Construction of Dual Stimuli-Responsive Platinum(IV) Hybrids with NQO1 Targeting Ability and Overcoming Cisplatin Resistance

Novel Pt(IV) complexes containing salvigenin ligand reverse cisplatin-induced resistance by inhibiting Rap1b-mediated cancer cell stemness in esophageal squamous cell carcinoma treatments

Esophageal squamous cell carcinoma (ESCC) is a malignant tumor that is highly susceptible to metastasis, recurrence and resistance, and few therapeutic targets have been identified and proven effective. Herein, we demonstrated for the first time that Rap1b can positively regulate ESCC cell stemness, as well as designed and synthesized a novel class of Pt(IV) complexes that can effectively inhibit Raplb. In vitro biological studies showed that complex-1 exhibited stronger cytotoxicity than cisplatin and oxaliplatin against a variety of ESCC cells, and effectively reversed cisplatin-induced resistance of TE6 cells by increasing cellular accumulation of platinum and inhibiting cancer cell stemness. Significantly, complex-1 also exhibited strong ability to reversal cisplatin-induced cancer cell resistance and inhibit tumor growth in TE6/cDDP xenograft mice models, with a tumor growth inhibition rate of 73.3 % at 13 mg/kg and did not show significant systemic toxicity. Overall, Rap1b is a promising target to be developed as an effective treatment for ESCC. Complex-1, as the first Pt(IV) complex that can strongly inhibit Rap1b, is also worthy of further in-depth study.

Synthesis and anticancer mechanisms of four novel platinum(II) 4'-substituted-2,2':6',2''-terpyridine complexes

Mitophagy, a selective autophagic process, has emerged as a pathway involved in degrading dysfunctional mitochondria. Herein, new platinum(II)-based chemotherapeutics with mitophagy-targeting properties are proposed. Four novel binuclear anticancer Pt(II) complexes with 4'-substituted-2,2':6',2''-terpyridine derivatives (tpy1-tpy4), i.e., [Pt2(tpy1)(DMSO)2Cl4]·CH3OH (tpy1Pt), [Pt(tpy2)Cl][Pt(DMSO)Cl3]·CH3COCH3 (tpy2Pt), [Pt(tpy3)Cl][Pt(DMSO)Cl3] (tpy3Pt), and [Pt(tpy4)Cl]Cl·CH3OH (tpy4Pt), were designed and prepared. Moreover, their potential antitumor mechanism was studied. Tpy1Pt-tpy4Pt exhibited more selective cytotoxicity against cisplatin-resistant SK-OV-3/DDP (SKO3cisR) cancer cells compared with those against ovarian SK-OV-3 (SKO3) cancer cells and normal HL-7702 liver (H702) cells. This selective cytotoxicity of Tpy1Pt-tpy4Pt was better than that of its ligands (i.e., tpy1-tpy4), the clinical drug cisplatin, and cis-Pt(DMSO)2Cl2. The results of various experiments indicated that tpy1Pt and tpy2Pt kill SKO3cisR cancer cells via a mitophagy pathway, which involves the disruption of the mitophagy-related protein expression, dissipation of the mitochondrial membrane potential, elevation of the [Ca2+] and reactive oxygen species levels, promotion of mitochondrial DNA damage, and reduction in the adenosine triphosphate and mitochondrial respiratory chain levels. Furthermore, in vivo experiments indicated that the dinuclear anticancer Pt(II) coordination compound (tpy1Pt) has remarkable therapeutic efficiency (ca. 52.4%) and almost no toxicity. Therefore, the new 4'-substituted-2,2':6',2''-terpyridine Pt(II) coordination compound (tpy1Pt) is a potential candidate for next-generation mitophagy-targeting dinuclear Pt(II)-based anticancer drugs.

Novel design of dual-action Pt(IV) anticancer pro-drugs based on cisplatin and derivatives of the tyrosine kinase inhibitors imatinib and nilotinib

Tyrosine kinases (TKs) are emerging as important targets in cancer therapy and some of their inhibitors, TKIs (e.g. imatinib and nilotinib), are FDA-approved drugs that are used as selective anti-cancer therapeutics against cell lines that overexpress TKs. Many examples of metal-based complexes functionalised with TKIs are reported in the literature but very few have been functionalised with platinum. Here we report the design, a detailed computational analysis/simulation, the complete chemical characterisation and the preliminary biological evaluation of two novel Pt(IV) anticancer pro-drugs based on cisplatin tethered with a derivative of either imatinib or nilotinib in the axial position. Pt(IV) complexes are a strategic scaffold in combination therapy due to their axial ligands that can be functionalised to form dual action drugs. The activation by reduction releases the Pt(II) core and the axial ligands upon cellular internalisation. The antiproliferative activity and the TK inhibition properties of the novel adducts are analysed with a theoretical approach and confirmed in vitro with preliminary biological assays.

