McBain J A, Eastman A, Nobel C S, Mueller G C
Veteran's Affairs Medical Center, White River Junction, VT 05009, U.S.A.
Biochem Pharmacol. 1997 May 9;53(9):1357-68. doi: 10.1016/s0006-2952(96)00904-5.
n-Butyrate inhibits the growth of colon cancer cell lines. In the HCT 116 cell line, butyrate-induced growth inhibition is almost fully reversible, whereas in the VACO 5 cell line, a subpopulation undergoes apoptosis within 30 hr of treatment with butyrate. Concurrent treatment of VACO 5 cells with butyrate and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) accelerates and increases the incidence of cell death to nearly 100% of the population, whereas HCT 116 cells largely remain alive during treatment with this combination. The action of butyrate as an inhibitor of histone deacetylase was assessed in these cell lines by examining extracted core histones for their electrophoretic mobility in Triton/acid/urea gels. The concentrations of butyrate that were effective for inducing apoptosis were similar to the concentrations that caused hyperacetylation of core histones in the VACO 5 cell line. Furthermore, an examination of other carboxylic acids for induction of apoptosis revealed a rank order that corresponded to the order of potency in causing hyperacetylation of core histones. Specifically, the active acids were 3-5 carbons in length and lacked substitution at the 2-position. Isovaleric and propionic acids, in particular, proved to be effective inducers of both hyperacetylation and apoptosis at 5 mM concentrations, a finding of potential relevance to the unusual pancytopenia occurring after acidotic episodes in isovaleric and propionic acidemias. The duration of butyrate treatment required for chromatin fragmentation (10-20 hr) corresponded to the time required for histone H4 to become predominantly tetraacetylated. Furthermore, trichostatin A, a structurally dissimilar inhibitor of histone deacetylase, mimicked butyrate-induced apoptosis of VACO 5 cells and growth inhibition of HCT 116 cells. The dramatic enhancement of VACO 5 cell death by TPA, and the high level resistance of HCT 116 cells to butyrate were not evident from histone acetylation determinations. Thus, applications of butyrate for cytoreduction therapy will benefit from pharmacodynamic assessment of histone acetylation, but will require additional work to predict susceptibility to butyrate-induced death.
丁酸盐可抑制结肠癌细胞系的生长。在HCT 116细胞系中，丁酸盐诱导的生长抑制几乎完全可逆，而在VACO 5细胞系中，一部分细胞群在丁酸盐处理30小时内会发生凋亡。用丁酸盐和佛波酯12 - O - 十四烷酰佛波醇13 - 乙酸酯（TPA）同时处理VACO 5细胞，可加速并增加细胞死亡率，几乎达到细胞总数的100%，而HCT 116细胞在用这种组合处理期间大多仍存活。通过检测提取的核心组蛋白在Triton/酸/尿素凝胶中的电泳迁移率，评估了丁酸盐作为组蛋白去乙酰化酶抑制剂在这些细胞系中的作用。在VACO 5细胞系中，有效诱导凋亡的丁酸盐浓度与导致核心组蛋白超乙酰化的浓度相似。此外，对其他羧酸诱导凋亡的研究揭示了一个与导致核心组蛋白超乙酰化的效力顺序相对应的排序。具体而言，活性酸的长度为3至5个碳，且在2位无取代。特别是异戊酸和丙酸，在5 mM浓度下被证明是超乙酰化和凋亡的有效诱导剂，这一发现可能与异戊酸血症和丙酸血症酸中毒发作后出现的异常全血细胞减少有关。染色质片段化所需的丁酸盐处理持续时间（10 - 20小时）与组蛋白H4主要变为四乙酰化所需的时间相对应。此外，曲古抑菌素A，一种结构不同的组蛋白去乙酰化酶抑制剂，模拟了丁酸盐诱导的VACO 5细胞凋亡和HCT 116细胞生长抑制。从组蛋白乙酰化测定中未明显看出TPA对VACO 5细胞死亡的显著增强作用以及HCT 116细胞对丁酸盐的高度抗性。因此，丁酸盐用于细胞减灭疗法的应用将受益于组蛋白乙酰化的药效学评估，但需要更多工作来预测对丁酸盐诱导死亡的易感性。
