Department of Biochemistry, School of Life Sciences, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India.
Department of Biotechnology, School of Biotechnology, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India.
Invest New Drugs. 2017 Dec;35(6):691-705. doi: 10.1007/s10637-017-0489-1. Epub 2017 Aug 3.
Histone deacetylases (HDACs) play an important role in the epigenetic regulation of gene expression through their effects on the compact chromatin structure. In clinical studies, several classes of histone deacetylase inhibitors (HDACi) have demonstrated potent anticancer activities with metal complexes. Hence, we synthesized cadmium-proline complexes using both the D- and L-isomers of proline and evaluated their biological activities by observing the efficiency of their inhibition of HDAC activity, ability to reduce the expression of HDAC isoforms in A549 cells and effect on apoptosis. The synthesized compounds were characterized by UV, IR, NMR spectroscopy and elemental analysis. In-vitro cell toxicity was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and the 50% inhibitory concentration (IC; 2 μM) was obtained at 12 h. The morphological study at nuclear levels was performed by acridine orange/ethidium bromide (AO/EB) and Hoechst staining, and the results showed an association with cell cycle arrest at the G2/M phase. Both cadmium-proline complexes intensely inhibited HDAC activity at 2 μM concentration. Interestingly, Cd[L-proline] was found to be a potent inhibitor for all HDAC isoforms, whereas Cd[D-proline] inhibited only HDAC1 and 2. HDACi are novel chemotherapeutic drugs that induce hyperacetylation of histones H3 and H4, counteracting the aberrant repression of genes, such as insulin-like growth factor-binding protein 3 (IGFBP-3), p53, and p21. ERK/MAPK signaling pathway resulted in the downregulation of the expression of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), contributing to the inhibition of metastasis in A549 cells. Apoptosis induction was accompanied by the activation of death receptors and their ligands which recruit initiator caspase 8, decrease in mitochondrial membrane potential (ΔΨm), as well as increased Bax/Bcl ratio, followed by activation of caspases 9 and 3. Our finding suggests that Cd[L-proline] complex accelerates epigenetic rearrangement by HDAC inhibition, which may be the key mechanism for its anticancer activity.
组蛋白去乙酰化酶 (HDACs) 通过影响致密染色质结构，在基因表达的表观遗传调控中发挥重要作用。在临床研究中，几类组蛋白去乙酰化酶抑制剂 (HDACi) 已证明具有金属配合物的强大抗癌活性。因此，我们使用脯氨酸的 D-和 L-异构体合成了镉-脯氨酸配合物，并通过观察其抑制 HDAC 活性的效率、降低 A549 细胞中 HDAC 同工型表达的能力以及对细胞凋亡的影响来评估其生物学活性。合成的化合物通过紫外、红外、NMR 光谱和元素分析进行了表征。通过 3-(4,5-二甲基噻唑-2-基)-2,5-二苯基四唑溴化盐 (MTT) 测定法评估了细胞毒性，在 12 小时时获得了 50%抑制浓度 (IC；2 μM)。通过吖啶橙/溴化乙锭 (AO/EB) 和 Hoechst 染色进行核水平的形态学研究，结果表明与细胞周期阻滞在 G2/M 期有关。两种镉-脯氨酸配合物在 2 μM 浓度下强烈抑制 HDAC 活性。有趣的是，Cd[L-proline]被发现是所有 HDAC 同工型的有效抑制剂，而 Cd[D-proline]仅抑制 HDAC1 和 2。HDACi 是诱导组蛋白 H3 和 H4 乙酰化的新型化疗药物，抵消了胰岛素样生长因子结合蛋白 3 (IGFBP-3)、p53 和 p21 等基因的异常抑制。ERK/MAPK 信号通路导致基质金属蛋白酶 2 和 9 (MMP-2 和 MMP-9) 的表达下调，从而抑制 A549 细胞的转移。凋亡诱导伴随着死亡受体及其配体的激活，这些受体募集起始半胱天冬酶 8，降低线粒体膜电位 (ΔΨm)，以及 Bax/Bcl 比值增加，随后激活半胱天冬酶 9 和 3。我们的发现表明，Cd[L-proline]复合物通过抑制 HDAC 加速表观遗传重排，这可能是其抗癌活性的关键机制。
