Metal-Based Anticancer Complexes and p53: How Much Do We Know?

P53 plays a key role in protecting the human genome from DNA-related mutations; however, it is one of the most frequently mutated genes in cancer. The P53 family members p63 and p73 were also shown to play important roles in cancer development and progression. Currently, there are various organic molecules from different structural classes of compounds that could reactivate the function of wild-type p53, degrade or inhibit mutant p53, etc. It was shown that: (1) the function of the wild-type p53 protein was dependent on the presence of Zn atoms, and (2) Zn supplementation restored the altered conformation of the mutant p53 protein. This prompted us to question whether the dependence of p53 on Zn and other metals might be used as a cancer vulnerability. This review article focuses on the role of different metals in the structure and function of p53, as well as discusses the effects of metal complexes based on Zn, Cu, Fe, Ru, Au, Ag, Pd, Pt, Ir, V, Mo, Bi and Sn on the p53 protein and p53-associated signaling.

A Ru(ii)-arene-ferrocene complex with promising antibacterial activity

The evolution of high virulence bacterial strains has necessitated the development of novel therapeutic agents to treat resistant infections.

Zn(ii), Cd(ii) and Hg(ii) saccharinate complexes with 2,6-bis(2-benzimidazolyl)pyridine as promising anticancer agents in breast and lung cancer cell lines via ROS-induced apoptosis

New Zn(ii), Cd(ii) and Hg(ii) complexes of saccharinate (sac) and 2,6-bis(2-benzimidazolyl)pyridine (bzimpy), [Zn(bzimpy)2](sac)2·2H2O (Zn), [Cd(sac)2(bzimpy)] (Cd) and [Hg(sac)2(bzimpy)] (Hg), were prepared and fully characterized by spectroscopic methods and X-ray crystallography. In vitro anticancer screening in A549 (lung), MCF-7 (breast) and HT29 (colon) cell lines showed that Zn was highly cytotoxic against A549 and MCF-7 cells with IC50 values of 1.74 ± 0.06 and 3.15 ± 0.10 μM, respectively, and Hg demonstrated potent cytotoxic activity in MCF-7 cells (8.61 ± 0.98 μM), while Cd and bzimpy exhibited moderate growth inhibitory activities in all of the cell lines. In addition, they showed significantly lower toxicity towards normal human breast epithelial MCF10A cells. Moreover, the complexes exhibited significantly high nuclease activity towards plasmid DNA and their interactions with DNA were assessed by gel electrophoresis and DNA docking. Zn and Hg induced G0/G1 cell arrest and apoptotic cell death detected via typical DNA condensation/fragmentation, annexin V staining and caspase 3/7 activity in A549 and MCF-7 cells. These complexes further caused depolarization of mitochondria and oxidative damage of genomic DNA following excessive production of reactive oxygen species (ROS).

Molecular targets and anticancer activity of quinoline-chalcone hybrids: literature review

α,β-Unsaturated chalcone moieties and quinoline scaffolds play an important role in medicinal chemistry, especially in the identification and development of potential anticancer agents. The multi-target approach or hybridization is considered as a promising strategy in drug design and discovery. Hybridization may improve the affinity and potency while simultaneously decreasing the resistance and/or side effects. The conjugation of quinolines with chalcones has been a promising approach to the identification of potential anticancer agents. Most of these hybrids showed anticancer activities through the inhibition of tubulin polymerization, different kinases, topoisomerases, or by affecting DNA cleavage activity. Accordingly, this class of compounds can be classified based on their molecular modes of action. In this article, the quinolone-chalcone hybrids with potential anticancer activity have been reviewed. This class of compounds might be helpful for the design, discovery and development of new and potential multi-target anticancer agents or drugs.

Unconventional DNA-relevant π-stacked hydrogen bonded arrays involving supramolecular guest benzoate dimers and cooperative anion–π/π–π/π–anion contacts in coordination compounds of Co(ii) and Zn(ii) phenanthroline: experimental and theoretical studies

Antiproliferative evaluation and supramolecular assemblies of Co(ii) and Zn(ii) coordination compounds involving cooperative anion–π and unconventional DNA-relevant π-stacked hydrogen bonded arrays.

