Visible and Red Light-Triggered Anticancer Profile of a Ferrocene-Re(I)-Tricarbonyl Conjugate: Experimental and Theoretical Studies

We have red-shifted the light absorbance property of a Re(I)-tricarbonyl complex via distant conjugation of a ferrocene moiety and developed a novel complex ReFctp, [Re(Fctp)(CO)3Cl], where Fctp = 4'-ferrocenyl-2,2':6',2″-terpyridine. ReFctp showed green to red light absorption ability and blue emission, indicating its potential for photodynamic therapy (PDT) application. The conjugation of ferrocene introduced ferrocene-based transitions, which lie at a higher wavelength within the PDT therapeutic window. The time-dependent density functional theory and excited state calculations revealed an efficient intersystem crossing for ReFctp, which is helpful for PDT. ReFctp elicited both PDT type I and type II pathways for reactive oxygen species (ROS) generation and facilitated NADH (1,4-dihydro-nicotinamide adenine dinucleotide) oxidation upon exposure to visible light. Importantly, ReFctp showed effective penetration through the layers of clinically relevant 3D multicellular tumor spheroids and localized primarily in mitochondria (Pearson's correlation coefficient, PCC = 0.65) of A549 cancer cells. ReFctp produced more than 20 times higher phototoxicity (IC50 ∼1.5 μM) by inducing ROS generation and altering mitochondrial membrane potential in A549 cancer cells than the nonferrocene analogue Retp, [Re(CO)3(tp)Cl], where tp = 2,2':6',2″-terpyridine. ReFctp induced apoptotic mode of cell death with a notable photocytotoxicity index (PI, PI = IC50dark/IC50light) and selectivity index (SI, SI = normal cell's IC50dark/cancer cell's IC50light) in the range of 25-33.

3D-Shaped Binders of Unfolded Proteins Inducing Cancer Cell-Specific Endoplasmic Reticulum Stress In Vitro and In Vivo

The amount of unfolded proteins is increased in cancer cells, leading to endoplasmic reticulum (ER) stress. Therefore, cancer cells are sensitive to drugs capable of further enhancing ER stress. Examples of such drugs include the clinically approved proteosome inhibitors bortezomib and carfilzomib. Unfortunately, the known ER stress inducers exhibit dose-limiting side effects that justify the search for better, more cancer-specific drugs of this type. Herein, we report on FeC 2, which binds to unfolded proteins prevents their further processing, thereby leading to ER stress and ROS increase in cancer cells, but not in normal cells. FeC 2 exhibits low micromolar toxicity toward human acute promyelocytic leukemia HL-60, Burkitt's lymphoma BL-2, T-cell leukemia Jurkat, ovarian carcinoma A2780, lung cancer SK-MES-1, and murine lung cancer LLC1 cells. Due to the cancer-specific mode of action, 2 is not toxic in vivo up to the dose of 147 mg/kg, does not affect normal blood and bone marrow cells at the therapeutically active dose, but strongly suppresses both primary tumor growth (confirmed in Nemeth-Kellner lymphoma and LLC1 lung cancer models of murine tumor) and spreading of metastases (LLC1).

Ferrocene-containing hybrids as potential anticancer agents: Current developments, mechanisms of action and structure-activity relationships

Cancer is one of the most fatal threatens to human health throughout the world. The major challenges in the control and eradication of cancers are the continuous emergency of drug-resistant cancer and the low specificity of anticancer agents, creating an urgent need to develop novel anticancer agents. Organometallic compounds especially ferrocene derivatives possess remarkable structural and mechanistic diversity, inherent stability towards air, heat and light, low toxicity, low cost, reversible redox, ligand exchange, and catalytic properties, making them promising drug candidates for cancer therapy. Ferrocifen, a ferrocene-phenol hybrid, has demonstrated promising anticancer properties on drug-resistant cancers. Currently, Ferrocifen is in pre-clinical trial against cancers. Obviously, ferrocene moiety is a useful template for the development of novel anticancer agents. This review will provide an overview of ferrocene-containing hybrids with potential application in the treatment of cancers covering articles published between 2010 and 2020. The mechanisms of action, the critical aspects of design and structure-activity relationships are also discussed.

