Targeting HIF-2α as therapy for advanced cancers

Astragali Radix-Curcumae Rhizoma herb pair reduces the stemness of colorectal cancer cells through HIF-2α/β-catenin pathway

BACKGROUND

Colorectal cancer (CRC) is one of the most common causes of cancer-related mortality and significantly impairs quality of life. Astragali Radix-Curcumae Rhizoma (AC) is widely employed in the treatment of CRC in Chinese medicine, but the precise mechanisms remain unclear.

PURPOSE

This study aimed to elucidate the mechanisms by which AC inhibits CRC progression.

METHODS

The active components of AC were identified using UPLC-MS/MS analysis. An orthotopic transplantation colorectal tumor model was established in BALB/c mice using the CT26-Lucifer cell line to evaluate the effects of AC. Tumor volumes were monitored using IVIS imaging technology. Histological examination of tumor morphology was performed with hematoxylin and eosin (H&E) staining. Transcriptomic sequencing of mouse tumor samples was conducted to identify critical pathways and molecular targets. The impact of AC on cell viability and migration was assessed using CCK-8 and wound healing assays, respectively. To investigate the effects of AC on CRC cells, an in vitro hypoxic model was established using cobalt chloride (CoCl2), a hypoxia inducer. HIF-2α overexpression was achieved by constructing stable lentiviral vectors. Key targets identified from RNA-seq, such as c-Myc, Ki-67, β-catenin, cleaved caspase 3, CD133, and CD44, were evaluated using western blotting, qRT-PCR, and immunofluorescence assays. Epithelial-Mesenchymal Transition (EMT) and spheroid cloning assays were employed to evaluate phenotypic changes in cancer stem cells.

RESULTS

Twelve components of AC were identified. AC effectively inhibited CRC progression in vivo. Transcriptomic analysis highlighted hypoxic signaling as a significantly enriched pathway, implicating its role in suppressing CRC progression by AC. In the hypoxic model, AC inhibited the proliferation and migration of CRC cells in vitro. Furthermore, AC reduced cancer stemness by downregulating stemness markers, inhibiting EMT, and decreasing tumor sphere formation. The downregulation of hypoxic responses and the shift in stemness by AC involved attenuation of HIF-2α and WNT/β-catenin signaling.

CONCLUSION

This study provides the first evidence that AC reduces the stemness of CRC and the inhibition of the transition of CRC to stem-like cells by AC is closely related to the downregulation of the HIF-2α/β-catenin pathway, especially under hypoxic conditions.

Regulation of the HIF switch in human endothelial and cancer cells

Hypoxia-inducible factors (HIFs) are transcription factors that reprogram the transcriptome for cells to survive hypoxic insults and oxidative stress. They are important during embryonic development and reprogram the cells to utilize glycolysis when the oxygen levels are extremely low. This metabolic change facilitates normal cell survival as well as cancer cell survival. The key feature in survival is the transition between acute hypoxia and chronic hypoxia, and this is regulated by the transition between HIF-1 expression and HIF-2/HIF-3 expression. This transition is observed in many human cancers and endothelial cells and referred to as the HIF Switch. Here we discuss the mechanisms involved in the HIF Switch in human endothelial and cancer cells which include mRNA and protein levels of the alpha chains of the HIFs. A major continuing effort in this field is directed towards determining the differences between normal and tumor cell utilization of this important pathway, and how this could lead to potential therapeutic approaches.

Novel cancer treatment paradigm targeting hypoxia-induced factor in conjunction with current therapies to overcome resistance

Chemotherapy, radiotherapy, targeted therapy, and immunotherapy are established cancer treatment modalities that are widely used due to their demonstrated efficacy against tumors and favorable safety profiles or tolerability. Nevertheless, treatment resistance continues to be one of the most pressing unsolved conundrums in cancer treatment. Hypoxia-inducible factors (HIFs) are a family of transcription factors that regulate cellular responses to hypoxia by activating genes involved in various adaptations, including erythropoiesis, glucose metabolism, angiogenesis, cell proliferation, and apoptosis. Despite this critical function, overexpression of HIFs has been observed in numerous cancers, leading to resistance to therapy and disease progression. In recent years, much effort has been poured into developing innovative cancer treatments that target the HIF pathway. Combining HIF inhibitors with current cancer therapies to increase anti-tumor activity and diminish treatment resistance is one strategy for combating therapeutic resistance. This review focuses on how HIF inhibitors could be applied in conjunction with current cancer treatments, including those now being evaluated in clinical trials, to usher in a new era of cancer therapy.

