The versatile utility of cysteine as a target for cancer treatment

T330M Substitution in the Sodium-Dependent Phosphate Transporter NaPi2b Abolishes the Efficacy of Monoclonal Antibodies Against MX35 Epitope

Background: Monoclonal antibodies against the sodium-dependent phosphate transporter NaPi2b (SLC34A2) represent a promising approach in the treatment of ovarian and lung cancer. Of particular interest is the potential cancer-specific MX35 epitope of NaPi2b, as it serves as a target for monoclonal antibodies studied at various stages of preclinical and clinical trials. However, variations in the NaPi2b protein structure may limit the efficacy of therapeutic antibodies by affecting the accessibility of the MX35 epitope. Methods: An in silico analysis was performed using data from 101,562 tumor samples. Genomic DNA sequencing was conducted on blood samples from patients with ovarian carcinoma, breast cancer, and renal carcinoma to access the frequency of germline mutations in the SLC34A2 gene region encoding the MX35 epitope. To assess the impact of the selected mutation, we generated a model cell line through site-directed mutagenesis carrying the mutant NaPi2b variant. Results: Using in silico analysis, we identified 17 unique variants in the SLC34A2 gene leading to amino acid substitutions within the MX35 epitope of the NaPi2b. Among these, the most prevalent mutation, c.989C>T, resulting in p.T330M substitution, was detected in 5 out of 64 patients through genomic DNA sequencing. Using site-directed mutagenesis, we created the OVCAR-8/NaPi2bp.T330M model cell line. L3 (28/1) monoclonal antibodies specific to the MX35 epitope failed to recognize the mutant NaPi2bp.T330M variant compared to the wild-type of the NaPi2b in both Western blot and confocal microscopy experiments. Conclusions: The obtained data may serve as a basis for predicting the efficacy of monoclonal antibody-based targeted therapy binding to the MX35 epitope of NaPi2b in the treatment of oncological diseases.

Multiple Classes of Antigen Contribute to the Antigenic Landscape of Mesothelioma

Mesothelioma is an incurable, asbestos-exposure-related cancer that typically affects the lining or pleura of the lungs. Symptoms typically develop many decades after initial asbestos exposure, leaving an enduring legacy of disease. The current disease burden is peaking worldwide and thus there is a massive unmet clinical need for curative therapies. Recently, immune checkpoint blockade-based therapy has been adopted as a first-line of treatment for mesothelioma. Vaccine-induced augmentation of immune responses unleashed during checkpoint blockade may provide further clinical benefit in mesothelioma. In this study, we explore the human leukocyte antigen class I landscape (or immunopeptidome) of mesothelioma in patient-derived cell lines and clinical material (pleural effusion samples). We identify a range of peptide antigens derived from targets including cancer testis antigens, endogenous retroviruses as well as novel post-translational modification of peptides. This information will facilitate the characterization of the immune response to these antigens to determine which class of antigen is most immunogenic and has the potential to be tested in future vaccine studies.

Metabolic reprogramming in malignant A375 cells treated with a ruthenium (II) complex: insights from GCxGC-TOF/MS metabolomics

INTRODUCTION

Melanoma is an aggressive form of cancer characterised by its high metabolic adaptability that contributes to drug resistance. To this end, ruthenium complexes have emerged as a promising class of compounds in the discovery of cancer drugs due to their unique chemical properties and potential to overcome some of the limitations of conventional chemotherapy. In our previous study, we synthesised, characterised, and performed cytotoxicity tests of a ruthenium (II) complex (GA113) against the malignant A375 melanoma cell line. Our previous findings revealed favourable cytotoxicity, with an IC50 value of 8.76 µM which formed the basis current study.

OBJECTIVE

Elucidate the metabolic mechanism of GA113 in malignant A753 melanoma cells.

METHOD

A two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOF/MS) cellular metabolomics approach was used, and univariate and multivariate statistical methods were applied to the metabolomics data.

RESULTS

33 metabolites were identified as significant discriminators between GA113-treated and untreated A375 melanoma cells. Changes in 19 of these 33 metabolites were mapped to pantothenate and coenzyme A biosynthesis, citrate cycle, cysteine and methionine metabolism, arginine and proline metabolism, and alanine, aspartate, and glutamate metabolism.

CONCLUSION

These findings suggest that GA113 exerts its anticancer effects by disrupting essential metabolic pathways in melanoma cells, which presents a promising therapeutic avenue to target melanoma metabolism.

