Qi-Pin Qin

Stabilization of G-quadruplex DNA, inhibition of telomerase activity, and tumor cell apoptosis by organoplatinum(II) complexes with oxoisoaporphine.

Two G-quadruplex ligands [Pt(L(a))(DMSO)Cl] (Pt1) and [Pt(L(b))(DMSO)Cl] (Pt2) have been synthesized and fully characterized. The two complexes are more selective for SK-OV-3/DDP tumor cells versus normal cells (HL-7702). It was found that both Pt1 and Pt2 could be a telomerase inhibitor targeting G-quadruplex DNA. This is the first report demonstrating that telomeric, c-myc, and bcl-2 G-quadruplexes and caspase-3/9 preferred to bind with Pt2 rather than Pt1, which also can induce senescence and apoptosis. The different biological behavior of Pt1 and Pt2 may correlate with the presence of a 6-hydroxyl group in L(b). Importantly, Pt1 and Pt2 exhibited higher safety in vivo and more effective inhibitory effects on tumor growth in the HCT-8 and NCI-H460 xenograft mouse model, compared with cisplatin. Taken together, these mechanistic insights indicate that both Pt1 and Pt2 display low toxicity and could be novel anticancer drug candidates.

Water-Soluble Ruthenium(II) Complexes with Chiral 4-(2,3-Dihydroxypropyl)-formamide Oxoaporphine (FOA): In Vitro and in Vivo Anticancer Activity by Stabilization of G-Quadruplex DNA, Inhibition of Telomerase Activity, and Induction of Tumor Cell Apoptosis.

Three water-soluble ruthenium(II) complexes with chiral 4-(2,3-dihydroxypropyl)-formamide oxoaporphine (FOA) were synthesized and characterized. It was found that these ruthenium(II) complexes exhibited considerable in vitro anticancer activities and that they were the effective stabilizers of telomeric and G-quadruplex-DNA (G4-DNA) in promoter of c-myc, which acted as a telomerase inhibitor targeting G4-DNA and induced cell senescence and apoptosis. Interestingly, the in vitro anticancer activity of 6 (LC-003) was higher than those of 4 (LC-001) and 5 (LC-002), more selective for BEL-7404 cells than for normal HL-7702 cells, and preferred to activate caspases-3/9. The different biological behaviors of the ruthenium complexes could be correlated with the chiral nature of 4-(2,3-dihydroxypropyl)-formamide oxoaporphine. More significantly, 6 exhibited effective inhibitory on tumor growth in BEL-7402 xenograft mouse model and higher in vivo safety than cisplatin. These mechanistic insights indicate that 6 displays low toxicity and can be a novel anticancer drug candidate.

Studies on antitumor mechanism of two planar platinum(II) complexes with 8-hydroxyquinoline: synthesis, characterization, cytotoxicity, cell cycle and apoptosis.

[Pt(Q)2] (1) and [Pt(MQ)2] (2) exhibited enhanced cytotoxicity against BEL-7404, Hep-G2, NCI-H460, T-24, A549 tumor cells but low cytotoxicity on normal HL-7702 cells. 1 and 2 could cause the cell cycle arrest in G2 and S phase, respectively. While pifithrin-α, a specific p53 inhibitor, induced cell cycle arrest in G1 phase. Although 1, 2 and pifithrin-α caused serious inhibition on p53, 1 and 2 significantly cause the loss of mitochondrial membrane potential and increase of the reactive oxygen species level, cytochrome c, apaf-1 and caspase-3/9 ratio in BEL-7404 cells. 1 and 2 may trigger the cell apoptosis through a mitochondrial dysfunction pathway whereas pifithrin-α does not. The interactions of 1 and 2 with DNA are most probably via an intercalation.

Synthesis, crystal structure, cytotoxicity and DNA interaction of 5,7-dibromo-8-quinolinolato-lanthanides.

Four isostructural lanthanide complexes with 5,7-dichloro-8-quinolinoline (H-ClQ): [Sm(ClQ)(3)(H(2)O)(2)]·1.33EtOH·0.33H(2)O (1), [Eu(ClQ)(3)(H(2)O)(2)]·0.5EtOH, (2), [Tb(ClQ)(3)(H(2)O)(2)]·0.5EtOH (3) and [Ho(ClQ)(3)(H(2)O)(2)]·H(2)O (4) were synthesized, in which the lanthanide was coordinated by three ClQ(-) anions and two aqua ligands. The in vitro cytotoxicities of complexes 1-4 against five human tumor cells were evaluated. The IC(50) values of complexes 1-4 against BEL7404, HeLa and A549 were in the range 1.2-6.3, 3.5-6.6 and 10.8-25.2 μM, respectively; except for complex 3 toward BEL7404, they all exhibited enhanced cytotoxicity in comparison to H-ClQ. The binding properties of complexes 1-4 to DNA examined by various methods indicated that complexes 1-4 interacted with DNA more strongly than free quinolinoline, and intercalation was the most probable binding mode for both the complexes and quinolinoline.