Functionalization and cancer-targeting design of ruthenium complexes for precise cancer therapy

The successful clinical application of the three generation platinum anticancer drugs, cisplatin, carboplatin and oxaliplatin, has promoted research interest in metallodrugs; however, the problems of drug resistance and adverse effects have hindered their further application and effects. Thus, scientists are searching for new anticancer metallodrugs with lower toxicity and higher efficacy. The ruthenium complexes have emerged as the most promising alternatives to platinum-based anticancer agents because of their unique multifunctional biochemical properties. In this review, we first focus on the anticancer applications of various ruthenium complexes in different signaling pathways, including the mitochondria-mediated pathway, the DNA damage-mediated pathway, and the death receptor-mediated pathway. We then discuss the functionalization and cancer-targeting designs of different ruthenium complexes in conjunction with other therapies such as photodynamic therapy, photothermal therapy, radiosensitization, targeted therapy and nanotechnology for precise cancer therapy. This review will help in designing and accelerating the research progress regarding new anticancer ruthenium complexes.

Antitumor effects of arsenic disulfide on the viability, migratory ability, apoptosis and autophagy of breast cancer cells

In the present study, the antitumor effects of arsenic disulfide (As₂S₂) on the proliferative, survival and migratory ability of human breast cancer MCF-7 and MDA-MB-231 cells were investigated, and its potential underlying molecular mechanisms with an emphasis on cell cycle arrest, apoptosis induction, autophagy induction and reactive oxygen species (ROS) generation were determined. The results indicated that As₂S₂ significantly inhibited the viability, survival and migration of breast cancer cells in a dose-dependent manner. In addition, it was identified that As₂S₂ induced cell cycle arrest primarily at G₂/M phase in the two breast cancer cell lines by regulating the expression of associated proteins, including cyclin B1 and cell division cycle protein 2. In addition to cell cycle arrest, As₂S₂ also triggered the induction of apoptosis in cells by activating the expression of pro-apoptotic proteins, including caspase-7 and −8, as well as increasing the B-cell lymphoma 2 (Bcl-2)-associated X protein/Bcl-2 ratio, while decreasing the protein expression of anti-apoptotic B-cell lymphoma extra-large. In addition, As₂S₂ stimulated the accumulation of microtubule-associated protein 1A/1B-light chain 3 (LC3)-II and increased the LC3-II/LC3-I ratio, indicating the occurrence of autophagy. As₂S₂ treatment also inhibited the protein expression of matrix metalloproteinase-9 (MMP-9), but increased the intracellular accumulation of ROS in the two breast cancer cell lines, which may assist in alleviating metastasis and attenuating the progression of breast cancer. Taken together, the results of the present study suggest that As₂S₂ inhibits the progression of human breast cancer cells through the regulation of cell cycle arrest, intrinsic and extrinsic apoptosis, autophagy, MMP-9 signaling and ROS generation.

Iron(II)-Polypyridyl Complexes Inhibit the Growth of Glioblastoma Tumor and Enhance TRAIL-Induced Cell Apoptosis

A promising cancer-targeting agent for the induction of apoptosis in tumor necrosis factor (TNF) proteins, the TNF-related apoptosis-inducing ligand (TRAIL) ligand, has found limited applications in the treatment of cancer cells, owing to its resistance by cancer cell lines. Therefore, the rational design of anticancer agents that could sensitize cancer cells towards TRAIL is of great significance. Herein, we report that synthetic iron(II)-polypyridyl complexes are capable of inhibiting the proliferation of glioblastoma cancer cells and efficiently enhancing TRAIL-induced cell apoptosis. Mechanistic studies demonstrated that the synthesized complexes induced cancer-cell apoptosis through triggering the activation of p38 and p53 and inhibiting the activation of ERK. Moreover, uPA and MMP-2/MMP-9, among the most important metastatic regulatory proteins, were also found to be significantly alerted after the treatment. Furthermore, we also found that tumor growth in nude mice was significantly inhibited by iron complex Fe2 through the induction of apoptosis without clear systematic toxicity, as indicated by histological analysis. Taken together, this study provides evidence for the further development of metal-based anticancer agents and chemosensitizers of TRAIL for the treatment of human glioblastoma cancer cells.