Chemotherapy induces immune checkpoint VISTA expression in tumor cells via HIF-2alpha

Tumor cells can evade the innate and adaptive immune systems, which play important roles in tumor recurrence and metastasis. Malignant tumors that recur after chemotherapy are more aggressiveciscis, suggesting an increased ability of the surviving tumor cells to evade innate and adaptive immunity. Therefore, in order to reduce patient mortality, it is important to discover the mechanisms by which tumor cells develop resistance to chemotherapeutics. In the present study we focused on the tumor cells that survived chemotherapy. We found that chemotherapy could promote the expression of VISTA in tumor cells, and that this change was mediated by HIF-2α. In addition, VISTA overexpression on melanoma cells promoted immune evasion, and the application of the VISTA-blocking antibody 13F3 enhanced the therapeutic effect of carboplatin. These results offer an insight into the immune evasion of chemotherapy-resistant tumors, and provide a theoretical basis for the combined application of chemotherapy drugs and VISTA inhibitors to treat tumors.

Microparticle Phosphatidylserine Mediates Coagulation: Involvement in Tumor Progression and Metastasis

Tumor progression and cancer metastasis has been linked to the release of microparticles (MPs), which are shed upon cell activation or apoptosis and display parental cell antigens, phospholipids such as phosphatidylserine (PS), and nucleic acids on their external surfaces. In this review, we highlight the biogenesis of MPs as well as the pathophysiological processes of PS externalization and its involvement in coagulation activation. We review the available evidence, suggesting that coagulation factors (mainly tissue factor, thrombin, and fibrin) assist in multiple steps of tumor dissemination, including epithelial-mesenchymal transition, extracellular matrix remodeling, immune escape, and tumor angiogenesis to support the formation of the pre-metastatic niche. Platelets are not just bystander cells in circulation but are functional players in primary tumor growth and metastasis. Tumor-induced platelet aggregation protects circulating tumor cells (CTCs) from the blood flow shear forces and immune cell attack while also promoting the binding of CTCs to endothelial cells and extravasation, which activates tumor invasion and sustains metastasis. Finally, in terms of therapy, lactadherin can inhibit coagulation by competing effectively with coagulation factors for PS binding sites and may similarly delay tumor progression. Furthermore, we also investigate the therapeutic potential of coagulation factor inhibitors within the context of cancer treatment. The development of multiple therapies targeting platelet activation and platelet-tumor cell interactions may not only reduce the lethal consequences of thrombosis but also impede tumor growth and spread.

JAK1 inactivation promotes proliferation and migration of endometrial cancer cells via upregulating the hypoxia-inducible factor signaling pathway

BACKGROUND

Loss-of-function (LOF) mutations of JAK1, a member of the JAK kinase family, were frequently observed in EC, indicating that JAK1 may act as a tumor suppressor, at least in EC. However, the mechanism of JAK1 mediated regulation of tumorigenesis remains poorly understood.

METHODS

The genetic alterations of JAK1 in EC using latest sequencing dataset of EC deposited in TCGA database. The RNA-Seq dataset of EC and normal endometrial tissues from TCGA cohort was analyzed. The expression of JAK1 in EC and normal endometrial tissues were investigated using immunohistochemistry. The expression levels of genes in endometrial cancer cells were detected by quantitative reverse transcription-PCR (RT-qPCR) and western blotting. JAK1 protein was efficiently depleted by the two shRNAs. HIF1/2-α protein was efficiently depleted by siRNAs. JAK1 overexpressed EC cells were generated by an expressing plasmid. The proliferation and migration ability of cancer cells were evaluated by CCK8, colony formation assays and transwell assays. The global transcriptomic changes in JAK1-depleted KLE cells were investigated using RNA-Seq. Gene Ontology (GO) Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to identify the most significant pathways that were altered in JAK1-depleted KLE cells. The physical association between HIF-1/2α and JAK1 using co-immunoprecipitation (co-IP) assays.

RESULTS

In the present study, we found that JAK1 was frequently mutated and downregulated in EC. JAK1 knockdown promotes EC cell proliferation and migration. JAK1 overexpression reduces EC cell proliferation and migration. We examined the transcriptional profiling changes in JAK1-depleted EC cells and unexpectedly found that the hypoxia inducible factor (HIF) pathway was activated. Mechanistically, JAK1 interacts with HIF-1/2α, and reduces HIF1/2-α protein expression under hypoxia. HIF-1/2α knockdown reverses the JAK1 knockdown-induced growth and migration of EC cells under hypoxia. JAK1 knockdown or pharmacological inhibition of JAK1 kinase activity by Ruxolitinib upregulates transcription of HIF target genes under hypoxia. JAK1 overexpression downregulates transcription of HIF target genes under hypoxia.