Stabilization of c-myc G-Quadruplex DNA, inhibition of telomerase activity, disruption of mitochondrial functions and tumor cell apoptosis by platinum(II) complex with 9-amino-oxoisoaporphine.

[Pd(L)(DMSO)Cl2] (1) and [Pt(L)(DMSO)Cl2] (2) with 9-amino-oxoisoaporphine (L), were synthesized and characterized. 1 and 2 are more selectively cytotoxic to Hep-G2 cells versus normal liver cells (HL-7702). Various experiments showed that 2 acted as telomerase inhibitors targeting G4-DNA and triggered cell apoptosis by interacting with c-myc G4-DNA. Furthermore, 2 significantly induced cell cycle arrest at both G2/M and S phase, which leading to the down-regulation of cdc25 A, cyclin D, cyclin B, cyclin A and CDK2 and the up-regulation of p53, p27, p21,chk1 and chk2. In addition, 2 also caused mitochondrial dysfunction. Taken together, we found that 2 exerted its cytotoxic activity mainly via inhibiting telomerase by interaction with c-myc G4-DNA and disruption of mitochondrial function.

A platinum(II) complex of liriodenine from traditional Chinese medicine (TCM): Cell cycle arrest, cell apoptosis induction and telomerase inhibition activity via G-quadruplex DNA stabilization.

Liriodenine (L), an antitumor active ingredient from the traditional Chinese medicine (TCM), Zanthoxylum nitidum, afforded a platinum(II) complex (1) of L, cis-[PtCl2(L)(DMSO)], which previously reported for its in vitro antitumor activity and intercalative binding with DNA. In this study, complex 1 was further discussed for its antitumor mechanism and structure-activity relationship, comparing with L and cisplatin. Towards the most sensitive BEL-7404 human hepatoma cells, complex 1 significantly induced cell cycle arrest at both G2/M phase and S phase. It suggests that double helix DNA is not the simplex intracellular target for 1. On the other hand, the BEL-7404 cells incubated with 1 and stained by Hoechst 33258 and AO/EB showed typical cell apoptosis in dose-dependent manner. The BEL-7404 cells incubated with 1 and stained by JC-1 were also characteristic for cell apoptosis on the loss of mitochondrial membrane potential. Furthermore, the G-quadruplex DNA binding property of complex 1 was also investigated by spectroscopic analyses, fluorescent indicator displacement (FID) assay and fluorescence resonance energy transfer (FRET) assay. The results indicated that 1 stabilized the human telomeric G4-HTG21 DNA better than L. The telomerase inhibition ratio of 1 ((62.50±0.03)%), which was examined by telomerase polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), was much higher than L ((21.77±0.01)%). It can be ascribed to the better G4-HTG21 DNA stabilization of 1 than L. The results suggested that the nuclei, mitochondria and telomerase via G-quadruplex DNA stabilization all should be key targets for the antitumor mechanism of 1, in which the central platinum(II) played a key role.

Cytotoxicity, DNA binding and cell apoptosis induction of a zinc(II) complex of HBrQ

A new zinc(II) complex (1) of 5-bromo-8-hydroxyquinoline (HBrQ) was prepared and structurally characterized using IR, ESI-MS, elemental analysis, 1H and 13C NMR, as well as single crystal X-ray diffraction analysis. The DNA binding study on complex 1, which was performed using UV-vis, fluorescence and circular dichroism (CD) spectral analyses, suggested that complex 1 interacts with ct-DNA mainly via an intercalative binding mode. The in vitro cytotoxicity of complex 1, compared with Zn(OAc)2·H2O, HBrQ and cisplatin, was screened against a series of tumor cell lines as well as the normal liver cell line HL-7702 using the MTT assay. Complex 1 showed much higher cytotoxicity than Zn(OAc)2·H2O and HBrQ against most of the tumor cell lines, in which BEL-7404 was the most sensitive tumor cell line towards 1, with an IC50 value of 8.69 ± 0.04 μM. Complex 1 was found to greatly induce cell cycle arrest in the BEL-7404 cells at the G2 phase, and consequently to induce cell apoptosis in a dose-dependent mode, which is suggested by the cell apoptosis analysis via the Hoechst 33258 and AO/EB staining assays. Targeting the mitochondria pathway due to the redox activity of Zn, the apoptotic mechanism in the BEL-7404 cells treated by 1 was investigated using reactive oxygen species (ROS) detection, intracellular calcium concentration measurement and caspase-9/3 activity assay, which showed that the cell apoptosis induced by 1 was closely related to the loss of mitochondrial membrane potential, ROS production and enhancement of intracellular [Ca2+], which trigger caspase-9/3 activation via the mitochondrial dysfunction pathway.

