SPATA20 deficiency enhances the metastatic and angiogenic potential of cancer cells by promoting HIF-1α synthesis.

Hypoxia-inducible factors (HIFs) regulate cellular oxygen balance and play a central role in cancer metastasis and angiogenesis. Despite extensive research on HIFs, successful therapeutic strategies remain limited due to the intricate nature of their regulation. In this study, we identified SPATA20, a relatively understudied protein with a thioredoxin-like domain, as an upstream regulator of HIF-1α. Depleting SPATA20 induced HIF-1α expression, suggesting a tumor-suppressive role for SPATA20 in cancer cells. SPATA20 depletion increased HIF-1α protein levels and transcriptional activity without affecting its degradation. It appears that SPATA20 inhibits the de novo synthesis of HIF-1α, possibly by repressing the cap-dependent translation process involving AKT phosphorylation. Additionally, depletion of SPATA20 promoted cancer cell migration and invasion, which can be reversed by pharmacological inhibition of HIF-1α. Clinical data analysis revealed an inverse correlation between SPATA20 expression and colorectal cancer progression, providing evidence of its role as a potential biomarker. Utilizing SPATA20 as an indicator for HIF-1α-targeting therapy may be an attractive strategy for treating patients with hypoxia-driven cancers. In conclusion, this study demonstrates that SPATA20 deficiency promotes cancer progression by activating the HIF-1α signaling pathway.

The polyol pathway and nuclear ketohexokinase A signaling drive hyperglycemia-induced metastasis of gastric cancer.

Diabetes might be associated with increased cancer risk, with several studies reporting hyperglycemia as a primary oncogenic stimulant. Since glucose metabolism is linked to numerous metabolic pathways, it is difficult to specify the mechanisms underlying hyperglycemia-induced cancer progression. Here, we focused on the polyol pathway, which is dramatically activated under hyperglycemia and causes diabetic complications. We investigated whether polyol pathway-derived fructose facilitates hyperglycemia-induced gastric cancer metastasis. We performed bioinformatics analysis of gastric cancer datasets and immunohistochemical analyses of gastric cancer specimens, followed by transcriptomic and proteomic analyses to evaluate phenotypic changes in gastric cancer cells. Consequently, we found a clinical association between the polyol pathway and gastric cancer progression. In gastric cancer cell lines, hyperglycemia enhanced cell migration and invasion, cytoskeletal rearrangement, and epithelial-mesenchymal transition (EMT). The hyperglycemia-induced acquisition of metastatic potential was mediated by increased fructose derived from the polyol pathway, which stimulated the nuclear ketohexokinase-A (KHK-A) signaling pathway, thereby inducing EMT by repressing the CDH1 gene. In two different xenograft models of cancer metastasis, gastric cancers overexpressing AKR1B1 were found to be highly metastatic in diabetic mice, but these effects of AKR1B1 were attenuated by KHK-A knockdown. In conclusion, hyperglycemia induces fructose formation through the polyol pathway, which in turn stimulates the KHK-A signaling pathway, driving gastric cancer metastasis by inducing EMT. Thus, the polyol and KHK-A signaling pathways could be potential therapeutic targets to decrease the metastatic risk in gastric cancer patients with diabetes.

Neddylation of insulin receptor substrate acts as a bona fide regulator of insulin signaling and its implications for cancer cell migration.

Irregularities in insulin signaling have significantly increased the risk of various cancers, yet the precise underlying mechanisms remain unclear. Within our study, we observed that inhibiting neddylation enhances cancer cell migration across different cancer types by activating both insulin receptor substrates 1 and 2 (IRS1 and IRS2), along with the PI3K/AKT signaling pathway. Notably, in the context of high-grade serous carcinoma (HGSC) patients, whether they had type 2 diabetes mellitus or not, IRS1 and IRS2 displayed a parallel relationship with each other while exhibiting an inverse relationship with NEDD8. We also identified C-CBL as an E3 ligase responsible for neddylating IRS1 and IRS2, with clinical evidence further confirming a reciprocal relationship between C-CBL and pAKT, thereby reinforcing the tumor suppressive role of C-CBL. Altogether, these findings suggest that neddylation genuinely participates in IRS1 and IRS2-dependent insulin signaling, effectively suppressing cancer cell migration. Thus, caution is advised when considering neddylation inhibitors as a treatment option for cancer patients, particularly those presenting with insulin signaling dysregulations linked to conditions like obesity-related type 2 diabetes or hyperinsulinemia.