CONCLUSIONS

These findings provide novel insights into the functional link between JAK1 LOF mutations and abnormal HIF pathway activation in EC and suggest that pharmacological inhibition of HIF1/2 represents a promising therapeutic strategy targeting JAK1-mutated ECs. Video Abstract.

Emerging role of circRNAs in cancer under hypoxia (Review)

Circular RNA (circRNA), a recently identified type of non-coding RNAs (ncRNAs), forms a covalently closed loop with neither a 5′ cap structure nor a 3′ polyadenylated tail. Due to their lack of free ends, circRNAs are not easily cleaved by RNase R, thus avoiding degradation and being more stable than linear RNAs. Recent studies have suggested that circRNAs play a crucial role in regulating gene expression by acting as microRNAs sponges, RNA binding protein sponges and translational regulators. Currently, circRNAs are hot research topics due to their close association with the development of cancer and other diseases. Hypoxia is the most common microenvironment during tumor growth, and hypoxia-inducible factors have different effects on tumor growth and influence important cancer characteristics, including cell proliferation, apoptosis, differentiation, vascularization/angiogenesis, genetic instability, tumor metabolism, tumor immune response, invasion and metastasis. The present review aimed to study the biogenesis and mechanisms of gene regulation of circRNAs in hypoxia, to summarize the latest studies on circRNAs as potential diagnostic and prognostic biomarkers in hypoxia, and to understand the role of circRNAs in the process of tumor drug resistance under hypoxia.

HIF-2α Inhibits Ameloblast Differentiation via Hey2 in Tooth Development

Enamel is the highly mineralized outer layer of teeth; the cells responsible for enamel formation are ameloblasts. Local hypoxia and hypoxia inducible factor (HIF) in embryonic tissues are important to promote normal organogenesis. However, hypoxic state in tooth germs and the roles of HIF in ameloblast differentiation have not been understood. The aim of this study is to clarify the role of HIF in ameloblast differentiation during tooth germ development. We found that tooth germs were under hypoxia and HIF-1α and HIF-2α were expressed in tooth germs in embryonic mice. Then, we used HIF inhibitors to evaluate the function of HIF during tooth germ development. The HIF-2α inhibitor significantly decreased the size of tooth germs in organ culture, while the HIF-1α inhibitor did not apparently affect the size of tooth germs. The HIF-2α inhibitor enhanced the expression of amelogenin, a marker of ameloblast differentiation, in the tooth germs in organ culture and rat dental epithelial SF2 cells. Moreover, we found that the HIF-2α inhibitor-stimulating amelogenin expression was regulated by hes-related family basic helix-loop-helix transcription factor with YRPW motif 2(Hey2) in SF2 cells. These findings suggest that the HIF-2α-Hey2 axis plays an important role in ameloblast differentiation during tooth germ development.

Crosstalk among m6A RNA methylation, hypoxia and metabolic reprogramming in TME: from immunosuppressive microenvironment to clinical application

The tumor microenvironment (TME), which is regulated by intrinsic oncogenic mechanisms and epigenetic modifications, has become a research hotspot in recent years. Characteristic features of TME include hypoxia, metabolic dysregulation, and immunosuppression. One of the most common RNA modifications, N6-methyladenosine (m⁶A) methylation, is widely involved in the regulation of physiological and pathological processes, including tumor development. Compelling evidence indicates that m⁶A methylation regulates transcription and protein expression through shearing, export, translation, and processing, thereby participating in the dynamic evolution of TME. Specifically, m⁶A methylation-mediated adaptation to hypoxia, metabolic dysregulation, and phenotypic shift of immune cells synergistically promote the formation of an immunosuppressive TME that supports tumor proliferation and metastasis. In this review, we have focused on the involvement of m⁶A methylation in the dynamic evolution of tumor-adaptive TME and described the detailed mechanisms linking m⁶A methylation to change in tumor cell biological functions. In view of the collective data, we advocate treating TME as a complete ecosystem in which components crosstalk with each other to synergistically achieve tumor adaptive changes. Finally, we describe the potential utility of m⁶A methylation-targeted therapies and tumor immunotherapy in clinical applications and the challenges faced, with the aim of advancing m⁶A methylation research.

