Targeting Cancer Cells using 3-bromopyruvate for Selective Cancer Treatment

The cubosome-based nanoplatforms in cancer therapy: Seeking new paradigms for cancer theranostics

Lyotropic liquid crystals are self-assembled, non-lamellar, and mesophase nanostructured materials that have garnered significant attention as drug carriers. Cubosomes, a subtype of lyotropic liquid crystalline nanoparticles, possess three-dimensional structures that display bicontinuous cubic liquid-crystalline patterns. These patterns are formed through the self-organization of unsaturated monoglycerides (amphphilic lipids such as glyceryl monooleate or phytantriol), followed by stabilization using steric polymers (poloxamers). Owing to their bicontinuous structure and steric polymer-based stabilization, cubosomes have been demonstrated to possess greater entrapment efficiency for hydrophobic drugs compared to liposomes, while also exhibiting high stability. In the past decade, there has been significant interest in cubosomes due to their ability to deliver therapeutic and contrast agents for cancer treatment and imaging with minimal side effects, establishing them as a safe and effective approach. Concerning these advantages, the present review elaborates on the general aspects, composition, and preparation techniques of cubosomes, followed by explanations of their mechanisms of drug loading and release patterns. Furthermore, the review provides meticulous discussions on the use of cubosomes in the treatment and imaging of various types of cancer, culminating in the enumeration of patents related to cubosome-based drug delivery systems.

Stimuli-responsive cancer nanomedicines inhibit glycolysis and impair redox homeostasis

The solid tumors are characterized with oxidative stress and metabolic reprogramming, which has been independently used for targeted tumor monotherapy. However, the potential of targeting metabolism-redox circuit in tumor therapy has long been neglected. Herein, we report a hybrid nanocarrier for concurrent targeting of glycolysis and redox balance in the current work. The nanocarriers are made of pH- and ATP-responsive zeolitic imidazolate framework (ZIF-8) as the porous core that was further coated with poloxamer 407 as the steric stabilizer. Two active cargos, glucose oxidase (GOx) and 3-bromopyruvate (3-BrPA) were co-loaded in the core of nanocarrier. GOx is well-known for its ability of producing hydrogen peroxide at the expense of glucose and oxygen. 3-BrPA can reduce oxygen and glucose consumption through glycolysis, which sensitized cancer cells to GOx-induced apoptosis. At the cellular level, the hybrid nanocarrier significantly impaired the redox balance in the liver hepatocellular carcinoma cell line (HepG2), as evidenced by the depletion of glutathione and boost of reactive oxygen species. The potency of hybrid nanocarrier in terms of suppressing HepG2 cell energy metabolism was proven by the exhaustion of ATP. As a consequence, cell viability was greatly reduced. The in vivo efficacy of hybrid nanocarriers was demonstrated in HepG2 tumor-bearing mice. The current work presents an approach of targeting metabolism-redox circuit for tumor treatment, which may enrich the available anti-tumor strategies. STATEMENT OF SIGNIFICANCE: Metabolic alterations and elevated reactive oxygen species (ROS) are two characteristics of cancer. The metabolic patterns of cancer cells are elaborately reprogrammed to enable the rapid propagation of cancer cells. However, the potential of targeting the metabolism-redox circuit in anti-tumor therapy has long been neglected. As a proof-of-concept, we report an engineered stimuli-responsive nanomedicine that can eradicate cancer cells via cooperative glycolysis inhibition and redox impairment. The current work presents an approach of targeting the metabolism-redox circuit for tumor treatment, which may enrich the available anti-tumor strategies.

Cancer on-target: Selective enhancement of 3-bromopyruvate action by an electromagnetic field in vitro

Cancer is one of the leading causes of death in the modern world. Nowadays, most often treatment methods used in clinical oncology are drug therapies applied as monotherapy or combined therapy. Additionally, recent studies focus on developing approaches with the use of a drug in combination with other factors, not only chemical, to improve the probability and magnitude of therapeutic responses and reduce the possibility of chemoresistance. Such a promising factor seems to be an electromagnetic field (EMF) application. Here, we tested the effect of continuous or pulsed EMF on human cancer cells of different origin treated or not with 3-bromopyruvate, a small and powerful alkylating agent with a broad spectrum of anticancer activities. We provide strong evidence suggesting that ELF-EMF potentiates the anti-cancer activity of 3BP in human cancer cells through inhibition of TNFα secretion leading to irreversible p21/p27-dependent G2/M cell cycle arrest and finally cancer cell death. Our findings suggest a novel approach combining pharmacotherapy with ELF-EMF. In conclusion, electromagnetic field seems to be a potential modulator of anti-cancer efficacy of 3BP while combined therapy offers off-target activity. These features contribute to the development of innovative therapeutic strategies for cancer treatment.