Palmitoylation-driven PHF2 ubiquitination remodels lipid metabolism through the SREBP1c axis in hepatocellular carcinoma.

Palmitic acid (PA) is the most common fatty acid in humans and mediates palmitoylation through its conversion into palmitoyl coenzyme A. Although palmitoylation affects many proteins, its pathophysiological functions are only partially understood. Here we demonstrate that PA acts as a molecular checkpoint of lipid reprogramming in HepG2 and Hep3B cells. The zinc finger DHHC-type palmitoyltransferase 23 (ZDHHC23) mediates the palmitoylation of plant homeodomain finger protein 2 (PHF2), subsequently enhancing ubiquitin-dependent degradation of PHF2. This study also reveals that PHF2 functions as a tumor suppressor by acting as an E3 ubiquitin ligase of sterol regulatory element-binding protein 1c (SREBP1c), a master transcription factor of lipogenesis. PHF2 directly destabilizes SREBP1c and reduces SREBP1c-dependent lipogenesis. Notably, SREBP1c increases free fatty acids in hepatocellular carcinoma (HCC) cells, and the consequent PA induction triggers the PHF2/SREBP1c axis. Since PA seems central to activating this axis, we suggest that levels of dietary PA should be carefully monitored in patients with HCC.

Protein stabilization of ITF2 by NF-κB prevents colitis-associated cancer development.

Chronic colonic inflammation is a feature of cancer and is strongly associated with tumorigenesis, but its underlying molecular mechanisms remain poorly understood. Inflammatory conditions increased ITF2 and p65 expression both ex vivo and in vivo, and ITF2 and p65 showed positive correlations. p65 overexpression stabilized ITF2 protein levels by interfering with the binding of Parkin to ITF2. More specifically, the C-terminus of p65 binds to the N-terminus of ITF2 and inhibits ubiquitination, thereby promoting ITF2 stabilization. Parkin acts as a E3 ubiquitin ligase for ITF2 ubiquitination. Intestinal epithelial-specific deletion of ITF2 facilitated nuclear translocation of p65 and thus increased colitis-associated cancer tumorigenesis, which was mediated by Azoxymethane/Dextran sulfate sodium or dextran sulfate sodium. Upregulated ITF2 expression was lost in carcinoma tissues of colitis-associated cancer patients, whereas p65 expression much more increased in both dysplastic and carcinoma regions. Therefore, these findings indicate a critical role for ITF2 in the repression of colitis-associated cancer progression and ITF2 would be an attractive target against inflammatory diseases including colitis-associated cancer.

Tumor regionalization after surgery: Roles of the tumor microenvironment and neutrophil extracellular traps.

Surgery is unanimously regarded as the primary strategy to cure solid tumors in the early stages but is not always used in advanced cases. However, tumor surgery must be carefully considered because the risk of metastasis could be increased by the surgical procedure. Tumor surgery may result in a deep wound, which induces many biological responses favoring tumor metastasis. In particular, NETosis, which is the process of forming neutrophil extracellular traps (NETs), has received attention as a risk factor for surgery-induced metastasis. To reduce cancer mortality, researchers have made efforts to prevent secondary metastasis after resection of the primary tumor. From this point of view, a better understanding of surgery-induced metastasis might provide new strategies for more effective and safer surgical approaches. In this paper, recent insights into the surgical effects on metastasis will be reviewed. Moreover, in-depth opinions about the effects of NETs on metastasis will be discussed.

AURKB, in concert with REST, acts as an oxygen-sensitive epigenetic regulator of the hypoxic induction of MDM2.

