Synergistic Roles of Curcumin in Sensitising the Cisplatin Effect on a Cancer Stem Cell-Like Population Derived from Non-Small Cell Lung Cancer Cell Lines

Cancer stem cells (CSCs) represent a small subpopulation within a tumour. These cells possess stem cell-like properties but also initiate resistance to cytotoxic agents, which contributes to cancer relapse. Natural compounds such as curcumin that contain high amounts of polyphenols can have a chemosensitivity effect that sensitises CSCs to cytotoxic agents such as cisplatin. This study was designed to investigate the efficacy of curcumin as a chemo-sensitiser in CSCs subpopulation of non-small cell lung cancer (NSCLC) using the lung cancer adenocarcinoma human alveolar basal epithelial cells A549 and H2170. The ability of curcumin to sensitise lung CSCs to cisplatin was determined by evaluating stemness characteristics, including proliferation activity, colony formation, and spheroid formation of cells treated with curcumin alone, cisplatin alone, or the combination of both at 24, 48, and 72 h. The mRNA level of genes involved in stemness was analysed using quantitative real-time polymerase chain reaction. Liquid chromatography-mass spectrometry was used to evaluate the effect of curcumin on the CSC niche. A combined treatment of A549 subpopulations with curcumin reduced cellular proliferation activity at all time points. Curcumin significantly (p < 0.001) suppressed colonies formation by 50% and shrank the spheroids in CSC subpopulations, indicating inhibition of their self-renewal capability. This effect also was manifested by the down-regulation of SOX2, NANOG, and KLF4. Curcumin also regulated the niche of CSCs by inhibiting chemoresistance proteins, aldehyde dehydrogenase, metastasis, angiogenesis, and proliferation of cancer-related proteins. These results show the potential of using curcumin as a therapeutic approach for targeting CSC subpopulations in non-small cell lung cancer.     

Berberine and Cisplatin Exhibit Synergistic Anticancer Effects on Osteosarcoma MG-63 Cells by Inhibiting the MAPK Pathway

Berberine (BBR) has been reported to have potent anticancer activity and can increase the anticancer effects of chemotherapy drugs. The present study aims to investigate whether BBR and cisplatin (DDP) exert synergistic effects on the osteosarcoma (OS) MG-63 cell line. In the present study, MG-63 cells were treated with BBR and DDP alone or in combination. The effects of these therapeutics on cell viability, colony formation, migration, invasion, nuclear morphology, apoptosis, and the cell cycle, as well as their role in regulating the expression of proteins related to apoptosis, the cell cycle, and the mitogen-activated protein kinase (MAPK) pathway, were determined. The results demonstrated that BBR or DDP significantly inhibited the proliferation of MG-63 cells in a dose- and time-dependent manner. The combination treatment of BBR and DDP exerted a prominent inhibitory effect on proliferation and colony formation. Furthermore, the results showed that the combination treatment of BBR and DDP enhanced the inhibition of cell migration and invasion and reversed the changes in nuclear morphology. The results showed that the combination treatment of BBR and DDP induced apoptosis and cell cycle arrest in the G0/G1 phase. Mechanistically, the combination treatment of BBR and DDP inhibited the expression of MMP-2/9, Bcl-2, CyclinD1, and CDK4, enhanced the expression of Bax and regulated the activity of the MAPK pathway. Collectively, our data suggest that the combination therapy of BBR and DDP markedly enhanced OS cell death.     

Direct evidence for co‐binding of cisplatin and cadmium to a native zinc‐ and cadmium‐containing metallothionein

Cisplatin is widely used to treat a number of cancers, and its covalent binding to DNA is believed to cause cell death; however, the roles of cisplatin–protein interactions in the mechanisms of action, toxicity, and resistance of the drug largely remain to be elucidated. Here, we investigate the interactions of cisplatin and a native rabbit metallothionein (MT), containing 1.4% zinc and 7.9% cadmium, using nanospray tandem quadrupole time‐of‐flight mass spectrometry (MS) and size‐exclusion high‐performance liquid chromatography with inductively coupled plasma MS. At near‐neutral pH conditions, reactions between cisplatin and MT resulted in the formation of complexes that contained Cd₄–Pt_n–MT (n = 1–7). While zinc was displaced by cisplatin, both platinum and cadmium were bound to the same MT molecule. This is the first report to provide direct evidence for the co‐binding of cadmium and platinum to MT, which suggests that the mechanism of the binding of cisplatin to the native MT may not be through the displacement of cadmium as previously proposed. A tandem MS investigation into the binding sites of the platinum and cadmium to MT showed platinum‐ and cadmium‐related fragments, such as (PtS₂C₂H₇N)⁺ and (CdS₃C₅H₁₇N₂)⁺, demonstrating the platinum–cysteine and cadmium–cysteine binding. In addition, detection of Cd₄–Pt₇–MT demonstrated more than ten metals bound to a single MT molecule. This finding was extended to the binding of MT with a five‐fold excess of CdCl₂. As many as 14 metal atoms (13 cadmium and one zinc) were detected bound to a single MT molecule, the complexes being Cd_x–Zn–MT (x = 5–13). The high binding capacity of MT for cadmium and platinum is consistent with the role of MT in reduction of metal toxicity and its involvement in drug resistance. Copyright © 2003 John Wiley & Sons, Ltd.     

