Miyashita T, Reed J C
La Jolla Cancer Research Foundation, Cancer Research Institute, CA 92037.
Blood. 1993 Jan 1;81(1):151-7.
Previous studies have shown that the bcl-2 gene encodes a mitochondrial protein that contributes to neoplastic cell expansion primarily by promoting cell survival through interference with "programmed cell death" (PCD), also termed "apoptosis." Because many chemotherapeutic drugs are capable of initiating pathways leading to apoptosis, we determined whether deregulated bcl-2 expression could render cells resistant to several drugs commonly used in the treatment of non-Hodgkin's lymphomas, including dexamethasone (DEX), methotrexate (MTX), 1-beta-D-arabinofuranosyl-cytosine (Ara-C), etoposide (VP-16), vincristine (VC), cisplatin (CP), and hydroperoxycyclophosphamide (4-HC). For these experiments, we achieved high levels of p26-Bcl-2 protein production in a human pre-B-cell leukemia line 697 by stable infection with a recombinant bcl-2-containing retrovirus and then compared these cells with control virus-infected 697 cells. Control 697 cells were induced to undergo apoptosis by all drugs tested as defined by DNA degradation into oligonucleosomal-length fragments, cell shrinkage, and subsequent cell death. In contrast, 697 cells with elevated Bcl-2 protein levels exhibited strikingly prolonged cell survival and markedly reduced DNA fragmentation when cultured in the presence of these antineoplastic agents. Although high levels of Bcl-2 protein protected 697 cells from the acute cytotoxic effects of DEX and the other drugs tested, Bcl-2 did not prevent these drugs from suppressing the proliferation of 697 cells. However, when 697 cells were treated with DEX or MTX for 3 days, then washed and cultured in semisolid media without drugs, bcl-2-virus-infected cells gave rise to colonies at much higher frequencies than 697 cells stably infected with control virus. These results indicate that by protecting 697 leukemic cells from the acute cytotoxicity of DEX and some other chemotherapeutic drugs, high levels of p26-Bcl-2 can create the opportunity for re-initiation of cell growth when drugs are withdrawn. The findings may be relevant to clinical correlative studies of non-Hodgkin's lymphoma patients that have found an association between worse prognosis and bcl-2 gene rearrangements or t[14;18] translocations.
先前的研究表明，bcl-2基因编码一种线粒体蛋白，该蛋白主要通过干扰“程序性细胞死亡”（PCD）（也称为“凋亡”）来促进细胞存活，从而有助于肿瘤细胞的增殖。由于许多化疗药物能够启动导致凋亡的途径，我们研究了bcl-2表达失调是否会使细胞对几种常用于治疗非霍奇金淋巴瘤的药物产生耐药性，这些药物包括地塞米松（DEX）、甲氨蝶呤（MTX）、1-β-D-阿拉伯呋喃糖基胞嘧啶（Ara-C）、依托泊苷（VP-16）、长春新碱（VC）、顺铂（CP）和氢过氧环磷酰胺（4-HC）。在这些实验中，我们通过用含重组bcl-2的逆转录病毒稳定感染人前B细胞白血病系697，实现了高水平的p26-Bcl-2蛋白表达，然后将这些细胞与对照病毒感染的697细胞进行比较。所有测试药物均可诱导对照697细胞发生凋亡，表现为DNA降解为寡核小体长度片段、细胞收缩以及随后的细胞死亡。相比之下，当在这些抗肿瘤药物存在的情况下培养时，Bcl-2蛋白水平升高的697细胞表现出显著延长的细胞存活时间和明显减少的DNA片段化。虽然高水平的Bcl-2蛋白保护697细胞免受DEX和其他测试药物的急性细胞毒性作用，但Bcl-2并不能阻止这些药物抑制697细胞的增殖。然而，当697细胞用DEX或MTX处理3天，然后洗涤并在无药物的半固体培养基中培养时，感染bcl-2病毒的细胞形成集落的频率比稳定感染对照病毒的697细胞高得多。这些结果表明，高水平的p26-Bcl-2通过保护697白血病细胞免受DEX和其他一些化疗药物的急性细胞毒性作用，在药物撤除时为细胞生长的重新启动创造了机会。这些发现可能与非霍奇金淋巴瘤患者的临床相关性研究有关，这些研究发现预后较差与bcl-2基因重排或t[14;18]易位之间存在关联。