Endoplasmic reticulum stress: an arising target for metal-based anticancer agents

Metal anticancer agents are rapidly emerging as selective, potent therapeutics that exhibit anticancer activity by inducing endoplasmic reticulum stress.

Intramolecular electron transfer in Cu(ii) complexes with aryl-imidazo-1,10-phenanthroline derivatives: experimental and quantum chemical calculation studies

First observation of Cu(ii)–Cu(i) autoreduction in complex with aryl-imidazo-1,10-phenanthroline derivatives.

Photocytotoxic copper(II) complexes of N-salicylyl-l-tryptophan and phenanthroline bases

Four ternary copper(II) complexes of N-salicylyl-l-Tryptophan (Sal-TrpH) and phenanthroline bases of general formula [Cu(Sal-Trp)(L)], where L is 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2), dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3) and 2-(anthracen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (aip, 4), were synthesized and fully characterized. The complexes were evaluated for their affinity for biomolecules and photocytotoxic activities. Single crystal X-ray diffraction studies of complex 1 revealed that it has a square pyramidal CuN₃O₂ core with the phenolate oxygen of salicylaldehyde occupying the axial coordination site in the solid state. Complexes 1-4 displayed the Cu(II)-Cu(I) redox couples at ~-0.3 V vs. Ag/AgCl reference electrode in DMF-0.1 M [Buⁿ₄N](ClO₄). A Cu(II)-based weak d-d band ~650 nm and a moderately strong ligand to metal charge transfer band at ~430 nm were observed in DMF-Tris-HCl buffer (pH 7.2) (1:4 v/v). The complexes are efficient binders to calf thymus DNA and model proteins such as bovine serum albumin and lysozyme. They cleave supercoiled plasmid DNA efficiently when exposed to 446 and 660 nm laser radiation. They are cytotoxic to HeLa (human cervical cancer) and MCF-7 (human breast cancer) cells showing significant enhancement of cytotoxicity upon photo-excitation with low energy visible light. The complexes are found to kill cancer cells through generation of reactive oxygen species (ROS) as confirmed by DCFDA (2',7'-dichlorofluorescin diacetate) assay. The apoptotic cell death induced by complex 4 was confirmed by Annexin V-Fluorescein isothiocyanate-Propidium iodide assay. Confocal microscopic images using 4 showed its primary cytosolic localization in the HeLa and MCF-7 cells.

DNA and BSA binding and cytotoxic properties of copper(ii) and iron(iii) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands

Copper(ii) and iron(iii) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands show DNA and BSA binding and anticancer abilities.

A Photoactivatable Platinum(IV) Anticancer Complex Conjugated to the RNA Ligand Guanidinoneomycin

A photoactivatable platinum(IV) complex, trans,trans,trans-[Pt(N3 )2 (OH)(succ)(py)2 ] (succ=succinylate, py=pyridine), has been conjugated to guanidinoneomycin to study the effect of this guanidinum-rich compound on the photoactivation, intracellular accumulation and phototoxicity of the pro-drug. Surprisingly, trifluoroacetic acid treatment causes the replacement of an azido ligand and the axial hydroxide ligand by trifluoroacetate, as shown by NMR spectroscopy, MS and X-ray crystallography. Photoactivation of the platinum-guanidinoneomycin conjugate in the presence of 5'-guanosine monophosphate (5'-GMP) led to the formation of trans-[Pt(N3 )(py)2 (5'-GMP)](+) , as does the parent platinum(IV) complex. Binding of the platinum(II) photoproduct {PtN3 (py)2 }(+) to guanine nucleobases in a short single-stranded oligonucleotide was also observed. Finally, cellular uptake studies showed that guanidinoneomycin conjugation improved the intracellular accumulation of the platinum(IV) pro-drug in two cancer cell lines, particularly in SK-MEL-28 cells. Notably, the higher phototoxicity of the conjugate in SK-MEL-28 cells than in DU-145 cells suggests a degree of selectivity towards the malignant melanoma cell line.