In vitro and in vivo antitumour effects of novel, orally active bile acid-conjugated platinum complexes on rat hepatoma

Current Status of Novel Multifunctional Targeted Pt(IV) Compounds and Their Reductive Release Properties

Platinum-based drugs are widely used in chemotherapy for various types of cancer and are considered crucial. Tetravalent platinum (Pt(IV)) compounds have gained significant attention and have been extensively researched among these drugs. Traditionally, Pt(IV) compounds are reduced to divalent platinum (Pt(II)) after entering cells, causing DNA lesions and exhibiting their anti-tumor effect. However, the available evidence indicates that some Pt(IV) derivatives may differ from the traditional mechanism and exert their anti-tumor effect through their overall structure. This review primarily focuses on the existing literature regarding targeted Pt(II) and Pt(IV) compounds, with a specific emphasis on their in vivo mode of action and the properties of reduction release in multifunctional Pt(IV) compounds. This review provides a comprehensive summary of the design and synthesis strategies employed for Pt(II) derivatives that selectively target various enzymes (glucose receptor, folate, telomerase, etc.) or substances (mitochondria, oleic acid, etc.). Furthermore, it thoroughly examines and summarizes the rational design, anti-tumor mechanism of action, and reductive release capacity of novel multifunctional Pt(IV) compounds, such as those targeting p53-MDM2, COX-2, lipid metabolism, dual drugs, and drug delivery systems. Finally, this review aims to provide theoretical support for the rational design and development of new targeted Pt(IV) compounds.

Combined theoretical and experimental insights on DNA and BSA binding interactions of Cu(ii) and Ni(ii) complexes along with the DPPH method of antioxidant assay and cytotoxicity studies

This present study delineates the syntheses, detailed characterization and anti-proliferative potential against SiHa (cervical cancer cell) of two mononuclear complexes of Cu(ii) and Ni(ii) using a Schiff base ligand (L) derived from 2-hydroxybenzaldehyde and N-methyl-propane 1,3-diamine. The crystallographic results show the centro-symmetric space group of orthorhombic nature (Pccn) for Cu(ii) complex (1) where the central Cu(ii) has an inversion center symmetry with six co-ordinations resulting in a distorted octahedral geometry. Whereas, in complex (2), the two independent Ni(ii) atoms present in the special position within version symmetry and form a distorted geometry of octahedral nature with six coordinations. Absorption spectral titrations with Calf Thymus (CT) DNA and the extent of the decrease in relative emission intensities of DNA-bound ethidium bromide (EB) upon adding the complexes reveal the parallel trend in DNA binding affinities for both the complexes but with a small extent of binding capabilities. Bovine serum albumin (BSA) interaction studies demonstrate that complex 1 exhibits more promiscuous binding with BSA as compared to complex 2 from the spectroscopic and theoretical approaches. α,α-Diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging method shows a little antioxidant or free radical scavenging activity for both the studied complexes. Cytotoxicity studies against SiHa expressed that the percentage of cell viability was reduced with time whereas in the same concentration and conditions, the viability percentage was higher for 3T3-L1 (several normal cell lines of mouse). The fluorescence imaging obtained from acridine orange (AO) and ethidium bromide (EtBr) demonstrates that the colour of the cancer cells has changed gradually dictating the cell apoptosis from day 1 to day 3.

Transition Metal-Based Prodrugs for Anticancer Drug Delivery

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Transition metal complexes, of which the platinum(II) complex cisplatin is an example, have been used in medicine to treat cancer for more than 40 years. Although many successes have been achieved, there are problems associated with the use of these drugs, such as side effects and drug resistance. Converting them into prodrugs, to make them more inert, so that they can travel to the tumour site unchanged and release the drug in its active form only there, is a strategy which is the subject of much research nowadays. The new prodrugs may be activated and release the cytotoxic agent by differences in oxygen concentration or in pH, by the action of overexpressed enzymes, by differences in metabolic rates, etc., which characteristically distinguish cancer cells from normal ones, or even by the input of radiation, which can be visible light. Converting a metal complex into a prodrug may also be used to improve its pharmacological properties. In some cases, the metal complex is a carrier which transports the active drug as a ligand. Some platinum prodrugs have reached clinical trials. So far platinum, ruthenium and cobalt have been the most studied metals. This review presents the recent developments in this area, including the types of complexes used, the mechanisms of drug action and in some cases the techniques applied to monitor drug delivery to cells.