Hypoxia-inducible factors: master regulators of hypoxic tumor immune escape

Hypoxia, a common feature of the tumor microenvironment in various types of cancers, weakens cytotoxic T cell function and causes recruitment of regulatory T cells, thereby reducing tumoral immunogenicity. Studies have demonstrated that hypoxia and hypoxia-inducible factors (HIFs) 1 and 2 alpha (HIF1A and HIF2A) are involved in tumor immune escape. Under hypoxia, activation of HIF1A induces a series of signaling events, including through programmed death receptor-1/programmed death ligand-1. Moreover, hypoxia triggers shedding of complex class I chain-associated molecules through nitric oxide signaling impairment to disrupt immune surveillance by natural killer cells. The HIF-1-galactose-3-O-sulfotransferase 1-sulfatide axis enhances tumor immune escape via increased tumor cell-platelet binding. HIF2A upregulates stem cell factor expression to recruit tumor-infiltrating mast cells and increase levels of cytokines interleukin-10 and transforming growth factor-β, resulting in an immunosuppressive tumor microenvironment. Additionally, HIF1A upregulates expression of tumor-associated long noncoding RNAs and suppresses immune cell function, enabling tumor immune escape. Overall, elucidating the underlying mechanisms by which HIFs promote evasion of tumor immune surveillance will allow for targeting HIF in tumor treatment. This review discusses the current knowledge of how hypoxia and HIFs facilitate tumor immune escape, with evidence to date implicating HIF1A as a molecular target in such immune escape. This review provides further insight into the mechanism of tumor immune escape, and strategies for tumor immunotherapy are suggested.

Hypoxia responsive phytonanotheranostics: A novel paradigm towards fighting cancer

Hypoxia enhances tumor aggressiveness, thereby reducing the efficacy of anticancer therapies. Phytomedicine, which is nowadays considered as the new panacea owing to its dynamic physiological properties, is often plagued by shortcomings. Incorporating these wonder drugs in nanoparticles (phytonanomedicine) for hypoxia therapy is a new prospect in the direction of cancer management. Similarly, the concept of phytonanotheranostics for the precise tumor lesion detection and treatment monitoring in the hypoxic scenario is going on a rampant speed. In the same line, smart nanoparticles which step in for "on-demand" drug release based on internal or external stimuli are also being explored as a new tool for cancer management. However, studies regarding these smart and tailor-made nanotheranostics in the hypoxic tumor microenvironment are very limited. The present review is an attempt to collate these smart stimuli-responsive phytonanotherapeutics in one place for initiating future research in this upcoming field for better cancer treatment.

HIF-2α-targeted interventional chemoembolization multifunctional microspheres for effective elimination of hepatocellular carcinoma

Transcatheter arterial chemoembolization (TACE) is widely used for the treatment of advanced hepatocellular carcinoma (HCC). However, the long-term hypoxic microenvironment caused by TACE seriously affects the therapeutic effect of TACE. HIF-2α plays a crucial role on the chronic hypoxia process, which might be an ideal target for TACE therapy. Herein, a multifunctional polyvinyl alcohol (PVA)/hyaluronic acid (HA)-based microsphere (PT/DOX-MS) co-loaded with doxorubicin (DOX) and PT-2385, an effective HIF-2α inhibitor, was developed for enhanced TACE treatment efficacy. In vitro and in vivo studies revealed that PT/DOX-MS had a superior ability to treat HCC by blocking the tumor cells in G2/M phase, prompting cell apoptosis, and inhibiting tumor angiogenesis. The antitumor mechanisms of PT/DOX-MS were possibly due to that the introduction of PT-2385 could effectively inhibit the expression level of HIF-2α in hypoxic HCC cells, thereby down-regulating the expression levels of Cyclin D1, VEGF and TGF-α. In addition, the combination of DOX and PT-2385 could jointly inhibit VEGF expression, which was another reason accounting for the combined anti-cancer effect of PT/DOX-MS. Overall, our study demonstrated that PT/DOX-MS is a promising embolic agent for enhanced HCC treatment via the combined effect of hypoxia microenvironment improvement, chemotherapy, and embolization.

