SUMOylation controls the binding of hexokinase 2 to mitochondria and protects against prostate cancer tumorigenesis

Recent research and development of inhibitors targeting sentrin-specific protease 1 for the treatment of cancers

Small ubiquitin-like modifier (SUMO)/sentrin-specific protease 1 (SENP1), is a cysteine protease that promotes SUMO maturation and deSUMOylation of target proteins and regulates transcription factors or co-regulatory factors to mediate gene transcription. Many studies have shown that SENP1 is the driving factor for a multitude of cancers including prostate cancer, liver cancer, and breast cancer. Inhibition of SENP1 activity has been proved to inhibit the survival, proliferation, invasion, and migration of cancer cells, and increase their chemical and radiation sensitivity. Therefore, SENP1 is a promising anti-tumor target. At present, peptide inhibitors of SENP1 have entered clinical trials. Recently, many small molecule compounds and natural products were synthesized and identified as SENP1 inhibitors, and showed good tumor inhibitory activity in vitro and in vivo. This review summarizes the structure, physiological function, and role of SENP1 in tumorigenesis and development, focusing on the design and discovery of small molecule inhibitors of SENP1 from the perspective of medicinal chemistry, providing ideas for the development and research of small molecule inhibitors of SENP1 in the future.

Tumor glycolysis, an essential sweet tooth of tumor cells

Cancer cells undergo metabolic alterations to meet the immense demand for energy, building blocks, and redox potential. Tumors show glucose-avid and lactate-secreting behavior even in the presence of oxygen, a process known as aerobic glycolysis. Glycolysis is the backbone of cancer cell metabolism, and cancer cells have evolved various mechanisms to enhance it. Glucose metabolism is intertwined with other metabolic pathways, making cancer metabolism diverse and heterogeneous, where glycolysis plays a central role. Oncogenic signaling accelerates the metabolic activities of glycolytic enzymes, mainly by enhancing their expression or by post-translational modifications. Aerobic glycolysis ferments glucose into lactate which supports tumor growth and metastasis by various mechanisms. Herein, we focused on tumor glycolysis, especially its interactions with the pentose phosphate pathway, glutamine metabolism, one-carbon metabolism, and mitochondrial oxidation. Further, we describe the role and regulation of key glycolytic enzymes in cancer. We summarize the role of lactate, an end product of glycolysis, in tumor growth, and the metabolic adaptations during metastasis. Lastly, we briefly discuss limitations and future directions to improve our understanding of glucose metabolism in cancer.

Druggable Metabolic Vulnerabilities Are Exposed and Masked during Progression to Castration Resistant Prostate Cancer

There is an urgent need for exploring new actionable targets other than androgen receptor to improve outcome from lethal castration-resistant prostate cancer. Tumor metabolism has reemerged as a hallmark of cancer that drives and supports oncogenesis. In this regard, it is important to understand the relationship between distinctive metabolic features, androgen receptor signaling, genetic drivers in prostate cancer, and the tumor microenvironment (symbiotic and competitive metabolic interactions) to identify metabolic vulnerabilities. We explore the links between metabolism and gene regulation, and thus the unique metabolic signatures that define the malignant phenotypes at given stages of prostate tumor progression. We also provide an overview of current metabolism-based pharmacological strategies to be developed or repurposed for metabolism-based therapeutics for castration-resistant prostate cancer.

Small Extracellular Vesicles and Their Involvement in Cancer Resistance: An Up-to-Date Review

In recent years, tremendous progress has been made in understanding the roles of extracellular vesicles (EVs) in cancer. Thanks to advancements in molecular biology, it has been found that the fraction of EVs called exosomes or small EVs (sEVs) modulates the sensitivity of cancer cells to chemotherapeutic agents by delivering molecularly active non-coding RNAs (ncRNAs). An in-depth analysis shows that two main molecular mechanisms are involved in exosomal modified chemoresistance: (1) translational repression of anti-oncogenes by exosomal microRNAs (miRs) and (2) lack of translational repression of oncogenes by sponging of miRs through long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). At the cellular level, these processes increase the proliferation and survival of cancer cells and improve their ability to metastasize and resist apoptosis. In addition, studies in animal models have shown enhancing tumor size under the influence of exosomal ncRNAs. Ultimately, exosomal ncRNAs are responsible for clinically significant chemotherapy failures in patients with different types of cancer. Preliminary data have also revealed that exosomal ncRNAs can overcome chemotherapeutic agent resistance, but the results are thoroughly fragmented. This review presents how exosomes modulate the response of cancer cells to chemotherapeutic agents. Understanding how exosomes interfere with chemoresistance may become a milestone in developing new therapeutic options, but more data are still required.

