Prolyl-hydroxylase inhibitors reconstitute tumor blood vessels in mice

[The effect of PHD inhibitor on tumor microenvironment and tumor immune response]

Since the approval of HIF-PH inhibitors, HIF-PH inhibitors have been used clinically, and many studies and clinical case reports have been reported in Japan. A lot of information has been accumulated on clinical usage. However, HIF-PH inhibitors require careful administration for cancer patients due to their action mechanism through upregulating hypoxia-inducible factors (HIFs) level. In cancer cells, HIFs affect tumor progression and contribute to chemo- and radio-resistance. On the other hand, upregulation of HIFs in immune cells is associated with inflammation and suppress tumor progression. However, these controversial effects are not clear in in vivo model. It is needed to reveal whether upregulating HIFs level is beneficial for cancer therapy or not. We have previously reported that HIF-PH inhibitor treatment in tumor bearing mice model led to reconstitute tumor blood vessel and inhibit tumor growth. In addition, these phenomena were caused by tumor infiltrated macrophages and they altered these phenotypes. In this review, we will describe our findings on the mechanism of tumor growth suppression by HIF-PH inhibitors. We also want to mention the risks and benefits of future HIF-PH inhibitors.

Harnessing EGLN1 Gene Editing to Amplify HIF-1α and Enhance Human Angiogenic Response

Therapeutic angiogenesis has been the focus of hundreds of clinical trials but approval for human treatment remains elusive. Current strategies often rely on the upregulation of a single proangiogenic factor, which fails to recapitulate the complex response needed in hypoxic tissues. Hypoxic oxygen tensions dramatically decrease the activity of hypoxia inducible factor prolyl hydroxylase 2 (PHD2), the primary oxygen sensing portion of the hypoxia inducible factor 1 alpha (HIF-1α) proangiogenic master regulatory pathway. Repressing PHD2 activity increases intracellular levels of HIF-1α and impacts the expression of hundreds of downstream genes directly associated with angiogenesis, cell survival, and tissue homeostasis. This study explores activating the HIF-1α pathway through Sp Cas9 knockout of the PHD2 encoding gene EGLN1 as an innovative in situ therapeutic angiogenesis strategy for chronic vascular diseases. Our findings demonstrate that even low editing rates of EGLN1 lead to a strong proangiogenic response regarding proangiogenic gene transcription, protein production, and protein secretion. In addition, we show that secreted factors of EGLN1 edited cell cultures may enhance human endothelial cell neovascularization activity in the context of proliferation and motility. Altogether, this study reveals that EGLN1 gene editing shows promise as a potential therapeutic angiogenesis strategy.

Pleotropic effects of hypoxia-inducible factor-prolyl hydroxylase domain inhibitors: are they clinically relevant?

Anemia is common in patients with chronic kidney disease (CKD) and is mainly caused by insufficient production of erythropoietin from fibrotic kidney. Because anemia impairs quality of life and overall prognosis, recombinant human erythropoietin-related products (erythropoiesis-stimulating agents, ESAs) have been developed to increase hemoglobin level for decades. However, many safety concerns have been announced regarding the use of ESAs, including an increased occurrence of cardiovascular events, vascular access thrombosis, cancer progression, and recurrence. Hypoxia-inducible factor (HIF) is crucial to erythropoietin production, as a result, prolyl hydroxylase domain (PHD) enzyme inhibitors have been new therapeutic agents for the treatment of anemia in CKD. They can be administered orally, which is a preferred route for patients not undergoing hemodialysis. In clinical trials, PHD inhibitor could induce noninferior effect on erythropoiesis and improve functional iron deficiency compared with ESAs. Although no serious adverse events were reported, safety is still a concern because HIF stabilization induced by PHD inhibitor has pleotropic effects, such as angiogenesis, metabolic change, and cell survival, which might lead to unwanted deleterious effects, including fibrosis, inflammation, cardiovascular risk, and tumor growth. More molecular mechanisms of PHD inhibition and long-term clinical trials are needed to observe these pleotropic effects for the confirmation of safety and efficacy of PHD inhibitors.