Considerations about Hypoxic Changes in Neuraxis Tissue Injuries and Recovery

Hypoxia represents the temporary or longer-term decrease or deprivation of oxygen in organs, tissues, and cells after oxygen supply drops or its excessive consumption. Hypoxia can be (para)-physiological-adaptive-or pathological. Thereby, the mechanisms of hypoxia have many implications, such as in adaptive processes of normal cells, but to the survival of neoplastic ones, too. Ischemia differs from hypoxia as it means a transient or permanent interruption or reduction of the blood supply in a given region or tissue and consequently a poor provision with oxygen and energetic substratum-inflammation and oxidative stress damages generating factors. Considering the implications of hypoxia on nerve tissue cells that go through different ischemic processes, in this paper, we will detail the molecular mechanisms by which such structures feel and adapt to hypoxia. We will present the hypoxic mechanisms and changes in the CNS. Also, we aimed to evaluate acute, subacute, and chronic central nervous hypoxic-ischemic changes, hoping to understand better and systematize some neuro-muscular recovery methods necessary to regain individual independence. To establish the link between CNS hypoxia, ischemic-lesional mechanisms, and neuro-motor and related recovery, we performed a systematic literature review following the" Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA") filtering method by interrogating five international medical renown databases, using, contextually, specific keywords combinations/"syntaxes", with supplementation of the afferent documentation through an amount of freely discovered, also contributive, bibliographic resources. As a result, 45 papers were eligible according to the PRISMA-inspired selection approach, thus covering information on both: intimate/molecular path-physiological specific mechanisms and, respectively, consequent clinical conditions. Such a systematic process is meant to help us construct an article structure skeleton giving a primary objective input about the assembly of the literature background to be approached, summarised, and synthesized. The afferent contextual search (by keywords combination/syntaxes) we have fulfilled considerably reduced the number of obtained articles. We consider this systematic literature review is warranted as hypoxia's mechanisms have opened new perspectives for understanding ischemic changes in the CNS neuraxis tissue/cells, starting at the intracellular level and continuing with experimental research to recover the consequent clinical-functional deficits better.

SHARPIN regulates the development of clear cell renal cell carcinoma by promoting von Hippel-Lindau protein ubiquitination and degradation

SHANK-associated RH domain interacting protein (SHARPIN) plays an important role in carcinogenesis, as well as inflammation and immunity. Our study explored the effects and underlying mechanisms of SHARPIN in clear cell renal cell carcinoma (ccRCC). By analyzing The Cancer Genome Atlas database, we found that upregulated SHARPIN in patients with ccRCC led to a poor prognosis. Semiquantitative immunohistochemical analysis of clinical samples was carried out and the results suggested the positive association between SHARPIN and hypoxia-induced factor-2α (HIF-2α). Von Hippel-Lindau protein (pVHL) is a tumor suppressor that contributes to degrading HIF-2α. Mechanically, SHARPIN promoted the ubiquitination and proteasomal degradation of pVHL, resulting in the sustained activation of HIF-2α. The α and β domains of pVHL and ubiquitin-like domain of SHARPIN are required for the interaction. The knockdown of SHARPIN effectively inhibited acquired sorafenib resistance in ccRCC cell lines and tumor growth in xenograft models. In conclusion, our work reveals a novel posttranslational regulation of SHARPIN on pVHL, indicating that SHARPIN could be a potential target for ccRCC treatment.

Effect of the Hypoxia Inducible Factor on Sorafenib Resistance of Hepatocellular Carcinoma

Sorafenib a multi-target tyrosine kinase inhibitor, is the first-line drug for treating advanced hepatocellular carcinoma (HCC). Mechanistically, it suppresses tumor angiogenesis, cell proliferation and promotes apoptosis. Although sorafenib effectively prolongs median survival rates of patients with advanced HCC, its efficacy is limited by drug resistance in some patients. In HCC, this resistance is attributed to multiple complex mechanisms. Previous clinical data has shown that HIFs expression is a predictor of poor prognosis, with further evidence demonstrating that a combination of sorafenib and HIFs-targeted therapy or HIFs inhibitors can overcome HCC sorafenib resistance. Here, we describe the molecular mechanism underlying sorafenib resistance in HCC patients, and highlight the impact of hypoxia microenvironment on sorafenib resistance.

