Accumulation Of Hypoxia-inducible Factor Research Articles

Targeting hypoxia-inducible factors with 32-134D safely and effectively treats diabetic eye disease in mice.

Many patients with diabetic eye disease respond inadequately to anti-VEGF therapies, implicating additional vasoactive mediators in its pathogenesis. We demonstrate that levels of angiogenic proteins regulated by HIF-1 and -2 remain elevated in the eyes of people with diabetes despite treatment with anti-VEGF therapy. Conversely, by inhibiting HIFs, we normalized the expression of multiple vasoactive mediators in mouse models of diabetic eye disease. Accumulation of HIFs and HIF-regulated vasoactive mediators in hyperglycemic animals was observed in the absence of tissue hypoxia, suggesting that targeting HIFs may be an effective early treatment for diabetic retinopathy. However, while the HIF inhibitor acriflavine prevented retinal vascular hyperpermeability in diabetic mice for several months following a single intraocular injection, accumulation of acriflavine in the retina resulted in retinal toxicity over time, raising concerns for its use in patients. Conversely, 32-134D, a recently developed HIF inhibitor structurally unrelated to acriflavine, was not toxic to the retina, yet effectively inhibited HIF accumulation and normalized HIF-regulated gene expression in mice and in human retinal organoids. Intraocular administration of 32-134D prevented retinal neovascularization and vascular hyperpermeability in mice. These results provide the foundation for clinical studies assessing 32-134D for the treatment of patients with diabetic eye disease.

Immunological Aspects of Von Hippel-Lindau Disease: A Focus on Neuro-Oncology and Myasthenia Gravis

Von Hippel-Lindau (VHL) disease is an autosomal dominant condition that predisposes affected individuals to a variety of malignant and benign neoplasms. The pathogenetic turning point of this illness is the accumulation of hypoxia-inducible factor (HIF)-1α, a transcription factor of several genes involved in oncogenesis, angiogenesis, tissue regeneration, metabolic regulation, hematopoiesis, and inflammatory responses. From an oncological perspective, increased awareness of the molecular pathways underlying this disease is bringing us closer to the development of specific and targeted therapies. Meanwhile, on the surgical side, improved understanding can help to better identify the patients to be treated and the surgical timing. Overall, pathogenesis research is crucial for developing patient-tailored therapies. One of the actual key topics of interest is the link between the VHL/HIF axis and inflammation. The present study aims to outline the fundamental mechanisms that link VHL disease and immune disorders, as well as to explore the details of the overlap between VHL disease and myasthenia gravis (MG) pathogenetic pathways. As a result, MG becomes a paradigm for autoimmune disorders that might be related with VHL disease.

Effects of Ultrafine Single-Nanometer Oxygen Bubbles on Radiation Sensitivity in a Tumor-Bearing Mouse Model.

Radiation therapy against cancer cells often causes radiation resistance via accumulation of hypoxia-inducible factor 1 subunit alpha (HIF-1α) under hypoxic conditions and severe side effects. Radiation sensitizers without side effects are required to overcome hypoxia-induced radiation resistance and decrease radiation-related side effects in patients with refractory cancer. We previously developed oxygen nanobubble water (NBO2 water) and demonstrated that it suppresses hypoxia-induced radiation resistance in cancer cell lines within the single-nanometer range. This study aimed to elucidate whether NBO2 water could act as a radiosensitizer via regulation of HIF-1α in a tumor-bearing mouse model. Six-week-old female BALB/c mice subcutaneously injected with tumor cells received control water or NBO2 water for 28 days, after which biochemical examinations and radiation treatment were performed. Hypoxic tumor regions were detected immunohistochemically. We found that NBO2 water sensitized radiation reactivity in the xenografted tumors. Notably, NBO2 water administration downregulated the accumulation of HIF-1α in xenografted tumors and did not affect the vital organs of healthy mice. The combination of radiation and single-nanometer NBO2 water without severe side effects may be a promising therapeutic option to improve radiation sensitivity in cancer patients without tolerance to invasive treatments.