Targeting mitochondrial metabolism for metastatic cancer therapy

Primary tumors evolve metabolic mechanisms favoring glycolysis for adenosine triphosphate (ATP) generation and antioxidant defenses. In contrast, metastatic cells frequently depend on mitochondrial respiration and oxidative phosphorylation (OxPhos). This reliance of metastatic cells on OxPhos can be exploited using drugs that target mitochondrial metabolism. Therefore, therapeutic agents that act via diverse mechanisms, including the activation of signaling pathways that promote the production of reactive oxygen species (ROS) and/or a reduction in antioxidant defenses may elevate oxidative stress and inhibit tumor cell survival. In this review, we will provide (1) a mechanistic analysis of function-selective extracellular signal-regulated kinase-1/2 (ERK1/2) inhibitors that inhibit cancer cells through enhanced ROS, (2) a review of the role of mitochondrial ATP synthase in redox regulation and drug resistance, (3) a rationale for inhibiting ERK signaling and mitochondrial OxPhos toward the therapeutic goal of reducing tumor metastasis and treatment resistance. Recent reports from our laboratories using metastatic melanoma and breast cancer models have shown the preclinical efficacy of novel and rationally designed therapeutic agents that target ERK1/2 signaling and mitochondrial ATP synthase, which modulate ROS events that may prevent or treat metastatic cancer. These findings and those of others suggest that targeting a tumor's metabolic requirements and vulnerabilities may inhibit metastatic pathways and tumor growth. Approaches that exploit the ability of therapeutic agents to alter oxidative balance in tumor cells may be selective for cancer cells and may ultimately have an impact on clinical efficacy and safety. Elucidating the translational potential of metabolic targeting could lead to the discovery of new approaches for treatment of metastatic cancer.

SUMOylation of SYNJ2BP-COX16 promotes breast cancer progression through DRP1-mediated mitochondrial fission

Treatments targeting oncogenic fusion proteins are notable examples of successful drug development. Abnormal splicing of genes resulting in fusion proteins is a critical driver of various tumors, but the underlying mechanism remains poorly understood. Here, we show that SUMOylation of the fusion protein Synaptojanin 2 binding protein-Cytochrome-c oxidase 16 (SYNJ2BP-COX16) at K107 induces mitochondrial fission in breast cancer and that the K107 site regulates SYNJ2BP-COX16 mitochondrial subcellular localization. Compared with a non-SUMOylated K107R mutant, wild-type SYNJ2BP-COX16 contributed to breast cancer cell proliferation and metastasis in vivo and in vitro by increasing adenosine triphosphate (ATP) production and cytochrome-c oxidase (COX) activity. SUMOylated SYNJ2BP-COX16 recruits dynamin-related protein 1 (DRP1) to the mitochondria to promote ubiquitin-conjugating enzyme 9 (UBC9) binding to DRP1, enhance SUMOylation of DRP1 and phosphorylation of DRP1 at S616, and then induce mitochondrial fission. Moreover, Mdivi-1, an inhibitor of DRP1 phosphorylation, decreased the localization of DRP1 in mitochondria, and prevents SYNJ2BP-COX16 induced mitochondrial fission, cell proliferation and metastasis. Based on these data, SYNJ2BP-COX16 promotes breast cancer progression through the phosphorylation of DRP1 and subsequent induction of mitochondrial fission, indicating that SUMOylation at the K107 residue of SYNJ2BP-COX16 is a novel potential treatment target for breast cancer.

Hexokinase 2 promoted cell motility and proliferation by activating Akt1/p-Akt1 in human ovarian cancer cells

Background

Recently, increasing evidence has indicated that elevation of Hexokinase 2 (HK2) plays an important role in several cancers on regulating cell motility and growth. However, its role on regulating cell EMT in human ovarian cancer still less to known.