Evolving Strategies in the Treatment of Anaemia in Chronic Kidney Disease: The HIF-Prolyl Hydroxylase Inhibitors

Chronic kidney disease (CKD) affects approximately 10% of the worldwide population; anaemia is a frequent complication. Inadequate erythropoietin production and absolute or functional iron deficiency are the major causes. Accordingly, the current treatment is based on iron and erythropoiesis stimulating agents (ESAs). Available therapy has dramatically improved the management of anaemia and the quality of life. However, safety concerns were raised over ESA use, especially when aiming to reach near-to-normal haemoglobin levels with high doses. Moreover, many patients show hypo-responsiveness to ESA. Hypoxia-inducible factor (HIF) prolyl hydroxylase domain (PHD) inhibitors (HIF-PHIs) were developed for the oral treatment of anaemia in CKD to overcome these concerns. They simulate the body's exposure to moderate hypoxia, stimulating the production of endogenous erythropoietin. Some molecules are already approved for clinical use in some countries. Data from clinical trials showed non-inferiority in anaemia correction compared to ESA or superiority for placebo. Hypoxia-inducible factor-prolyl hydroxylase domain inhibitors may also have additional advantages in inflamed patients, improving iron utilisation and mobilisation and decreasing LDL-cholesterol. Overall, non-inferiority was also shown in major cardiovascular events, except for one molecule in the non-dialysis population. This was an unexpected finding, considering the lower erythropoietin levels reached using these drugs due to their peculiar mechanism of action. More data and longer follow-ups are necessary to better clarifying safety issues and further investigate the variety of pathways activated by HIF, which could have either positive or negative effects and could differentiate HIF-PHIs from ESAs.

Roxadustat: Not just for anemia

Roxadustat is a recently approved hypoxia-inducible factor prolyl hydroxylase inhibitor that has demonstrated favorable safety and efficacy in the treatment of renal anemia. Recent studies found it also has potential for the treatment of other hypoxia-related diseases. Although clinical studies have not yet found significant adverse or off-target effects of roxadustat, clinicians must be vigilant about these possible effects. Hypoxia-inducible factor regulates the expression of many genes and physiological processes in response to a decreased level of oxygen, but its role in the pathogenesis of different diseases is complex and controversial. In addition to increasing the expression of hypoxia-inducible factor, roxadustat also has some effects that may be HIF-independent, indicating some potential off-target effects. This article reviews the pharmacological characteristics of roxadustat, its current status in the treatment of renal anemia, and its possible effects on other pathological mechanisms.

Clinical Potential of Hypoxia Inducible Factors Prolyl Hydroxylase Inhibitors in Treating Nonanemic Diseases

Hypoxia inducible factors (HIFs) and their regulatory hydroxylases the prolyl hydroxylase domain enzymes (PHDs) are the key mediators of the cellular response to hypoxia. HIFs are normally hydroxylated by PHDs and degraded, while under hypoxia, PHDs are suppressed, allowing HIF-α to accumulate and transactivate multiple target genes, including erythropoiesis, and genes participate in angiogenesis, iron metabolism, glycolysis, glucose transport, cell proliferation, survival, and so on. Aiming at stimulating HIFs, a group of small molecules antagonizing HIF-PHDs have been developed. Of these HIF-PHDs inhibitors (HIF-PHIs), roxadustat (FG-4592), daprodustat (GSK-1278863), vadadustat (AKB-6548), molidustat (BAY 85-3934) and enarodustat (JTZ-951) are approved for clinical usage or have progressed into clinical trials for chronic kidney disease (CKD) anemia treatment, based on their activation effect on erythropoiesis and iron metabolism. Since HIFs are involved in many physiological and pathological conditions, efforts have been made to extend the potential usage of HIF-PHIs beyond anemia. This paper reviewed the progress of preclinical and clinical research on clinically available HIF-PHIs in pathological conditions other than CKD anemia.