Extracellular acidity in tumor tissue upregulates programmed cell death protein 1 expression on tumor cells via proton-sensing G protein-coupled receptors

Acidity in the tumor microenvironment has been reported to promote cancer growth and metastasis. In our study, we examined a potential relation between extracellular acidity and expression level of the immune checkpoint molecule programmed cell death protein 1 (PD-L1) in murine squamous cell carcinoma (SCC) and melanoma cell lines. PD-L1 expression in the tumor cells was upregulated by culturing in a low pH culture medium. Tumor-bearing mice were allowed to ingest sodium bicarbonate, resulting in neutralization of acidity in the tumor tissue, a decrease in PD-L1 expression in tumor cells and suppression of tumor growth in vivo. Proton-sensing G protein-coupled receptors, T-cell death-associated gene 8 (TDAG8) and ovarian cancer G-protein-coupled receptor 1 (OGR1), were upregulated by low pH, and essentially involved in the acidity-induced elevation of PD-L1 expression in the tumor cells. Human head and neck SCC RNAseq data from the Cancer Genome Atlas also suggested a statistically significant correlation between expression levels of the proton sensors and PD-L1 mRNA expression. These findings strongly suggest that neutralization of acidity in tumor tissue may result in reduction of PD-L1 expression, potentially leading to inhibition of an immune checkpoint and augmentation of antitumor immunity.

Overcoming Chemoresistance: Altering pH of Cellular Compartments by Chloroquine and Hydroxychloroquine

Resistance to the anti-cancer effects of chemotherapeutic agents (chemoresistance) is a major issue for people living with cancer and their providers. A diverse set of cellular and inter-organellar signaling changes have been implicated in chemoresistance, but it is still unclear what processes lead to chemoresistance and effective strategies to overcome chemoresistance are lacking. The anti-malaria drugs, chloroquine (CQ) and its derivative hydroxychloroquine (HCQ) are being used for the treatment of various cancers and CQ and HCQ are used in combination with chemotherapeutic drugs to enhance their anti-cancer effects. The widely accepted anti-cancer effect of CQ and HCQ is their ability to inhibit autophagic flux. As diprotic weak bases, CQ and HCQ preferentially accumulate in acidic organelles and neutralize their luminal pH. In addition, CQ and HCQ acidify the cytosolic and extracellular environments; processes implicated in tumorigenesis and cancer. Thus, the anti-cancer effects of CQ and HCQ extend beyond autophagy inhibition. The present review summarizes effects of CQ, HCQ and proton pump inhibitors on pH of various cellular compartments and discuss potential mechanisms underlying their pH-dependent anti-cancer effects. The mechanisms considered here include their ability to de-acidify lysosomes and inhibit autophagosome lysosome fusion, to de-acidify Golgi apparatus and secretory vesicles thus affecting secretion, and to acidify cytoplasm thus disturbing aerobic metabolism. Further, we review the ability of these agents to prevent chemotherapeutic drugs from accumulating in acidic organelles and altering their cytosolic concentrations.

Delphinidin Increases the Sensitivity of Ovarian Cancer Cell Lines to 3-Bromopyruvate

3-Bromopyruvic acid (3-BP) is a promising anticancer compound. Two ovary cancer (OC) cell lines, PEO1 and SKOV3, showed relatively high sensitivity to 3-BP (half maximal inhibitory concentration (IC₅₀) of 18.7 and 40.5 µM, respectively). However, the further sensitization of OC cells to 3-BP would be desirable. Delphinidin (D) has been reported to be cytotoxic for cancer cell lines. We found that D was the most toxic for PEO1 and SKOV3 cells from among several flavonoids tested. The combined action of 3-BP and D was mostly synergistic in PEO1 cells and mostly weakly antagonistic in SKOV3 cells. The viability of MRC-5 fibroblasts was not affected by both compounds at concentrations of up to 100 µM. The combined action of 3-BP and D decreased the level of ATP and of dihydroethidium (DHE)-detectable reactive oxygen species (ROS), cellular mobility and cell staining with phalloidin and Mitotracker Red in both cell lines but increased the 2’,7’-dichlorofluorescein (DCFDA)-detectable ROS level and decreased the mitochondrial membrane potential and mitochondrial mass only in PEO1 cells. The glutathione level was increased by 3-BP+D only in SKOV3 cells. These differences may contribute to the lower sensitivity of SKOV3 cells to 3-BP+D. Our results point to the possibility of sensitization of at least some OC cells to 3-BP by D.

