Cytotoxic activities, cellular uptake, gene regulation, and optical imaging of novel platinum(II) complexes

Current Development of Metal Complexes with Diamine Ligands as Potential Anticancer Agents

Background::

The discovery of cisplatin and the subsequent research revealed the importance of dinitrogen-containing moiety for the anticancer action of metal complexes. Moreover, certain diamine ligands alone display cytotoxicity that contributes to the overall activity of corresponding complexes.

Objective::

To summarize the current knowledge on the anticancer efficacy, selectivity, and the mechanisms of action of metal complexes with various types of diamine ligands.

Method::

The contribution of aliphatic acyclic, aliphatic cyclic, and aromatic diamine ligands to the anticancer activity and selectivity/toxicity of metal complexes with different metal ions were analyzed by comparison with organic ligand alone and/or conventional platinum-based chemotherapeutics.

Results::

The aliphatic acyclic diamine ligands are present mostly in complexes with platinum. Aliphatic cyclic diamines are part of Pt(II), Ru(II) and Au(III) complexes, while aromatic diamine ligands are found in Pt(II), Ru(II), Pd(II) and Ir(III) complexes. The type and oxidation state of metal ions greatly influences the cytotoxicity of metal complexes with aliphatic acyclic diamine ligands. Lipophilicity of organic ligands, dependent on alkyl-side chain length and structure, determines their cellular uptake, with edda and eddp/eddip ligands being most useful in this regard. Aliphatic cyclic diamine ligands improved the activity/toxicity ratio of oxaliplatin-type complexes. The complexes with aromatic diamine ligands remain unexplored regarding their anticancer mechanism. The investigated complexes mainly caused apoptotic or necrotic cell death.

Conclusion::

Metal complexes with diamine ligands are promising candidates for efficient and more selective alternatives to conventional platinum-based chemotherapeutics. Further research is required to reveal the chemico-physical properties and molecular mechanisms underlying their biological activity.

Fluorescent antitumor titanium(iv) salen complexes for cell imaging

First live cell imaging using florescent salen Ti(iv) complexes, which are cytotoxic and inactive, both entering the cell but with different subcellular accumulations.

Research progress in modern structure of platinum complexes

Since the antitumor activity of cisplatin was discovered in 1967 by Rosenberg, platinum-based anticancer drugs have played an important role in chemotherapy in clinic. Nevertheless, platinum anticancer drugs also have caused severe side effects and cross drug resistance which limited their applications. Therefore, a significant amount of efforts have been devoted to developing new platinum-based anticancer agents with equal or higher antitumor activity but lower toxicity. Until now, a large number of platinum-based complexes have been prepared and extensively investigated in vitro and in vivo. Among them, some platinum-based complexes revealing excellent anticancer activity showed the potential to be developed as novel type of anticancer agents. In this account, we present such platinum-based anticancer complexes which owning various types of ligands, such as, amine carrier ligands, leaving groups, reactive molecule, steric hindrance groups, non-covalently binding platinum (II) complexes, Platinum(IV) complexes and polynuclear platinum complexes. Overall, platinum-based anticancer complexes reported recently years upon modern structure are emphasized.

Antitumoral activity of 1,2-diaminocyclohexane derivatives in breast, colon and skin human cancer cells

Aim: Cancer is among the leading causes of death worldwide. Medical interest has focused on macrocyclic polyamines because of their properties as antitumor agents. Results/Methodology: We have designed and synthesized a series of 1,2-diaminocyclohexane derivatives with notable in vitro antiproliferative activities against the MCF-7, HCT-116 and A375 cancer cell lines. Cell cycle and apoptosis analyses were also carried out. Our results show that all the compounds are potent cytotoxic agents, especially against the A375 cell line. Conclusion: The selective activity of the macrocyclic derivative against A375, via apoptosis, supposes a great advantage for future therapeutic use. This exemplifies the potential of 1,2-diaminocyclohexane derivatives to qualify as lead structures for future anticancer drug development due to their easy syntheses and noteworthy bioactivity.