Preparation of 6/8/11-Amino/Chloro-Oxoisoaporphine and Group-10 Metal Complexes and Evaluation of Their in Vitro and in Vivo Antitumor Activity

A series of group-10 metal complexes 1–14 of oxoisoaporphine derivatives were designed and synthesized. 1–14 were more selectively cytotoxic to Hep-G2 cells comparing with normal liver cells. In vitro cytotoxicity results showed that complexes 1–6, 7, 8, 10 and 11, especially 3, were telomerase inhibitors targeting c-myc, telomeric, and bcl-2 G4s and triggered cell senescence and apoptosis; they also caused telomere/DNA damage and S phase arrest. In addition, 1–6 also caused mitochondrial dysfunction. Notably, 3 with 6-amino substituted ligand La exhibited less side effects than 6 with 8-amino substituted ligand Lb and cisplatin, but similar tumor growth inhibition efficacy in BEL-7402 xenograft model. Complex 3 has the potential to be developed as an effective anticancer agent.

Evaluation of the effect of iodine substitution of 8-hydroxyquinoline on its platinum(II) complex: cytotoxicity, cell apoptosis and telomerase inhibition

Two platinum(II) complexes, [PtCl(Q)(DMSO)] (1) and [PtCl(IQ)(DMSO)] (2), bearing 8-hydroxyquinoline (H-Q) and 5,7-diiodo-8-hydroxyquinoline (H-IQ) as the bioactive ligand, respectively, were synthesized and structurally characterized. By MTT assay, complex 2 bearing the IQ ligand showed significantly higher growth inhibition than complex 1 against all the five typical tumor cell lines in the test, but showed no more cytotoxicity against the normal liver cell line HL-7702, suggesting the much better cytotoxic selectivity of 2 than that of 1. In addition, the HepG2 cell line was found to be the most sensitive towards both complexes. Aiming at the HepG2 cell line, both complexes arrested the cell cycle of HepG2 cells in the S phase, as examined by flow cytometry, in which complex 2 showed higher S-phase arrest than 1. This was supported by the down-regulation of cdc25 A, cyclin B, cyclin A, and CDK2 and the up-regulation of p53, p27 and p21 based on western blot assay. Complex 2 also acted as a more effective telomerase inhibitor than 1 by interacting with telomeric/c-myc G-quadruplexes and triggering cell senescence and cell apoptosis. Furthermore, both complexes caused mitochondrial dysfunction, suggesting a potential mitochondrion-mediated apoptotic pathway induced by each complex. From the platinum uptake assay, complex 2 exhibited obvious priority on the cell uptake effect than 1, which should be undoubtedly correlated with the key roles of the 5- and 7-iodo-substituted groups in the IQ ligand of 2. This may well explain the better cytotoxicity and the more significant antitumor mechanism of 2 throughout the study. This work further demonstrated that rational halogen substitution on selected ligands would be greatly beneficial to achieve more promising metal-based antitumor agents.

Three novel transition metal complexes of 6-methyl-2-oxo-quinoline-3-carbaldehyde thiosemicarbazone: synthesis, crystal structure, cytotoxicity, and mechanism of action

Three novel 6-methyl-2-oxo-quinoline-3-carbaldehyde thiosemicarbazone (H-L) transition metal complexes, [Cu(H-L)NO3H2O]·NO3 (1), [Zn(H-L)NO3H2O]·NO3 (2) and [CoL2] (3), were synthesized. In vitro antitumor screening revealed that complex 1 exhibited better inhibitory activities than the commercial anticancer drug cisplatin against SK-OV-3 and MGC80-3 tumor cell lines, with IC50 values of 10.35 ± 1.26 μM and 10.17 ± 0.95 μM, respectively. All three complexes showed low cytotoxicity toward the normal human liver HL-7702 cells compared with cisplatin. Their binding properties to DNA were investigated by various methods. It was found that the complexes interacted with DNA mainly through intercalation, and their binding affinities ranked in the order of 3 > 1 > 2. Complex 1 induced the highest apoptosis rate of MGC80-3 cells, and it caused cell arrest in the S phase according to flow cytometry. Further experiments confirmed that complex 1 triggered MGC80-3 cells apoptosis via a mitochondrial dysfunction pathway.