Phenotype-based drug screening in primary ovarian carcinoma cultures identifies intracellular iron depletion as a promising strategy for cancer treatment

A review on metal complexes and its anti-cancer activities: Recent updates from in vivo studies

Research into cancer therapeutics has uncovered various potential medications based on metal-containing scaffolds after the discovery and clinical applications of cisplatin as an anti-cancer agent. This has resulted in many metallodrugs that can be put into medical applications. These metallodrugs have a wider variety of functions and mechanisms of action than pure organic molecules. Although platinum-based medicines are very efficient anti-cancer agents, they are often accompanied by significant side effects and toxicity and are limited by resistance. Some of the most studied and developed alternatives to platinum-based anti-cancer medications include metallodrugs based on ruthenium, gold, copper, iridium, and osmium, which showed effectiveness against many cancer cell lines. These metal-based medicines represent an exciting new category of potential cancer treatments and sparked a renewed interest in the search for effective anti-cancer therapies. Despite the widespread development of metal complexes touted as powerful and promising in vitro anti-cancer therapeutics, only a small percentage of these compounds have shown their worth in vivo models. Metallodrugs, which are more effective and less toxic than platinum-based drugs and can treat drug-resistant cancer cells, are the focus of this review. Here, we highlighted some of the most recently developed Pt, Ru, Au, Cu, Ir, and Os complexes that have shown significant in vivo antitumor properties between 2017 and 2023.

Capn4 regulates migration and invasion of ovarian carcinoma cells via targeting osteopontin-mediated PI3K/AKT signaling pathway

Previous studies have demonstrated that calpain small subunit 4 (Capn4) is able to regulate the viability and metastasis of cancer cells. However, the regulatory effects and underlying molecular mechanism of Capn4 in ovarian carcinoma cells are not well understood. The purpose of the present study was to investigate the role of Capn4 in ovarian carcinoma cells and analyze the possible mechanism mediated by Capn4. The expression levels of Capn4 and osteopontin (OPN) were determined and the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway was analyzed in ovarian carcinoma cells. The results of the present study revealed that Capn4 and OPN were overexpressed in clinical ovarian carcinoma tissues and ovarian carcinoma cells. Capn4 silencing downregulated OPN expression, and suppressed ovarian carcinoma cell viability and migration. Capn4 silencing enhanced apoptosis of ovarian carcinoma cells by increasing activity of the capase-3 apoptosis signaling pathway. Capn4 promoted the metastasis of ovarian carcinoma cells by interacting with the PI3K/AKT signaling pathway via upregulation of OPN expression. In conclusion, the results of the present study indicate that Capn4 may be a potential therapeutic target for the treatment of ovarian carcinoma.

Mechanistic characterization of a copper containing thiosemicarbazone with potent antitumor activity

Background

The thiosemicarbazone CD 02750 (VLX50) was recently reported as a hit compound in a phenotype-based drug screen in primary cultures of patient tumor cells. We synthesized a copper complex of VLX50, denoted VLX60, and characterized its antitumor and mechanistic properties.

Materials and Methods

The cytotoxic effects and mechanistic properties of VLX60 were investigated in monolayer cultures of multiple human cell lines, in tumor cells from patients, in a 3-D spheroid cell culture system and in vivo and were compared with those of VLX50.

Results

VLX60 showed ≥ 3-fold higher cytotoxic activity than VLX50 in 2-D cultures and, in contrast to VLX50, retained its activity in the presence of additional iron. VLX60 was effective against non-proliferative spheroids and against tumor xenografts in vivo in a murine model. In contrast to VLX50, gene expression analysis demonstrated that genes associated with oxidative stress were considerably enriched in cells exposed to VLX60 as was induction of reactive oxygen. VLX60 compromised the ubiquitin-proteasome system and was more active in BRAF mutated versus BRAF wild-type colon cancer cells.