Advances of antitumor drug discovery in traditional Chinese medicine and natural active products by using multi-active components combination

The antitumor efficacy of Chinese herbal medicines has been widely recognized. Leading compounds such as sterols, glycosides, flavonoids, alkaloids, terpenoids, phenylpropanoids, and polyketides constitute their complex active components. The antitumor monomers derived from Chinese medicine possess an attractive anticancer activity. However, their use was limited by low bioavailability, significant toxicity, and side effects, hindering their clinical applications. Recently, new chemical entities have been designed and synthesized by combining natural drugs with other small drug molecules or active moieties to improve the antitumor activity and selectivity, and reduce side effects. Such a novel conjugated drug that can interact with several vital biological targets in cells may have a more significant or synergistic anticancer activity than a single-molecule drug. In addition, antitumor conjugates could be obtained by combining pharmacophores containing two or more known drugs or leading compounds. Based on these studies, the new drug research and development could be greatly shortened. This study reviews the research progress of conjugates with antitumor activity based on Chinese herbal medicine. It is expected to serve as a valuable reference to antitumor drug research and clinical application of traditional Chinese medicine.

Supramolecular fluorescent probe based on acyclic cucurbituril for detection of cancer Labels in human urine

Spermine (Spm) and spermidine (Spmd) are considered as potential biomarker for early diagnosis of human cancer. Herein, a novel acyclic cucurbituril derivative (UL-ACB) was firstly designed and synthesized, which fluoresces at 460 nm after excitation at 365 nm. UL-ACB is rich in oxygen atoms which are capable of forming coordinate bonds with copper (Cu²⁺) that cause quenching of UL-ACB fluorescence. Moreover, the addition of biological endogenous substances Spm and Spmd can turn on fluorescence of UL-ACB. Interestingly, the probe showed a remarkable detection efficiency for Spm and Spmd in human urine (the detection limits of Spm and Spmd were 0.156 μM and 0.762 μM, and the linear ranges are 0.156 ∼ 43.06 μM and 0.762 ∼ 29.10 μM), which completely covered the early diagnosis of urinary Spm (1 ∼ 10 μM) and urine Spmd (1 ∼ 20 μM) required concentration range in cancer patients. The probe for Spm and Spmd is simple, time-saving and selective, which may provide a new promising strategy for early cancer diagnosis.

(8-Hydroxyquinoline) Gallium(III) Complex with High Antineoplastic Efficacy for Treating Colon Cancer via Multiple Mechanisms

A series of (8-hydroxyquinoline) gallium(III) complexes (CP-1-4) was synthesized and characterized by single X-ray crystallography and density functional theory (DFT) calculation. The cytotoxicity of the four gallium complexes toward a human nonsmall cell lung cancer cell line (A549), human colon cancer cell line (HCT116), and human normal hepatocyte cell line (LO2) was evaluated using MTT assays. CP-4 exhibited excellent cytotoxicity against HCT116 cancer cells (IC₅₀ = 1.2 ± 0.3 μM) and lower toxicity than cisplatin and oxaliplatin. We also evaluated the anticancer mechanism studies in cell uptake, reactive oxygen species analysis, cell cycle, wound-healing, and Western blotting assays. The results showed that CP-4 affected the expression of DNA-related proteins, which led to the apoptosis of cancer cells. Moreover, molecular docking tests of CP-4 were performed to predict other binding sites and to confirm its higher binding force to disulfide isomerase (PDI) proteins. The emissive properties of CP-4 suggest that this complex can be used for colon cancer diagnosis and treatment, as well as in vivo imaging. These results also provide a foundation for the development of gallium complexes as potent anticancer agents.

