Witzig T E, Timm M, Stenson M, Svingen P A, Kaufmann S H
Division of Internal Medicine and Hematology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Clin Cancer Res. 2000 Feb;6(2):681-92.
Phenylacetate (PA) and phenylbutyrate (PB) are aromatic fatty acids that are presently undergoing evaluation as potential antineoplastic agents. In vitro, PA and PB cause differentiation or growth inhibition of malignant cells. Clinical trials of these drugs as single agents indicate that they are not myelosuppressive; therefore, combinations with other chemotherapy agents may be possible. The goals of this study were to determine whether PA and PB (a) are cytotoxic to malignant B cells from patients with non-Hodgkin's lymphoma and B-cell chronic lymphocytic leukemia and (b) exhibit additive or synergistic induction of apoptosis when administered to myeloma cell lines in combination with conventional drugs. In the clinical specimens, cytotoxicity was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and percent apoptosis was measured using 7-aminoactinomycin D and flow cytometry. Viability was decreased by > 50% in 7% (1/15) of non-Hodgkin's lymphoma samples treated with 5 mM PA, 27% treated with 1 mM PB, and 60% treated with 2 mM PB. Likewise, viability was decreased by > 50% in 44% (4/9) of chronic lymphocytic leukemia samples treated with 5 mM PA, 67% treated with 1 mM PB, and 100% treated with 2 mM PB. Studies in the myeloma cell lines demonstrated that PB treatment induced activation of caspases 3, 7, and 9 accompanied by cleavage of their substrates and internucleosomal DNA degradation. Combinations of PA or PB with conventional drugs (cytarabine, topotecan, doxorubicin, etoposide, chlorambucil, melphalan, fludarabine, carboplatin, and cisplatin) were examined for synergism (combination index < 1 in median effect analysis) in inducing apoptosis of both the MY5 and 8226 human myeloma cell lines. At concentrations that killed > 50% of cells, most combinations were additive; however, PB was synergistic with cytarabine, etoposide, and topotecan, with the combination index < 1 at each of the 50, 75, and 95% apoptosis levels. These observations indicate that PA and PB can induce apoptosis in malignant B cells and enhance the cytotoxicity of agents used in the treatment of these malignancies.
苯乙酸（PA）和苯丁酸（PB）是芳香族脂肪酸，目前正在作为潜在的抗肿瘤药物进行评估。在体外，PA和PB可导致恶性细胞分化或生长抑制。这些药物作为单一药物的临床试验表明它们不会引起骨髓抑制；因此，有可能与其他化疗药物联合使用。本研究的目的是确定PA和PB：（a）对非霍奇金淋巴瘤和B细胞慢性淋巴细胞白血病患者的恶性B细胞是否具有细胞毒性；（b）与传统药物联合应用于骨髓瘤细胞系时，是否表现出凋亡诱导的相加或协同作用。在临床标本中，通过3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四氮唑溴盐法测定细胞毒性，使用7-氨基放线菌素D和流式细胞术测定凋亡百分比。用5 mM PA处理的非霍奇金淋巴瘤样本中有7%（1/15）、用1 mM PB处理的有27%、用2 mM PB处理的有60%，细胞活力下降>50%。同样，用5 mM PA处理的慢性淋巴细胞白血病样本中有44%（4/9）、用1 mM PB处理的有67%、用2 mM PB处理的有100%，细胞活力下降>50%。对骨髓瘤细胞系的研究表明，PB处理可诱导半胱天冬酶3、7和9的激活，伴随着其底物的裂解和核小体间DNA降解。检测了PA或PB与传统药物（阿糖胞苷、拓扑替康、阿霉素、依托泊苷、苯丁酸氮芥、美法仑、氟达拉滨、卡铂和顺铂）联合使用时，对MY5和8226人骨髓瘤细胞系凋亡诱导的协同作用（中位效应分析中联合指数<1）。在杀死>50%细胞的浓度下，大多数联合用药是相加的；然而，PB与阿糖胞苷、依托泊苷和拓扑替康具有协同作用，在凋亡水平为50%、75%和95%时联合指数均<1。这些观察结果表明，PA和PB可诱导恶性B细胞凋亡，并增强用于治疗这些恶性肿瘤的药物的细胞毒性。