Influence of substituents on DNA and protein binding of cyclometalated Ir(iii) complexes and anticancer activity

Synthesis of terpyridyl based ligands 3-([2,2':6',2''-terpyridin]-4'-yl)-7-methoxy-2-(methylthio)-quinolone, (L1); 3-([2,2':6',2''-terpyridin]-4'-yl)-6-methoxyquinolin-2(1H)-one, (L2); 3-([2,2'-:6',2''-terpyridin]-4'-yl)-6-methylquinolin-2(1H)-one (L3) and cyclometalated iridium(iii) complexes [[Ir(ppy)₂L1]⁺PF₆^- (1), [Ir(ppy)₂L2]⁺PF₆^- (2), [Ir(ppy)₂L3]⁺PF₆^- (3) (2-phenylpyridine = Hppy)] involving these ligands has been described. The ligands L1-L3 and complexes 1-3 have been thoroughly characterized by elemental analyses, spectral studies (IR, ¹H, ¹³C NMR, UV/vis and fluorescence) ESI-MS, and the structure of 3 has been unambiguously authenticated by single crystal X-ray analyses. UV/vis, fluorescence and circular dichroism spectroscopic studies showed rather efficient binding of 1 with CT-DNA (calf thymus DNA) and BSA (bovine serum albumin) relative to 2 and 3. Molecular docking studies unveiled binding of 1-3 with minor groove of CT-DNA via van der Waal's forces and electrostatically with the hydrophobic moiety of HSA (human serum albumin). The ligands and complexes exhibited moderate cytotoxicity towards MDA-MB-231 (breast cancer cell line) and significant influence on HeLa (cervical cancer cell line) cells. Cytotoxicity, morphological changes, and apoptosis have been followed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assay, Hoechst 33342/PI (PI = propidium iodide) staining, cell cycle analysis by FACS (fluorescence activated cell sorting), and ROS (reactive oxygen species) generation by DCFH-DA (dichlorodihydrofluorescein diacetate) dye. Confocal microscopy images revealed that the drug efficiently initiates apoptosis in the cell cytosol. The IC₅₀ values showed superior cytotoxicity of 1-3 against the HeLa cell line relative to cisplatin, and their ability to induce apoptosis is in the order 1 > 2 > 3.

Licochalcone D induces apoptosis and inhibits migration and invasion in human melanoma A375 cells

The aim of the present study was to determine the effects of Licochalcone D (LD) on the apoptosis and migration and invasion in human melanoma A375 cells. Cell proliferation was determined by sulforhodamine B assay. Apoptosis was assessed by Hoechst 33258 and Annexin V‑FITC/PI staining and JC‑1 assay. Total intracellular reactive oxygen species (ROS) was examined by DCFH‑DA. Wound healing and Transwell assays were used to detect migration and invasion of the cells. The activities of matrix metalloproteinase (MMP‑2 and MMP‑9) were assessed via gelatin zymography. Tumor growth in vivo was evaluated in C57BL/6 mice. RT‑PCR, qPCR, ELISA and western blot analysis were utilized to measure the mRNA and protein levels. Our results showed that LD inhibited the proliferation of A375 and SK‑MEL‑5 cells in a concentration‑dependent manner. After treatment with LD, A375 cells displayed obvious apoptotic characteristics, and the number of apoptotic cells was significantly increased. Pro‑apoptotic protein Bax, caspase‑9 and caspase‑3 were upregulated, while anti‑apoptotic protein Bcl‑2 was downregulated in the LD‑treated cells. Meanwhile, LD induced the loss of mitochondrial membrane potential (ΔΨm) and increased the level of ROS. ROS production was inhibited by the co‑treatment of LD and free radical scavenger N‑acetyl‑cysteine (NAC). Furthermore, LD also blocked A375 cell migration and invasion in vitro which was associated with the downregulation of MMP‑9 and MMP‑2. Finally, intragastric administration of LD suppressed tumor growth in the mouse xenograft model of murine melanoma B16F0 cells. These results suggest that LD may be a potential drug for human melanoma treatment by inhibiting proliferation, inducing apoptosis via the mitochondrial pathway and blocking cell migration and invasion.

Selenadiazole derivatives antagonize hyperglycemia-induced drug resistance in breast cancer cells by activation of AMPK pathways

Hyperglycemia is an important factor for chemoresistance of breast cancer patients with diabetes. In the present study, a novel selenadiazole derivative has been evaluated and found to be able to antagonize the doxorubicin (DOX) resistance of MCF-7 cells under simulated diabetes conditions. Hyperglycemia promotes the proliferation, invasion and migration of MCF-7 cells through activation of ERK and AKT pathways, which could be inhibited by the synthetic selenadiazole derivative. The antitumor effects of the selenadiazole derivative were attributed to its ability to activate AMPK pathways. Furthermore, the high lipophilicity (log P = 1.9) of the synthetic selenadiazole derivative facilitated its uptake by cancer cells and subsequently potentiated the cellular uptake of DOX, leading to a strong enhancment of the antiproliferative activity of DOX on MCF-7 cells by induction of apoptosis. The apoptosis was initiated by the ROS overproduction induced by the cooperation of the selenadiazole derivative and DOX. The excessive ROS then caused damage to DNA, which upregulated the expression of proapoptosis Bcl-2 family proteins and led to fragmentation of mitochondria, which finally caused apoptosis of the cancer cells. Taken together, this study provides a rational strategy for using selenadiazole derivatives to overcome hyperglycemia-induced drug resistance in breast cancer by activation of AMPK-mediated pathways.