Vascularized Tumor Spheroid-on-a-Chip Model Verifies Synergistic Vasoprotective and Chemotherapeutic Effects

Prolyl hydroxylases (PHD) inhibitors have been observed to improve drug distribution in mice tumors via blood vessel normalization, increasing the effectiveness of chemotherapy. These effects are yet to be demonstrated in human cell models. Tumor spheroids are three-dimensional cell clusters that have demonstrated great potential in drug evaluation for personalized medicine. Here, we used a perfusable vascularized tumor spheroid-on-a-chip to simulate the tumor microenvironment in vivo and demonstrated that the PHD inhibitor dimethylallyl glycine prevents the degradation of normal blood vessels while enhancing the efficacy of the anticancer drugs paclitaxel and cisplatin in human esophageal carcinoma (Eca-109) spheroids. Our results point to the potential of this model to evaluate anticancer drugs under more physiologically relevant conditions.

Role of the Epigenetic Modifier JMJD6 in Tumor Development and Regulation of Immune Response

JMJD6 is a member of the Jumonji (JMJC) domain family of histone demethylases that contributes to catalyzing the demethylation of H3R2me2 and/or H4R3me2 and regulating the expression of specific genes. JMJD6-mediated demethylation modifications are involved in the regulation of transcription, chromatin structure, epigenetics, and genome integrity. The abnormal expression of JMJD6 is associated with the occurrence and development of a variety of tumors, including breast carcinoma, lung carcinoma, colon carcinoma, glioma, prostate carcinoma, melanoma, liver carcinoma, etc. Besides, JMJD6 regulates the innate immune response and affects many biological functions, as well as may play key roles in the regulation of immune response in tumors. Given the importance of epigenetic function in tumors, targeting JMJD6 gene by modulating the role of immune components in tumorigenesis and its development will contribute to the development of a promising strategy for cancer therapy. In this article, we introduce the structure and biological activities of JMJD6, followed by summarizing its roles in tumorigenesis and tumor development. Importantly, we highlight the potential functions of JMJD6 in the regulation of tumor immune response, as well as the development of JMJD6 targeted small-molecule inhibitors for cancer therapy.

Liposomal PHD2 Inhibitors and the Enhanced Efficacy in Stabilizing HIF-1α

Prolyl hydroxylase domain-containing protein 2 (PHD2) inhibition, which stabilizes hypoxia-inducible factor (HIF)-1α and thus triggers adaptation responses to hypoxia in cells, has become an important therapeutic target. Despite the proven high potency, small-molecule PHD2 inhibitors such as IOX2 may require a nanoformulation for favorable biodistribution to reduce off-target toxicity. A liposome formulation for improving the pharmacokinetics of an encapsulated drug while allowing a targeted delivery is a viable option. This study aimed to develop an efficient loading method that can encapsulate IOX2 and other PHD2 inhibitors with similar pharmacophore features in nanosized liposomes. Driven by a transmembrane calcium acetate gradient, a nearly 100% remote loading efficiency of IOX2 into liposomes was achieved with an optimized extraliposomal solution. The electron microscopy imaging revealed that IOX2 formed nanoprecipitates inside the liposome’s interior compartments after loading. For drug efficacy, liposomal IOX2 outperformed the free drug in inducing the HIF-1α levels in cell experiments, especially when using a targeting ligand. This method also enabled two clinically used inhibitors—vadadustat and roxadustat—to be loaded into liposomes with a high encapsulation efficiency, indicating its generality to load other heterocyclic glycinamide PHD2 inhibitors. We believe that the liposome formulation of PHD2 inhibitors, particularly in conjunction with active targeting, would have therapeutic potential for treating more specifically localized disease lesions.