Conclusions

The cytotoxic effects of the copper thiosemicarbazone VLX60 differ from those of VLX50 and shows interesting features as a potential antitumor drug, notably against BRAF mutated colorectal cancer.

Iron chelators target both proliferating and quiescent cancer cells

Poorly vascularized areas of solid tumors contain quiescent cell populations that are resistant to cell cycle-active cancer drugs. The compound VLX600 was recently identified to target quiescent tumor cells and to inhibit mitochondrial respiration. We here performed gene expression analysis in order to characterize the cellular response to VLX600. The compound-specific signature of VLX600 revealed a striking similarity to signatures generated by compounds known to chelate iron. Validation experiments including addition of ferrous and ferric iron in excess, EXAFS measurements, and structure activity relationship analyses showed that VLX600 chelates iron and supported the hypothesis that the biological effects of this compound is due to iron chelation. Compounds that chelate iron possess anti-cancer activity, an effect largely attributed to inhibition of ribonucleotide reductase in proliferating cells. Here we show that iron chelators decrease mitochondrial energy production, an effect poorly tolerated by metabolically stressed tumor cells. These pleiotropic features make iron chelators an attractive option for the treatment of solid tumors containing heterogeneous populations of proliferating and quiescent cells.

The use of high-throughput screening in identifying chemotherapeutic agents for gastric cancer

Gastric cancer claims many lives around the world, particularly in Asia. Although diagnosis and treatment has improved, long-term survival of patients is still poor and there is an urgent need to develop more effective treatments for this disease. This review outlines some of the more innovative high-throughput screening-based approaches and strategies that may be used to identify compounds that have new or novel mechanisms of action and could be developed further as possible gastric cancer treatments in the future.

Drug screen in patient cells suggests quinacrine to be repositioned for treatment of acute myeloid leukemia

To find drugs suitable for repositioning for use against leukemia, samples from patients with chronic lymphocytic, acute myeloid and lymphocytic leukemias as well as peripheral blood mononuclear cells (PBMC) were tested in response to 1266 compounds from the LOPAC¹²⁸⁰ library (Sigma). Twenty-five compounds were defined as hits with activity in all leukemia subgroups (<50% cell survival compared with control) at 10 μM drug concentration. Only one of these compounds, quinacrine, showed low activity in normal PBMCs and was therefore selected for further preclinical evaluation. Mining the NCI-60 and the NextBio databases demonstrated leukemia sensitivity and the ability of quinacrine to reverse myeloid leukemia gene expression. Mechanistic exploration was performed using the NextBio bioinformatic software using gene expression analysis of drug exposed acute myeloid leukemia cultures (HL-60) in the database. Analysis of gene enrichment and drug correlations revealed strong connections to ribosomal biogenesis nucleoli and translation initiation. The highest drug–drug correlation was to ellipticine, a known RNA polymerase I inhibitor. These results were validated by additional gene expression analysis performed in-house. Quinacrine induced early inhibition of protein synthesis supporting these predictions. The results suggest that quinacrine have repositioning potential for treatment of acute myeloid leukemia by targeting of ribosomal biogenesis.

NMR spectroscopy-based metabolic profiling of drug-induced changes in vitro can discriminate between pharmacological classes