Novel glycosylation zinc(II)-cryptolepine complexes perturb mitophagy pathways and trigger cancer cell apoptosis and autophagy in SK-OV-3/DDP cells

With the aim of shedding some light on the mechanism of action of zinc(II) complexes in antiproliferative processes and molecular signaling pathways, three novel glycosylated zinc(II)-cryptolepine complexes, i.e., [Zn(QA1)Cl₂] (Zn(QA1)), [Zn(QA2)Cl₂] (Zn(QA2)), and [Zn(QA3)Cl₂] (Zn(QA3)), were prepared by conjugating a glucose moiety with cryptolepine, followed by complexation of the resulting glycosylated cryptolepine compounds N-((1-(2-morpholinoethyl)-1H-1,2,3-triazol-4-yl)methyl)-benzofuro[3,2-b]quinolin-11-amine (QA1), 2-(4-((benzofuro[3,2-b]quinolin-11-ylamino)methyl)-1H-1,2,3-triazol-1-yl)ethan-1-ol (QA2), and (2S,3S,4R,5R,6S)-2-(4-((benzofuro[3,2-b]quinolin-11-ylamino)-methyl)-1H-1,2,3-triazol-1-yl)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol (QA3) with zinc(II), and their anticancer activity was evaluated. In MTT assays, Zn(QA1)-Zn(QA3) were more active against cisplatin-resistant ovarian SK-OV-3/DDP cancer cells (SK-OV-3cis) than ZnCl₂ and the QA1-QA3 ligands, with IC₅₀ values of 1.81 ± 0.50, 2.92 ± 0.32, and 1.01 ± 0.11 μM, respectively. Complexation of glycosylated cryptolepine QA3 with zinc(II) increased the antiproliferative activity of the ligand, suggesting that Zn(QA3) could act as a chaperone to deliver the active ligand intracellularly, in contrast with other cryptolepine metal complexes previously reported. In vivo and in vitro investigations suggested that Zn(QA3) exhibited enhanced anticancer activity with treatment effects comparable to those of the clinical drug cisplatin. Furthermore, Zn(QA1)-Zn(QA3) triggered SK-OV-3cis cell apoptosis through mitophagy pathways in the order Zn(QA1) > Zn(QA1) > Zn(QA2). These results demonstrate the potential of glycosylated zinc(II)-cryptolepine complexes for the development of chemotherapy drugs against cisplatin-resistant SK-OV-3cis cells.

The strong in vitro and vivo cytotoxicity of three new cobalt(II) complexes with 8-methoxyquinoline

Three new cobalt(II) complexes, [Co(MQL)₂Cl₂] (CoCl), [Co(MQL)₂Br₂] (CoBr), and [Co(MQL)₂I₂] (CoI), bearing 8-methoxyquinoline (MQL) have been designed for the first time. MTT assays showed that CoCl, CoBr, and CoI exhibit much better antiproliferative activities than cisplatin toward cisplatin-resistant SK-OV-3/DDP and SK-OV-3 ovarian cancer cells, with IC₅₀ values of as low as 0.32-5.49 μM. Further, CoCl and CoI can regulate autophagy-related proteins in SK-OV-3/DDP cells and, therefore, they can induce primarily autophagy-mediated cell apoptosis in the following order: CoCl > CoI. The different antiproliferative activities of the MQL complexes CoCl, CoBr, and CoI could be correlated with the lengths of their Co-X bonds, which adopted the following order: CoI > CoBr > CoCl. The 8-HOMQ complexes CoCl (ca. 60.1%) and CoI (ca. 48.8%) also showed potent in vivo anticancer effects after 15 days of treatment. In summary, the MQL ligand highly enhances the antiproliferative activities of cobalt(II) complexes in comparison to other previously reported 8-hydroxyquinoline metal complexes.

Complexes of Zn(II) with a mixed tryptanthrin derivative and curcumin chelating ligands as new promising anticancer agents

In this study, two novel curcumin (H-Cur)-tryptanthrin metal compounds-[Zn(TA)Cl₂], i.e., Zn(TA), and [Zn(TA)(Cur)]Cl, i.e., Zn(TAC)-were synthesized and investigated using 5-(bis-pyridin-2-ylmethyl-amino)-pentanoic acid (6,12-dioxo-6,12-dihydro-indolo[2,1-b]quinazolin-8-yl)-amide (TA) and H-Cur as the targeting and high-activity anticancer chemotherapeutic moieties, respectively. They were then compared with the di-(2-picolyl)amine (PA) Zn(II) complex [Zn(PA)Cl₂], i.e., Zn(PA). When compared with Zn(PA) and cisplatin, the IC₅₀ values of Zn(TA) and Zn(TAC) indicated that the compounds had high cytotoxicity against A549/DDP cancer cells, implying that the H-Cur-tryptanthrin Zn(II) compounds have the potential for use as anticancer drugs. We propose the use of synthesized theragnostic H-Cur-tryptanthrin Zn(II) complexes with nuclear-targeting and DNA-damaging capabilities as a simple therapeutic strategy against tumors. The Zn(TA) and Zn(TAC) complexes could be traced via red fluorescence and were found to accumulate in the cell nuclei and induce DNA damage, cell cycle arrest, mitochondrial dysfunction, and cell apoptosis both in vitro and in vivo. In addition, Zn(TAC) exhibited a higher antiproliferative effect on A549/DDP than Zn(TA) and Zn(PA), which was undoubtedly associated with the key roles of the novel tryptanthrin derivative TA and H-Cur in the Zn(TAC) complex.

