Inhibition of hexokinase-2 with targeted liposomal 3-bromopyruvate in an ovarian tumor spheroid model of aerobic glycolysis

PI3K-AKT Pathway Modulation by Thymoquinone Limits Tumor Growth and Glycolytic Metabolism in Colorectal Cancer

Colorectal cancer (CRC) is the third leading cause of death in men and the fourth in women worldwide and is characterized by deranged cellular energetics. Thymoquinone, an active component from Nigella sativa, has been extensively studied against cancer, however, its role in affecting deregulated cancer metabolism is largely unknown. Further, the phosphoinositide 3-kinase (PI3K) pathway is one of the most activated pathways in cancer and its activation is central to most deregulated metabolic pathways for supporting the anabolic needs of growing cancer cells. Herein, we provide evidence that thymoquinone inhibits glycolytic metabolism (Warburg effect) in colorectal cancer cell lines. Further, we show that such an abrogation of deranged cell metabolism was due, at least in part, to the inhibition of the rate-limiting glycolytic enzyme, Hexokinase 2 (HK2), via modulating the PI3/AKT axis. While overexpression of HK2 showed that it is essential for fueling glycolytic metabolism as well as sustaining tumorigenicity, its pharmacologic and/or genetic inhibition led to a reduction in the observed effects. The results decipher HK2 mediated inhibitory effects of thymoquinone in modulating its glycolytic metabolism and antitumor effects. In conclusion, we provide evidence of metabolic perturbation by thymoquinone in CRC cells, highlighting its potential to be used/repurposed as an antimetabolite drug, though the latter needs further validation utilizing other suitable cell and/or preclinical animal models.

Mitochondria-targeted nanoplatforms for enhanced photodynamic therapy against hypoxia tumor

Background

Photodynamic therapy (PDT) is a promising therapeutic modality that can convert oxygen into cytotoxic reactive oxygen species (ROS) via photosensitizers to halt tumor growth. However, hypoxia and the unsatisfactory accumulation of photosensitizers in tumors severely diminish the therapeutic effect of PDT. In this study, a multistage nanoplatform is demonstrated to overcome these limitations by encapsulating photosensitizer IR780 and oxygen regulator 3-bromopyruvate (3BP) in poly (lactic-co-glycolic acid) (PLGA) nanocarriers.

Results

The as-synthesized nanoplatforms penetrated deeply into the interior region of tumors and preferentially remained in mitochondria due to the intrinsic characteristics of IR780. Meanwhile, 3BP could efficiently suppress oxygen consumption of tumor cells by inhibiting mitochondrial respiratory chain to further improve the generation of ROS. Furthermore, 3BP could abolish the excessive glycolytic capacity of tumor cells and lead to the collapse of ATP production, rendering tumor cells more susceptible to PDT. Successful tumor inhibition in animal models confirmed the therapeutic precision and efficiency. In addition, these nanoplatforms could act as fluorescence (FL) and photoacoustic (PA) imaging contrast agents, effectuating imaging-guided cancer treatment.

Conclusions

This study provides an ideal strategy for cancer therapy by concurrent oxygen consumption reduction, oxygen-augmented PDT, energy supply reduction, mitochondria-targeted/deep-penetrated nanoplatforms and PA/FL dual-modal imaging guidance/monitoring. It is expected that such strategy will provide a promising alternative to maximize the performance of PDT in preclinical/clinical cancer treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01196-6.

CircHIPK3/miR-381-3p axis modulates proliferation, migration, and glycolysis of lung cancer cells by regulating the AKT/mTOR signaling pathway