Cytotoxicity profile of novel sterically hindered platinum(II) complexes with (1R,2R)-N(1),N(2)-dibutyl-1,2-diaminocyclohexane

Four Pt(II) complexes of (1R,2R)-N(1),N(2)-dibutyl-1,2-diaminocyclohexane with two alkyl branches as steric hindrance have been designed and synthesized. In vitro cytotoxicity of these compounds indicated complex 4 is a cytotoxic agent more potent than its parent molecule, oxaliplatin, against almost all the tested cell lines. Agarose gel electrophoresis study showed that the kinetic reactivity of complex 4 with DNA is slow down due to the sterically hindered effect, demonstrating that it may possess a different mechanism of action from cisplatin. Flow cytometry results revealed that complex 4 induced apoptosis of tumor cells by blocking the cell-cycle progression in the G2/M phase. Western blot analysis showed it had a similar apoptotic mechanism to cisplatin which could induce apoptosis via a mitochondrial-dependent pathway.

NanoSIMS combined with fluorescence microscopy as a tool for subcellular imaging of isotopically labeled platinum-based anticancer drugs

Multi-elemental, isotope selective nano-scale secondary ion mass spectrometry (NanoSIMS) combined with confocal laser-scanning microscopy was used to characterize the subcellular distribution of 15N-labeled cisplatin in human colon cancer cells. These analyses indicated predominant cisplatin colocalisation with sulfur-rich structures in both the nucleus and cytoplasm. Furthermore, colocalisation of platinum with phosphorus-rich chromatin regions was observed, which is consistent with its binding affinity to DNA as the generally accepted crucial target of the drug. Application of 15N-labeled cisplatin and subsequent measurement of the nitrogen isotopic composition and determination of the relative intensities of platinum and nitrogen associated secondary ion signals in different cellular compartments with NanoSIMS suggested partial dissociation of Pt-N bonds during the accumulation process, in particular within nucleoli at elevated cisplatin concentrations. This finding raises the question as to whether the observed intracellular dissociation of the drug has implications for the mechanism of action of cisplatin. Within the cytoplasm, platinum mainly accumulated in acidic organelles, as demonstrated by a direct combination of specific fluorescent staining, confocal laser scanning microscopy and NanoSIMS. Different processing of platinum drugs in acidic organelles might be relevant for their detoxification, as well as for their mode of action.

NanoSIMS multi-element imaging reveals internalisation and nucleolar targeting for a highly-charged polynuclear platinum compound

Simultaneous multi-element imaging using NanoSIMS (nano-scale secondary ion mass spectrometry), exploiting the novel combination of (195)Pt and (15)N in platinum-am(m)ine antitumour drugs, provides information on the internalisation and subcellular localisation of both metal and ligands, and allows identification of ligand exchange.

Combination therapy with carboplatin and thalidomide suppresses tumor growth and metastasis in 4T1 murine breast cancer model

Carboplatin, efficient cytostatics for cancer therapy, could induce apoptosis and inhibit the growth of vascular endothelium in several tumor cell lines and xenograft models. It has been suggested that the antitumor effect of chemotherapy could be increased by combining it with an antiangiogenesis agent in anticancer strategy. The present study explored the potential to increase the antitumor effect of carboplatin by combining it with thalidomide in mouse 4T1 breast cancer models, and the underlining mechanism was investigated. The systemic administration of carboplatin and thalidomide significantly decreased tumor growth through increased tumor cell apoptosis compared with either control group. Collectively, these findings suggest that combined treatment has shown synergistic suppression in tumor progression according to the analysis. Furthermore, also was observed reduction in number of lung metastases as compared to isolated treatments and increased survival of the animals. The present study may be important in future exploration of the potential application of the combined approach in the treatment of breast cancer.

Controlled release of cisplatin from pH-thermal dual responsive nanogels

In this study, a pH-thermal dual responsive nanogel was applied for cisplatin (CDDP) delivery. CDDP was loaded into the nanogels via conjugation with the carboxyl groups in the nanogels. The conjugation was confirmed by FTIR and XPS. The bonding between CDDP and COOH can be broken by the H(+) or Cl(-). We found that the CDDP released much faster at more acidic environment. The Cl(-) concentration in the human body is about 95-105 mm. The conjugated bond could be easily attacked by Cl(-) while the nanosystem is injected into the body. In order to diminish the Cl(-) triggering release of CDDP from the nanogels, we introduced a thermal-responsive units-NIPAm into the nanogel structure. After NIPAm introduced, the CDDP released much slower from the nanogels at 37 °C in pH = 7.38 buffer in the present of Cl(-) (150 mm) than that without NIPAm. And the CDDP also released slower from the nanogels at 37 °C than at 25 °C. By in vitro release behavior studying, we found that CDDP release from the NIPAm containing nanogels can be accelerated by H(+) attacking and reduced by temperature arising. By cellular uptake observation, we found that the nanogels were mainly localized in the cytoplasm of the cancer cells. The CDDP-loaded nanogels exhibited longer circulation time in vivo while compared to free CDDP. And it has better anti-cancer performance than free CDDP in vivo therapy of breast cancer in mice model. Furthermore, some side effects of CDDP, such as renal toxicity, phlebitis, bone marrow suppression etc. have also been reduced by nanogels loading. The in vitro and in vivo results demonstrated that the dual responsible nanogel is a suitable CDDP delivery candidate.