Molidustat for Japanese Patients With Renal Anemia Receiving Dialysis

INTRODUCTION

Molidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor for renal anemia treatment, was evaluated in 5 phase 3 studies (MIYABI program). We report the results of the MIYABI hemodialysis-maintenance study.

METHODS

This 52-week, randomized, double-blinded, double-dummy study compared the efficacy and safety of molidustat and darbepoetin in Japanese patients receiving hemodialysis and erythropoiesis-stimulating agents. Molidustat (starting dose: 75 mg/day) and darbepoetin were titrated to maintain hemoglobin (Hb) levels in the target range (≥10.0 and <12.0 g/dl). Primary outcomes were mean Hb level during the evaluation period (weeks 33-36) and its change from baseline. Safety outcomes included adverse events.

RESULTS

Overall, 229 patients were randomized (molidustat, n = 153; darbepoetin, n = 76). Baseline characteristics were well balanced. Mean baseline Hb level was 10.8 g/dl. Mean (95% confidence interval [CI]) for mean Hb levels during the evaluation period were within the target range in both groups (molidustat: 10.63 [10.42-10.84] g/dl; darbepoetin: 10.77 [10.59-10.95] g/dl). Least-squares mean (95% CI) change in mean Hb level during the evaluation period from baseline was -0.14 (-0.37 to 0.09) g/dl for molidustat and -0.07 (-0.30 to 0.16) g/dl for darbepoetin; molidustat was noninferior to darbepoetin (least-squares mean difference [95% CI] [molidustat-darbepoetin]: -0.13 [-0.46 to 0.19] g/dl), based on a noninferiority margin of 1.0 g/dl. In line with published literature, and as expected in this patient population, most participants had ≥1 treatment-emergent adverse event.

CONCLUSION

Molidustat maintained Hb levels throughout the trial in patients receiving dialysis and previously treated with erythropoiesis-stimulating agents, and was noninferior to darbepoetin.

HIF-α Prolyl Hydroxylase Inhibitors and Their Implications for Biomedicine: A Comprehensive Review

Oxygen is essential for the maintenance of the body. Living organisms have evolved systems to secure an oxygen environment to be proper. Hypoxia-inducible factor (HIF) plays an essential role in this process; it is a transcription factor that mediates erythropoietin (EPO) induction at the transcriptional level under hypoxic environment. After successful cDNA cloning in 1995, a line of studies were conducted for elucidating the molecular mechanism of HIF activation in response to hypoxia. In 2001, cDNA cloning of dioxygenases acting on prolines and asparagine residues, which play essential roles in this process, was reported. HIF-prolyl hydroxylases (PHs) are molecules that constitute the core molecular mechanism of detecting a decrease in the partial pressure of oxygen, or hypoxia, in the cells; they can be called oxygen sensors. In this review, I discuss the process of molecular cloning of HIF and HIF-PH, which explains hypoxia-induced EPO expression; the development of HIF-PH inhibitors that artificially or exogenously activate HIF by inhibiting HIF-PH; and the significance and implications of medical intervention using HIF-PH inhibitors.

Oncolytic adenovirus: A tool for reversing the tumor microenvironment and promoting cancer treatment (Review)

Immunogene therapy can enhance the antitumor immune effect by introducing genes encoding co‑stimulation molecules, cytokines, chemokines and tumor‑associated antigens into treatment cells or human cells through genetic engineering techniques. Oncolytic viruses can specifically target tumor cells and replicate indefinitely until they kill tumor cells. If combined with immunogene therapy, oncolytic viruses can play a more powerful antitumor role. The high pressure, hypoxia and acidity in the tumor microenvironment (TME) provide suitable conditions for tumor cells to survive. To maximize the potency of oncolytic viruses, various methods are being developed to promote the reversal of the TME, thereby maximizing transmission of replication and immunogenicity. The aim of the present review was to discuss the basic mechanisms underlying the effects of oncolytic adenoviruses on the TME, and suggest how to combine the modification of the adenovirus with the TME to further combat malignant tumors.