The non-canonical functions of HIF prolyl hydroxylases and their dual roles in cancer

The hypoxia-inducible factor (HIF) prolyl hydroxylases (PHDs) are dioxygenases using oxygen and 2-oxoglutarate as co-substrates. Under normoxia, PHDs hydroxylate the conserved prolyl residues of HIFα, leading to HIFα degradation. In hypoxia PHDs are inactivated, which results in HIFα accumulation. The accumulated HIFα enters nucleus and initiates gene transcription. Many studies have shown that PHDs have substrates other than HIFα, implying that they have HIF-independent non-canonical functions. Besides modulating protein stability, the PHDs-mediated prolyl hydroxylation affects protein-protein interaction and protein activity for alternative substrates. Increasing evidence indicates that PHDs also have hydroxylase-independent functions. They influence protein stability, enzyme activity, and protein-protein interaction in a hydroxylase-independent manner. These findings highlight the functional diversity and complexity of PHDs. Due to having inhibitory activity on HIFα, PHDs are proposed to act as tumor suppressors. However, research shows that PHDs exert either tumor-promoting or tumor-suppressing features. Here, we try to summarize the current understanding of PHDs hydroxylase-dependent and -independent functions and their roles in cancer.

Key genes and drug delivery systems to improve the efficiency of chemotherapy

Cancer cells can develop resistance to anticancer drugs, thereby becoming tolerant to treatment through different mechanisms. The biological mechanisms leading to the generation of anticancer treatment resistance include alterations in transmembrane proteins, DNA damage and repair mechanisms, alterations in target molecules, and genetic responses, among others. The most common anti-cancer drugs reported to develop resistance to cancer cells include cisplatin, doxorubicin, paclitaxel, and fluorouracil. These anticancer drugs have different mechanisms of action, and specific cancer types can be affected by different genes. The development of drug resistance is a cellular response which uses differential gene expression, to enable adaptation and survival of the cell to diverse threatening environmental agents. In this review, we briefly look at the key regulatory genes, their expression, as well as the responses and regulation of cancer cells when exposed to anticancer drugs, along with the incorporation of alternative nanocarriers as treatments to overcome anticancer drug resistance.

Effect of isoform-specific HIF-1α and HIF-2α antisense oligonucleotides on tumorigenesis, inflammation and fibrosis in a hepatocellular carcinoma mouse model

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. For advanced HCC, there is still an unmet need for more effective therapeutic strategies. HCC is typically associated with hypoxia and the hypoxia-inducible factor (HIF) regulatory pathway plays an important role in HCC development and progression. Therefore, we investigated the therapeutic potential of isoform-specific HIF-1α and HIF-2α antisense oligonucleotides (ASOs), along with their effect on the inflammatory and fibrotic component of the tumor microenvironment (TME), in an experimental HCC mouse model. Based on its efficacy and safety, a dosage regimen of 20 mg/kg intraperitoneal injection of HIFα ASO twice per week was selected for further investigation in a preventive and therapeutic setting in a N,N-diethylnitrous amide (DEN)-induced HCC mouse model. DEN administration resulted in 100% tumor formation and HIFα ASO administration led to effective and selective hepatic downregulation of its target genes. HIFα ASO treatment had no effect on tumor numbers, but even enhanced the increased hepatic expression of HCC tumor markers, α-fetoprotein and glypican-3, compared to scrambled control ASO treatment in HCC mice. Especially HIF-1α ASO treatment resulted in an enhanced increase of monocytes and monocyte-derived macrophages in the liver and an enhanced hepatic upregulation of inflammatory markers. Both HIFα ASOs aggravated liver fibrosis in HCC mice compared to scrambled ASO treatment. The observed effects of our dosing regimen for HIF-1α and HIF-2α ASO treatment in the DEN-induced HCC mouse model discourage the use of HIFα isoforms as targets for the treatment of HCC.

Epigenetic crosstalk between hypoxia and tumor driven by HIF regulation

Hypoxia is the major influence factor in physiological and pathological courses which are mainly mediated by hypoxia-inducible factors (HIFs) in response to low oxygen tensions within solid tumors. Under normoxia, HIF signaling pathway is inhibited due to HIF-α subunits degradation. However, in hypoxic conditions, HIF-α is activated and stabilized, and HIF target genes are successively activated, resulting in a series of tumour-specific activities. The activation of HIFs, including HIF-1α, HIF-2α and HIF-3α, subsequently induce downstream target genes which leads to series of responses, the resulting abnormal processes or metabolites in turn affect HIFs stability. Given its functions in tumors progression, HIFs have been regarded as therapeutic targets for improved treatment efficacy. Epigenetics refers to alterations in gene expression that are stable between cell divisions, and sometimes between generations, but do not involve changes in the underlying DNA sequence of the organism. And with the development of research, epigenetic regulation has been found to play an important role in the development of tumors, which providing accumulating basic or clinical evidences for tumor treatments. Here, given how little has been reported about the overall association between hypoxic tumors and epigenetics, we made a more systematic review from epigenetic perspective in hope of helping others better understand hypoxia or HIF pathway, and providing more established and potential therapeutic strategies in tumors to facilitate epigenetic studies of tumors.