The acute response to hypoxia is mainly driven by hypoxiainducible factors, but their effects gradually subside with time. Hypoxia-specific histone modifications may be important for the stable maintenance of long-term adaptation to hypoxia. However, little is known about the molecular mechanisms underlying the dynamic alterations of histones under hypoxic conditions. We found that the phosphorylation of histone H3 at Ser-10 (H3S10) was noticeably attenuated after hypoxic challenge, which was mediated by the inhibition of aurora kinase B (AURKB). To understand the role of AURKB in epigenetic regulation, DNA microarray and transcription factor binding site analyses combined with proteomics analysis were performed. Under normoxia, phosphorylated AURKB, in concert with the repressor element-1 silencing transcription factor (REST), phosphorylates H3S10, which allows the AURKB-REST complex to access the MDM2 proto-oncogene. REST then acts as a transcriptional repressor of MDM2 and downregulates its expression. Under hypoxia, AURKB is dephosphorylated and the AURKB-REST complex fails to access MDM2, leading to the upregulation of its expression. In this study, we present a case of hypoxia-specific epigenetic regulation of the oxygen-sensitive AURKB signaling pathway. To better understand the cellular adaptation to hypoxia, it is worthwhile to further investigate the epigenetic regulation of genes under hypoxic conditions. [BMB Reports 2022; 55(6): 287-292].

DEP-induced ZEB2 promotes nasal polyp formation via epithelial-to-mesenchymal transition.

BACKGROUND: Diesel exhaust particles (DEPs) are associated with the prevalence and exacerbation of allergic respiratory diseases, including allergic rhinitis and allergic asthma. However, DEP-induced mechanistic pathways promoting upper airway disease and their clinical implications remain unclear. OBJECTIVE: We sought to investigate the mechanisms by which DEP exposure contributes to nasal polyposis using human-derived epithelial cells and a murine nasal polyp (NP) model. METHODS: Gene set enrichment and weighted gene coexpression network analyses were performed. Cytotoxicity, epithelial-to-mesenchymal transition (EMT) markers, and nasal polyposis were assessed. Effects of DEP exposure on EMT were determined using epithelial cells from normal people or patients with chronic rhinosinusitis with or without NPs. BALB/c mice were exposed to DEP through either a nose-only exposure system or nasal instillation, with or without house dust mite, followed by zinc finger E-box-binding homeobox (ZEB)2 small hairpin RNA delivery. RESULTS: Bioinformatics analyses revealed that DEP exposure triggered EMT features in airway epithelial cells. Similarly, DEP-exposed human nasal epithelial cells exhibited EMT characteristics, which were dependent on ZEB2 expression. Human nasal epithelial cells derived from patients with chronic rhinosinusitis presented more prominent EMT features after DEP treatment, when compared with those from control subjects and patients with NPs. Coexposure to DEP and house dust mite synergistically increased the number of NPs, epithelial disruptions, and ZEB2 expression. Most importantly, ZEB2 inhibition prevented DEP-induced EMT, thereby alleviating NP formation in mice. CONCLUSIONS: Our data show that DEP facilitated NP formation, possibly via the promotion of ZEB2-induced EMT. ZEB2 may be a therapeutic target for DEP-induced epithelial damage and related airway diseases, including NPs.

Antibiotic-Dependent Relationships Between the Nasal Microbiome and Secreted Proteome in Nasal Polyps.

PURPOSE: Chronic rhinosinusitis (CRS) is a heterogeneous chronic inflammatory condition of the paranasal sinuses and nasal passages. Although antibiotics are used to reduce inflammation or to treat an episode of acute rhinosinusitis, their effects on the nasal environment and host response in CRS is unclear. METHODS: We analyzed the effects of antibiotics on the nasal microbiome and secreted proteome in CRS using multi-omic analysis. Nasal secretions were collected from 29 controls, 30 CRS patients without nasal polyps (NP), and 40 CRS patients with NP. A total of 99 subjects were divided into 2 groups that included subjects who had taken antibiotics 3 months prior to sampling and those who had not. We performed 16S ribosomal DNA sequence analyses and Orbitrap mass spectrometry-based proteomic analyses. Spearman correlation was used to assess the correlations between the nasal microbiome and secreted proteome. RESULTS: The associations between the nasal microbiome and secreted proteome were noted in subjects who had used antibiotics. Antibiotics could have stronger effects on their associations in patients with CRS with NP than in those without. It remains unknown whether these holistic changes caused by antibiotics are beneficial or harmful to CRS, however, the associations could be differentially affected by disease severity. CONCLUSION: These findings provide new insight into the nasal environment and the host response in CRS.