Research advances in NQO1-responsive prodrugs and nanocarriers for cancer treatment

NAD(P)H: quinine oxidoreductase (NQO1) is a class of flavoprotein enzymes commonly expressed in eukaryotic cells. It actively participates in the metabolism of various quinones and their in vivo bioactivation through electron reduction reactions. The expression level of NQO1 is highly upregulated in many solid tumor cells compared with that in normal cells. NQO1 has been considered a candidate molecular target because of its overexpression and bioactivity in different tumors. NQO1-responsive prodrugs and nanocarriers have recently been identified as effective objectives for achieving controlled drug release, reducing adverse reactions and improving clinical efficacy. This review systematically introduces the research advances in applying NQO1-responsive prodrugs and nanocarriers to cancer treatment. It also discusses the existing problems and the developmental prospects of these two antitumor drug delivery systems.

A new class of nickel(II) oxyquinoline-bipyridine complexes as potent anticancer agents induces apoptosis and autophagy in A549/DDP tumor cells through mitophagy pathways

A new class of nickel(II) oxyquinoline-bipyridine complexes, namely, [Ni(La1)2(Lb6)] (Ni1), [Ni(La1)2(Lb2)] CH3OH (Ni2), [Ni(La7)2(Lb11)]2H2O (Ni3), [Ni(La1)2(Lb9)] (Ni4), [Ni(La1)2(Lb8)] (Ni5), [Ni(La2)2(Lb1)] (Ni6), [Ni(La2)2(Lb6)]CH3OH (Ni7), [Ni(La2)2(Lb11)]CH3OH (Ni8), [Ni(La2)2(Lb3)] (Ni9), [Ni(La2)2(Lb2)]CH3OH (Ni10), [Ni(La2)2(Lb5)]CH3OH...

19F NMR Allows to Investigate the Fate of Platinum(IV) Prodrugs in Physiological Conditions

Pt(IV) prodrugs can overcome resistance and side effects of conventional Pt(II) anticancer therapies. By 19 F-labeling of a Pt(IV) prodrug (Pt-FBA, FBA = p -fluorobenzoate), the activation under physiological conditions could be investigated. It is found that, unlike single-electron reductants, multi-electron agents can efficiently promote the two electrons reduction of Pt(IV) to Pt(II). Moreover, the activation of Pt-FBA in cell lysate is highly dependent upon the type of cancer cells. When administered to E. coli , Pt-FBA is reduced intracellularly and free FBA can shuttle out of the cell. Interestingly, the reduction rate greatly increases by inducing metallothionein overexpression and is lowered by addition of Zn(II) ions. Finally, when injected into mice, Pt-FBA undergoes fast reduction in the bloodstream accompanied by metabolic degradation of FBA; nevertheless, unreduced Pt-FBA can accumulate to detectable levels in liver and kidneys. The proposed 19 F-NMR approach has the advantage of avoiding the interference of all background signals.

Synthesis and biological evaluation of mixed-ligand cyclometalated iridium(III)-quinoline complexes

With the aim of gaining new insight into the underlying apoptosis mechanisms and in vivo efficacy of cyclometalated Ir(III) complexes as metalodrugs, six new cyclometalated Ir(III)-quinoline complexes, [Ir(1a)(2pq)2] (2a), [Ir(1b)(2pq)2] (2b), [Ir(1c)(2pq)2] (2c), [Ir(1d)(2pq)2] (2d), [Ir(1e)(2pq)2] (2e), and [Ir(1f)(2pq)2] (2f) (2pq = 2-phenylisoquinoline), have been synthesized using 5,7-dihalo-8-hydroxylquinoline ligands (1a-1f) and [Ir(2pq)2Cl]2 precursors and characterized. Complexes 2a-2f have shown potent anticancer activity against cisplatin-resistant SK-OV-3/DDP and A549/DDP cells (IC50 = 0.11-1.83 μM), following the order 2e > 2f > 2b > 2c > 2d > 2a. Confocal microscopy images suggest that 2e and 2b could act as red-color probes for specific cell imaging and efficiently initiate apoptosis and autophagy in the mitochondria, cell cytosol, and nucleus. Overexpression of beclin1, caspase-9, cytochrome c, LC3II, and apaf-1; inhibition of p62, cyclin D1, cyclin A2, and CDK2; and a substantial rapid accumulation suggest a paraptotic mode of cell death induced by autophagy, DNA damage, and mitochondrial stress. In addition, the inhibitory rate of 2e on A549/DDP tumor growth was 64.1% at a concentration of 10.0 mg kg-1, which is clearly higher than that of cisplatin. According to the biological assay, the cyclometalated Ir(III)-quinoline complex 2e exhibited a higher anticancer effect than 2b, which may be associated with the electronic effect of the methyl group of the 1e ligand of 2e playing a key role in the mechanism.