Methods

The transwell and wound-healing assay were used to detect the effective of HK2 on regulating motility of ovarian cancer cells. Real Time PCR and Western Blotting were used to explore the changing of EMT-related proteins in HK2-modified cells. The clonogenic formation, cell growth curves and MTT assays were used to evaluate the effective of HK2 on regulating cell proliferation in HK2-modified cells. The flow cytometry was used to detect the differences in the distribution of cells in the cell cycle between the HK2-modified cells and their control cells. The correlation of HK2 and Akt1/p-Akt1 was explored by using Western Blotting, Akt1 inhibitor (MK2206) and transient transfection of an Akt1 recombinant plasmid. The potential correlation between HK2 and EMT-related proteins in human ovarian cancer tissues and OV (ovarian serous cystadenocarcinoma) was confirmed by using Pearson correlation analysis and TIMER 2.0.

Results

In ovarian cancer cells, overexpressing of HK2 enhanced cell motility by inducing of EMT-related proteins, such as CDH2, fibronectin, MMP9, ZEB1, ZEB2 and vimentin. Moreover, overexpressing of HK2 promoted cell growth by reducing p21 and p27 expression in ovarian cancer cells. Further studies demonstrated that this promotion of cell motility and growth by HK2 was probably a result of it activating of Akt1 (p-Akt1) in ovarian cancer cells. Additionally, the positive correlation between HK2 and p-Akt1, fibronectin, MMP9 expression in human ovarian cancer samples was verified by using Pearson correlation analysis. The positive correlation between HK2 and CDH2, fibronectin, MMP9, ZEB1, ZEB2 and vimentin in OV (ovarian serous cystadenocarcinoma) was confirmed by using TIMER 2.0.

Conclusion

This study demonstrated that HK2 could induce EMT-related proteins and reduce cell cycle inhibitor by activating Akt1 in human ovarian cancer cells, subsequently enhancing cell motility and growth, suggesting that HK2 participate in the malignant process of ovarian cancer by interacting with Akt1.

Hexokinase 2: The preferential target of trehalose-6-phosphate over hexokinase 1

Cancer-related metabolic features are in part maintained by hexokinase 2 upregulation, which leads to high levels of glucose-6-phosphate (G6P) and is needed to provide energy and biomass to support rapid proliferation. Using a humanized model of the yeast Saccharomyces cerevisiae, we explored how human hexokinase 2 (HK2) behaves under different nutritional conditions. At high glucose levels, yeast presents aerobic glycolysis through a regulatory mechanism known as catabolic repression, which exerts a metabolic adaptation like the Warburg effect. At high glucose concentrations, HK2 did not translocate into the nucleus and was not able to shift the metabolism toward a highly glycolytic state, in contrast to the effect of yeast hexokinase 2 (Hxk2), which is a crucial protein for the control of aerobic glycolysis in S. cerevisiae. During the stationary phase, when glucose is exhausted, Hxk2 is shuttled out of the nucleus, ceasing catabolic repression. Cells harvested at this condition display low glucose consumption rates. However, glucose-starved cells expressing HK2 had an increased capacity to consume glucose. In those cells, HK2 localized to mitochondria, becoming insensitive to G6P inhibition. We also found that the sugar trehalose-6-phosphate (T6P) is a human HK2 inhibitor, like yeast Hxk2, but was not able to inhibit human HK1, the isoform that is ubiquitously expressed in almost all mammalian tissues. In contrast to G6P, T6P inhibited HK2 even when HK2 was associated with mitochondria. The binding of HK2 to mitochondria is crucial for cancer survival and proliferation. T6P was able to reduce the cell viability of tumor cells, although its toxicity was not impressive. This was expected as cell absorption of phosphorylated sugars is low, which might be counteracted using nanotechnology. Altogether, these data suggest that T6P may offer a new paradigm for cancer treatment based on specific inhibition of HK2.

Humic acids alleviate the toxicity of reduced graphene oxide modified by nanosized palladium in microalgae

The use of graphene-family materials modified by nanosized palladium (Pd/GFMs) has intensified rapidly in various fields; however, the effects of environmental factors (e.g., natural organic matter (NOM)) on the transformation and ecotoxicity of Pd/GFMs remain largely unknown. In this study, reduced graphene oxide modified by nanosized Pd (Pd/rGO) was incubated with humic acid (HA) under light irradiation for 56 d to explore the effects of NOM on the physicochemical transformations (e.g., defects, surface charges and dispersity) and biological toxicity (e.g., growth inhibition, oxidative stress and ultrastructural damage on algae cells) of Pd/GFMs. The results revealed that HA increased the defects and dispersity of Pd/rGO. Growth inhibition, damage to cellular ultrastructures, and oxidative stress in microalgae cells were induced by Pd/rGO, and corresponding defense responses (e.g., superoxide dismutase, peroxidase and glutathione) were activated. HA diminished the above defense responses in microalgae triggered by Pd/rGO by regulating GSH metabolism and the alanine biosynthesis pathway. In the presence of HA, cell wall damage (i.e., hole formation) caused by exposure to Pd/rGO was restored, and the plasmolysis area was reduced by 28.6 %. In addition, growth inhibition, lipid peroxidation, loss of mitochondrial membrane potential and ROS formation induced by 1.0 mg/L MoS₂NPs were decreased by 1.4-65.6 %, 13.9-26.1 %, 21.8-58.3 % and 9.6-16.1 %, respectively. These findings highlight the need to consider the effects of HA on the environmental transformation and biological toxicity of Pd/GFMs, which presents significant implications for the management of Pd/GFMs.