Bone morphogenetic protein-2 as a novel biomarker for refractory chronic rhinosinusitis with nasal polyps.

BACKGROUND: Bone morphogenetic proteins (BMPs), which are members of the TGF-ß superfamily, regulate bone remodeling by stimulating osteoblasts and osteoclasts. Although the association between osteitis and poor surgical outcomes is well known in patients with chronic rhinosinusitis (CRS), BMPs have not been fully investigated as potential biomarkers for the prognosis of CRS. OBJECTIVE: Our aim was to investigate the role of BMPs in osteitis in patients with CRS with nasal polyps (NPs) (CRSwNPs), as well as associations between BMPs and inflammatory markers in sinonasal tissues from patients with CRSwNP. METHODS: We investigated the expression of 6 BMPs (BMP-2, BMP-4, BMP-6, BMP-7, BMP-9, and BMP-10) and their cellular origins in NPs of human subjects by using immunohistochemistry and ELISA of NP tissues. Exploratory factor analysis was performed to identify associations between BMPs and inflammatory markers. Air-liquid interface cell culture of human nasal epithelial cells was performed to evaluate the induction of the epithelial-mesenchymal transition by BMPs. RESULTS: Of the 6 BMPs studied, BMP-2 and BMP-7 were associated with refractoriness. Only BMP-2 concentrations were higher in patients with severe osteitis and advanced disease extent according to the computed tomography findings. Eosinophils and some macrophages were identified as cellular sources of BMP-2 in immunofluorescence analysis. An in vitro experiment revealed that BMP-2 induced epithelial-mesenchymal transition in air-liquid interface-cultured human nasal epithelial cells, particularly in a TH2 milieu. CONCLUSION: BMP-2 could reflect the pathophysiology of mucosa and bone remodeling and may be a novel biomarker for refractory CRSwNP.

Metastasis-on-a-chip reveals adipocyte-derived lipids trigger cancer cell migration via HIF-1α activation in cancer cells.

Although obesity is a newly considered risk factor for cancer, the mechanisms by which adipocyte-derived metabolites accelerate cancer malignancy have yet to be elucidated. To identify the connection among heterogeneous cell types, conventional methods including Transwell assays or conditioned media (CM) have been used; however, these methods do not fully reflect niche effects in the tumor microenvironment (TME). Here, we established an oxygen permeable polydimethylsiloxane (PDMS)-based three-dimensional (3D) culture system to allow direct attachment between human adipocyte derived stem cells (ADSCs) and cancer cells. By doing so, a physiologically bioactive TME was created, which could be used to reveal further the relationships between different cell types. We found that co-culture of cancer cells with ADSCs resulted in a dispersion phenomenon, and the dispersed spheroid was well matched with the enhanced metastatic potential of cancer cells. Lipid profiling and in vitro migration assays suggested that lipids are the driving force for cancer cell migration via HIF-1α upregulation. In addition, the lipid/HIF-1α axis promoted tumor metastasis in a xenograft mouse model. This study presents an in vitro model of a biomimetic TME and provides new mechanistic insights into the effects of ADSC-released fatty acids on cancer cells as oncometabolites.

Ketohexokinase-A acts as a nuclear protein kinase that mediates fructose-induced metastasis in breast cancer.

Harmful effects of high fructose intake on health have been widely reported. Although fructose is known to promote cancer, little is known about the underlying mechanisms. Here, we found that fructose triggers breast cancer metastasis through the ketohexokinase-A signaling pathway. Molecular experiments showed that ketohexokinase-A, rather than ketohexokinase-C, is necessary and sufficient for fructose-induced cell invasion. Ketohexokinase-A-overexpressing breast cancer was found to be highly metastatic in fructose-fed mice. Mechanistically, cytoplasmic ketohexokinase-A enters into the nucleus during fructose stimulation, which is mediated by LRRC59 and KPNB1. In the nucleus, ketohexokinase-A phosphorylates YWHAH at Ser25 and the YWHAH recruits SLUG to the CDH1 promoter, which triggers cell migration. This study provides the effect of nutrition on breast cancer metastasis. High intake of fructose should be restricted in cancer patients to reduce the risk of metastasis. From a therapeutic perspective, the ketohexokinase-A signaling pathway could be a potential target to prevent cancer metastasis.