Loss of miR-145-5p Causes Ceruloplasmin Interference with PHD-Iron Axis and HIF-2α Stabilization in Lung Adenocarcinoma-Mediated Angiogenesis

For decades, lung cancer has been the leading cause of cancer-related death worldwide. Hypoxia-inducible factors (HIFs) play critical roles in mediating lung cancer development and metastasis. The present study aims to clarify how HIF’s over-activation affects lung cancer angiogenesis not only in a normoxic condition, but also a hypoxic niche. Our study shows that human lung cancer exhibits elevated levels of ceruloplasmin (CP), which has a negative impact on the prognosis of patients. CP affects the cellular Fe²⁺ level, which inactivates prolyl hydroxylase (PHD) 1 and 2, resulting in HIF-2α enhancement. Increased HIF-2α leads to vascular endothelial growth factor-A (VEGF-A) secretion and angiogenesis. The expression of CP is under the epigenetic control of miR-145-5p. Restoration of miR-145-5p by miRNA mimics transfection decreases CP expression, increases Fe²⁺ and PHD1/2 levels and HIF hydroxylation while reduced HIF-2α levels resulting in the inhibition of tumor angiogenesis. In contrast, inhibition of miR-145-5p by miRNA inhibitors increases the expression of CP and VEGF-A in lung cancer cells. Significantly, miR-145-5p expression is lost in the tumor samples of lung cancer patients, and low miR-145-5p expression is strongly correlated with a shorter overall survival time. In conclusion, the current study reveals the clinical importance and prognostic value of miR-145-5p and CP. It identifies a unique mechanism of HIF-2α over-activation, which is mediated by iron imbalance of the iron-PHD coupling that modulates tumor angiogenesis.

Danger matrix molecules orchestrate CD14/CD44 signaling in cancer development

The tumor matrix together with inflammation and autophagy are crucial regulators of cancer development. Embedded in the tumor stroma are numerous proteoglycans which, in their soluble form, act as danger-associated molecular patterns (DAMPs). By interacting with innate immune receptors, the Toll-like receptors (TLRs), DAMPs autonomously trigger aseptic inflammation and can regulate autophagy. Biglycan, a known danger proteoglycan, can regulate the cross-talk between inflammation and autophagy by evoking a switch between pro-inflammatory CD14 and pro-autophagic CD44 co-receptors for TLRs. Thus, these novel mechanistic insights provide some explanation for the plethora of reports indicating that the same matrix-derived DAMP acts either as a promoter or suppressor of tumor growth. In this review we will summarize and critically discuss the role of the matrix-derived DAMPs biglycan, hyaluronan, and versican in regulating the TLR-, CD14- and CD44-signaling dialogue between inflammation and autophagy with particular emphasis on cancer development.

DUBs, Hypoxia, and Cancer

Alterations in protein ubiquitylation and hypoxia are commonly associated with cancer. Ubiquitylation is carried out by three sequentially acting ubiquitylating enzymes and can be opposed by deubiquitinases (DUBs), which have emerged as promising drug targets. Apart from protein localization and activity, ubiquitylation regulates degradation of proteins, among them hypoxia-inducible factors (HIFs). Thereby, various E3 ubiquitin ligases and DUBs regulate HIF abundance. Conversely, several E3s and DUBs are regulated by hypoxia. While hypoxia is a powerful HIF regulator, less is known about hypoxia-regulated DUBs and their impact on HIFs. Here, we review current knowledge about the relationship of E3s, DUBs, and hypoxia signaling. We also discuss the reciprocal regulation of DUBs by hypoxia and use of DUB-specific drugs in cancer.

The Role of Metabolic Plasticity in Blood and Brain Stem Cell Pathophysiology

Our understanding of intratumoral heterogeneity in cancer continues to evolve, with current models incorporating single-cell signatures to explore cell-cell interactions and differentiation state. The transition between stem and differentiation states in nonneoplastic cells requires metabolic plasticity, and this plasticity is increasingly recognized to play a central role in cancer biology. The insights from hematopoietic and neural stem cell differentiation pathways were used to identify cancer stem cells in leukemia and gliomas. Similarly, defining metabolic heterogeneity and fuel-switching signals in nonneoplastic stem cells may also give important insights into the corresponding molecular mechanisms controlling metabolic plasticity in cancer. These advances are important, because metabolic adaptation to anticancer therapeutics is rooted in this inherent metabolic plasticity and is a therapeutic challenge to be overcome.