Carboplatin delays mammary cancer 4T1 growth in mice

Carboplatin is commonly used to treat a variety of tumors. We investigated the effects of carboplatin (100mg/kg) in the development and metastatic dissemination of the 4T1 mice mammary carcinoma. Carboplatin was able to reduce tumor volume and the number of lung metastases in 50% compared to the control animals. Mitotic and apoptotic indices were also decreased by the treatment. Assessment of the vascularization of the tumors revealed a significant decrease in blood vessel formation by carboplatin. A decrease in nuclear positivity of CDC47 and cyclin D1 was observed in the group treated with carboplatin when compared to the control group. Positivity for p53 was observed in the control group (2/28; 5%) and the treated group (5/71; 4%). Carboplatin has been demonstrated to be an efficient regulator of 4T1MMT growth and dissemination. The action of this chemotherapeutic agent seems to be related to the induction of apoptosis and inhibition of angiogenesis and cell proliferation.

Cell death-inducing effect of novel palladium(II) and platinum(II) complexes on non-small cell lung cancer cells in vitro

PURPOSE

Treatment for lung cancer is still far from satisfying rates. Therefore, there is a need for novel anticancer agents. For this purpose, novel platinum and palladium complexes {[Pd(sac)(terpy)](sac)·4H(2)O (Complex 1), [Pt(sac)(terpy)](sac)·5H(2)O (Complex 2), [PdCl(terpy)](sac)·2H(2)O (Complex 3), [PtCl(terpy)](sac)·2H(2)O (Complex 4)} have been tested against three different non-small cell lung cancer cell lines (A549, H1299, PC-3).

METHODS

Growth-inhibiting effects have been tested by the MTT and ATP viability assays. Apoptosis has been detected by the caspase-cleaved cytokeratin 18 (M30-antigen) assay. Necrosis has been detected by staining the cells with fluorescent dyes. Mitotic index has been calculated by counting the mitotic figures after staining with hematoxylin.

RESULTS

The complex 3 exhibited significant anti-growth effects, and its anti-growth effect was more powerful than that of cisplatin that is a standard chemotherapeutic agent for this type of cancer. The complexes did not induce apoptosis, while necrosis clearly took place.

CONCLUSIONS

Novel Pd(II) complex ([PdCl(terpy)](sac)·2H(2)O) seems to represent a potentially active drug against non-small cell lung cancer cell lines, and further studies in vivo are warranted.

Uptake and Distribution of a Platinum(II)-Carborane Complex Within a Tumour Cell Using Synchrotron XRF Imaging

Treatment of A549 human lung carcinoma cells with a DNA metallointercalator complex containing a PtII-terpy (terpy = 2,2′:6′,2′′-terpyridine) unit linked to a functionalized closo-carborane cage results in the uptake of the complex within the cells, as determined by synchrotron X-ray fluorescence (XRF) imaging. Although a significant cellular uptake of Pt existed, there was no significant accumulation of the element within the cell nuclei. Other statistically significant changes from the XRF data included an increase in Cl, K, and Cu and a decrease in Fe within the treated cells.

Recent Advances in Mapping the Sub-cellular Distribution of Metal-Based Anticancer Drugs

There are increasing reports of novel metal-based chemotherapeutics that have either improved cancer cell selectivity, or alternative mechanisms of action, to existing anticancer drugs, and techniques are required for determining their sub-cellular molecular targets. Imaging methods offer many distinct advantages over destructive fractionation techniques, including the preservation of useful morphological information; however, mapping the intracellular distribution of metal ions inside tumour cells still remains challenging. Recent advances in three modes of imaging are discussed in this review, with a particular focus on the application to metal-based cancer chemotherapy – fluorescence microscopy, electron microscopy (including energy-filtered transmission electron microscopy (EFTEM)), and a new technique, Nano-scale secondary ion mass spectrometry (NanoSIMS).