HIF-Prolyl Hydroxylase Domain Proteins (PHDs) in Cancer-Potential Targets for Anti-Tumor Therapy?

Solid tumors are typically associated with unbridled proliferation of malignant cells, accompanied by an immature and dysfunctional tumor-associated vascular network. Consequent impairment in transport of nutrients and oxygen eventually leads to a hypoxic environment wherein cells must adapt to survive and overcome these stresses. Hypoxia inducible factors (HIFs) are central transcription factors in the hypoxia response and drive the expression of a vast number of survival genes in cancer cells and in cells in the tumor microenvironment. HIFs are tightly controlled by a class of oxygen sensors, the HIF-prolyl hydroxylase domain proteins (PHDs), which hydroxylate HIFs, thereby marking them for proteasomal degradation. Remarkable and intense research during the past decade has revealed that, contrary to expectations, PHDs are often overexpressed in many tumor types, and that inhibition of PHDs can lead to decreased tumor growth, impaired metastasis, and diminished tumor-associated immune-tolerance. Therefore, PHDs represent an attractive therapeutic target in cancer research. Multiple PHD inhibitors have been developed that were either recently accepted in China as erythropoiesis stimulating agents (ESA) or are currently in phase III trials. We review here the function of HIFs and PHDs in cancer and related therapeutic opportunities.

Tumor Hypoxia Regulates Immune Escape/Invasion: Influence on Angiogenesis and Potential Impact of Hypoxic Biomarkers on Cancer Therapies

The environmental and metabolic pressures in the tumor microenvironment (TME) play a key role in molding tumor development by impacting the stromal and immune cell fractions, TME composition and activation. Hypoxia triggers a cascade of events that promote tumor growth, enhance resistance to the anti-tumor immune response and instigate tumor angiogenesis. During growth, the developing angiogenesis is pathological and gives rise to a haphazardly shaped and leaky tumor vasculature with abnormal properties. Accordingly, aberrantly vascularized TME induces immunosuppression and maintains a continuous hypoxic state. Normalizing the tumor vasculature to restore its vascular integrity, should hence enhance tumor perfusion, relieving hypoxia, and reshaping anti-tumor immunity. Emerging vascular normalization strategies have a great potential in achieving a stable normalization, resulting in mature and functional blood vessels that alleviate tumor hypoxia. Biomarkers enabling the detection and monitoring of tumor hypoxia could be highly advantageous in aiding the translation of novel normalization strategies to clinical application, alone, or in combination with other treatment modalities, such as immunotherapy.

Germline mutations and blood malignancy (Review)

Germline mutations are congenital genetic mutations in germ cells that originate from sperm or ovum and are generally incorporated into every cell of the offspring's body. Somatic mutations are acquired genetic mutations that form under the influence of environmental factors during embryo formation and epigenetic development. Generally, only a portion of the cells in the human body have the same somatic mutations. Clinical detection of germline mutations is intended to determine inherited malignancies and identify high‑risk families, and detection of somatic mutation is proposed to find targeted drugs, monitor tumor loading for guided therapy, and evaluate prognosis. Large‑scale population cohort studies have shown that germline mutations are closely related to the occurrence, development, and prognosis of diseases. Patients with cancer‑predisposition germline mutations can be used as sentinels in high‑risk families. Traditional histopathology is no longer enough to identify types of cancers. Even within a particular type of tumor, there is great heterogeneity between internal molecules. The Pan‑Cancer Research Program as well as other projects seek to use large quantities of data from different types of tumor research databases to carry out integrated analysis in order to establish potential non‑tumor‑specific tumor markers and targets by increasing the sample size to identify more molecular mechanisms. This review intends to summarize some of the relevant mechanisms underlying germline mutations in blood disorders.