Drug-induced changes in mammalian cell line models have already been extensively profiled at the systemic mRNA level and subsequently used to suggest mechanisms of action for new substances, as well as to support drug repurposing, i.e., identifying new potential indications for drugs already licensed for other pharmacotherapy settings. The seminal work in this field, which includes a large database and computational algorithms for pattern matching, is known as the "Connectivity Map" (CMap). However, the potential of similar exercises at the metabolite level is still largely unexplored. Only recently, the first high-throughput metabolomic assay pilot study was published, which involved screening the metabolic response to a set of 56 kinase inhibitors in a 96-well format. Here, we report results from a separately developed metabolic profiling assay, which leverages (1)H NMR spectroscopy to the quantification of metabolic changes in the HCT116 colorectal cancer cell line, in response to each of 26 compounds. These agents are distributed across 12 different pharmacological classes covering a broad spectrum of bioactivity. Differential metabolic profiles, inferred from multivariate spectral analysis of 18 spectral bins, allowed clustering of the most-tested drugs, according to their respective pharmacological class. A more-advanced supervised analysis, involving one multivariate scattering matrix per pharmacological class and using only 3 spectral bins (3 metabolites), showed even more distinct pharmacology-related cluster formations. In conclusion, this type of relatively fast and inexpensive profiling seems to provide a promising alternative to that afforded by mRNA expression analysis, which is relatively slow and costly. As also indicated by the present pilot study, the resulting metabolic profiles do not seem to provide as information-rich signatures as those obtained using systemic mRNA profiling, but the methodology holds strong promise for significant refinement.

Protective role of humanin on bortezomib-induced bone growth impairment in anticancer treatment

BACKGROUND

Bortezomib is a proteasome inhibitor currently studied in clinical trials of childhood cancers. So far, no side effects on bone growth have been reported in treated children. However, bortezomib was recently found to induce apoptosis in growth plate chondrocytes and impair linear bone growth in treated mice. We hypothesize that [Gly(14)]-humanin (HNG), a 24-amino acid synthetic antiapoptotic peptide, can prevent bortezomib-induced bone growth impairment.

METHODS

Mice with human neuroblastoma or medulloblastoma tumor xenografts (9-13 animals/group) received one 2-week cycle (2 injections/week) of bortezomib (0.8 mg/kg or 1.0mg/kg), or HNG (1 µg/mouse), or the combination of HNG/bortezomib, or vehicle. Cultures of human growth plate cartilage, chondrogenic- and cancer cell lines, and immunohistochemistry for detection of proapoptotic proteins were also used. Statistical significance was evaluated by two-sided Mann-Whitney U test or by parametric or nonparametric analysis of variance.

RESULTS

Bortezomib efficiently blocked the proteasome and induced pronounced impairment of linear bone growth from day 0 to day 13 (0.09 mm/day, 95% confidence interval [CI] = 0.07 to 0.11 mm/day; vs 0.19 mm/day, 95% CI = 0.15 to 0.23 mm/day in vehicle; P < .001), an effect significantly prevented by the addition of HNG (0.15 mm growth/day, 95% CI = 0.14 to 0.16 mm/day; P < .001 vs bortezomib only; P = 0.03 vs vehicle). Bortezomib was highly toxic when added to cultures of human growth plate cartilage, with markedly increased apoptosis compared with control (P < .001). However, when combining with HNG, bortezomib-induced apoptosis was entirely prevented, as was Bax and PARP activation. Bortezomib delayed tumor growth, and HNG did not interfere with the anticancer effect when studied in human tumor xenografts or cell lines.

CONCLUSIONS

HNG prevents bortezomib-induced bone growth impairment without interfering with bortezomib's desired anticancer effects.

Pharmacologic characterization of a kinetic in vitro human co-culture angiogenesis model using clinically relevant compounds

Angiogenesis, the formation of new vessels from preexisting vessels, involves multiple cell types acting in concert to cause endothelial cell proliferation, migration, and differentiation into microvascular arrays. Under pathologic conditions, microenvironment changes result in altered blood vessel production. Historically, in vitro angiogenesis assays study individual aspects of the process and tend to be variable, difficult to quantify, and limited in clinical relevance. Here, we describe a kinetic, quantitative, co-culture angiogenesis model and demonstrate its relevance to in vivo pharmacology. Similar to in vivo angiogenesis, a co-culture of human umbilical vein endothelial cells with normal human dermal fibroblasts remains sensitive to multiple cytokines, resulting in a concentration-dependent stimulation of tube formation over time. Treatment with axitinib, a selective vascular endothelial growth factor (VEGF) antagonist, inhibited VEGF-mediated tube length and branch point formation and was selective for inhibiting VEGF over basic fibroblast growth factor (bFGF), similar to previous studies. Conversely, an FGFR-1 selective compound, PD-161570, was more potent at inhibiting bFGF-mediated angiogenesis. These results demonstrate the cytokine dynamics, selective pharmacology, and translational application of this model system. Finally, combining quantitative angiogenic biology with kinetic, live-content imaging highlights the importance of using validated in vitro models in drug discovery research.