Recent Progresses in Conjugation with Bioactive Ligands to Improve the Anticancer Activity of Platinum Compounds

Platinum (Pt) drugs, including cisplatin, are widely used for the treatment of solid tumors. Despite the clinical success, side effects and occurrence of resistance represent major limitations to the use of clinically available Pt drugs. To overcome these problems, a variety of derivatives have been designed and synthetized. Here, we summarize the recent progress in the development of Pt(II) and Pt(IV) complexes with bioactive ligands. The development of Pt(II) and Pt(IV) complexes with targeting molecules, clinically available agents, and other bioactive molecules is an active field of research. Even if none of the reported Pt derivatives has been yet approved for clinical use, many of these compounds exhibit promising anticancer activities with an improved pharmacological profile. Thus, planning hybrid compounds can be considered as a promising approach to improve the available Pt-based anticancer agents and to obtain new molecular tools to deepen the knowledge of cancer progression and drug resistance mechanisms.

Dual-target platinum(IV) complexes exhibit antiproliferative activity through DNA damage and induce ER-stress-mediated apoptosis in A549 cells

Platinum(II)-based chemotherapeutics are commonly used to treat various types of solid tumors, such as lung cancers. However, these compounds can cause serious side effects, including nephrotoxicity and ototoxicity, which affect the quality of life of patients. In our work, four novel dual target platinum(IV) complexes were designed and synthesized. In vitro results indicated that the title platinum(IV) complexes exhibited effective antitumor activities against the tested cancer cells and had lower toxicity and resistance factors than oxaliplatin and cisplatin. Further mechanistic experiments demonstrated that complex 11 accumulated in mitochondria and induced an elevation in ROS and an ER stress response via mitochondrial dysfunction. Notably, complex 11 significantly modulated the expression levels of proapoptosis proteins including cleaved-Caspase-3, Bax, and p53, and decreased the level of the prosurvival protein Bcl-2. Together, these results suggested that complex 11 might be a potential lead compound for future cancer therapy due to its potency and selectivity.

On the hydrolytic stability of unsymmetric platinum(iv) anticancer prodrugs containing axial halogens

The hydrolytic stability of Pt(iv) complexes is determined by all the six ligands that coordinate to the Pt(iv) center. By appropriately choosing all the ligands during the design of Pt(iv) prodrugs, the stability of Pt(iv) prodrugs can be improved.

Cyanide Bridged Platinum-Iron Complexes as Cisplatin Prodrug Systems: Design and Computational Study

The potential role of cyanide-bridged platinum-iron complexes as an anti-cancer Pt(IV) prodrug is studied. We present design principles of a dual-function prodrug that can upon reduction dissociate and release concurrently six cisplatin units and a ferricyanide anion per prodrug unit. The prodrug molecule is a unique complex of hepta metal centers consisting of a ferricyanide core with six Pt(IV) centers each bonded to the Fe(III) core through a cyano ligand. The functionality of the prodrug is addressed through density functional theory (DFT) calculations.

Platinum(IV) complexes conjugated with chalcone analogs as dual targeting anticancer agents: In vitro and in vivo studies

For the sake to develop novel platinum(IV) complexes to reverse cisplatin (CDDP) resistence, four multifunctional platinum(IV) prodrugs via conjugating chalcones with the related platinum(IV) complexes derived from cisplatin were designed and evaluated for anti-tumor actyivities in vitro and in vivo. Among them, complex 9 exhibited excellent anticancer activities in vitro with IC₅₀ values at the submicromolar level against the tested human cancer cells, whereas showed low cytotoxicity towards human normal liver cells HL-7702. Further mechanistic studies indicated that complex 9 induced G2/M phase arrest and apoptosis in A549 cells, which was associated with a collapse of the mitochondrial membrane potential (MMP), alterations in the expression of some apoptosis-related proteins, and enhanced level of the intracellular reactive oxygen species (ROS). More importantly, complex 9 significantly suppressed the tumor growth in the A549 xenograft model without obvious hints of toxicity.

