A palladium(II)–saccharinate complex of terpyridine exerts higher anticancer potency and less toxicity than cisplatin in a mouse allograft model

Modulation of the Cytotoxic Properties of Pd(II) Complexes Based on Functionalized Carboxamides Featuring Labile Phosphoryl Coordination Sites

Platinum-based drugs are commonly recognized as a keystone in modern cancer chemotherapy. However, intrinsic and acquired resistance as well as serious side effects often caused by the traditional Pt(II) anticancer agents prompt a continuous search for more selective and efficient alternatives. Today, significant attention is paid to the compounds of other transition metals, in particular those of palladium. Recently, our research group has suggested functionalized carboxamides as a useful platform for the creation of cytotoxic Pd(II) pincer complexes. In this work, a robust picolinyl- or quinoline-carboxamide core was combined with a phosphoryl ancillary donor group to achieve hemilabile coordination capable of providing the required level of thermodynamic stability and kinetic lability of the ensuing Pd(II) complexes. Several cyclopalladated derivatives featuring either a bi- or tridentate pincer-type coordination mode of the deprotonated phosphoryl-functionalized amides were selectively synthesized and fully characterized using IR and NMR spectroscopy as well as X-ray crystallography. The preliminary evaluation of the anticancer potential of the resulting palladocycles revealed a strong dependence of their cytotoxic properties on the binding mode of the deprotonated amide ligands and demonstrated certain advantages of the pincer-type ligation.

Dual LSD1 and HDAC6 Inhibition Induces Doxorubicin Sensitivity in Acute Myeloid Leukemia Cells

Defects in epigenetic pathways are key drivers of oncogenic cell proliferation. We developed a LSD1/HDAC6 multitargeting inhibitor (iDual), a hydroxamic acid analogue of the clinical candidate LSD1 inhibitor GSK2879552. iDual inhibits both targets with IC₅₀ values of 540, 110, and 290 nM, respectively, against LSD1, HDAC6, and HDAC8. We compared its activity to structurally similar control probes that act by HDAC or LSD1 inhibition alone, as well as an inactive null compound. iDual inhibited the growth of leukemia cell lines at a higher level than GSK2879552 with micromolar IC₅₀ values. Dual engagement with LSD1 and HDAC6 was supported by dose dependent increases in substrate levels, biomarkers, and cellular thermal shift assay. Both histone methylation and acetylation of tubulin were increased, while acetylated histone levels were only mildly affected, indicating selectivity for HDAC6. Downstream gene expression (CD11b, CD86, p21) was also elevated in response to iDual treatment. Remarkably, iDual synergized with doxorubicin, triggering significant levels of apoptosis with a sublethal concentration of the drug. While mechanistic studies did not reveal changes in DNA repair or drug efflux pathways, the expression of AGPAT9, ALOX5, BTG1, HIPK2, IFI44L, and LRP1, previously implicated in doxorubicin sensitivity, was significantly elevated.

Copper(II) and oxidovanadium(IV) complexes of chromone Schiff bases as potential anticancer agents

We report the synthesis, characterization and biological screening of new chromone Schiff bases derived from the condensation of three 6-substituted-3-formyl-chromones with pyridoxal (HL^1-3) and its Cu(II) complexes [Cu(L^1-3)Cl], 1-3. For the 6-methyl derivative, HL², the V^IVO-complex [VO(L²)Cl] (5), as well as ternary Cu and V^IVO complexes with 1,10-phenanthroline (phen), [Cu(L²)(phen)Cl] (4) and [VO(L²)(phen)Cl] (6), were also prepared and evaluated. Their stability in aqueous medium and radical scavenging activity toward DPPH are screened, with [Cu(L²)(phen)Cl] (4) showing hydrolytic stability and [VO(L²)(phen)Cl] (6) high radical scavenging activity. Spectroscopic studies establish bovine serum albumin (BSA), a model for HSA, as a potential reversible carrier of [Cu(L²)(phen)Cl] in blood with K_BC ≈ 10⁵ M^-1. The cytotoxic activity of a group of compounds is evaluated against a panel of human cancer cell lines of different origin (ovary, cervix, brain and breast) and compared to normal cells. Our results indicate that Cu complexes are more cytotoxic than the ligands but not selective towards cancer cells. The most potent complexes (4 and 6) are further evaluated for their apoptotic potential, induction of reactive oxygen species (ROS) and genotoxicity. Both complexes efficiently triggered cell death through apoptosis as evaluated by DNA morphology and TUNEL assay, increased ROS formation as determined by DCFDA (2',7'-dichlorodihydrofluorescein diacetate) analysis, and induced genotoxic damage as visualized via COMET assay in all cancer cells under study. Therefore, 4 and 6 may be potential precursor anticancer molecules, yet they need to be targeted toward cancer cells.

Antitumor activity of tridentate pincer and related metal complexes

Pincer complexes featuring tunable tridentate ligand frameworks are one of the most actively studied classes of metal-based complexes. Currently, growing attention is devoted to the cytotoxicity of pincer and related metal complexes. The antiproliferative activity of numerous pincer complexes has been reported. Pincer tridentate ligand scaffolds show different coordination modes and offer multiple options for directed structural modifications. This review summarizes the significant progress in the research studies of the antitumor activity of pincer and related platinum(ii), gold(iii), palladium(ii), copper(ii), iron(iii), ruthenium(ii), nickel(ii) and some other metal complexes, in order to provide a reference for designing novel metal coordination drug candidates with promising antitumor activity.