Ruthenium complex exerts antineoplastic effects that are mediated by oxidative stress without inducing toxicity in Walker-256 tumor-bearing rats

The present study evaluated the in vivo antitumor effects and toxicity of a new Ru(II) compound, cis-(Ru[phen]₂[ImH]₂)²⁺ (also called RuphenImH [RuC]), against Walker-256 carcinosarcoma in rats. After subcutaneous inoculation of Walker-256 cells in the right pelvic limb, male Wistar rats received 5 or 10mgkg^-1 RuC orally or intraperitoneally (i.p.) every 3 days for 13 days. A positive control group (2mgkg^-1 cisplatin) and negative control group (vehicle) were also used. Tumor progression was checked daily. After treatment, tumor weight, plasma biochemistry, hematology, oxidative stress, histology, and tumor cell respiration were evaluated. RuC was effective against tumors when administered i.p. but not orally. The highest i.p. dose of RuC (10mgkg^-1) significantly reduced tumor volume and weight, induced oxidative stress in tumor tissue, reduced the respiration of tumor cells, and induced necrosis but did not induce apoptosis in the tumor. No clinical signs of toxicity or death were observed in tumor-bearing or healthy rats that were treated with RuC. These results suggest that RuC has antitumor activity through the modulation of oxidative stress and impairment of oxidative phosphorylation, thus promoting Walker-256 cell death without causing systemic toxicity. These effects make RuC a promising anticancer drug for clinical evaluation.

Functionalized Selenium Nanosystem as Radiation Sensitizer of 125I Seeds for Precise Cancer Therapy

Although radiotherapy has been extensively applied in cancer treatment, external beam radiation therapy is still unable to avoid damage to adjacent normal tissues in the process of delivering a sufficient radiation dose to the tumor sites of patients. To overcome this limitation, chemoradiotherapy, as a combination of chemotherapy and radiotherapy of a radioactive seed, has been proposed to decrease the damage to tumor-surrounding tissues and enhance the radiosensitivity of solid tumors. In this study, we designed and synthesized folic acid-conjugated selenium nanoparticles (FA@SeNPs) as a cancer-targeting agent that could be synergistically enhanced by radioactive ¹²⁵I seeds to realize anticancer efficacy and inhibited colony formation ability. Interestingly, when compared with X-ray irradiation, ¹²⁵I seeds demonstrate a larger synergistic effect with the FA@SeNPs, drastically increasing reactive oxygen species overproduction to trigger apoptosis and influencing the cell cycle distribution in human breast cancer cells, inducing DNA damage and activating the mitogen-activated protein kinase and p53 signaling pathways. Moreover, this combination treatment demonstrates better in vivo antitumor activity and lower systemic toxicity. Therefore, this study demonstrates a new strategy for using functionalized SeNPs as a radiation sensitizer for ¹²⁵I seeds for cancer therapy.

Transferrin-functionalized nanographene oxide for delivery of platinum complexes to enhance cancer-cell selectivity and apoptosis-inducing efficacy

Rational design and construction of delivery nanosystems for anticancer metal complexes is a crucial strategy to improve solubility under physiological conditions and permeability and retention behavior in tumor cells. Therefore, in this study, we designed and synthesize a transferrin (Tf)-conjugated nanographene oxide (NGO) nanosystem as a cancer-targeted nanocarrier of Pt complexes (Tf-NGO@Pt). This nanodelivery system exhibited good solubility under physiological conditions. Moreover, Tf-NGO@Pt showed higher anticancer efficacy against MCF human breast cancer cells than the free Pt complex, and effectively inhibited cancer-cell migration and invasion, with involvement of reactive oxygen species overproduction. In addition, nanolization also enhanced the penetration ability and inhibitory effect of the Pt complex toward MCF7 breast cancer-cell tumor spheroids. The enhancement of anticancer efficacy was positively correlated with increased cellular uptake and cellular drug retention. This study provides a new strategy to facilitate the future application of metal complexes in cancer therapy.