A chemical genetic approach identifies piperazine antipsychotics as promoters of CNS neurite growth on inhibitory substrates

Injury to the central nervous system (CNS) can result in lifelong loss of function due in part to the regenerative failure of CNS neurons. Inhibitory proteins derived from myelin and the astroglial scar are major barriers for the successful regeneration of injured CNS neurons. Previously, we described the identification of a novel compound, F05, which promotes neurite growth from neurons challenged with inhibitory substrates in vitro, and promotes axonal regeneration in vivo (Usher et al., 2010). To identify additional regeneration-promoting compounds, we used F05-induced gene expression profiles to query the Broad Institute Connectivity Map, a gene expression database of cells treated with >1300 compounds. Despite no shared chemical similarity, F05-induced changes in gene expression were remarkably similar to those seen with a group of piperazine phenothiazine antipsychotics (PhAPs). In contrast to antipsychotics of other structural classes, PhAPs promoted neurite growth of CNS neurons challenged with two different glial derived inhibitory substrates. Our pharmacological studies suggest a mechanism whereby PhAPs promote growth through antagonism of calmodulin signaling, independent of dopamine receptor antagonism. These findings shed light on mechanisms underlying neurite-inhibitory signaling, and suggest that clinically approved antipsychotic compounds may be repurposed for use in CNS injured patients.

Loss of cancer drug activity in colon cancer HCT-116 cells during spheroid formation in a new 3-D spheroid cell culture system

Clinically relevant in vitro methods are needed to identify new cancer drugs for solid tumors. We report on a new 3-D spheroid cell culture system aimed to mimic the properties of solid tumors in vivo. The colon cancer cell lines HCT-116 wt and HCT-116 wt/GFP were grown as monolayers and for 3 or 6 days on 96-well NanoCulture® plates to form spheroids. Expression of surface markers, genes and hypoxia were assessed to characterize the spheroids and drug induced cytotoxicity was evaluated based on fluorescein diacetate (FDA) conversion by viable cells to fluorescent fluorescein or by direct measurement of fluorescence of GFP marked cells after a 72 h drug incubation. The cells reproducibly formed spheroids in the NanoCulture® plates with tight cell-attachment after 6 days. Cells in spheroids showed geno- and phenotypical properties reminiscent of hypoxic stem cells. Monolayer cultured cells were sensitive to standard and investigational drugs, whereas the spheroids gradually turned resistant. Similar results for cytotoxicity were observed using simplified direct measurement of fluorescence of GFP marked cells compared with FDA incubation. In conclusion, this new 3-D spheroid cell culture system provides a convenient and clinically relevant model for the identification and characterization of cancer drugs for solid tumors.

Genetic and proteomic approaches to identify cancer drug targets

While target-based small-molecule discovery has taken centre-stage in the pharmaceutical industry, there are many cancer-promoting proteins not easily addressed with a traditional target-based screening approach. In order to address this problem, as well as to identify modulators of biological states in the absence of knowing the protein target of the state switch, alternative phenotypic screening approaches, such as gene expression-based and high-content imaging, have been developed. With this renewed interest in phenotypic screening, however, comes the challenge of identifying the binding protein target(s) of small-molecule hits. Emerging technologies have the potential to improve the process of target identification. In this review, we discuss the application of genomic (gene expression-based), genetic (short hairpin RNA and open reading frame screening), and proteomic approaches to protein target identification.