Lung cancer is a lethal malignancy. Plenty of circular RNAs (circRNAs) have been identified to be the vital regulators in lung cancer development. Here, we intended to clarify the functional role of circRNA HIPK3 (circHIPK3, also called hsa_circ_0021593) and its underlying mechanism of action. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was employed to evaluate the levels of circHIPK3 and miR-381-3p. Cell viability and apoptosis rate were monitored by Cell Counting Kit-8 assay and flow cytometry, respectively. Cell migration was estimated through the Transwell assay. To assess glycolysis, commercial kits were utilized to measure the levels of glucose and lactate and the enzyme activity of hexokinase-2 (HK2). Expression of related proteins was detected via western blot analysis. The target connection between circHIPK3 and miR-381-3p was validated by dual-luciferase reporter, RIP, and pull-down assays. The role of circHIPK3 in vivo was determined via the xenograft assay. CircHIPK3 was upregulated, while miR-381-3p was downregulated in lung cancer tissues and cells. And circHIPK3 deficiency inhibited lung cancer progression by lowering cell proliferation, migration, glycolysis, and promoting apoptosis of lung cancer cells in vitro. MiR-381-3p was a target of circHIPK3, and miR-381-3p interference alleviated circHIPK3 knockdown-induced lung cancer progression inhibition. CircHIPK3 could activate the protein kinase B/mammalian target of rapamycin (AKT/mTOR) signaling pathway. Moreover, circHIPK3 knockdown suppressed tumor growth in vivo by inactivating the AKT/mTOR signaling pathway. In conclusion, the silencing of circHIPK3 inhibited lung cancer progression, at least in part, by sponging miR-381-3p and inactivating the AKT/mTOR signaling pathway.

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.

Exploiting Mitochondrial Vulnerabilities to Trigger Apoptosis Selectively in Cancer Cells

The transformation of normal cells to the cancerous stage involves multiple genetic changes or mutations leading to hyperproliferation, resistance to apoptosis, and evasion of the host immune system. However, to accomplish hyperproliferation, cancer cells undergo profound metabolic reprogramming including oxidative glycolysis and acidification of the cytoplasm, leading to hyperpolarization of the mitochondrial membrane. The majority of drug development research in the past has focused on targeting DNA replication, repair, and tubulin polymerization to induce apoptosis in cancer cells. Unfortunately, these are not cancer-selective targets. Recently, researchers have started focusing on metabolic, mitochondrial, and oxidative stress vulnerabilities of cancer cells that can be exploited as selective targets for inducing cancer cell death. Indeed, the hyperpolarization of mitochondrial membranes in cancer cells can lead to selective importing of mitocans that can induce apoptotic effects. Herein, we will discuss recent mitochondrial-selective anticancer compounds (mitocans) that have shown selective toxicity against cancer cells. Increased oxidative stress has also been shown to be very effective in selectively inducing cell death in cancer cells. This oxidative stress could lead to mitochondrial dysfunction, which in turn will produce more reactive oxygen species (ROS). This creates a vicious cycle of mitochondrial dysfunction and ROS production, irreversibly leading to cell suicide. We will also explore the possibility of combining these compounds to sensitize cancer cells to the conventional anticancer agents. Mitocans in combination with selective oxidative-stress producing agents could be very effective anticancer treatments with minimal effect on healthy cells.

Tumor Energy Metabolism and Potential of 3-Bromopyruvate as an Inhibitor of Aerobic Glycolysis: Implications in Tumor Treatment

Tumor formation and growth depend on various biological metabolism processes that are distinctly different with normal tissues. Abnormal energy metabolism is one of the typical characteristics of tumors. It has been proven that most tumor cells highly rely on aerobic glycolysis to obtain energy rather than mitochondrial oxidative phosphorylation (OXPHOS) even in the presence of oxygen, a phenomenon called “Warburg effect”. Thus, inhibition of aerobic glycolysis becomes an attractive strategy to specifically kill tumor cells, while normal cells remain unaffected. In recent years, a small molecule alkylating agent, 3-bromopyruvate (3-BrPA), being an effective glycolytic inhibitor, has shown great potential as a promising antitumor drug. Not only it targets glycolysis process, but also inhibits mitochondrial OXPHOS in tumor cells. Excellent antitumor effects of 3-BrPA were observed in cultured cells and tumor-bearing animal models. In this review, we described the energy metabolic pathways of tumor cells, mechanism of action and cellular targets of 3-BrPA, antitumor effects, and the underlying mechanism of 3-BrPA alone or in combination with other antitumor drugs (e.g., cisplatin, doxorubicin, daunorubicin, 5-fluorouracil, etc.) in vitro and in vivo. In addition, few human case studies of 3-BrPA were also involved. Finally, the novel chemotherapeutic strategies of 3-BrPA, including wafer, liposomal nanoparticle, aerosol, and conjugate formulations, were also discussed for future clinical application.