Green tea polyphenols induce cell death in breast cancer MCF-7 cells through induction of cell cycle arrest and mitochondrial-mediated apoptosis

In order to study the molecular mechanisms of green tea polyphenols (GTPs) in treatment or prevention of breast cancer, the cytotoxic effects of GTPs on five human cell lines (MCF-7, A549, Hela, PC3, and HepG2 cells) were determined and the antitumor mechanisms of GTPs in MCF-7 cells were analyzed. The results showed that GTPs exhibited a broad spectrum of inhibition against the detected cancer cell lines, particularly the MCF-7 cells. Studies on the mechanisms revealed that the main modes of cell death induced by GTPs were cell cycle arrest and mitochondrial-mediated apoptosis. Flow cytometric analysis showed that GTPs mediated cell cycle arrest at both G1/M and G2/M transitions. GTP dose dependently led to apoptosis of MCF-7 cells via the mitochondrial pathways, as evidenced by induction of chromatin condensation, reduction of mitochondrial membrane potential (ΔΨ_m), improvement in the generation of reactive oxygen species (ROS), induction of DNA fragmentation, and activations of caspase-3 and caspase-9 in the present paper.

Nucleolin-targeted selenium nanocomposites with enhanced theranostic efficacy to antagonize glioblastoma

Glioblastoma is considered as the most lethal cancer, due to the inability of chemotherapeutic agents to reach the glioma core as well as the infiltration zone of the invasive glioma cells. Nanotechnology based delivery systems bring new hope to cancer targeted therapy and diagnosis owing to their enhancement of selective cellular uptake and cytotoxicity to cancer cells through various smart designs. We prepared a novel selenium-based composite nanosystem (QDs/Se@Ru(A)) surface functionalized with the AS1411 aptamer and loaded with quantum dots to realize selectivity against glioblastoma and enhance theranostic effects. This cancer targeted nanosystem significantly enhanced the cellular uptake in glioma cells through nucleolin mediated endocytosis, and increased selectivity between cancer and normal cells. The QDs/Se@Ru(A) nanosystem can also be used for spontaneous fluorescence of biological probes to explore their localization in cancer cells, because of the green fluorescent quantum dots loaded into the selenium nanoparticles. QDs/Se@Ru(A) promotes excess reactive oxygen species (ROS) production in glioma cells to induce DNA damage, thus activating diverse downstream signaling pathways, and inhibiting proliferation of U87 cells through the G2/M phase cycle. Thus, this study provides an effective strategy to design a theranostic agent to simultaneously realize cell imaging and therapy for glioblastoma treatment.

Ruthenium complexes with phenylterpyridine derivatives target cell membrane and trigger death receptors-mediated apoptosis in cancer cells

Elucidation of the communication between metal complexes and cell membrane may provide useful information for rational design of metal-based anticancer drugs. Herein we synthesized a novel class of ruthenium (Ru) complexes containing phtpy derivatives (phtpy = phenylterpyridine), analyzed their structure-activity relationship and revealed their action mechanisms. The result showed that, the increase in the planarity of hydrophobic Ru complexes significantly enhanced their lipophilicity and cellular uptake. Meanwhile, the introduction of nitro group effectively improved their anticancer efficacy. Further mechanism studies revealed that, complex (2c), firstly accumulated on cell membrane and interacted with death receptors to activate extrinsic apoptosis signaling pathway. The complex was then transported into cell cytoplasm through transferrin receptor-mediated endocytosis. Most of the intracellular 2c accumulated in cell plasma, decreasing the level of cellular ROS, inducing the activation of caspase-9 and thus intensifying the apoptosis. At the same time, the residual 2c can translocate into cell nucleus to interact with DNA, induce DNA damage, activate p53 pathway and enhance apoptosis. Comparing with cisplatin, 2c possesses prolonged circulation time in blood, comparable antitumor ability and importantly, much lower toxicity in vivo. Taken together, this study uncovers the role of membrane receptors in the anticancer actions of Ru complexes, and provides fundamental information for rational design of membrane receptor targeting anticancer drugs.

Phycocyanin-based nanocarrier as a new nanoplatform for efficient overcoming of cancer drug resistance

The rational design of a novel phycocyanin-based nanosystem with bio-responsive properties to achieve prolonged blood circulation and overcome drug resistance without causing systemic toxicity.

Highly stable selenadiazole derivatives induce bladder cancer cell apoptosis and inhibit cell migration and invasion through the activation of ROS-mediated signaling pathways

Herein highly stable selenadiazole derivatives were synthesized and found to be able to induce bladder cancer cell apoptosis and inhibit cell migration and invasion through the activation of ROS-mediated pathways.

