Modulating the Chemical and Biological Properties of Cancer Stem Cell-Potent Copper(II)-Nonsteroidal Anti-Inflammatory Drug Complexes

Fifty Shades of Phenanthroline: Synthesis Strategies to Functionalize 1,10-Phenanthroline in All Positions

1,10-Phenanthroline (phen) is one of the most popular ligands ever used in coordination chemistry due to its strong affinity for a wide range of metals with various oxidation states. Its polyaromatic structure provides robustness and rigidity, leading to intriguing features in numerous fields (luminescent coordination scaffolds, catalysis, supramolecular chemistry, sensors, theranostics, etc.). Importantly, phen offers eight distinct positions for functional groups to be attached, showcasing remarkable versatility for such a simple ligand. As a result, phen has become a landmark molecule for coordination chemists, serving as a must-use ligand and a versatile platform for designing polyfunctional arrays. The extensive use of substituted phenanthroline ligands with different metal ions has resulted in a diverse array of complexes tailored for numerous applications. For instance, these complexes have been utilized as sensitizers in dye-sensitized solar cells, as luminescent probes modified with antibodies for biomaterials, and in the creation of elegant supramolecular architectures like rotaxanes and catenanes, exemplified by Sauvage's Nobel Prize-winning work in 2016. In summary, phen has found applications in almost every facet of chemistry. An intriguing aspect of phen is the specific reactivity of each pair of carbon atoms ([2,9], [3,8], [4,7], and [5,6]), enabling the functionalization of each pair with different groups and leading to polyfunctional arrays. Furthermore, it is possible to differentiate each position in these pairs, resulting in non-symmetrical systems with tremendous versatility. In this Review, the authors aim to compile and categorize existing synthetic strategies for the stepwise polyfunctionalization of phen in various positions. This comprehensive toolbox will aid coordination chemists in designing virtually any polyfunctional ligand. The survey will encompass seminal work from the 1950s to the present day. The scope of the Review will be limited to 1,10-phenanthroline, excluding ligands with more intracyclic heteroatoms or fused aromatic cycles. Overall, the primary goal of this Review is to highlight both old and recent synthetic strategies that find applicability in the mentioned applications. By doing so, the authors hope to establish a first reference for phenanthroline synthesis, covering all possible positions on the backbone, and hope to inspire all concerned chemists to devise new strategies that have not yet been explored.

Cu(ii)-BODIPY photosensitizer for CAIX overexpressed cancer stem cell therapy

Chemoresistance originating from cancer stem cells (CSCs) is a major cause of cancer treatment failure and highlights the need to develop CSC-targeting therapies. Although enormous progress in both photodynamic therapy (PDT) and chemodynamic therapy (CDT) has been made in recent decades, the efficacy of these modalities against CSC remains limited. Here, we report a new generation photosensitizer, CA9-BPS-Cu(ii), a system that combines three subunits within a single molecule, namely a copper catalyst for CDT, a boron dipyrromethene photosensitizer for PDT, and acetazolamide for CSC targeting via carbonic anhydrase-9 (CA9) binding. A therapeutic effect in MDA-MB-231 cells was observed that is ascribed to elevated oxidative stress mediated by a combined CDT/PDT effect, as well as through copper-catalysed glutathione oxidation. The CSC targeting ability of CA9-BPS-Cu(ii) was evident from the enhanced affinity of CA9-BPS-Cu(ii) towards CD133-positive MDA-MB-231 cells where CA9 is overexpressed vs. CD133-negative cells. Moreover, the efficacy of CA9-BPS-Cu(ii) was successfully demonstrated in a xenograft mouse tumour model.

NSAIDs: Old Acquaintance in the Pipeline for Cancer Treatment and Prevention─Structural Modulation, Mechanisms of Action, and Bright Future

The limitations of current chemotherapeutic drugs are still a major issue in cancer treatment. Thus, targeted multimodal therapeutic approaches need to be strategically developed to successfully control tumor growth and prevent metastatic burden. Inflammation has long been recognized as a hallmark of cancer and plays a key role in the tumorigenesis and progression of the disease. Several epidemiological, clinical, and preclinical studies have shown that traditional nonsteroidal anti-inflammatory drugs (NSAIDs) exhibit anticancer activities. This Perspective reports the most recent outcomes for the treatment and prevention of different types of cancers for several NSAIDs alone or in combination with current chemotherapeutic drugs. Furthermore, an extensive review of the most promising structural modifications is reported, such as phospho, H₂S, and NO releasing-, selenium-, metal complex-, and natural product-NSAIDs, among others. We also provide a perspective about the new strategies used to obtain more efficient NSAID- or NSAID derivative- formulations for targeted delivery.

Metal complexes against breast cancer stem cells

With the highest incidence, breast cancer is the leading cause of cancer deaths among women in the world. Tumor metastasis is the major contributor of high mortality in breast cancer, and the existence of cancer stem cells (CSCs) has been proven to be the cause of tumor metastasis. CSCs are a small proportion of tumor cells, and they are associated with self-renewal and tumorigenic potential. Given the significance of CSCs in tumor initiation, expansion, relapse, resistance, and metastasis, studies should investigate and discover effective anticancer agents that can not only inhibit the proliferation of differentiated tumor cells but also reduce the tumorigenic capability of CSCs. Thus, new therapies must be discovered to treat and prevent this severely hazardous disease of human beings. The success of platinum complexes in cancer treatment has laid the basic foundation for the utilization of metal complexes in the treatment of malignant cancers, in particular the highly aggressive triple-negative breast cancer. Importantly, metal complexes currently have diverse and versatile competences in the therapeutic targeting of CSCs. The anti-CSC properties provide a strong impetus for the development of novel metal-based compounds for the targeting of CSCs and treatment of chemotherapy-resistant and relapsed tumors. In this review, we provide the latest advances in metal complexes including platinum, ruthenium, osmium, iridium, manganese, cobalt, nickel, copper, zinc, palladium, and tin complexes against breast CSCs obtained over the past decade, with pertinent literature including those published until 2021.

Cancer stem cell-targeted bio-imaging and chemotherapeutic perspective

Cancer stem cells (CSCs), also called tumor-initiating cells (TICs), have been studied intensively due to their rapid proliferation, migration, and role in the recurrence of cancer. In general, CSC marker-positive cells [CD133, CD44, CD166, aldehyde dehydrogenase (ALDH), and epithelial cell adhesion molecule (EpCAM)] exhibit a 100-fold increased capacity to initiate cancer. Within a heterogeneous tumor mass, only approximately 0.05-3% of cells are suspected to be CSCs and able to proliferate under hypoxia. Interestingly, CSCs, cancer cells, and normal stem cells share many cytochemical properties, such as inhibition of the redox system for reactive oxygen species (ROS) production and high expression of drug resistance transporters. However, compared to normal stem cells, CSCs develop unique metabolic flexibility, which involves switching between oxidative phosphorylation (OXPHOS) and glycolysis as their main source of energy. Due to the similarities between CSCs and other cancer cells and normal stem cells, limited chemotherapeutic and bio-imaging reagents specific for CSCs have been developed. In this short review, we address the current knowledge regarding CSCs with a focus on designing chemotherapeutic and bio-imaging reagents that target CSCs.