Cancer-Associated Dysregulation of Sumo Regulators: Proteases and Ligases

SUMOylation is a post-translational modification that has emerged in recent decades as a mechanism involved in controlling diverse physiological processes and that is essential in vertebrates. The SUMO pathway is regulated by several enzymes, proteases and ligases being the main actors involved in the control of sumoylation of specific targets. Dysregulation of the expression, localization and function of these enzymes produces physiological changes that can lead to the appearance of different types of cancer, depending on the enzymes and target proteins involved. Among the most studied proteases and ligases, those of the SENP and PIAS families stand out, respectively. While the proteases involved in this pathway have specific SUMO activity, the ligases may have additional functions unrelated to sumoylation, which makes it more difficult to study their SUMO-associated role in cancer process. In this review we update the knowledge and advances in relation to the impact of dysregulation of SUMO proteases and ligases in cancer initiation and progression.

SENP1 regulates the transformation of lung resident mesenchymal stem cells and is associated with idiopathic pulmonary fibrosis progression

BACKGROUND

Lung resident mesenchymal stem cells (LR-MSCs) play an important role in idiopathic pulmonary fibrosis (IPF) by transforming into myofibroblasts, thereby losing their repair ability. Evidence suggests that key proteins of multiple signaling pathways are involved in myofibroblast differentiation of LR-MSCs, such as β-Catenin and GLI family zinc finger 1 (GLI1). These proteins are regulated by SUMO (small ubiquitin-like modifier) modification, which is a post-translational modification that promotes protein degradation, while Sumo specific protein 1 (SENP1)-mediated deSUMOylation produces the opposite biological effects. Therefore, we speculated that SENP1 might be a potential target for treating pulmonary fibrosis by preventing the myofibroblast differentiation of LR-MSCs.

METHODS

LR-MSCs were isolated from mice by using immunomagnetic beads. The extracted LR-MSCs were identified by flow cytometric analysis and multilineage differentiation assays. Lentivirus packaged shRNA silenced the expression of SENP1 in vitro and vivo. The silencing efficacy of SENP1 was verified by real-time quantitative PCR. The effect of down-regulated SENP1 on the myofibroblast differentiation of LR-MSCs was assessed by Immunofluorescence and Western blot. Immunoprecipitation was used to clarify that SENP1 was a key target for regulating the activity of multiple signaling pathways in the direction of LR-MSCs differentiation. LR-MSCs resident in the lung was analyzed with in vivo imaging system. HE and Masson staining was used to evaluate the therapeutic effect of LR-MSCs with SENP1 down-regulation on the lung of BLM mice.

RESULTS

In this study, we found that the myofibroblast differentiation of LR-MSCs in IPF lung tissue was accompanied by enhanced SENP1-mediated deSUMOylation. The expression of SENP1 increased in LR-MSCs transition of bleomycin (BLM)-induced lung fibrosis. Interfering with expression of SENP1 inhibited the transformation of LR-MSCs into myofibroblasts in vitro and in vivo and restored their therapeutic effect in BLM lung fibrosis. In addition, activation of the WNT/β-Catenin and Hedgehog/GLI signaling pathways depends on SENP1-mediated deSUMOylation.

CONCLUSIONS

SENP1 might be a potential target to restore the repair function of LR-MSCs and treat pulmonary fibrosis. Video Abstract.

Cyclophilin D: Guardian or Executioner for Tumor Cells?