Fatty-acid-induced FABP5/HIF-1 reprograms lipid metabolism and enhances the proliferation of liver cancer cells.

Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor essential for cancer cell survival. The reprogramming of lipid metabolism has emerged as a hallmark of cancer, yet the relevance of HIF-1α to this process remains elusive. In this study, we profile HIF-1α-interacting proteins using proteomics analysis and identify fatty acid-binding protein 5 (FABP5) as a critical HIF-1α-binding partner. In hepatocellular carcinoma (HCC) tissues, both FABP5 and HIF-1α are upregulated, and their expression levels are associated with poor prognosis. FABP5 enhances HIF-1α activity by promoting HIF-1α synthesis while disrupting FIH/HIF-1α interaction at the same time. Oleic-acid treatment activates the FABP5/HIF-1α axis, thereby promoting lipid accumulation and cell proliferation in HCC cells. Our results indicate that fatty-acid-induced FABP5 upregulation drives HCC progression through HIF-1-driven lipid metabolism reprogramming.

Neddylation blockade induces HIF-1α driven cancer cell migration via upregulation of ZEB1.

Neddylation is a process by which NEDD8 is covalently conjugated to target proteins by sequential enzymatic reaction. Its role in cancer cell migration has only been recently acknowledged. Previously in cancer cell migration, the epithelial to mesenchymal transition (EMT) process has been well-known to play an important role in both invasion and metastasis by promoting mesenchymal phenotype in epithelial cells. However, the role of neddylation in the EMT process and its mechanistic details are yet to be elucidated. We recently reported that neddylation plays a crucial role in cancer cell migration through the PI3K-Akt pathway. Here, we report that inhibiting neddylation activates the hypoxia-inducible factor 1α (HIF-1α) through the PI3K-Akt pathway, which eventually regulates the EMT-activator ZEB1 (zinc finger E-box binding homeobox 1) in various cancer cell lines. As induction of HIF-1α is known to deteriorate the state of cancer and EMT process is one of the hallmarks of metastasis in cancer, our findings uncover the role of neddylation between HIF-1α and ZEB1.

Loss of EGR3 is an independent risk factor for metastatic progression in prostate cancer.

Identification of pro-metastatic genomic alterations is urgently needed to help understand and prevent the fatal course of prostate cancer. Here, we found that the transcription factor EGR3, located at chromosome 8p21.3, is a critical metastasis suppressor. Aberrant deletion of EGR3 was found in up to 59.76% (deep deletions, 16.87%; shallow deletions, 42.89%) of prostate cancer patients. In informatics analysis, EGR3 loss was associated with prostate cancer progression and low survival rates. EGR3 expression inversely correlated with the expressions of epithelial-to-mesenchymal transition (EMT) and metastasis-related gene sets in prostate cancer tissues. In prostate cancer cells, EGR3 blocked the EMT process and suppressed cell migration and invasion. In a mouse model for cancer metastasis, EGR3 overexpression significantly suppressed bone metastases of PC3 and 22Rv1 prostate cancer cells. Mechanistically, EGR3 transcriptionally activated ZFP36, GADD45B, and SOCS3 genes by directly binding to their promoter regions. The EMT-inhibitory and tumor-suppressive roles of the EGR3 downstream genes were identified through in vitro and in silico analyses. Together, our results showed that EGR3 may be a biomarker to predict clinical outcomes and that it plays an important role in the metastatic progression of prostate cancer.

Hypoxia-driven epigenetic regulation in cancer progression: A focus on histone methylation and its modifying enzymes.