Synthesis of platinum(II) and palladium(II) complexes with 9,9-dihexyl-4,5-diazafluorene and their in vivo antitumour activity against Hep3B xenografted mice

Two complexes dichloro(9,9-dihexyl-4,5-diazafluorene)platinum(II) (Pt-DHF) and dichloro(9,9-dihexyl-4,5-diazafluorene)palladium(II) (Pd-DHF) were synthesized and their in vivo antitumour activity was investigated using an athymic nude mice model xenografted with human Hep3B carcinoma cells. Pt-DHF- and Pd-DHF-treated groups showed significant tumour growth inhibition (with about 9-fold and 3-fold tumour growth retardation) when compared with the vehicle control group. The liver toxicology effects on the animals of the two compounds were investigated. Pt-DHF and Pd-DHF-treated groups had a lower alanine transaminase and aspartate transaminase values than those of the vehicle treated group as the animals from the vehicle control group had very heavy hepatoma burden. We assume that both complexes could be further investigated as effective antitumour agents and it is worthwhile to study their underlying working mechanism.

The Next Generation of Platinum Drugs: Targeted Pt(II) Agents, Nanoparticle Delivery, and Pt(IV) Prodrugs

The platinum drugs, cisplatin, carboplatin, and oxaliplatin, prevail in the treatment of cancer, but new platinum agents have been very slow to enter the clinic. Recently, however, there has been a surge of activity, based on a great deal of mechanistic information, aimed at developing nonclassical platinum complexes that operate via mechanisms of action distinct from those of the approved drugs. The use of nanodelivery devices has also grown, and many different strategies have been explored to incorporate platinum warheads into nanomedicine constructs. In this Review, we discuss these efforts to create the next generation of platinum anticancer drugs. The introduction provides the reader with a brief overview of the use, development, and mechanism of action of the approved platinum drugs to provide the context in which more recent research has flourished. We then describe approaches that explore nonclassical platinum(II) complexes with trans geometry or with a monofunctional coordination mode, polynuclear platinum(II) compounds, platinum(IV) prodrugs, dual-threat agents, and photoactivatable platinum(IV) complexes. Nanoparticles designed to deliver platinum(IV) complexes will also be discussed, including carbon nanotubes, carbon nanoparticles, gold nanoparticles, quantum dots, upconversion nanoparticles, and polymeric micelles. Additional nanoformulations, including supramolecular self-assembled structures, proteins, peptides, metal-organic frameworks, and coordination polymers, will then be described. Finally, the significant clinical progress made by nanoparticle formulations of platinum(II) agents will be reviewed. We anticipate that such a synthesis of disparate research efforts will not only help to generate new drug development ideas and strategies, but also will reflect our optimism that the next generation of approved platinum cancer drugs is about to arrive.

Transition metal complexes with bioactive ligands: mechanisms for selective ligand release and applications for drug delivery

The unique properties of transition metal complexes, such as environment-responsive ligand exchange kinetics, diverse photochemical and photophysical properties, and the ability to form specific interactions with biomolecules, make them interesting platforms for selective drug delivery. This minireview will focus on recent examples of rationally designed complexes with bioactive ligands, exploring the different roles of the metal, and mechanisms of ligand release. Developments in the techniques used to study the mechanisms of action of metal-drug complexes will also be discussed, including X-ray protein crystallography, fluorescence lifetime imaging, and X-ray absorption spectroscopy.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

Inhibition of hepatitis C virus RNA translation by antisense bile acid conjugated phosphorothioate modified oligodeoxynucleotides (ODN)

BACKGROUND

The 5'-noncoding region (5'NCR) of the HCV-genome comprises an internal ribosome entry site essential for HCV-translation/replication. Phosphorothioate oligodeoxynucleotides (tS-ODN) complementary to this region can inhibit HCV-translation in vitro. In this study, bile acid conjugated tS-ODN were generated to increase cell-selective inhibition of 5'NCR-dependent HCV-translation.