Imaging and therapeutic applications of Zn(ii)-cryptolepine-curcumin molecular probes in cell apoptosis detection and photodynamic therapy

Novel red Zn(ii) complex-based fluorescent probes featuring cryptolepine-curcumin derivatives, namely, [Zn(BQ)Cl₂] (BQ-Zn) and [Zn(BQ)(Cur)]Cl (BQCur-Zn), were developed for the simple and fluorescent label-free detection of apoptosis, an important biological process. The probes could synergistically promote mitochondrion-mediated apoptosis and enhance tumor therapeutic effects in vitro and vivo.

Construction of redox-responsive tumor targeted cisplatin nano-delivery system for effective cancer chemotherapy

Cisplatin is one of the most widely used platinum-based anticancer chemotherapeutic drugs. However, its low solubility, serious side effects and the development of cisplatin resistance limit its further use in the clinic. Controlling the delivery and release of cisplatin at the targeted site efficiently is a meaningful way to overcome these undesirable side effects of cisplatin. Herein, a tumor targeted and stimuli responsive nano-delivery system for cisplatin was constructed using branched polyethyleneimine (BPEI) as the backbone, disulfide bond as the redox-responsive covalent linker and hyaluronic acid (HA) as targeting recognition unit which can bind selectively to the receptor of CD44, which is highly expressed on the A549 tumor cells. The cisplatin-polyethyleneimine conjugate BPEI-SS-Pt was prepared and the drug loading of cisplatin was up to 32.66 ± 0.06%. After optimized the coating weight ratio of HA and BPEI-SS-Pt, the nanoparticle delivery system HA-(BPEI-SS-Pt)-1/4 outperformed with smaller particle size of 159.0 ± 21.0 nm, narrow polydispersity index (PDI) of 0.069 ± 0.022 and higher cisplatin loading of 29.23 ± 0.18%, showing specific tumor-targeting ability and redox-responsive drug release manner. Moreover, for the treatment of cancer in vivo, it achieved more effective antitumor performance along with minor side effects and systemic toxicity compared with cisplatin which is of great significance for the chemotherapeutic drug in the clinic.

Cyclometalated Ir(III)-8-oxychinolin complexes acting as red-colored probes for specific mitochondrial imaging and anticancer drugs

A new class of luminescent Ir^III antitumor agents, namely, [Ir(CP1)(PY1)₂] (Ir-1), [Ir(CP1)(PY2)₂] (Ir-2), [Ir(CP1)(PY4)₂] (Ir-3), [Ir(CP2)(PY1)₂] (Ir-4), [Ir(CP2)(PY4)₂] (Ir-5), [Ir(CP3)(PY1)₂]⋅CH₃OH (Ir-6), [Ir(CP4)(PY4)₂]⋅CH₃OH (Ir-7), [Ir(CP5)(PY2)₂] (Ir-8), [Ir(CP5)(PY4)₂]⋅CH₃OH (Ir-9), [Ir(CP6)(PY1)₂] (Ir-10), [Ir(CP6)(PY2)₂]⋅CH₃OH (Ir-11), [Ir(CP6)(PY3)₂] (Ir-12), [Ir(CP6)(PY41)₂] (Ir-13), and [Ir(CP7)(PY1)₂] (Ir-14), supported by 8-oxychinolin derivatives and 1-phenylpyrazole ligands was prepared. Compared with SK-OV-3/DDP and HL-7702 cells, the Ir-1-Ir-14 compounds exhibited half maximal inhibitory concentration (IC₅₀) values within the high nanomolar range (50 nM-10.99 μM) in HeLa cells. In addition, Ir-1 and Ir-3 accumulated and stained the mitochondrial inner membrane of HeLa cells with high selectivity and exhibited a high antineoplastic activity in the entire cervical HeLa cells, with IC₅₀ values of 1.22 ± 0.36 μM and 0.05 ± 0.04 μM, respectively. This phenomenon induced mitochondrial dysfunction, suggesting that these cyclometalated Ir^III complexes can be potentially used in biomedical imaging and Ir(III)-based anticancer drugs. Furthermore, the high cytotoxicity activity of Ir-3 is correlated with the 1-phenylpyrazole (H-PY4) secondary ligands in the luminescent Ir^III antitumor complex.