Cross-disease analysis identified novel common genes for both lung adenocarcinoma and lung squamous cell carcinoma

Lung squamous cell carcinoma (LSCC) exhibits a number of similarities with lung adenocarcinoma (LA) in terms of copy number alterations. However, compared with LA, the range of genetic alterations in LSCC is less understood. In the present study, a large-scale literature-based search of LA-associated genes and LSCC-associated genes was performed to identify the genetic basis in common with these two diseases. For each of the LA-associated genes, a mega-analysis was performed to test its expression variations in LSCC using 11 RNA expression datasets, with significant genes identified using statistical analysis. Subsequently, a functional pathway analysis was performed to identify a possible association between any of the significant genes identified from the mega-analysis and LSCC, followed by a co-expression analysis. A multiple linear regression (MLR) model was employed to investigate the possible influence of sample size, country of origin and study date on gene expression in patients with LSCC. Disease-gene association data analysis identified 1,178 genes involved in LA, 334 in LSCC, with a significant overlap of 187 genes (P<1.02×⁻¹⁶¹). Mega-analysis revealed that three LA-associated genes, such as solute carrier family 2 member 1 (SLC2A1), endothelial PAS domain protein 1 (EPAS1) and cyclin-dependent kinase 4 (CDK4), were significantly associated with LSCC (P<1.60×10⁻⁸), with multiple potential pathways identified by functional pathway analysis, which were further validated by co-expression analysis. The present MLR analysis suggested that the country of origin was a significant factor for the levels of expression of all three genes in patients with LSCC (P<4.0×10⁻³). Collectively, the present results suggested that genes associated with LA should be further investigated for their association with LSCC. In addition, SLC2A1, EPAS1 and CDK4 may be novel risk genes associated with LA and LSCC.

The Clinicopathologic and Prognostic Value of Hypoxia-Inducible Factor-2α in Cancer Patients: A Systematic Review and Meta-Analysis

Hypoxia-inducible factor-2α (HIF2α) plays an important role in the development of tumors. However, the clinicopathologic and prognostic significance of HIF2α in cancer patients remains controversial. Therefore, we performed a meta-analysis to investigate the relationship between the HIF2α status and clinical outcome in human cancer. Studies were screened online using electronic databases. The pooled risk ratios or hazard ratios (HR) with their 95% confidence intervals (CI) were calculated from available publications. Subgroup analysis, sensitivity analysis, heterogeneity, and publication bias were also conducted. A total of 854 studies with 4,345 patients were obtained in this meta-analysis. The results indicated that the increased expression of HIF2α could predict unfavorable overall survival of cancer patients on both univariate analysis (HR, 1.64; 95% CI, 1.41-1.92, P < 0.001) and multivariate analysis (HR, 2.21; 95% CI, 1.70-2.87, P < 0.001). Moreover, HIF2α overexpression was associated closely with tumor differentiation, tumor-node-metastasis stage, and lymph metastasis. In addition, there was no obvious evidence for significant publication bias in this meta-analysis. Our study indicated that HIF2α might be an indicator of poor prognosis and clinicopathologic features of tumors and could serve as a novel biomarker in human cancer.

Current insights and future perspectives of hypoxia-inducible factor-targeted therapy in cancer

Hypoxia-inducible factors (HIFs) are transcription factors that are expressed in the hypoxic tumor microenvironment. They are involved in the cellular adaptations by improving the metabolism of glucose and enhance the expression of vascular endothelial growth factor, platelet-derived growth factor and angiopoietin, thereby they play a pivotal role in the angiogenesis. Hypoxia can increase the expression of nuclear factor-kappa B which promotes the pro-inflammatory status. Abnormally high angiogenesis, inflammation, antiapoptosis and anaerobic glycolysis can augment the progression and metastasis of tumor. Hence, HIFs remain one of the promising antiangiogenic agents as well as a direct target for interfering with the energetic of cancer cells in order to regulate the tumor growth. Previous studies found agents like topotecan, acriflavine and benzophenone-1B etc. to block the HIF-α mediated angiogenesis. The effect is mediated through interfering any one of the processes in the activation of HIF such as nuclear translocation of HIF-1α; dimerization of HIF-1α with β in the nucleus; HIF-1α/HIF-2α mediated induction of VEGF or translation of HIF-1α mRNA. Despite the experimental studies on the inhibitory molecules of HIFs, none of them are available for the clinical use. This review article discusses the recent update on the HIF-targeted therapy in cancer.