Hypoxia-inducible factor expression is related to apoptosis and cartilage degradation in temporomandibular joint osteoarthritis

BackgroundIt remains unclear etiology of cartilaginous tissues in osteoarthritis (OA) lesions. In this study, we hypothesized the accumulation of hypoxia-inducible factor (HIF) and activated apoptosis relate to condylar cartilage degeneration in vivo.MethodsMalocclusion stress was applied for 2 weeks, 4 weeks and 8 weeks to induce an OA-like lesion animal model in rats. Histological analysis was performed by H&E staining and Safranin O/fast green staining. The expression levels of protein in condylar cartilage were examined by immunostaining to evaluate cartilage degeneration.ResultsWe found apparent histological phenotypes associated with degeneration in the occlusion disorder (OD) stress group. The OD group at 4 weeks and 8 weeks had obviously reduced expression of Aggrecan (Acan) and type II collagen (Col II) in cartilage. In contrast, the OD groups had higher levels of ADAM metallopeptidase with thrombospondin type 5 (ADAMTS5) and matrix metallopeptidase 13 (MMP13) in the condylar cartilage than the control group. Moreover, the OD group cartilage had prominent degenerative changes with reduced levels of hypoxia inducible factor 1 alpha (HIF1α) and increased levels of hypoxia inducible factor 2 alpha (HIF2α) and the apoptosis factor Caspase3 in condylar cartilage at 8 weeks.ConclusionThus, abnormal hypoxic conditions inducing Occlusion disorder stress results in cartilage degeneration. opposite expression patterns of HIF1α and HIF2α could be involved in the pathogenesis of condylar cartilage degeneration and chondrocyte apoptosis. HIF2α may provide a potential negative feedback mechanism for HIF1α during cartilage damage.

Abstract 2351: MYB plays an essential role in the hypoxic survival of pancreatic cancer cells via its impact on metabolic reprogramming

Abstract Pancreatic ductal adenocarcinoma exhibits high degree of intratumoral hypoxia due to its unique histopathological features contributing to its extremely aggressive nature and unusual chemoresistance. It is however not yet very clear what drives and sustains the growth of pancreatic cancer cells under an adverse hypoxic tumor microenvironment. Previously we reported that MYB was overexpressed in pancreatic cancer cells and supported the tumorigenicity and metastatic progression of pancreatic cancer cells. Here, we examined the role of MYB in hypoxic survival of pancreatic cancer cells. We found that the silencing of MYB expression in pancreatic cancer cells severely reduced their growth under hypoxia whereas its forced overexpression promoted hypoxic survival. We also observed that MYB was upregulated under hypoxia and its silencing was associated with a reduced accumulation of hypoxia inducible factor-1 α (HIF1α). Additionally, we confirmed HIF1α as a direct transcriptional target of MYB and its transcripts level and promoter activity correlated positively with MYB expression under both normoxia and hypoxia. Interestingly, restoration of HIF1α expression in MYB-silenced cells was not sufficient to rescue their survival under hypoxia. MYB knockdown pancreatic cancer cells failed to optimally reprogram their metabolism under hypoxia to meet their energetic and biosynthetic demands despite restored HIF1α overexpression. Specifically, MYB knockdown cells exhibited a large decrease in intracellular glucose and several metabolic intermediates of glycolysis, TCA cycle, and amino acid metabolism, whereas glycogenolysis and pentose phosphate pathway metabolites were increased. MYB silencing also altered the expression of several metabolic genes, including established hypoxia-responsive gene targets. MYB co-occupied the promoter regions of GLUT3, HK2, PFKL, ENO2, and MCT4 with HIF1α and its silencing reduced HIF1α binding to these promoters despite its forced overexpression. We also confirmed MYB interaction with HIF1α and p300 and demonstrated enhanced recruitment of p300 to these gene promoters in MYB-overexpressing pancreatic cancer cells. Altogether, our studies suggest that MYB acts as major regulator of metabolic reprogramming and HIF1α signaling and thus acts as an important driver of hypoxic survival of pancreatic cancer cells. Citation Format: Shashi Anand, Mohammad Aslam Khan, Haseeb Zubair, Sarabjeet Kour Sudan, Kunwar Somesh Vikramdeo, Sachin Kumar Deshmukh, Shafquat Azim, Sanjeev Kumar Srivastava, Seema Singh, Ajay Pratap Singh. MYB plays an essential role in the hypoxic survival of pancreatic cancer cells via its impact on metabolic reprogramming [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2351.