Two telomerase-targeting Pt(ii) complexes of jatrorrhizine and berberine derivatives induce apoptosis in human bladder tumor cells

Two novel Pt(ii) complexes, [Pt(B-TFA)Cl]Cl (Pt1) and [Pt(J-TFA)Cl]Cl (Pt2) with jatrorrhizine and berberine derivatives (B-TFA and J-TFA) were first prepared as desirable luminescent agents for cellular applications and potent telomerase inhibitors, which can induce bladder T-24 tumor cell apoptosis by targeting telomerase, together with induction of mitochondrial dysfunction, telomere DNA damage and cell-cycle arrest. Importantly, T-24 tumor inhibition rate (TIR) was 50.4% for Pt2, which was higher than that of Pt1 (26.4%) and cisplatin (37.1%). Taken together, all the results indicated that jatrorrhizine and berberine derivatives Pt1 and Pt2 show low toxicity and could be novel Pt-based anti-cancer drug candidates.

Novel triorganotin complexes based on phosphonic acid ligands: Syntheses, structures and in vitro cytostatic activity

Six novel organotin phosphonate complexes, [(Me₃Sn)₄(HL¹)₄]_n1, [(Me₃Sn)₂(HL²)₂]_n2, [(Me₃Sn)₂L³(H₂O)]_n3, [(Ph₃Sn)(HL¹)]₆4, [(Ph₃Sn)₂L²]_n5 and [(Ph₃Sn)₂L³]₆6, derived from phosphonic acid ligands [NaHL¹ = 1-C₁₀H₇OPO₂(OH)Na, H₂L² = 1-C₁₀H₇PO(OH)₂, H₂L³ = 2-C₁₀H₇PO(OH)₂], have been synthesized and characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy and X-ray crystallography. The structural analysis reveals that complexes 1 and 5 display 1D infinite zig-zag chain structures, and complex 2 shows 1D right-handed helical chain structure, while complex 3 displays 1D left-handed helical chain structure. Complexes 4 and 6 are 24-membered macrocyclic rings interconnected by P, O and Sn atoms. Additionally, the molecules of complexes 1 and 3 are further linked through intermolecular π···π and O-H···O interaction into supramolecular structures, respectively. Furthermore, we preliminarily estimated in vitro cytostatic activity of complexes 1-6 against the human cervix tumor cells (HeLa), human hepatocellular carcinoma cells (HepG-2) and human normal breast cells (HBL-100). Importantly, the anti-proliferative properties and possible pathway of complex 6 are investigated, and the results demonstrate that complex 6 could induce apoptotic cell death via an overload of intracellular reactive oxygen species (ROS) levels and the dysfunctional depolarization of mitochondrial membranes.

Complexes of oxoplatin with rhein and ferulic acid ligands as platinum(iv) prodrugs with high anti-tumor activity

We herein designed two new Pt^IV prodrugs of oxoplatin (cis,cis,cis-[PtCl₂(NH₃)₂(OH)₂]), [Pt^IVCl₂(NH₃)₂(O₂C-FA)₂] (Pt-2) and [Pt^IVCl₂(NH₃)₂(O₂C-RH)₂] (Pt-3), by conjugating with ferulic acid (FA-COOH) and rhein (RH-COOH) which have well-known biological activities. Three other Pt(iv) complexes of [Pt^IVCl₂(NH₃)₂(O₂C-BA)₂] (Pt-1), [Pt^IVCl₂(NH₃)₂(O₂C-CA)₂] (Pt-4) and [Pt^IVCl₂(NH₃)₂(O₂C-TCA)₂] (Pt-5) (where BA-COOH = benzoic acid, CA-COOH = crotonic acid and TCA-COOH = trans-cinnamic acid) were also prepared for the comparative study. Like most Pt^IV prodrug complexes, the cytotoxicity of Pt-3 containing the biologically active rhein (RH-COOH) ligand against lung carcinoma (A549 and A549/DDP) cells was higher than those of Pt-1, Pt-2, Pt-4, cisplatin and Pt-5. Moreover, the cytotoxicity of Pt-3 in HL-7702 normal cells was lower than those of Pt^IV derivatives bearing BA-COOH, FA-COOH, TCA-COOH and CA-COOH ligands. The highly efficacious Pt-2 and Pt-3 were found to accumulate strongly in the A549/DDP cells, with the prodrug Pt-3 showing highest levels of penetration into the mitochondria. The prodrug Pt-3 effectively entered the A549/DDP cells and caused mitochondrial damage, significantly greater than Pt-2. In addition, the prodrug Pt-3 exhibited higher antitumor efficacy (inhibition rates (IR) = 67.45%) than Pt-2 (28.12%) and cisplatin (33.05%) in the A549/DDP xenograft mouse model. Thus, the prodrug Pt-3 containing the rhein (RH-COOH) ligand is a promising candidate drug targeting the mitochondria.