The potential anti-proliferative effect of β-sitosterol on human mast cell line-1 cells

Thymic stromal lymphopoietin (TSLP) was reported to induce mast cell proliferation and aggravate allergic reactions through activation of mouse double minute 2 (MDM2). We aimed to ascertain that β-sitosterol (SI), which is one of the several phytosterols found mostly in foods, would regulate TSLP-induced mast cell proliferation. The results showed that SI significantly decreased the proliferation of human mast cell line (HMC-1) cells promoted by TSLP. SI significantly decreased the mRNA expression of Ki-67 in the TSLP-treated HMC-1 cells. SI significantly suppressed the production and mRNA expression of interleukin-13 in the TSLP-treated HMC-1 cells. Furthermore, SI downregulated the expression of MDM2 and phosphorylation of STAT6, whereas it upregulated the expression of p53, activation of caspase-3, and cleavage of poly ADP-ribose polymerase in the TSLP-treated HMC-1 cells. Results of this study suggest that SI may be a potential therapeutic agent for mast cell-mediated allergic diseases.

New benzimidazole acridine derivative induces human colon cancer cell apoptosis in vitro via the ROS-JNK signaling pathway

AIM

To investigate the mechanisms underlying anticancer action of the benzimidazole acridine derivative N-{(1H-benzo[d]imidazol-2-yl)methyl}-2-butylacridin-9-amine(8m) against human colon cancer cells in vitro.

METHODS

Human colon cancer cell lines SW480 and HCT116 were incubated in the presence of 8m, and then the cell proliferation and apoptosis were measured. The expression of apoptotic/signaling genes and proteins was detected using RT-PCR and Western blotting. ROS generation and mitochondrial membrane depolarization were visualized with fluorescence microscopy.

RESULTS

8m dose-dependently suppressed the proliferation of SW480 and HCT116 cells with IC50 values of 6.77 and 3.33 μmol/L, respectively. 8m induced apoptosis of HCT116 cells, accompanied by down-regulation of Bcl-2, up-regulation of death receptor-5 (DR5), truncation of Bid, cleavage of PARP, and activation of caspases (including caspase-8 and caspase-9 as well as the downstream caspases-3 and caspase-7). Moreover, 8m selectively activated JNK and p38 without affecting ERK in HCT116 cells. Knockout of JNK1, but not p38, attenuated 8m-induced apoptosis. In addition, 8m induced ROS production and mitochondrial membrane depolarization in HCT116 cells. Pretreatment with the antioxidants N-acetyl cysteine or glutathione attenuated 8m-induced apoptosis and JNK activation in HCT116 cells.

CONCLUSION

The new benzimidazole acridine derivative, 8m exerts anticancer activity against human colon cancer cells in vitro by inducing both intrinsic and extrinsic apoptosis pathways via the ROS-JNK1 pathway.

Mixed-ligand ruthenium polypyridyl complexes as apoptosis inducers in cancer cells, the cellular translocation and the important role of ROS-mediated signaling

Ruthenium (Ru) polypyridyl complexes have emerged as leading players among the potential metal-based candidates for cancer treatment. However, the roles of cellular translocation in their action mechanisms remain elusive. Herein we present the synthesis and characterization of a series of ruthenium (Ru) complexes containing phenanthroline derivatives with varying lipophilicities, and examine their mechanism of anticancer action. Results showed that increasing the lipophilicity of complexes can enhance the rates of cellular uptake. The in vitro anticancer efficacy of these complexes depended on the levels of ROS overproduction, rather than on cellular Ru uptake levels. The introduction of a phenolic group on the ligand effectively enhanced their intracellular ROS generation and anticancer activities. In particular, complex 4, with an ortho-phenolic group on the ligand, exhibited better selectivity between cancer and normal cells in comparison with cisplatin. Notably, complex 4 entered the cancer cells partially through transferrin receptor-mediated endocytosis, and then it translocated from lysosomes to the mitochondria, where it activated mitochondrial dysfunction by regulation of Bcl-2 family proteins, thus leading to intracellular ROS overproduction. Excess ROS amplified apoptotic signals by activating many downstream pathways such as p53 and MAPK pathways to promote cell apoptosis. Overall, this study provides a drug design strategy for discovery of Ru-based apoptosis inducers, and elucidates the intracellular translocation of these complexes.