Up-regulation of Key Glycolysis Proteins in Cancer Development

In rapid proliferating cancer cells, there is a need for fast ATP and lactate production, therefore cancer cells turn off oxidative phosphorylation and turn on the so called "Warburg effect". This regulating the expression of genes involved in glycolysis. According to many studies, glucose transporter 1, which supplies glucose to the cell, is the most abundantly expressed transporter in cancer cells. Hexokinase 2, is one of four hexokinase isoenzymes, is also another highly expressed enzyme in cancer cells and it functions to enhance the glycolytic rate. The up-regulation of these two proteins has been established as an important factor in promoting development and metastasis in many types of cancer. Furthermore, other enzymes involved in glycolysis pathway such as phosphoglucose isomerase and glyceraldehyde 3-phosphate dehydrogenase, exhibit additional functions in promoting tumor growth in a non-glycolytic way. This review demonstrates the pivotal role of GLUT1, HK2, PGI and GAPDH in cancer development. In particular, we look at how the multifunctional proteins, PGI and GAPDH, affect cancer cell survival. We also present various clinical cancer cases in terms of the overexpression of selected proteins, which may be considered as a therapeutic target.

The Sweet Surrender: How Myeloid Cell Metabolic Plasticity Shapes the Tumor Microenvironment

Immune cells are one of the most versatile cell types, as they can tailor their metabolic activity according to their required function. In response to diverse environmental cues, immune cells undergo metabolic reprogramming to support their differentiation, proliferation and pro-inflammatory effector functions. To meet a dramatic surge in energetic demand, immune cells rewire their metabolism to utilize aerobic glycolysis. This preferential use of glycolysis even under aerobic conditions is well established in tumor cells, and is known as the "Warburg effect." Tumor cells avidly use glucose for aerobic glycolysis, thereby creating a nutrient-starved microenvironment, outcompeting T cells for glucose, and directly inhibiting T-cell anti-tumoral effector function. Given that both immune and tumor cells use similar modes of metabolism in the tumor stroma, it is imperative to identify a therapeutic window in which immune-cell and tumor-cell glycolysis can be specifically targeted. In this review, we focus on the Warburg metabolism as well as other metabolic pathways of myeloid cells, which comprise a notable niche in the tumor environment and promote the growth and metastasis of malignant tumors. We examine how differential immune-cell activation triggers metabolic fate, and detail how this forbidding microenvironment succeeds in shutting down the vigorous anti-tumoral response. Finally, we highlight emerging therapeutic concepts that aim to target immune-cell metabolism. Improving our understanding of immunometabolism and immune-cell commitment to specific metabolic fates will help identify alternative therapeutic approaches to battle this intractable disease.

Ketoconazole and Posaconazole Selectively Target HK2-expressing Glioblastoma Cells

PURPOSE

Hexokinase II (HK2) protein expression is elevated in glioblastoma (GBM), and we have shown that HK2 could serve as an effective therapeutic target for GBM. Here, we interrogated compounds that target HK2 effectively and restrict tumor growth in cell lines, patient-derived glioma stem cells (GSCs), and mouse models of GBM.Experimental Design: We performed a screen using a set of 15 drugs that were predicted to inhibit the HK2-associated gene signature. We next determined the EC₅₀ of the compounds by treating glioma cell lines and GSCs. Selected compounds showing significant impact in vitro were used to treat mice and examine their effect on survival and tumor characteristics. The effect of compounds on the metabolic activity in glioma cells was also assessed in vitro.

RESULTS

This screen identified the azole class of antifungals as inhibitors of tumor metabolism. Among the compounds tested, ketoconazole and posaconazole displayed the greatest inhibitory effect on GBM both in vitro and in vivo. Treatment of mice bearing GBM with ketoconazole and posaconazole increased their survival, reduced tumor cell proliferation, and decreased tumor metabolism. In addition, treatment with azoles resulted in increased proportion of apoptotic cells.

CONCLUSIONS

Overall, we provide evidence that azoles exert their effect by targeting genes and pathways regulated by HK2. These findings shed light on the action of azoles in GBM. Combined with existing literature and preclinical results, these data support the value of repurposing azoles in GBM clinical trials.

