Breast Cancer Stem Cell Potency of Nickel(II)-Polypyridyl Complexes Containing Non-steroidal Anti-inflammatory Drugs.

We report the breast cancer stem cell (CSC) potency of two nickel(II)-3,4,7,8-tetramethyl-1,10-phenanthroline complexes, 1 and 3, containing the non-steroidal anti-inflammatory drugs (NSAIDs), naproxen and indomethacin, respectively. The nickel(II) complexes, 1 and 3 kill breast CSCs and bulk breast cancer cells in the micromolar range. Notably, 1 and 3 display comparable or better potency towards breast CSCs than salinomycin, an established CSC-active agent. The complexes, 1 and 3 also display significantly lower toxicity towards non-cancerous epithelial breast cells than breast CSCs or bulk breast cancer cells (up to 4.6-fold). Mechanistic studies suggest that 1 and 3 downregulate cyclooxygenase-2 (COX-2) in breast CSCs and kill breast CSCs in a COX-2 dependent manner. Furthermore, the potency of 1 and 3 towards breast CSCs decreased upon co-treatment with necroptosis inhibitors (necrostatin-1 and dabrafenib), implying that 1 and 3 induce necroptosis, an ordered form of necrosis, in breast CSCs. As apoptosis resistance is a hallmark of CSCs, compounds like 1 and 3, which potentially provide access to alternative (non-apoptotic) cell death pathways could hold the key to overcoming hard-to-kill CSCs. To the best of our knowledge, 1 and 3 are the first compounds to be associated to COX-2 inhibition and necroptosis induction in CSCs

Breast Cancer Stem Cell Active Copper(II) Complexes with Naphthol Schiff Base and Polypyridyl Ligands

Breast cancer stem cells (CSCs) are a sub-population of tumour cells that can promote breast cancer relapse and metastasis. Current treatments are unable to completely remove breast CSCs, therefore it is essential to develop new chemotherapeutics that can remove breast CSCs at clinically compatible doses. Here we present the synthesis, characterisation, and anti-breast CSC properties of copper(II) complexes, [Cu(L2)(1,10-phenanthroline)]PF6 (2) and [Cu(L3)(1,10-phenanthroline)]PF6 (3) comprising of a tridentate (O,N,S) coordinated naphthol Schiff base ligand (L2 = (E)-1-(((2-(methylthio)ethyl)imino)methyl)naphthalen-2-ol or L3 = (E)-1-(((2-(ethylthio)ethyl)imino)methyl)naphthalen-2-ol and 1,10-phenanthroline. The copper(II) complexes (2 and 3) kill breast CSCs, cultured in monolayer and three-dimensional systems, in the micromolar range. Notably, 2 and 3 are more potent towards breast CSC mammospheres than salinomycin (up to 4.5-fold), an established anti-breast CSC agent. Further, cell-based studies indicate that 2 and 3 are readily taken up by breast CSCs and elevate intracellular reactive oxygen species (ROS) levels upon short exposure times (0.5–1 h). The latter is likely to be the underlying mechanism by which 2 and 3 induces breast CSC death.</jats:p

The cancer stem cell potency of group 10‐Azadiphosphine metal complexes

Abstract: The cancer stem cell (CSC) potency of a series of structurally analogous Group 10‐azadiphosphine metal complexes is reported. The complexes comprise a Group 10 metal (Ni for 1, Pd for 2, or Pt for 3), an azadiphosphine ligand, and two chloride ligands. The complexes exhibit micromolar potency towards bulk breast cancer cells and breast CSCs cultured in monolayer systems. The cytotoxicity of the complexes is comparable to or better than clinically used metallopharmaceuticals, cisplatin and carboplatin, and the gold‐standard anti‐breast CSC agent, salinomycin. Notably, the breast CSC mammosphere inhibitory effect and potency of the complexes is dependent on the Group 10 metal present, increasing in the following order: 3<2<1. This study highlights the importance of the metal within a given series of structurally related compounds to their breast CSC mammosphere activity and reinforces the therapeutic potential of Group 10 coordination complexes as anti‐CSC agents

Necroptosis-Inducing Rhenium(V) Oxo Complexes

Rhenium(V) oxo complexes of general formula [ReO(OMe)(N^N)Cl₂], where N^N = 4,7-diphenyl-1,10-phenanthroline, 1, or 3,4,7,8-tetramethyl-1,10-phenanthroline, 2, effectively kill cancer cells by triggering necroptosis, a non-apoptotic form of cell death. Both complexes evoke necrosome (RIP1-RIP3)-dependent intracellular reactive oxygen species (ROS) production and propidium iodide uptake. The complexes also induce mitochondrial membrane potential depletion, a possible downstream effect of ROS production. Apparently, 1 and 2 are the first rhenium complexes to evoke cellular events consistent with programmed necrosis in cancer cells. Furthermore, 1 and 2 display low acute toxicity in C57BL/6 mice and reasonable stability in fresh human blood.National Cancer Institute (U.S.) (CA034992

