Gumireddy Kiranmai, Sutton Leslie N, Phillips Peter C, Reddy C Damodar
Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Clin Cancer Res. 2003 Sep 15;9(11):4052-9.
Current treatments for childhood brain tumor medulloblastoma (MB), radiation and chemotherapy, lead to undesirable side effects. Identification of antitumor agents that reduce the toxicity will thus have significant therapeutic value. In this study, we investigated all-trans-retinoic acid (ATRA) as an antitumor agent. Although high concentrations (1-10 microM) of retinoic acid derivatives are generally needed for significant antitumor effects in many cancer cells, we observed that pharmacologically relevant concentrations of ATRA were effective in inducing cell death in human MB cells. Using 10-fold lower concentrations (100-500 nM), we found that ATRA inhibits MB (DAOY, D283, D425, and D458) cell proliferation as determined by cell viability [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and bromodeoxyuridine incorporation assays. Furthermore, 100 nM ATRA was potent in inhibiting the anchorage-independent growth of the sensitive cell lines (D283, D425, and D458) in soft agar assays. We also demonstrate that the ATRA-induced decrease in cell viability was due to increased cell death by apoptosis, which was accompanied by a 20-fold induction of caspase-3 activity in the most sensitive cell line, D458. By contrast, induction of caspase-3 was only 2-fold in the relatively insensitive DAOY cells. Furthermore, ATRA-induced cell death in D283, D425, and D458 cells was accompanied by activation of caspase-3, a key executioner of apoptosis. We also demonstrate that activated caspase-3 resulted in cleavage of 116-kDa poly(ADP-ribose) polymerase 1 to its signature fragments (85 and 29 kDa). Pretreatment with a specific caspase-3 inhibitor, DEVD-CHO, significantly reduced ATRA-induced apoptotic cell death. Thus, we demonstrate for the first time that low concentrations of ATRA inhibit MB cell proliferation and induce apoptotic cell death in part by activating caspase-3/poly(ADP-ribose) polymerase 1 effector pathway, and we show that retinoic acids and novel retinoids are potential antitumor agents in MB therapy.
目前用于儿童脑肿瘤髓母细胞瘤（MB）的治疗方法，即放疗和化疗，会产生不良副作用。因此，鉴定出能降低毒性的抗肿瘤药物将具有重要的治疗价值。在本研究中，我们研究了全反式维甲酸（ATRA）作为一种抗肿瘤药物。尽管在许多癌细胞中通常需要高浓度（1 - 10 microM）的维甲酸衍生物才能产生显著的抗肿瘤作用，但我们观察到药理学相关浓度的ATRA能有效诱导人MB细胞死亡。使用低10倍的浓度（100 - 500 nM），我们发现ATRA抑制MB（DAOY、D283、D425和D458）细胞增殖，这通过细胞活力[3 -（4,5 - 二甲基噻唑 - 2 - 基）- 2,5 - 二苯基四氮唑溴盐]和溴脱氧尿苷掺入试验来确定。此外，在软琼脂试验中，100 nM ATRA能有效抑制敏感细胞系（D283、D425和D458）的非锚定依赖性生长。我们还证明，ATRA诱导的细胞活力下降是由于凋亡导致的细胞死亡增加，在最敏感的细胞系D458中，这伴随着caspase - 3活性20倍的诱导。相比之下，在相对不敏感的DAOY细胞中，caspase - 3的诱导仅为2倍。此外，ATRA诱导D283、D425和D458细胞死亡伴随着凋亡关键执行者caspase - 3的激活。我们还证明，激活的caspase - 3导致116 kDa聚（ADP - 核糖）聚合酶1裂解为其标志性片段（85和29 kDa）。用特异性caspase - 3抑制剂DEVD - CHO预处理可显著减少ATRA诱导的凋亡细胞死亡。因此，我们首次证明低浓度的ATRA通过激活caspase - 3/聚（ADP - 核糖）聚合酶1效应途径部分抑制MB细胞增殖并诱导凋亡细胞死亡，并且我们表明维甲酸和新型类视黄醇是MB治疗中的潜在抗肿瘤药物。