A class of Pt(iv) triple-prodrugs targeting nucleic acids, thymidylate synthases and histone deacetylases

A Pt(iv)-triple-prodrug, comprising VPA, 5-FU, regulated TS, HDAC, and γH2AX, showing higher efficiency and lower toxicity than cisplatin.

Eighteen 5,7-Dihalo-8-quinolinol and 2,2'-Bipyridine Co(II) Complexes as a New Class of Promising Anticancer Agents

Here we first report the design of a series of bis-chelate Co(II) 5,7-dihalo-8-quinolinol-phenanthroline derivative complexes, [Co(py)(QL1)₂] (Co1), [Co(py)(QL2)₂] (Co2), [Co(Phen)(QL1)₂] (Co3), [Co(Phen)(QL2)₂] (Co4), [Co(DPQ)(QL1)₂]·(CH₃OH)₄ (Co5), [Co(DPQ)(QL2)₂] (Co6), [Co(DPPZ)(QL1)₂]·CH₃OH (Co7), [Co(MDP)(QL1)₂]·3H₂O (Co8), [Co(ODP)(QL1)₂]·CH₃OH (Co9), [Co(PPT)(QL1)₂]·CH₃OH (Co10), [Co(ClPT)(QL1)₂] (Co11), [Co(dpy)(QL3)₂] (Co12), [Co(mpy)(QL1)₂] (Co13), [Co(Phen)(QL4)₂] (Co14), [Co(ODP)(QL4)₂] (Co15), [Co(mpy)(QL4)₂]I (Co16), [Co(ClPT)(QL4)₂] (Co17), and [Co(ClPT)(QL5)₂] (Co18), with 5,7-dihalo-8-quinolinol and 2,2′-bipyridine mixed ligands. The antitumor activity of Co1–Co18 has been evaluated against human HeLa (cervical) cancer cells in vitro (IC₅₀ values = 0.8 nM–11.88 μM), as well as in vivo against HeLa xenograft tumor growth (TIR = 43.7%, p < 0.05). Importantly, Co7 exhibited high safety in vivo and was more effective in inhibiting HeLa tumor xenograft growth (43.7%) than cisplatin (35.2%) under the same conditions (2.0 mg/kg). In contrast, the H-QL1 and DPPZ ligands greatly enhanced the activity and selectivity of Co7 in comparison to Co1–Co6, Co8–Co18, and previously reported cobalt(II) compounds. In addition, Co7 (0.8 nM) inhibited telomerase activity, caused G2/M phase arrest, and induced mitochondrial dysfunction at a concentration 5662.5 times lower than Co1 (4.53 μM) in related assays. Taken together, Co7 showed low toxicity, and the combination could be a novel Co(II) antitumor compound candidate.

High in Vitro and in Vivo Tumor-Selective Novel Ruthenium(II) Complexes with 3-(2'-Benzimidazolyl)-7-fluoro-coumarin

Three novel Ru(II) complexes, namely, (RuCl₂[L^a][DMSO]₂)·H₂O (Ru1), (RuCl₂[L^b][DMSO]₂) (Ru2), and (RuCl₂[L^c][DMSO]₂) (Ru3), which respectively contain 3-(2'-benzimidazolyl)coumarin (L^a), 3-(2'-benzimidazolyl)-7-fluoro-coumarin (L^b), and 3-(2'-benzimidazolyl)-7-methoxyl-coumarin (L^c), were first designed and characterized. Ru2 showed potent antitumor activity against NCI-H460 cells (IC₅₀ = 0.30 ± 0.02 μM) and high selectivity between NCI-H460 cancer cells and normal HL-7702 cells. Ru2 induced NCI-H460 apoptosis via telomerase inhibition, which involved DNA damage, cell-cycle distribution, and S phase-protein down-regulation. However, Ru1 did not demonstrate such effects in NCI-H460 cells, which is undoubtedly associated with the key regulatory role of the 7-fluoro substituted group in the L^b ligand of Ru2. Ru2 exhibited considerably higher anticancer efficacy (inhibition rate [IR] = 61.3%) compared with cisplatin (IR= 25.5%) in a NCI-H460 xenograft mouse model. Thus, this coumarin Ru(II) compound is a promising Ru2-targeting telomerase anticancer agent.