Two half-sandwiched ruthenium (II) compounds containing 5-fluorouracil derivatives: synthesis and study of DNA intercalation

Two novel coordination compounds of half-sandwiched ruthenium(II) containing 2-(5-fluorouracil)-yl-N-(pyridyl)-acetamide were synthesized, and their intercalation binding modes with calf thymus DNA were revealed by hyperchromism of ultraviolet-visible spectroscopy; the binding constants were determined according to a Langmuir adsorption equation that was deduced on the base of careful cyclic voltammetry measurements. The two compounds exhibited DNA intercalation binding activities with the binding constants of 1.13×10⁶ M^-1 and 5.35 ×10⁵ M^-1, respectively.

Strategy to enhance the therapeutic effect of doxorubicin in human hepatocellular carcinoma by selenocystine, a synergistic agent that regulates the ROS-mediated signaling

Doxorubicin-based chemotherapy represents one of the most effective ways in combating human cancers. However, its clinical use is limited by severe side effects. Selenocystine (SeC) is a natural available selenoamino acid with novel anticancer efficacy. In this study, we used SeC to sensitize HepG2 human hepatocellular carcinoma (HCC) cells to DOX, and to achieve anticancer synergism in vitro and in vivo. Treatment with DOX dose-dependently reduced HepG2 cell viability through initiating cell apoptosis and strong G2/M phase cell cycle arrest. Mechanistic studies indicated that this sensitization of SeC to DOX was achieved by triggering inactivation of ERK and AKT and DNA damage through reactive oxygen species (ROS) overproduction. Pretreatment with inhibitors of ERK and AKT markedly enhanced combined treatment-induced cell killing, indicating that combined treatment-induced HCC cell killing with ERK- and AKT-dependent manner. Furthermore, inhibition of ROS effectively attenuated combined treatment-induced DNA damage and inactivation of ERK and AKT. Additionally, xenograft hepatocellular carcinoma growth was also effectively inhibited by combined treatment through induction of cell apoptosis in vivo. Taken together, our results suggest that the strategy to use SeC and DOX in combination could be a highly efficient way to achieve anticancer synergism against HCC.

Selenadiazole derivatives as theranostic agents for simultaneous cancer chemo-/radiotherapy by targeting thioredoxin reductase

Herein we have identified selenadiazole derivatives as effective and safe theranostic agents for simultaneous cancer chemo-/radiotherapy.

A selenium-containing ruthenium complex as a cancer radiosensitizer, rational design and the important role of ROS-mediated signalling

We have described the rational design of selenium-containing ruthenium complexes and their use as cancer radiosensitizers through regulating ROS-mediated pathways.

Antiangiogenic ruthenium(ii) benzimidazole complexes, structure-based activation of distinct signaling pathways

A series of ruthenium(ii) benzimidazole complexes has been synthesized and identified as antiangiogenic agents with distinct structure-based action mechanisms.

Metallomics insights into the programmed cell death induced by metal-based anticancer compounds

Since the discovery of cisplatin more than 40 years ago, enormous research efforts have been dedicated to developing metal-based anticancer agents and to elucidating the mechanisms involved in the action of these compounds. Abnormal metabolism and the evasion of apoptosis are important hallmarks of malignant transformation, and the induction of apoptotic cell death has been considered to be a main pathway by which cytotoxic metal complexes combat cancer. However, many cancers have cellular defects involving the apoptotic machinery, which results in an acquired resistance to apoptotic cell death and therefore reduced chemotherapeutic effectiveness. Over the past decade, it has been revealed that a growing number of cell death pathways induced by metal complexes are not dependent on apoptosis. Metal complexes specifically triggering these alternative cell death pathways have been identified and explored as novel cancer treatment options. In this review, we discuss recent examples of metallomics studies on the different types of cell death induced by metal-based anticancer drugs, especially on the three major forms of programmed cell death (PCD) in mammalian cells: apoptosis, autophagy and regulated necrosis, also called necroptosis.

Cytoxicity and apoptotic mechanism of ruthenium(II) amino acid complexes in sarcoma-180 tumor cells

Over the past several decades, much attention has been focused on ruthenium complexes in antitumor therapy. Ruthenium is a transition metal that possesses several advantages for rational antitumor drug design and biological applications. In the present study, five ruthenium complexes containing amino acids were studied in vitro to determine their biological activity against sarcoma-180 tumor cells. The cytotoxicity of the complexes was evaluated by an MTT assay, and their mechanism of action was investigated. The results demonstrated that the five complexes inhibited the growth of the S180 tumor cell line, with IC50 values ranging from 22.53 µM to 50.18 µM, and showed low cytotoxicity against normal L929 fibroblast cells. Flow cytometric analysis revealed that the [Ru(gly)(bipy)(dppb)]PF6 complex (2) inhibited the growth of the tumor cells by inducing apoptosis, as evidenced by an increased number of Annexin V-positive cells and G0/G1 phase cell cycle arrest. Further investigation showed that complex 2 caused a loss of mitochondrial membrane potential; activated caspases 3, caspase-8, and caspase-9 and caused a change in the mRNA expression levels of caspase 3, caspase-9 as well as the bax genes. The levels of the pro-apoptotic Bcl-2 family protein Bak were increased. Thus, we demonstrated that ruthenium amino acid complexes are promising drugs against S180 tumor cells, and we recommend further investigations of their role as chemotherapeutic agents for sarcomas.