Cyclophilin D (CypD) is a peptide-proline cis-trans isomerase (PPIase) distributed in the mitochondrial matrix. CypD regulates the opening of the mitochondrial permeability conversion pore (mPTP) and mitochondrial bioenergetics through PPIase activity or interaction with multiple binding partners in mitochondria. CypD initially attracted attention due to its regulation of mPTP overopening-mediated cell death. However, recent studies on the effects of CypD on tumors have shown conflicting results. Although CypD has been proven to promote the aerobic glycolysis in tumor cells, its regulation of malignant characteristics such as the survival, invasion and drug resistance of tumor cells remains controversial. Here, we elaborate the main biological functions of CypD and its relationships with tumor progression identified in recent years, focusing on the dual role of CypD in tumors.

Squalene epoxidase metabolic dependency is a targetable vulnerability in castration-resistant prostate cancer

Considering the dismal prognosis of castration-resistant prostate cancer (CRPC), it is critical to identify novel therapeutic targets in this disease. Malignant cells have metabolic dependencies distinct from their healthy counterparts, resulting in therapeutic vulnerabilities. While PTEN and TP53 are the most frequently co-mutated or co-deleted driver genes in lethal CRPC, the metabolic dependencies underlying PTEN/p53 deficiency-driven CRPC for therapeutic intervention remain largely elusive. In this study, PTEN/p53 deficient tumors were determined to be reliant on cholesterol metabolism. Moreover, PTEN/p53 deficiency transcriptionally upregulated squalene epoxidase (SQLE) via activation of sterol regulatory element-binding protein 2 (SREBP2). In addition, PTEN deficiency enhanced the protein stability of SQLE by inhibiting the PI3K/Akt/GSK3β-mediated proteasomal pathway. Consequently, SQLE increased cholesterol biosynthesis to facilitate tumor cell growth and survival. Pharmacological blockade of SQLE with FR194738 profoundly suppressed the invasive program of CRPC. Collectively, these results demonstrate a synergistic relationship between SQLE and PTEN/p53 deficiency in CRPC development and progression. Therefore, pharmacological interventions targeting SQLE may hold promise for the treatment of CRPC patients.

Signalling mechanisms and cellular functions of SUMO

Sumoylation is an essential post-translational modification that is catalysed by a small number of modifying enzymes but regulates thousands of target proteins in a dynamic manner. Small ubiquitin-like modifiers (SUMOs) can be attached to target proteins as one or more monomers or in the form of polymers of different types. Non-covalent readers recognize SUMO-modified proteins via SUMO interaction motifs. SUMO simultaneously modifies groups of functionally related proteins to regulate predominantly nuclear processes, including gene expression, the DNA damage response, RNA processing, cell cycle progression and proteostasis. Recent progress has increased our understanding of the cellular and pathophysiological roles of SUMO modifications, extending their functions to the regulation of immunity, pluripotency and nuclear body assembly in response to oxidative stress, which partly occurs through the recently characterized mechanism of liquid-liquid phase separation. Such progress in understanding the roles and regulation of sumoylation opens new avenues for the targeting of SUMO to treat disease, and indeed the first drug blocking sumoylation is currently under investigation in clinical trials as a possible anticancer agent.

Restricting α-synuclein transport into mitochondria by inhibition of α-synuclein-VDAC complexation as a potential therapeutic target for Parkinson's disease treatment

Involvement of alpha-synuclein (αSyn) in Parkinson's disease (PD) is complicated and difficult to trace on cellular and molecular levels. Recently, we established that αSyn can regulate mitochondrial function by voltage-activated complexation with the voltage-dependent anion channel (VDAC) on the mitochondrial outer membrane. When complexed with αSyn, the VDAC pore is partially blocked, reducing the transport of ATP/ADP and other metabolites. Further, αSyn can translocate into the mitochondria through VDAC, where it interferes with mitochondrial respiration. Recruitment of αSyn to the VDAC-containing lipid membrane appears to be a crucial prerequisite for both the blockage and translocation processes. Here we report an inhibitory effect of HK2p, a small membrane-binding peptide from the mitochondria-targeting N-terminus of hexokinase 2, on αSyn membrane binding, and hence on αSyn complex formation with VDAC and translocation through it. In electrophysiology experiments, the addition of HK2p at micromolar concentrations to the same side of the membrane as αSyn results in a dramatic reduction of the frequency of blockage events in a concentration-dependent manner, reporting on complexation inhibition. Using two complementary methods of measuring protein-membrane binding, bilayer overtone analysis and fluorescence correlation spectroscopy, we found that HK2p induces detachment of αSyn from lipid membranes. Experiments with HeLa cells using proximity ligation assay confirmed that HK2p impedes αSyn entry into mitochondria. Our results demonstrate that it is possible to regulate αSyn-VDAC complexation by a rationally designed peptide, thus suggesting new avenues in the search for peptide therapeutics to alleviate αSyn mitochondrial toxicity in PD and other synucleinopathies.