Redox,spectroscopic, photo-induced ligand exchange,and DNA interaction studies of a new Ru(II)Pt(II) bimetallic complex

A new bimetallic complex, [Ru(biq)₂(dpp)PtCl₂](PF₆)₂ (where biq = 2,2′-biquinoline and dpp = 2,3-bis(2-pyridyl)pyrazine), containing a cis-PtCl₂ moiety coupled to a sterically strained Ru(II)-based chromophore was designed, synthesized, and investigated with respect to its spectroscopic, redox, photo-induced ligand exchange, and DNA-interaction properties. The electrochemistry of the designed complex was found to be consistent with the bridging coordination of the dpp ligand and formation of the bimetallic complex. The complex displays intense ligand-based π → π* transitions in the UV region and metal-to-ligand charge-transfer transitions (MLCT) in the visible region. The loss of bridging coordination of the dpp ligand and formation of complexes, [Ru(biq)₂(CH₃CN)₂]²⁺ and [Pt(dpp)(CH₃CN)₂]²⁺ was observed when an acetonitrile solution of the metal complex was irradiated with visible light (λ_irr ≥ 550 nm). The designed complex displays covalent binding with DNA in dark through the cis-PtCl₂ moiety, as confirmed by agarose gel electrophoresis. Upon photoirradiation, the complex dissociates into two DNA-binding moieties and displays covalent binding through: (i) a cis-PtL₂ subunit of [Ptdpp(L)₂]²⁺ and (ii) open coordination sites of the ruthenium of [Ru(biq)₂(L)₂]²⁺ (L = solvent). The designed complex represents the first Ru(II)Pt(II) complex that undergoes photo-induced ligand exchange and displays multifunctional interactions with DNA upon photoirradiation.     

On the hydrolysis mechanism of the second-generation anticancer drug carboplatin

The hydrolysis reaction mechanisms of carboplatin, a second-generation anticancer drug, have been explored by combining density functional theory (DFT) with the conductor-like dielectric continuum model (CPCM) approach. The decomposition of carboplatin in water is expected to take place through a biphasic mechanism with a ring-opening process followed by the loss of the malonato ligand. We have investigated this reaction in water and acid conditions and established that the number of protons present in the malonato ligand has a direct effect on the energetics of this system. Close observation of the optimised structures revealed a necessary systematic water molecule in the vicinity of the amino groups of carboplatin. For this reason we have also investigated this reaction with an explicit water molecule. From the computed potential-energy surfaces it is established that the water hydrolysis takes place with an activation barrier of 30 kcal mol(-1), confirming the very slow reaction observed experimentally. The decomposition of carboplatin upon acidification was also investigated and we have computed a 21 kcal mol(-1) barrier to be overcome (experimental value 23 kcal mol(-1)). We have also established that the rate-limiting process is the first hydration, and ascertained the importance of a water molecule close to the two amine groups in lowering the activation barriers for the ring-opening reaction.     

顺铂化合物与鸟嘌呤异构体相互作用的理论研究

The influence of binding of cisplatin adducts on tautomeric equilibrium of guanine was investigated using quantum chemical method. The monoaqua adduct [Pt（NH3）2Cl（H2O）]^＋ and the diaqua adduct [Pt（NHa）2（H2O）2]^2＋ were chosen for coordination to the N（7） site of guanine tautomers. The results demonstrate that the platinum adducts influence moderately on tautomeric equilibrium, but do not change the relative stability of tautomers whether in gas phase or in aqueous solution. The keto form having H atom at N（1） and N（9） was always the predominant structure when cisplatin adducts were bound to guanine. However, other forms could coexist in water. Meanwhile, our calculations suggest that the tautomeric equilibrium should be via the same intermediate.     

Loss of amine from platinum(II) complexes: implications for cisplatin inactivation, storage, and resistance

Potential consequences of the binding of the anticancer drug cisplatin to various biomolecules in the cell have been investigated by using a combined density functional theory and continuum dielectric model approach. Since the amine ligands remain coordinated at the metal upon formation of the most frequent DNA adducts, whereas they were found to be displaced from the metal upon formation of drug metabolites, we have analyzed the factors governing amine loss from platinum(II) complexes as a possible pathway of cisplatin inactivation. The calculations systematically show the effect of 1) the trans ligand, 2) the charge of complex, 3) the nucleophile, and 4) the environment on the thermodynamic instability and kinetic lability of the platinum-amine bonds. After initial binding of cisplatin hydrolysis products to thioethers or thiols, loss of the amine trans to this sulfur ligand rather than replacement of the sulfur ligand itself by other nucleophiles like guanine-N7 is predicted to be the predominant reaction. The results of this study contribute to an understanding of the modes of cisplatin inactivation prior to DNA binding, for example, by elevated glutathione levels in cisplatin-resistant cancer cells.     

电感耦合等离子发射光谱法测定血清及组织中铂类药物

顺铂类药物是一类重要的抗癌药物，脂质体顺铂是其中的一种新剂型。针对这类药物临床研究的需要，建立了一种测定血清及组织样品中铂含量的ICP-AES方法。通过对5种组织样品前处理方法的比较，最后选用条件温和、便于操作的温育加混合酸消解法，并以实验证实该方法的灵敏度、重现性及回收率等均符合卫生部“临床及临床前研究指导原则“对药物代谢研究分析方法的要求。采用本法测定了给予一定剂量脂质体顺铂后，大鼠血清中顺铂含量随时间变化的曲线，以及给药后8h，大鼠心、肝、脾、肺、肾等主要器官中顺铂的含量，为研究脂质体顺铂的药物代谢奠定了基础。