Inhibition of islet amyloid polypeptide fibril formation by selenium-containing phycocyanin and prevention of beta cell apoptosis

Human islet amyloid polypeptide (hIAPP) fibril is the major constituent of amyloid deposits in pancreatic islets of type 2 diabetes. Misfolding and hIAPP fibril formation are thought to be important in the pathogenesis of diabetes. Studies have showed that selenium-containing phycocyanin (Se-PC) inhibited the fibrillation of hIAPP to form nanoscale particles, which is mainly by interfering with the combination between hIAPP. Small nanoscale oligomers tended to grow into larger nanoparticles and the size of nanoparticles increased with the incubation time. By interfering with the fibrillation of hIAPP and altering the structure, Se-PC alleviated hIAPP-induced cell apoptosis. Meantime, generation of ROS produced during the fibrillation process was inhibited, which was proposed to be the main factor for the hIAPP-cytotoxicity in beta cells. Taken together, Se-PC inhibited hIAPP fibrillation, thus suppressed the formation of ROS to show protective effect on hIAPP mediated cell apoptosis. Our studies provide useful information for our understanding of the interaction mechanisms of Se-PC on hIAPP structure and protective mechanisms on hIAPP cytotoxicity, presenting useful candidate for anti-diabetes drug development.

Recent advances in small organic molecules as DNA intercalating agents: synthesis, activity, and modeling

The interaction of small molecules with DNA plays an essential role in many biological processes. As DNA is often the target for majority of anticancer and antibiotic drugs, study about the interaction of drug and DNA has a key role in pharmacology. Moreover, understanding the interactions of small molecules with DNA is of prime significance in the rational design of more powerful and selective anticancer agents. Two of the most important and promising targets in cancer chemotherapy include DNA alkylating agents and DNA intercalators. For these last the DNA recognition is a critical step in their anti-tumor action and the intercalation is not only one kind of the interactions in DNA recognition but also a pivotal step of several clinically used anti-tumor drugs such as anthracyclines, acridines and anthraquinones. To push clinical cancer therapy, the discovery of new DNA intercalators has been considered a practical approach and a number of intercalators have been recently reported. The intercalative binding properties of such molecules can also be harnessed as diagnostic probes for DNA structure in addition to DNA-directed therapeutics. Moreover, the problem of intercalation site formation in the undistorted B-DNA of different length and sequence is matter of tremendous importance in molecular modeling studies and, nowadays, three models of DNA intercalation targets have been proposed that account for the binding features of intercalators. Finally, despite DNA being an important target for several drugs, most of the docking programs are validated only for proteins and their ligands. Therefore, a default protocol to identify DNA binding modes which uses a modified canonical DNA as receptor is needed.

Synthesis, characterization, and anticancer activity of ruthenium(II)-β-carboline complex

Four [Ru(tpy)(N-N)(L)] type complexes: [Ru(tpy)(bpy)(Nh)](2+) (Ru1, tpy = 2,2';6',2″-terpyridine, bpy = 2'2-bipyridine, Nh = Norharman), [Ru(tpy)(phen)(Nh)](2+) (Ru2, phen = 1,10-phenanthroline), [Ru(tpy)(dpa)(Nh)](2+) (Ru3, dpa = 2,2'-dipyridylamine) and [Ru(tpy)(dip)(Nh)](2+) (Ru4, dip = 4,7-diphenyl-1,10-phenanthroline) were presented as anticancer drugs. In vitro cytotoxicity assays indicated that these complexes showed anticancer activity against various cancer cells. Flow cytometry and signaling pathways analysis demonstrated that these complexes induced apoptosis via the mitochondrial pathway, as evidenced by the loss of mitochondrial membrane potential and the release of cytochrome c. The resulting accumulation of p53 proteins from phosphorylation at serine-15 and serine-392 was correlated with an increase in p21 and caspase activation. Taken together, these findings suggested that Ru1-Ru4 may contribute to the future development of improved chemotherapeutics against human cancers.