Cancer cell metabolism: Rewiring the mitochondrial hub

To adapt to tumoral environment conditions or even to escape chemotherapy, cells rapidly reprogram their metabolism to handle adversities and survive. Given the rapid rise of studies uncovering novel insights and therapeutic opportunities based on the role of mitochondria in tumor metabolic programing and therapeutics, this review summarizes most significant developments in the field. Taking in mind the key role of mitochondria on carcinogenesis and tumor progression due to their involvement on tumor plasticity, metabolic remodeling, and signaling re-wiring, those organelles are also potential therapeutic targets. Among other topics, we address the recent data intersecting mitochondria as of prognostic value and staging in cancer, by mitochondrial DNA (mtDNA) determination, and current inhibitors developments targeting mtDNA, OXPHOS machinery and metabolic pathways. We contribute for a holistic view of the role of mitochondria metabolism and directed therapeutics to understand tumor metabolism, to circumvent therapy resistance, and to control tumor development.

Physicochemical and in vitro cytotoxicity studies of inclusion complex between gemcitabine and cucurbit[7]uril host

Gemcitabine, a cytostatic drug from the pyrimidine antimetabolite group, exhibits limited storage stability and numerous side effects during therapy. One of the strategies to improve the effectiveness of therapy with such drugs is the use of supramolecular nano-containers, including dendrimers and macrocyclic compounds. The ability of gemcitabine to attach a proton in an aqueous environment necessitates the search for a carrier that is well-tolerated by an organism and capable of supramolecular binding of a ligand (drug) in a cationic form. In the current study a promising strategy was tested for using cucurbituril Q7 to bind gemcitabine cations for its efficient intracellular delivery on three selected cancer cell lines (MOLT4, THP-1 and U937). Based on physicochemical studies (equilibrium dialysis, UV and ¹H NMR titrations, DOSY ¹H NMR measurements, DSC calorimetry) and cytotoxicity tests on cells with a free and blocked hENT1 transporter, the conclusion was drawn about the binding and penetration of the cucurbituril-drug complex into cancer cells.

Dual inhibition of glycolysis and autophagy as a therapeutic strategy in the treatment of Ehrlich ascites carcinoma

Cancer cells have extra biosynthetic demands to sustain cell growth and redox homeostasis. Glycolysis and autophagy are crucial to fuel and recycle these biosynthetic demands. This plasticity of cancer cell metabolism participates in therapy resistances. The current study was designed to assess the therapeutic efficacy of dual targeting of glycolysis and autophagy in cancer. Using 3-bromopyruvate (3-BP; antiglycolytic inhibitor) and hydroxychloroquine (HCQ; autophagy inhibitor), we demonstrate their antitumor activity in Ehrlich ascites carcinoma (EAC)-bearing mice. A combination of 3-BP and HCQ significantly decreases tumor ascitic volume and cell count as compared with the EAC group and individual treatment groups. The enhanced antitumor activity is accompanied by hexokinase inactivation, inhibition of cellular protective autophagy, elevated antioxidant activity, and reduced oxidative stress levels. Together, these results suggest targeting both pathways in cancer as an effective therapeutic strategy. Further studies are required to validate this strategy in different cancer models and preclinical trials.

Diverse Stakeholders of Tumor Metabolism: An Appraisal of the Emerging Approach of Multifaceted Metabolic Targeting by 3-Bromopyruvate

Malignant cells possess a unique metabolic machinery to endure unobstructed cell survival. It comprises several levels of metabolic networking consisting of 1) upregulated expression of membrane-associated transporter proteins, facilitating unhindered uptake of substrates; 2) upregulated metabolic pathways for efficient substrate utilization; 3) pH and redox homeostasis, conducive for driving metabolism; 4) tumor metabolism-dependent reconstitution of tumor growth promoting the external environment; 5) upregulated expression of receptors and signaling mediators; and 6) distinctive genetic and regulatory makeup to generate and sustain rearranged metabolism. This feat is achieved by a "battery of molecular patrons," which acts in a highly cohesive and mutually coordinated manner to bestow immortality to neoplastic cells. Consequently, it is necessary to develop a multitargeted therapeutic approach to achieve a formidable inhibition of the diverse arrays of tumor metabolism. Among the emerging agents capable of such multifaceted targeting of tumor metabolism, an alkylating agent designated as 3-bromopyruvate (3-BP) has gained immense research focus because of its broad spectrum and specific antineoplastic action. Inhibitory effects of 3-BP are imparted on a variety of metabolic target molecules, including transporters, metabolic enzymes, and several other crucial stakeholders of tumor metabolism. Moreover, 3-BP ushers a reconstitution of the tumor microenvironment, a reversal of tumor acidosis, and recuperative action on vital organs and systems of the tumor-bearing host. Studies have been conducted to identify targets of 3-BP and its derivatives and characterization of target binding for further optimization. This review presents a brief and comprehensive discussion about the current state of knowledge concerning various aspects of tumor metabolism and explores the prospects of 3-BP as a safe and effective antineoplastic agent.