Mitochondria transfer and transplantation in human health and diseases

Mitochondria are dynamic organelles responsible for energy production and cell metabolism. Disorders in mitochondrial function impair tissue integrity and have been implicated in multiple human diseases. Rather than constrained in host cells, mitochondria were recently found to actively travel between cells through nanotubes or extracellular vesicles. Mitochondria transportation represents a key mechanism of intercellular communication implicated in metabolic homeostasis, immune response, and stress signaling. Here we reviewed recent progress in mitochondria transfer under physiological and pathological conditions. Specifically, tumor cells imported mitochondria from adjacent cells in the microenvironment which potentially modulated cancer progression. Intercellular mitochondria trafficking also inspired therapeutic intervention of human diseases with mitochondria transplantation. Artificial mitochondria, generated through mitochondria genome engineering or mitochondria-nucleus hybridization, further advanced our understanding of mitochondrial biology and its therapeutic potential. Innovative tools and animal models of mitochondria transplantation will assist the development of new therapies for mitochondrial dysfunction-related diseases.

Mitochondria Dysfunction-Mediated Molecular Subtypes and Gene Prognostic Index for Prostate Cancer Patients Undergoing Radical Prostatectomy or Radiotherapy

Background

Given the age relevance of prostate cancer (PCa) and the role of mitochondrial dysfunction (MIDS) in aging, we orchestrated molecular subtypes and identified key genes for PCa from the perspective of MIDS.

Methods

Cluster analysis, COX regression analysis, function analysis, and tumor immune environment were conducted. We performed all analyses using software R 3.6.3 and its suitable packages.

Results

CXCL14, SFRP4, and CD38 were eventually identified to classify the PCa patients in The Cancer Genome Atlas (TCGA) database and the Gene Expression Omnibus (GEO) dataset into two distinct clusters. Patients in the cluster 2 had shorter BCR-free survival than those in the cluster 1 in terms of both TCGA database and GEO dataset. We divided the patients from the TCGA database and the GEO dataset into high- and low-risk groups according to the median of MIDS-related genetic prognostic index. For patients in the TCGA database, the biochemical recurrence (BCR) risk in high-risk group was 2.34 times higher than that in low-risk group. Similarly, for patients in the GEO dataset, the risk of BCR and metastasis in high-risk group was 2.35 and 3.04 times higher than that in low-risk group, respectively. Cluster 2 was closely associated with advanced T stage and higher Gleason score for patients undergoing radical prostatectomy or radiotherapy. For patients undergoing radical prostatectomy, the number of CD8⁺ T cells was significantly lower in cluster 2 than in cluster 1, while cluster 2 had significantly higher stromal score than cluster 1. For patients undergoing radical radiotherapy, cluster 2 had significantly higher level of CD8⁺ T cells, neutrophils, macrophages, dendritic cells, stromal score, immune score, and estimate score, but showed lower level of tumor purity than cluster 1.

Conclusions

We proposed distinctly prognosis-related molecular subtypes at genetic level and related formula for PCa patients undergoing radical prostatectomy or radiotherapy, mainly to provide a roadmap for precision medicine.

Regulation of Glucose, Fatty Acid and Amino Acid Metabolism by Ubiquitination and SUMOylation for Cancer Progression

Ubiquitination and SUMOylation, which are posttranslational modifications, play prominent roles in regulating both protein expression and function in cells, as well as various cellular signal transduction pathways. Metabolic reprogramming often occurs in various diseases, especially cancer, which has become a new entry point for understanding cancer mechanisms and developing treatment methods. Ubiquitination or SUMOylation of protein substrates determines the fate of modified proteins. Through accurate and timely degradation and stabilization of the substrate, ubiquitination and SUMOylation widely control various crucial pathways and different proteins involved in cancer metabolic reprogramming. An understanding of the regulatory mechanisms of ubiquitination and SUMOylation of cell proteins may help us elucidate the molecular mechanism underlying cancer development and provide an important theory for new treatments. In this review, we summarize the processes of ubiquitination and SUMOylation and discuss how ubiquitination and SUMOylation affect cancer metabolism by regulating the key enzymes in the metabolic pathway, including glucose, lipid and amino acid metabolism, to finally reshape cancer metabolism.

