibinin may serve as a potential therapeutic agent for malignant human gliomas.
National Institute for Cellular Biotechnology, Dublin City University, Dublin, Ireland. verena.murphy@dcu.ie
Despite major improvements in the surgical management the prognosis for patients bearing malignant gliomas is still dismal. Malignant gliomas are notoriously resistant to treatment and the survival time of patients is between 3-8 years for low-grade and anaplastic gliomas and 6 - 12 month for glioblastoma. Increasing malignancy of gliomas correlates with an increase in cellularity and a poorly organized tumor vasculature leading to insufficient blood supply, hypoxic areas and ultimately to the formation of necrosis, a characteristic of glioblastoma. Hypoxic/necrotic tumors are more resistant to chemotherapy and radiation. Hypoxia induces either directly or indirectly (through the activation of transcription factors) changes in the biology of a tumor and its microenvironment leading to increased aggressiveness and tumor resistance to chemotherapy and radiation. This review is focused on hypoxia-induced molecular changes affecting glioma biology and therapy.
J Neurooncol. 2007 Nov;85(2):191-202. Epub 2007 Jun 8. 高压氧可以阻止裸鼠脑内的胶质瘤细胞生长,诱导肿瘤细胞凋亡,改变血管密度和基因表达 Hyperoxia retards growth and induces apoptosis, changes in vascular density and gene expression in transplanted gliomas in nude rats. Stuhr LE, Raa A, Oyan AM, Kalland KH, Sakariassen PO, Petersen K, Bjerkvig R, Reed RK. Department of Biomedicine, University of Bergen, Jonas Lies vei 91, Bergen, 5009, Norway, linda.stuhr@biomed.uib.no. This study describes the biological effects of hyperoxic treatment on BT4C rat glioma xenografts in vivo with special reference to tumor growth, angiogenesis, apoptosis, general morphology and gene expression parameters.One group of tumor bearing animals was exposed to normobaric hyperoxia (1 bar, pO(2) = 1.0) and another group was exposed to hyperbaric hyperoxia (2 bar, pO(2) = 2.0), whereas animals housed under normal atmosphere (1 bar, pO(2) = 0.2) served as controls. All treatments were performed at day 1, 4 and 7 for 90 min. Treatment effects were determined by assessment of tumor growth, vascular morphology (immunostaining for von Willebrand factor), apoptosis by TUNEL staining and cell proliferation by Ki67 staining. Moreover, gene expression profiles were obtained and verified by real time quantitative PCR.Hyperoxic treatment caused a approximately 60% reduction in tumor growth compared to the control group after 9 days (p < 0.01). Light microscopy showed that the tumors exposed to hyperoxia contained large "empty spaces" within the tumor mass. Moreover, hyperoxia induced a significant increase in the fraction of apoptotic cells ( approximately 21%), with no significant change in cell proliferation. After 2 bar treatment, the mean vascular density was reduced in the central parts of the tumors compared to the control and 1 bar group. The vessel diameters were significantly reduced (11-24%) in both parts of the tumor tissue. Evidence of induced cell death and reduced angiogenesis was reflected by gene expression analyses.Increased pO(2)-levels in experimental gliomas, using normobaric and moderate hyperbaric oxygen therapy, caused a significant reduction in tumor growth. This process is characterized by enhanced cell death, reduced vascular density and changes in gene expression corresponding to these effects.
a. 甘露醇:最常用的利尿剂,它可以将水分从脑组织中拉向血管内,作用快速,持续时间为2~8小时。还可以降低血浆粘稠度,在正常脑血流状态下能导致脑血管收缩,脑血管容积降低后颅内压亦降低。 通常剂量为0.25~1g/kg,每4~6小时一次。应用时应监测血浆渗透压,电解质平衡情况。另外还应该提供足够的液体来维持正常的血容量。极量为4g/kg/天。超过此剂量,则会引起肾功衰竭。甘露醇在病人血清钠离子在145mmol/L以上时或者血浆渗透压大于315mOsm时慎用。 甘露醇在导致电解质失衡方面的优于速尿。甘露醇和速尿在脱水方面有协同作用,但这种协同倾向于导致更严重的电解质紊乱。
b. 速尿 一个循环性利尿剂,通过两种机制来降低颅内压:一是通过影响血脑屏障的水钠交换而影响脑脊液形成,另一个机制是使得肾脏的远端小管选择性分泌水分而产生利尿作用。当与甘露醇同时应用时,尤其是当于甘露醇应用完后15分钟时使用速尿降压作用最强。20~80mg/天,可以加量,不要超过600mg/天。儿童剂量1~2 mg/kg/次 IV q6~12h。 禁忌症:过敏,肝昏迷,无尿和严重电解质紊乱。 相互作用:二甲双胍可以降低速尿的浓集。速尿干扰降血糖药物的降糖效应,拮抗筒箭毒碱的肌松作用。在氨基糖甙类抗生素和速尿联合应用时可以引起听力损害,可以增加华法令的抗凝作用。 避免低血压,需要血清电解质检测。
c. 3%高渗盐水 如果血浆渗透压> 320或者CVP很低或者有低血容量的担心,并且颅内压很高的话,则给以3%的生理盐水 0.1-1.0ml/kg/小时(如60公斤体重则给60ml每小时,那么600ml则需要10小时;3%生理盐水的配置方法:1瓶500ml生理盐水+15支10%的盐水10ml即可配制完成)作为首剂量或者持续点滴。每6小时测一次血浆渗透压。如果发现血浆渗透压大于360或者血钠大于150,. 停止输注3%的盐水,高渗盐水必须通过大静脉来输注,到底是选择高渗盐水还是甘露醇,尚无定论。3%盐水一般是在低血压和低血容量的情况下选用。