Metabolic Signaling in the Tumor Microenvironment

Cancer cells must reprogram their metabolism to sustain rapid growth. This is accomplished in part by switching to aerobic glycolysis, uncoupling glucose from mitochondrial metabolism, and performing anaplerosis via alternative carbon sources to replenish intermediates of the tricarboxylic acid (TCA) cycle and sustain oxidative phosphorylation (OXPHOS). While this metabolic program produces adequate biosynthetic intermediates, reducing agents, ATP, and epigenetic remodeling cofactors necessary to sustain growth, it also produces large amounts of byproducts that can generate a hostile tumor microenvironment (TME) characterized by low pH, redox stress, and poor oxygenation. In recent years, the focus of cancer metabolic research has shifted from the regulation and utilization of cancer cell-intrinsic pathways to studying how the metabolic landscape of the tumor affects the anti-tumor immune response. Recent discoveries point to the role that secreted metabolites within the TME play in crosstalk between tumor cell types to promote tumorigenesis and hinder the anti-tumor immune response. In this review, we will explore how crosstalk between metabolites of cancer cells, immune cells, and stromal cells drives tumorigenesis and what effects the competition for resources and metabolic crosstalk has on immune cell function.

Smart molecular designs and applications of activatable organic photosensitizers

Photodynamic therapy (PDT) - which combines light, oxygen and photosensitizers (PS) to generate reactive oxygen species - has emerged as an effective approach for targeted ablation of pathogenic cells with reduced risk of inducing resistance. Some organic PS are now being applied for PDT in the clinic or undergoing evaluation in clinical trials. A limitation of the first-generation organic PS was their potential off-target toxicity. This shortcoming prompted the design of constructs that can be activated by the presence of specific biomolecules - from small biomolecules to large enzymes - in the target cells. Here, we review advances in the design and synthesis of activatable organic PS and their contribution to PDT in the past decade. Important areas of research include novel synthetic methodologies to engineer smart PS with tuneable singlet oxygen generation, their integration into larger constructs such as bioconjugates, and finally, representative examples of their translational potential as antimicrobial and anticancer therapies.

CuO Nanozymes Catalyze Cysteine and Glutathione Depletion Induced Ferroptosis and Cuproptosis for Synergistic Tumor Therapy

The latest research identifies that cysteine (Cys) is one of the key factors in tumor proliferation, metastasis, and recurrence. The direct depletion of intracellular Cys shows a profound antitumor effect. However, using nanozymes to efficiently deplete Cys for tumor therapy has not yet attracted widespread attention. Here, a (3-carboxypropyl) triphenylphosphonium bromide-derived hyaluronic acid-modified copper oxide nanorods (denoted as MitCuOHA) are designed with cysteine oxidase-like, glutathione oxidase-like and peroxidase-like activities to realize Cys depletion and further induce cellular ferroptosis and cuproptosis for synergistic tumor therapy. MitCuOHA nanozymes can efficiently catalyze the depletion of Cys and glutathione (GSH), accompanied by the generation of H2O2 and the subsequent conversion into highly active hydroxyl radicals, thereby successfully inducing ferroptosis in cancer cells. Meanwhile, copper ions released by MitCuOHA under tumor microenvironment stimulation directly bind to lipoylated proteins of the tricarboxylic acid cycle, leading to the abnormal aggregation of lipoylated proteins and subsequent loss of iron-sulfur cluster proteins, which ultimately triggers proteotoxic stress and cell cuproptosis. Both in vitro and in vivo results show the drastically enhanced anticancer efficacy of Cys oxidation catalyzed by the MitCuOHA nanozymes, demonstrating the high feasibility of such catalytic Cys depletion-induced synergistic ferroptosis and cuproptosis therapeutic concept.

Epigenetic repression of de novo cysteine synthetases induces intra-cellular accumulation of cysteine in hepatocarcinoma by up-regulating the cystine uptake transporter xCT

BACKGROUND

The metabolic reprogramming of amino acids is critical for cancer cell growth and survival. Notably, intracellular accumulation of cysteine is often observed in various cancers, suggesting its potential role in alleviating the oxidative stress associated with rapid proliferation. The liver is the primary organ for cysteine biosynthesis, but much remains unknown about the metabolic alterations of cysteine and their mechanisms in hepatocellular carcinoma cells.

METHODS

RNA-seq data from patients with hepatocarcinoma were analyzed using the TNMplot database. The underlying mechanism of the oncogenic alteration of cysteine metabolism was studied in mice implanted with BNL 1ME A.7 R.1 hepatocarcinoma.