Enhancing anticancer effects, decreasing risks and solving practical problems facing 3-bromopyruvate in clinical oncology: 10 years of research experience

3-Bromopyruvate (3BP) is a promising powerful general anticancer agent. Unfortunately, 3BP release faces many practical and biochemical problems in clinical human oncology, for example, 3BP induces burning venous sensation (during intravenous infusion) and rapid inactivation by thiol groups of glutathione and proteins. 3BP exhibits resistance in glutathione-rich tumors without being able to exert selective targeting. 3BP does not cross the blood–brain barrier and cannot treat nervous system tumors. Importantly, 3BP cannot persist in tumor tissues due to the phenomenon of enhanced permeability and retention effect. Here, the author presents the practical solutions for clinical problems facing 3BP use in clinical oncology, based on over 10 years of experience in 3BP research. Crude (unformulated 3BP that is purchased from chemical companies without being formulated in liposomes or other nanocarriers) should not be administered in clinical oncology. Instead, 3BP is better formulated with liposomes, polyethylene glycol (PEG), PEGylated liposomes (stealth liposomes) or perillyl alcohol that are used currently with many chemotherapeutics for treating clinical tumors in cancer patients. Formulating 3BP with targeted liposomes, for example, with folate, transferrin or other ligands, improves tumor targeting. Formulating 3BP with liposomes, PEG, stealth liposomes or perillyl alcohol may improve its pharmacokinetics, hide it from thiols in the circulation, protect it from serum proteins and enzymes, prevent burning sensation, prolong 3BP’s longevity and facilitate crossing the BBB. Formulating 3BP with stealth liposomes protects 3BP from the reticuloendothelial cells. Liposomal 3BP formulations may retain 3BP better inside the relatively large tumor capillary pores (abolish enhanced permeability and retention effect) sparing normal tissues, facilitate new delivery routes for 3BP (eg, topical and intranasal 3BP administration using perillyl alcohol) and improve cancer cytotoxicity. Formulating 3BP may be promising in overcoming many obstacles in clinical oncology.

Glutathione in Ovarian Cancer: A Double-Edged Sword

Glutathione (GSH) has several roles in a cell, such as a reactive oxygen species (ROS) scavenger, an intervenient in xenobiotics metabolism and a reservoir of cysteine. All of these activities are important in the maintenance of normal cells homeostasis but can also constitute an advantage for cancer cells, allowing disease progression and resistance to therapy. Ovarian cancer is the major cause of death from gynaecologic disease and the second most common gynaecologic malignancy worldwide. In over 50 years, the overall survival of patients diagnosed with epithelial ovarian cancer has not changed, regardless of the efforts concerning early detection, radical surgery and new therapeutic approaches. Late diagnosis and resistance to therapy are the main causes of this outcome, and GSH is profoundly associated with chemoresistance to platinum salts, which, together with taxane-based chemotherapy and surgery, are the main therapy strategies in ovarian cancer treatment. Herein, we present some insights into the role of GSH in the poor prognosis of ovarian cancer, and also point out how some strategies underlying the dependence of ovarian cancer cells on GSH can be further used to improve the effectiveness of therapy.

Inihibition of Glycolysis by Using a Micro/Nano-Lipid Bromopyruvic Chitosan Carrier as a Promising Tool to Improve Treatment of Hepatocellular Carcinoma

Glucose consumption in many types of cancer cells, in particular hepatocellular carcinoma (HCC), was followed completely by over-expression of type II hexokinase (HKII). This evidence has been used in modern pharmacotherapy to discover therapeutic target against glycolysis in cancer cells. Bromopyruvate (BrPA) exhibits antagonist property against HKII and can be used to inhibit glycolysis. However, the clinical application of BrPA is mostly combined with inhibition effect for healthy cells particularly erythrocytes. Our strategy is to encapsulate BrPA in a selected vehicle, without any leakage of BrPA out of vehicle in blood stream. This structure has been constructed from chitosan embedded into oleic acid layer and then coated by dual combination of folic acid (FA) and bovine serum albumin (BSA). With FA as specific ligand for cancer folate receptor and BSA that can be an easy binding for hepatocytes, they can raise the potential selection of carrier system.

