Patties Ina, Kortmann Rolf-Dieter, Menzel Franziska, Glasow Annegret
Department of Radiation Therapy, University of Leipzig, Stephanstraße 9a, Leipzig, 04103, Germany.
Institute of Anatomy, University of Leipzig, Liebigstraße 13, 04103, Leipzig, Germany.
J Exp Clin Cancer Res. 2016 Jun 17;35(1):94. doi: 10.1186/s13046-016-0376-1.
Medulloblastoma (MB) is the most common pediatric brain tumor. Current treatment regimes consisting of primary surgery followed by radio- and chemotherapy, achieve 5-year overall survival rates of only about 60 %. Therapy-induced endocrine and neurocognitive deficits are common late adverse effects. Thus, improved antitumor strategies are urgently needed. In this study, we combined irradiation (IR) together with epigenetic modifiers and differentiation inducers in a multimodal approach to enhance the efficiency of tumor therapy in MB and also assessed possible late adverse effects on neurogenesis.
In three human MB cell lines (DAOY, MEB-Med8a, D283-Med) short-time survival (trypan blue exclusion assay), apoptosis, autophagy, cell cycle distribution, formation of gH2AX foci, and long-term reproductive survival (clonogenic assay) were analyzed after treatment with 5-aza-2'-deoxycytidine (5-azadC), valproic acid (VPA), suberanilohydroxamic acid (SAHA), abacavir (ABC), all-trans retinoic acid (ATRA) and resveratrol (RES) alone or combined with 5-aza-dC and/or IR. Effects of combinatorial treatments on neurogenesis were evaluated in cultured murine hippocampal slices from transgenic nestin-CFPnuc C57BL/J6 mice. Life imaging of nestin-positive neural stem cells was conducted at distinct time points for up to 28 days after treatment start.
All tested drugs showed a radiosynergistic action on overall clonogenic survival at least in two-outof-three MB cell lines. This effect was pronounced in multimodal treatments combining IR, 5-aza-dC and a second drug. Hereby, ABC and RES induced the strongest reduction of clongenic survival in all three MB cell lines and led to the induction of apoptosis (RES, ABC) and/or autophagy (ABC). Additionally, 5-aza-dC, RES, and ABC increased the S phase cell fraction and induced the formation of gH2AX foci at least in oneout-of-three cell lines. Thereby, the multimodal treatment with 5-aza-dC, IR, and RES or ABC did not change the number of normal neural progenitor cells in murine slice cultures.
In conclusion, the radiosensitizing capacities of epigenetic and differentiation-inducing drugs presented here suggest that their adjuvant administration might improve MB therapy. Thereby, the combination of 5-aza-dC/IR with ABC and RES seemed to be the most promising to enhance tumor control without affecting the normal neural precursor cells.
髓母细胞瘤（MB）是最常见的儿童脑肿瘤。目前的治疗方案包括初次手术，随后进行放疗和化疗，5年总生存率仅约为60%。治疗引起的内分泌和神经认知缺陷是常见的晚期不良反应。因此，迫切需要改进抗肿瘤策略。在本研究中，我们采用多模式方法将放疗（IR）与表观遗传修饰剂和分化诱导剂联合使用，以提高MB肿瘤治疗的效率，并评估对神经发生可能的晚期不良反应。
在用5-氮杂-2'-脱氧胞苷（5-氮杂-dC）、丙戊酸（VPA）、辛二酰苯胺异羟肟酸（SAHA）、阿巴卡韦（ABC）、全反式维甲酸（ATRA）和白藜芦醇（RES）单独或与5-氮杂-dC和/或IR联合处理后，分析三种人MB细胞系（DAOY、MEB-Med8a、D283-Med）的短期存活（台盼蓝排斥试验）、凋亡、自噬、细胞周期分布、γ-H2AX焦点形成以及长期生殖存活（克隆形成试验）。在来自转基因巢蛋白-CFPnuc C57BL/J6小鼠的培养鼠海马切片中评估联合治疗对神经发生的影响。在治疗开始后长达28天的不同时间点对巢蛋白阳性神经干细胞进行活体成像。
所有测试药物至少在三分之二的MB细胞系中对总体克隆形成存活显示出放射增敏作用。这种作用在联合IR、5-氮杂-dC和第二种药物的多模式治疗中尤为明显。据此，ABC和RES在所有三种MB细胞系中诱导克隆形成存活的最强降低，并导致凋亡（RES、ABC）和/或自噬（ABC）的诱导。此外，5-氮杂-dC、RES和ABC至少在三分之一的细胞系中增加S期细胞比例并诱导γ-H2AX焦点形成。因此，5-氮杂-dC、IR与RES或ABC的多模式治疗未改变鼠切片培养物中正常神经祖细胞的数量。
总之，本文提出的表观遗传和分化诱导药物的放射增敏能力表明其辅助给药可能改善MB治疗。因此，5-氮杂-dC/IR与ABC和RES的联合似乎最有希望增强肿瘤控制而不影响正常神经前体细胞。