Histone H2AX promotes metastatic progression by preserving glycolysis via hexokinase-2

Genomic stability is essential for organismal development, cellular homeostasis, and survival. The DNA double-strand breaks are particularly deleterious, creating an environment prone to cellular transformation and oncogenic activation. The histone variant H2AX is an essential component of the nucleosome responsible for initiating the early steps of the DNA repair process. H2AX maintains genomic stability by initiating a signaling cascade that collectively functions to promote DNA double-strand breaks repair. Recent advances have linked genomic stability to energetic metabolism, and alterations in metabolism were found to interfere with genome maintenance. Utilizing genome-wide transcripts profiling to identify differentially-expressed genes involved in energetic metabolism, we compared control and H2AX-deficient metastatic breast cancer cell lines, and found that H2AX loss leads to the repression of key genes regulating glycolysis, with a prominent effect on hexokinase-2 (HK2). These observations are substantiated by evidence that H2AX loss compromises glycolysis, effect which was reversed by ectopic expression of HK2. Utilizing models of experimental metastasis, we found that H2AX silencing halts progression of metastatic breast cancer cells MDA-MB-231. Most interestingly, ectopic expression of HK2 in H2AX-deficient cells restores their metastatic potential. Using multiple publicly available datasets, we found a significantly strong positive correlation between H2AX expression levels in patients with invasive breast cancer, and levels of glycolysis genes, particularly HK2. These observations are consistent with the evidence that high H2AX expression is associated with shorter distant metastasis-free survival. Our findings reveal a role for histone H2AX in controlling the metastatic ability of breast cancer cells via maintenance of HK2-driven glycolysis.

SIGNALING PATHWAYS THAT DRIVE 18F-FDG ACCUMULATION IN CANCER

2-¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) measures glucose consumption and is an integral part of cancer management. Most cancer types upregulate their glucose consumption, yielding elevated ¹⁸F-FDG PET accumulation in those cancer cells. The biochemical pathway through which ¹⁸F-FDG accumulates in cancer cells is well-established. However, beyond well-known regulators such as c-Myc, PI3K/Akt, and HIF1α, the proteins and signaling pathways that cancer cells modulate to activate the facilitated glucose transporters (GLUTs) and hexokinase enzymes that drive elevated ¹⁸F-FDG accumulation are less well-understood. Understanding these signaling pathways could yield additional biological insights from ¹⁸F-FDG PET scans and could suggest new uses of ¹⁸F-FDG PET in the management of cancer. Work over the past five years, building on studies from years prior, has identified new proteins and signaling pathways that drive glucose consumption in cancer. Here we review these recent studies and discuss current limitations to our understanding of glucose consumption in cancer.

Ubiquitination regulation of aerobic glycolysis in cancer

Aerobic glycolysis, or the Warburg effect, is regarded as a critical part of metabolic reprogramming and plays a crucial role in the occurrence and development of tumours. Ubiquitination and deubiquitination, essential post-translational modifications, have attracted increasing attention with regards to the regulation of metabolic reprogramming in cancer. However, the mechanism of ubiquitination in glycolysis remains unclear. In this review, we discuss the roles of ubiquitination and deubiquitination in regulating glycolysis, and their involvement in regulating important signalling pathways, enzymes, and transcription factors. Focusing on potential mechanisms may provide novel strategies for cancer treatment.

Dual Tumor Microenvironment Remodeling by Glucose-Contained Radical Copolymer for MRI-Guided Photoimmunotherapy

Aberrant glucose metabolism and immune evasion are recognized as two hallmarks of cancer, which contribute to poor treatment efficiency and tumor progression. Herein, a novel material system consisting of a glucose and TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) at the distal ends of PEO-b-PLLA block copolymer (glucose-PEO-b-PLLA-TEMPO), is designed to encapsulate clinical therapeutics CUDC101 and photosensitizer IR780. The specific core-shell rod structure formed by the designed copolymer renders TEMPO radicals excellent stability against reduction-induced magnetic resonance imaging (MRI) silence. Tumor-targeting moiety endowed by glucose provides the radical copolymer outstanding multimodal imaging capabilities, including MRI, photoacoustic imaging, and fluorescence imaging. Efficient delivery of CUDC101 and IR780 is achieved to synergize the antitumor immune activation through IR780-mediated photodynamic therapy (PDT) and CUDC101-triggered CD47 inhibition, showing M1 phenotype polarization of tumor-associated macrophages (TAMs). More intriguingly, this study demonstrates PDT-stimulated p53 can also re-educate TAMs, providing a combined strategy of using dual tumor microenvironment remodeling to achieve the synergistic effect in the transition from cold immunosuppressive to hot immunoresponsive tumor microenvironment.