Exploring the Potential of Metallodrugs as Chemotherapeutics for Triple Negative Breast Cancer

This review focuses on studies of coordination and organometallic compounds as potential chemotherapeutics against triple negative breast cancer (TNBC) which has one of the poorest prognoses and worst survival rates from all breast cancer types. At present, chemotherapy is still the standard of care for TNBC since only one type of targeted therapy has been recently developed. References for metal-based compounds studied in TNBC cell lines will be listed, and those of metal-specific reviews, but a detailed overview will also be provided on compounds studied in vivo (mostly in mice models) and those compounds for which some preliminary mechanistic data was obtained (in TNBC cell lines and tumors) and/or for which bioactive ligands have been used. The main goal of this review is to highlight the most promising metal-based compounds with potential as chemotherapeutic agents in TNBC.

Synthesis and structure of a new thiazoline-based palladium(II) complex that promotes cytotoxicity and apoptosis of human promyelocytic leukemia HL-60 cells

Cisplatin is one of the most widely used chemotherapeutic agents in the treatment of different tumors but has high toxicity and side effects. Therefore, the synthesis of new chemotherapeutic agents is necessary, so that they are effective in the treatment of cancer while avoiding such toxicity. In this study, we have synthesized and characterized a palladium(II) complex, [PdCl2(µ-PyTT)2]Cl2·4H2O (PdPyTT), with 2-(2-pyridyl)imine-N-(2-thiazolin-2-yl)thiazolidine (PyTT) as a ligand; besides, its cytotoxicity and pro-apoptotic capacity was tested in human promyelocytic leukemia HL-60 cell line. Similar to cisplatin, PdPyTT produced a time- and dose-dependent decrease in cell viability. Additionally, the palladium complex increased both the proportion of cells with apoptotic morphology and the activation of caspase-3 and -9. PdPyTT, like cisplatin, also increased intracellular ROS production and DNA oxidative damage. Therefore, our findings demonstrated the promising application of palladium(II) complexes as novel anti-leukemic agents.

Structures and anticancer activity of chlorido platinum(II) saccharinate complexes with mono- and dialkylphenylphosphines

cis-[PtCl(sac)(PPh₂Me)₂] (1), cis-[PtCl(sac)(PPhMe₂)₂] (2), trans-[PtCl(sac)(PPh₂Et)₂] (3) and trans-[PtCl(sac)(PPhEt₂)₂] (4) complexes (sac = saccharinate) were synthesized and characterized by elemental analysis and spectroscopic methods. The structures of 2-4 were determined by X-ray single-crystal diffraction. The interaction of the complexes with DNA was studied various biochemical, biophysical and molecular docking methods. Only the cis-configured complexes (1 and 2) showed nuclease activity and their binding affinity towards DNA was considerably higher than those of their trans-congeners (3 and 4). The chlorido ligand in the cis-configured complexes underwent aquation, making them more reactive towards DNA. Furthermore, 1 and 2 exhibited anticancer potency on breast (MCF-7) and colon (HCT116) cancer cells similar to cisplatin, whereas 3 and 4 were biologicallly inactive. Mechanistic studies on MCF-7 cells showed that higher nuclear uptake, cell cycle arrest at the S phase, dramatically increased DNA double-strand breaks, apoptosis induction, elevated levels of reactive oxygen species (ROS) and high mitochondrial membrane depolarization greatly contribute to the anticancer potency of 1 and 2.

Anticancer activity of palladium-based complexes against triple-negative breast cancer

Treatment of triple-negative breast carcinoma (TNBC) remains an unmet medical need with no targeted therapy available to date. Accounting for 10-30% of all human breast cancer tumors, this mammary carcinoma subtype has a particularly poor prognosis owing to its high metastatic potential, aggressive biology and limited pharmacological treatment options. Platinum chemotherapeutics are the mainstay therapy in patients with TNBC but their clinical use is limited by severe toxicity and acquired resistance. Palladium-based complexes are appealing alternative metal-based drugs because of significant similarities regarding structure and coordination chemistry with the platinum agents. This review summarizes the knowledge gathered so far on 121 Pd(II) complexes, emphasizing their anticancer activity and putative pharmacological targets toward TNBC.

Palladium(ii) and platinum(ii) saccharinate complexes with bis(diphenylphosphino)methane/ethane: synthesis, S-phase arrest and ROS-mediated apoptosis in human colon cancer cells

New neutral [M(sac)2(diphos)] and cationic [M(diphos)2](sac)2 complexes, where M = PdII or PtII, sac = saccharinate, and diphos = 1,1-bis(diphenylphosphino)methane (dppm) or 1,2-bis(diphenylphosphino)ethane (dppe), were synthesized and structurally characterized. The anticancer activity of the complexes was investigated against MCF-7 (breast), A549 (lung), HCT116 (colon), DU145 (prostate) cancer and BEAS-2B (normal bronchial epithelial) cells. Neutral Pt-dppm (2) and Pd-dppe complexes (5) did not show any biological activity. The cationic Pd-dppe (7) complex displayed antiproliferative activity, while the rest of the complexes exhibited potent cytotoxicity compared with cisplatin. The active Pd(ii)/Pt(ii) complexes were then included in further studies including interaction with DNA/HSA, nuclease activity, cellular uptake and lipophilicity. The potent complexes induced the apoptotic cell death as probed through annexin V positivity and caspase activation. Mechanistic studies on HCT116 cells showed that the complexes cause cell cycle arrest at the DNA synthesis (S) phase and excessive generation of reactive oxygen species (ROS), damaging to both mitochondria and DNA.