Warburg effect, hexokinase-II, and radioresistance of laryngeal carcinoma

Radiotherapy is now widely used as a part of multidisciplinary treatment approaches for advanced laryngeal carcinoma and preservation of laryngeal function. However, the mechanism of the radioresistance is still unclear. Some studies have revealed that the Warburg effect promotes the radioresistance of various malignant tumors, including laryngeal carcinoma. Among the regulators involved in the Warburg effect, hexokinase-II (HK-II) is a crucial glycolytic enzyme that catalyzes the first essential step of glucose metabolism. HK-II is reportedly highly expressed in some human solid carcinomas by many studies. But for laryngeal carcinoma, there is only one. Till now, no studies have directly targeted inhibited HK-II and enhanced the radiosensitivity of laryngeal carcinoma. Accumulating evidence has shown that dysregulated signaling pathways often result in HK-II overexpression. Here, we summarize recent advances in understanding the association among the Warburg effect, HK-II, and the radioresistance of laryngeal carcinoma. We speculate on the feasibility of enhancing radiosensitivity by targeted inhibiting HK-II signaling pathways in laryngeal carcinoma, which may provide a novel anticancer therapy.

Chaperone-mediated autophagy substrate proteins in cancer

All intracellular proteins undergo continuous synthesis and degradation. Chaperone-mediated autophagy (CMA) is necessary to maintain cellular homeostasis through turnover of cytosolic proteins (substrate proteins). This degradation involves a series of substrate proteins including both cancer promoters and suppressors. Since activating or inhibiting CMA pathway to treat cancer is still debated, targeting to the CMA substrate proteins provides a novel direction. We summarize the cancer-associated substrate proteins which are degraded by CMA. Consequently, CMA substrate proteins catalyze the glycolysis which contributes to the Warburg effect in cancer cells. The fact that the degradation of substrate proteins based on the CMA can be altered by posttranslational modifications such as phosphorylation or acetylation. In conclusion, targeting to CMA substrate proteins develops into a new anticancer therapeutic approach.

Interleukin-22 promotes aerobic glycolysis associated with tumor progression via targeting hexokinase-2 in human colon cancer cells

Interleukin-22 has been explored extensively in human cancer, but its functions and underlying mechanisms are incompletely understood. Here, we show that aberrant interleukin-22 expression facilitates aerobic glycolysis in colon cancer cells. Elevated interleukin-22 mRNA expression was observed and positively correlated with hexokinase-2 in colon cancer tissues. In vitro, interleukin-22 enhanced glucose consumption and lactate production via targeting hexokinase-2 in colon cancer cells. Moreover, the transcriptional factor c-Myc and signal transducer and activator of transcription 3 were involved in interleukin-22-induced up-regulation of hexokinase-2. We further demonstrated that hexokinase-2 partly accounted for interleukin-22-mediated cellular proliferation in DLD-1 cells. In vivo, our data demonstrated that interleukin-22 significantly promoted tumor growth along with elevated expression of c-Myc and hexokinase-2 in mice. In summary, our findings provide a new perspective on the pro-inflammatory cytokine interleukin-22 in promoting aerobic glycolysis associated with tumor progression in human colon cancer cells.

The HK2 Dependent "Warburg Effect" and Mitochondrial Oxidative Phosphorylation in Cancer: Targets for Effective Therapy with 3-Bromopyruvate

This review summarizes the current state of knowledge about the metabolism of cancer cells, especially with respect to the "Warburg" and "Crabtree" effects. This work also summarizes two key discoveries, one of which relates to hexokinase-2 (HK2), a major player in both the "Warburg effect" and cancer cell immortalization. The second discovery relates to the finding that cancer cells, unlike normal cells, derive as much as 60% of their ATP from glycolysis via the "Warburg effect", and the remaining 40% is derived from mitochondrial oxidative phosphorylation. Also described are selected anticancer agents which generally act as strong energy blockers inside cancer cells. Among them, much attention has focused on 3-bromopyruvate (3BP). This small alkylating compound targets both the "Warburg effect", i.e., elevated glycolysis even in the presence oxygen, as well as mitochondrial oxidative phosphorylation in cancer cells. Normal cells remain unharmed. 3BP rapidly kills cancer cells growing in tissue culture, eradicates tumors in animals, and prevents metastasis. In addition, properly formulated 3BP shows promise also as an effective anti-liver cancer agent in humans and is effective also toward cancers known as "multiple myeloma". Finally, 3BP has been shown to significantly extend the life of a human patient for which no other options were available. Thus, it can be stated that 3BP is a very promising new anti-cancer agent in the process of undergoing clinical development.