A Novel Risk Factor Model Based on Glycolysis-Associated Genes for Predicting the Prognosis of Patients With Prostate Cancer

BACKGROUND

Prostate cancer (PCa) is one of the most prevalent cancers among males, and its mortality rate is increasing due to biochemical recurrence (BCR). Glycolysis has been proven to play an important regulatory role in tumorigenesis. Although several key regulators or predictors involved in PCa progression have been found, the relationship between glycolysis and PCa is unclear; we aimed to develop a novel glycolysis-associated multifactor prediction model for better predicting the prognosis of PCa.

METHODS

Differential mRNA expression profiles derived from the Cancer Genome Atlas (TCGA) PCa cohort were generated through the "edgeR" package. Glycolysis-related genes were obtained from the GSEA database. Univariate Cox and LASSO regression analyses were used to identify genes significantly associated with disease-free survival. ROC curves were applied to evaluate the predictive value of the model. An external dataset derived from Gene Expression Omnibus (GEO) was used to verify the predictive ability. Glucose consumption and lactic production assays were used to assess changes in metabolic capacity, and Transwell assays were used to assess the invasion and migration of PC3 cells.

RESULTS

Five glycolysis-related genes were applied to construct a risk score prediction model. Patients with PCa derived from TCGA and GEO (GSE70770) were divided into high-risk and low-risk groups according to the median. In the TCGA cohort, the high-risk group had a poorer prognosis than the low-risk group, and the results were further verified in the GSE70770 cohort. In vitro experiments demonstrated that knocking down HMMR, KIF20A, PGM2L1, and ANKZF1 separately led to less glucose consumption, less lactic production, and inhibition of cell migration and invasion, and the results were the opposite with GPR87 knockdown.

CONCLUSION

The risk score based on five glycolysis-related genes may serve as an accurate prognostic marker for PCa patients with BCR.

Therapeutic Potential of Targeting the SUMO Pathway in Cancer

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer. The delicate balance between SUMOylation and deSUMOylation is regulated by SENP enzymes possessing SUMO-deconjugation activity. Dysregulation of SUMO machinery components can disrupt the balance of SUMOylation, contributing to the tumorigenesis and drug resistance of various cancers in a context-dependent manner. Many molecular mechanisms relevant to the pathogenesis of specific cancers involve SUMO, highlighting the potential relevance of SUMO machinery components as therapeutic targets. Recent advances in the development of inhibitors targeting SUMOylation and deSUMOylation permit evaluation of the therapeutic potential of targeting the SUMO pathway in cancer. Finally, the first drug inhibiting SUMO pathway, TAK-981, is currently also being evaluated in clinical trials in cancer patients. Intriguingly, the inhibition of SUMOylation may also have the potential to activate the anti-tumor immune response. Here, we comprehensively and systematically review the recent developments in understanding the role of SUMOylation in cancer and specifically focus on elaborating the scientific rationale of targeting the SUMO pathway in different cancers.

Hexokinase 2 in Cancer: A Prima Donna Playing Multiple Characters

Hexokinases are a family of ubiquitous exose-phosphorylating enzymes that prime glucose for intracellular utilization. Hexokinase 2 (HK2) is the most active isozyme of the family, mainly expressed in insulin-sensitive tissues. HK2 induction in most neoplastic cells contributes to their metabolic rewiring towards aerobic glycolysis, and its genetic ablation inhibits malignant growth in mouse models. HK2 can dock to mitochondria, where it performs additional functions in autophagy regulation and cell death inhibition that are independent of its enzymatic activity. The recent definition of HK2 localization to contact points between mitochondria and endoplasmic reticulum called Mitochondria Associated Membranes (MAMs) has unveiled a novel HK2 role in regulating intracellular Ca²⁺ fluxes. Here, we propose that HK2 localization in MAMs of tumor cells is key in sustaining neoplastic progression, as it acts as an intersection node between metabolic and survival pathways. Disrupting these functions by targeting HK2 subcellular localization can constitute a promising anti-tumor strategy.