The mechanism underlying hypoxia-driven chromatin remodeling is a long-lasting question. For the last two decades, this question has been resolved in part. It is now widely agreed that hypoxia dynamically changes the methylation status of histones to control gene expression. Hypoxia-inducible factor (HIF) plays a central role in cellular responses to hypoxia through transcriptional activation of numerous genes. At least in part, the hypoxic regulation of histone methylation is attributed to the HIF-mediated expression of histone modifying enzymes. Protein hydroxylation and histone demethylation have emerged as the oxygen sensing processes because they are catalyzed by a family of 2-oxoglutarate (2OG)-dependent dioxygenases whose activities depend upon the ambient oxygen level. Recently, it has been extensively investigated that the 2OG dioxygenases oxygen-dependently regulate histone methylation. Nowadays, the hypoxic change in the histone methylation status is regarded as an important event to drive malignant behaviors of cancer cells. In this review, we introduced and summarized the cellular processes that govern hypoxia-driven regulation of histone methylation in the context of cancer biology. We also discussed the emerging roles of histone methyltransferases and demethylases in epigenetic response to hypoxia.

Erratum: In-Depth, Proteomic Analysis of Nasal Secretions from Patients With Chronic Rhinosinusitis and Nasal Polyps.

This corrects the article on p. 691 in vol. 11, PMID: 31332980.

Validation of CDr15 as a new dye for detecting neutrophil extracellular trap.

Neutrophil extracellular trap (NET) is one of the first-line defenses against microbes. Under certain circumstances, however, it also plays an aggravating factor in diverse inflammation-related diseases including cancers and vascular diseases. Our aim is to develop a new method to detect NET in cells and tissues using a DNA-specific fluorescence probe CDr15. CDr15 was characterized to be impermeable to the cell membranes and to emit a strong fluorescence in association with extracellular DNAs in NET. Due to these properties, CDr15 was successfully shown to quantify NETs in vitro and to be applicable for real-time monitoring NET formation in PMA-stimulated neutrophils. Even in formaldehyde-fixed tumor specimens, CDr15 could detect NETs spreading around cancer cells. Compared with DAPI and SYTOX DNA dyes, CDr15 showed a lower level of background fluorescence and a higher specificity in NET detection. Based on these results, we propose CDr15 as a novel marker of NET to be applicable in experimental and clinical studies.

Extracellular Acidosis Promotes Metastatic Potency via Decrease of the BMAL1 Circadian Clock Gene in Breast Cancer.

Circadian oscillation is an essential process that influences many physiological and biological mechanisms and a decrease of circadian genes is associated with many diseases such as cancer. Despite many efforts to identify the detailed mechanism for decreasing circadian genes and recovering reduced circadian genes in cancer, it is still largely unknown. We found that BMAL1 was reduced in tumor hypoxia-induced acidosis, and recovered by selectively targeting acidic pH in breast cancer cell lines. Surprisingly, BMAL1 was reduced by decrease of protein stability as well as inhibition of transcription under acidosis. In addition, melatonin significantly prevented acidosis-mediated decrease of BMAL1 by inhibiting lactate dehydrogenase-A during hypoxia. Remarkably, acidosis-mediated metastasis was significantly alleviated by BMAL1 overexpression in breast cancer cells. We therefore suggest that tumor hypoxia-induced acidosis promotes metastatic potency by decreasing BMAL1, and that tumor acidosis could be a target for preventing breast cancer metastasis by sustaining BMAL1.

Neddylation of sterol regulatory element-binding protein 1c is a potential therapeutic target for nonalcoholic fatty liver treatment.

Nonalcoholic fatty liver disease (NAFLD) is a risk factor for progression of steatohepatitis, liver cirrhosis, and liver cancer. Although pathological condition of NAFLD, which arises from an excessive accumulation of triglyceride in the liver, is accompanied by elevated sterol regulatory element-binding protein 1c (SREBP1c) level, it is largely unknown which factors are involved in the modification of SREBP1c. In this study, we discovered that neddylation of SREBP1c competes with its ubiquitination and stabilizes SREBP1c protein level, and eventually promotes hepatic steatosis. We also demonstrated that human homolog of mouse double minute 2 (HDM2) acts as an E3 neddylation ligase of SREBP1c. Further, treatment with the neddylation inhibitor, MLN4924, attenuates high-fat diet-induced hepatic steatosis by reducing the levels of SREBP1c protein and hepatic triglyceride. Our results indicate that the blockade of SREBP1c neddylation could be a novel approach in the defense against NAFLD.