A bioinspired redox-modulating copper(II)– macrocyclic complex bearing non-steroidal anti-inflammatory drugs with anti-cancer stem cell activity

Copper(II) coordination compounds have been investigated for their anticancer properties for decades, however, none have reached advanced human clinical trials. The poor translation of copper(II) complexes from in vitro studies to (pre)clinical studies can be attributed to their limited efficacy in animal models, which is largely associated with copper leaching and speciation (in biological fluids). Here we report a biologically stable copper(II) complex based on the active site of Type I Cu electron transport proteins. The copper(II) complex 1 comprises of dithiacyclam (with soft and hard donor atoms) and two diclofenac units, a nonsteriodial anti-inflammatory drug (NSAID). Extensive biophysical and electrochemical studies show that the solid state structure of 1 is preserved in solution and that it can access both copper(I) and copper(II) oxidation states without leaching copper or undergoing speciation (in the presence of a cellular reductant). Cell studies show that 1 kills bulk breast cancer cells and highly resistant breast cancer stem cells (CSCs) at micromolar concentrations, and is significantly less toxic towards a panel of non-cancerous cells. Clinically relevant spheroid studies show that 1 is able to inhibit breast CSC-enriched mammosphere formation to a similar extent as salinomycin, a gold standard anti-CSC agent. Mechanistic studies show that 1 evokes breast CSC death by elevating intracellular reactive oxygen species (ROS) and inhibiting cyclooxygenase-2 (COX-2) activity. The former leads to the activation of stress pathways (JNK and p38), which culminates in caspase-dependent apoptosis. This study reinforces the therapeutic potential of copper(II)–NSAID complexes and provides a bioinspired route to develop stable, ROS-generating copper-based anti-CSC drug candidates

The anti-breast cancer stem cell properties of gold( i )-non-steroidal anti-inflammatory drug complexes

The anti-breast cancer stem cell (CSC) properties of a series of gold(i) complexes comprising various non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine 1–8 are reported. The most effective gold(i)-NSAID complex 1, containing indomethacin, exhibits greater potency for breast CSCs than bulk breast cancer cells (up to 80-fold). Furthermore, 1 reduces mammosphere viability to a better extent than a panel of clinically used breast cancer drugs and salinomycin, an established anti-breast CSC agent. Mechanistic studies suggest 1-induced breast CSC death results from breast CSC entry, cytoplasm localisation, an increase in intracellular reactive oxygen species levels, cyclooxygenase-2 downregulation and inhibition, and apoptosis. Remarkably, 1 also significantly inhibits tumour growth in a murine metastatic triple-negative breast cancer model. To the best of our knowledge, 1 is the first gold complex of any geometry or oxidation state to demonstrate anti-breast CSC properties

Integrated Design of a Membrane-Lytic Peptide-Based Intravenous Nanotherapeutic Suppresses Triple-Negative Breast Cancer.

Funder: KCL PhD scholarshipsFunder: Leverhulme Trust; Id: http://dx.doi.org/10.13039/501100000275Membrane-lytic peptides offer broad synthetic flexibilities and design potential to the arsenal of anticancer therapeutics, which can be limited by cytotoxicity to noncancerous cells and induction of drug resistance via stress-induced mutagenesis. Despite continued research efforts on membrane-perforating peptides for antimicrobial applications, success in anticancer peptide therapeutics remains elusive given the muted distinction between cancerous and normal cell membranes and the challenge of peptide degradation and neutralization upon intravenous delivery. Using triple-negative breast cancer as a model, the authors report the development of a new class of anticancer peptides. Through function-conserving mutations, the authors achieved cancer cell selective membrane perforation, with leads exhibiting a 200-fold selectivity over non-cancerogenic cells and superior cytotoxicity over doxorubicin against breast cancer tumorspheres. Upon continuous exposure to the anticancer peptides at growth-arresting concentrations, cancer cells do not exhibit resistance phenotype, frequently observed under chemotherapeutic treatment. The authors further demonstrate efficient encapsulation of the anticancer peptides in 20 nm polymeric nanocarriers, which possess high tolerability and lead to effective tumor growth inhibition in a mouse model of MDA-MB-231 triple-negative breast cancer. This work demonstrates a multidisciplinary approach for enabling translationally relevant membrane-lytic peptides in oncology, opening up a vast chemical repertoire to the arms race against cancer

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.National Cancer Institute (U.S.) (CA034992