METHODS

Different bile acid conjugated tS-ODN complementary to the HCV5'NCR were selected for their inhibitory potential in an in vitro transcription/translation assay. To analyze OATP (organic anion transporting polypeptides)-selective uptake of bile acid conjugated ODN, different hepatoma cells were stably transfected with the OATP1B1-transporter and primary human hepatocytes were used. An adenovirus encoding the HCV5'NCR fused to the luciferase gene (Ad-GFP-NCRluc) was generated to quantify 5'NCR-dependent HCV gene expression in OATP-overexpressing hepatoma cells and in vivo.

RESULTS

A 17mer phosphorothioate modified ODN (tS-ODN4_13) complementary to HCV5'NCR was able to inhibit 5'NCR-dependent HCV-translation in an in vitro transcription/translation test system by more than 90% and it was also effective in Huh7-cells containing the HCV subgenomic replicon. Conjugation to taurocholate (tS-ODN4_13T) significantly increased selective ODN uptake by primary human hepatocytes and by OATP1B1-expressing HepG2-cells compared to parental HepG2-cells. Correspondingly, tS-ODN4_13T significantly inhibited HCV gene expression in liver-derived OATP1B1-expressing HepG2- or CCL13-cells up to 70% compared to unconjugated tS-ODN and compared to mismatch taurocholate coupled tS-ODN. In vivo, tS-ODN4_13T showed also a trend to block 5'NCR-dependent HCV gene expression.

CONCLUSIONS

The tested taurocholate conjugated 17mer antisense ODN complementary to HCV5'NCV showed an increased and selective uptake by hepatocytes and liver-derived cells through OATP-mediated transport resulting in enhanced specific inhibition of HCV gene expression in vitro and in vivo. Thus, this novel approach may represent a promising strategy to improve antisense approaches with ODN in the control of hepatitis C infection.

Studies on the cytotoxic, apoptotic and antitumoral effects of Au(III) and Pt(II) complexes of 1, 10-phenanthroline on V79 379A and A549 cell lines

In the present study, Au(III) and Pt(II) complexes of 1, 10-phenanthroline (phen) were synthesized and used as the test compounds. The structure elucidation of the synthesized compounds was performed by IR, (1)H-NMR and MASS spectroscopic data and the results of elemental analyses. The cytotoxic and apoptotic effects of test compounds were elucidated on V79 379A (Chinese hamster lung fibroblast like) and A549 (human lung carcinoma epithelial like) cell lines. Cytotoxicity was measured with MTT assay and antitumoral effect was determined by colony forming ability methods. In addition, nuclear fragmentation and activation of apoptotic enzyme (caspase-3) and DAPI staining were used to detect the apoptotic effect of the compounds. All the test compounds induced time and concentration-dependent cytotoxic and antitumoral effects. Significant increases in the levels of apoptosis were observed with increasing exposure concentration.

Synthesis, characterization, plasmid cleavage and cytotoxicity of cancer cells by a copper(II) complex of anthracenyl-terpyridine

Metallo-organic compounds are interesting to study for their antitumor activity and related applications. This paper deals with the syntheses, characterization, structure determination of a copper complex of anthracenyl terpyridine (1) and its plasmid cleavage and cytotoxicity towards different cancer cell lines. The complex binds CT-DNA through partial intercalation mode. The plasmid cleavage studies carried out using pBR322 and pUC18 resulted in the formation of all the three forms of the plasmid DNA. Plasmid cleavage studies carried out with a non-redoxable Zn(2+) complex (2) supported the role of the redox activity of copper in 1. The complex 1 showed remarkable antiproliferative activity against cancer cell lines, viz., cervical (HeLa, SiHa, CaSki), breast (MCF-7), liver (HepG2) and lung (H1299). A considerable lowering was observed in the IC(50) values of HPV-infected (viz., HeLa, SiHa, CaSki) vs. non-HPV-infected cell lines (MCF-7, HepG2, H1299). Antiproliferative activity of 1 was found to be much higher than the carboplatin when treated with the same cell lines. Incubation of the cells with 1 results in granular structures only with the HPV-infected cells and not with others as studied by phase contrast and fluorescence microscopy. The lower IC(50) value observed in case of 1 with HPV-infected cell lines may be correlated with the involvement of HPV oncoprotein. The role of HPV has been further augmented by transfecting the MCF-7 cells (originally not possessing HPV copy) with e6 oncoprotein cDNA. To our knowledge this is the first copper complex that causes cell death by interacting with HPV oncoprotein followed by exhibition of remarkable antiproliferative activity.