RESULTS

Database analysis of patients with hepatocellular carcinoma revealed that the expression of enzymes involved in de novo cysteine synthesis was down-regulated accompanying with increased expression of the cystine uptake transporter xCT. Similar alterations in gene expression have also been observed in a syngeneic mouse model of hepatocarcinoma. The enhanced expression of DNA methyltransferase in murine hepatocarcinoma cells caused methylation of the upstream regions of cysteine synthesis genes, thereby repressing their expression. Conversely, suppression of de novo cysteine synthesis in healthy liver cells induced xCT expression by up-regulating the oxidative-stress response factor NRF2, indicating that reduced de novo cysteine synthesis repulsively increases cystine uptake via enhanced xCT expression, leading to intracellular cysteine accumulation. Furthermore, the pharmacological inhibition of xCT activity decreased intracellular cysteine levels and suppressed hepatocarcinoma tumor growth in mice.

CONCLUSIONS

Our findings indicate an underlying mechanism of the oncogenic alteration of cysteine metabolism in hepatocarcinoma and highlight the efficacy of alteration of cysteine metabolism as a viable therapeutic target in cancer.

Versatile roles of cysteine persulfides in tumor biology

Rewiring the transsulfuration pathway is recognized as a rapid adaptive metabolic response to environmental conditions in cancer cells to support their increased cysteine demand and to produce Reactive Sulfur Species (RSS) including hydrogen sulfide (H2S) and cysteine persulfide. This can directly (via RSS) or indirectly (by supplying Cys) trigger chemical or enzyme catalyzed persulfidation on critical protein cysteine residues to protect them from oxidative damage and to orchestrate protein functions, and thereby contribute to cancer cell plasticity. In this review key aspects of persulfide-mediated biological processes are highlighted and critically discussed in relation to cancer cell survival, bioenergetics, proliferation as well as in tumor angiogenesis, adaptation to hypoxia and oxidative stress, and regulation of epithelial to mesenchymal transition.

The Role of Amino Acids in Non-Enzymatic Antioxidant Mechanisms in Cancer: A Review

Currently, the antioxidant properties of amino acids and their role in the physicochemical processes accompanying oxidative stress in cancer remain unclear. Cancer cells are known to extensively uptake amino acids, which are used as an energy source, antioxidant precursors that reduce oxidative stress in cancer, and as regulators of inhibiting or inducing tumor cell-associated gene expression. This review examines nine amino acids (Cys, His, Phe, Met, Trp, Tyr, Pro, Arg, Lys), which play a key role in the non-enzymatic oxidative process in various cancers. Conventionally, these amino acids can be divided into two groups, in one of which the activity increases (Cys, Phe, Met, Pro, Arg, Lys) in cancer, and in the other, it decreases (His, Trp, Tyr). The review examines changes in the metabolism of nine amino acids in eleven types of oncology. We have identified the main nonspecific mechanisms of changes in the metabolic activity of amino acids, and described direct and indirect effects on the redox homeostasis of cells. In the future, this will help to understand better the nature of life of a cancer cell and identify therapeutic targets more effectively.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

Small molecule nitroalkenes inhibit RAD51-mediated homologous recombination and amplify triple-negative breast cancer cell killing by DNA-directed therapies

Nitro fatty acids (NO 2 -FAs) are endogenously generated lipid signaling mediators from metabolic and inflammatory reactions between conjugated diene fatty acids and nitric oxide or nitrite-derived reactive species. NO 2 -FAs undergo reversible Michael addition with hyperreactive protein cysteine thiolates to induce posttranslational protein modifications that can impact protein function. Herein, we report a novel mechanism of action of natural and non-natural nitroalkenes structurally similar to ( E ) 10-nitro-octadec-9-enoic acid (CP-6), recently de-risked by preclinical Investigational New Drug-enabling studies and Phase 1 and Phase 2 clinical trials and found to induce DNA damage in a TNBC xenograft by inhibiting homologous-recombination (HR)-mediated repair of DNA double-strand breaks (DSB). CP-6 specifically targets Cys319, essential in RAD51-controlled HR-mediated DNA DSB repair in cells. A nitroalkene library screen identified two structurally different nitroalkenes, a non-natural fatty acid [( E ) 8-nitro- nonadec-7-enoic acid (CP-8)] and a dicarboxylate ester [dimethyl ( E )nitro-oct-4-enedioate (CP- 23)] superior to CP-6 in TNBC cells killing, synergism with three different inhibitors of the poly ADP-ribose polymerase (PARP) and γ-IR. CP-8 and CP-23 effectively inhibited γ-IR-induced RAD51 foci formation and HR in a GFP-reported assay but did not affect benign human epithelial cells or cell cycle phases. In vivo, CP-8 and CP-23's efficacies diverged as only CP-8 showed promising anticancer activities alone and combined with the PARP inhibitor talazoparib in an HR-proficient TNBC mouse model. As preliminary preclinical toxicology analysis also suggests CP-8 as safe, our data endorse CP-8 as a novel anticancer molecule for treating cancers sensitive to homologous recombination-mediated DNA repair inhibitors.