Dimethyloxalylglycine (DMOG), a Hypoxia Mimetic Agent, Does Not Replicate a Rat Pheochromocytoma (PC12) Cell Biological Response to Reduced Oxygen Culture.

Cells respond to reduced oxygen availability predominately by activation of the hypoxia-inducible factor (HIF) pathway. HIF activation upregulates hundreds of genes that help cells survive in the reduced oxygen environment. The aim of this study is to determine whether chemical-induced HIF accumulation mimics all aspects of the hypoxic response of cells. We compared the effects of dimethyloxalylglycine (DMOG) (a HIF stabiliser) on PC12 cells cultured in air oxygen (20.9% O2, AO) with those cultured in either intermittent 20.9% O2 to 2% O2 (IH) or constant 2% O2 (CN). Cell viability, cell cycle, HIF accumulation, reactive oxygen species (ROS) formation, mitochondrial function and differentiation were used to characterise the PC12 cells and evaluate the impact of DMOG. IH and CN culture reduced the increase in cell numbers after 72 and 96 h and MTT activity after 48 h compared to AO culture. Further, DMOG supplementation in AO induced a dose-dependent reduction in the increase in PC12 cell numbers and MTT activity. IH-cultured PC12 cells displayed increased and sustained HIF-1 expression over 96 h. This was accompanied by increased ROS and mitochondrial burden. PC12 cells in CN displayed little changes in HIF-1 expression or ROS levels. DMOG (0.1 mM) supplementation resulted in an IH-like HIF-1 profile. The mitochondrial burden and action potential of DMOG-supplemented PC12 cells did not mirror those seen in other conditions. DMOG significantly increased S phase cell populations after 72 and 96 h. No significant effect on PC12 cell differentiation was noted with IH and CN culture without induction by nerve growth factor (NGF), while DMOG significantly increased PC12 cell differentiation with and without NGF. In conclusion, DMOG and reduced oxygen levels stabilise HIF and affect mitochondrial activity and cell behaviour. However, DMOG does not provide an accurate replication of the reduced oxygen environments.

SDHB knockout and succinate accumulation are insufficient for tumorigenesis but dual SDHB/NF1 loss yields SDHx-like pheochromocytomas.

SUMMARYInherited pathogenic succinate dehydrogenase (SDHx) gene mutations cause the hereditary pheochromocytoma and paraganglioma tumor syndrome. Syndromic tumors exhibit elevated succinate, an oncometabolite that is proposed to drive tumorigenesis via DNA and histone hypermethylation, mitochondrial expansion, and pseudohypoxia-related gene expression. To interrogate this prevailing model, we disrupt mouse adrenal medulla SDHB expression, which recapitulates several key molecular features of human SDHx tumors, including succinate accumulation but not 5hmC loss, HIF accumulation, or tumorigenesis. By contrast, concomitant SDHB and the neurofibromin 1 tumor suppressor disruption yields SDHx-like pheochromocytomas. Unexpectedly, in vivo depletion of the 2-oxoglutarate (2-OG) dioxygenase cofactor ascorbate reduces SDHB-deficient cell survival, indicating that SDHx loss may be better tolerated by tissues with high antioxidant capacity. Contrary to the prevailing oncometabolite model, succinate accumulation and 2-OG-dependent dioxygenase inhibition are insufficient for mouse pheochromocytoma tumorigenesis, which requires additional growth-regulatory pathway activation.

The Endothelial Landscape and Its Role in Von Hippel-Lindau Disease.

Von Hippel–Lindau disease (VHL) is a rare hereditary disease characterized by the predisposal to develop different types of highly vascularized tumors. VHL patients carry a VHL mutation that causes partial lack of functional VHL protein (pVHL) in all cells, and a total lack thereof in cells harboring a second hit mutation. Absence of pVHL generates a prolonged state of pseudo-hypoxia in the cell due to accumulation of hypoxia inducible factor, an important transcription factor regulating pro-tumorigenic genes. The work here presented focuses on characterizing the endothelium of VHL patients, by means of blood outgrowth endothelial cells (BOECs). Transcriptome analysis of VHL-derived BOECs, further supported by in vitro assays, shows that these cells are at a disadvantage, as evidenced by loss of cell adhesion capacity, angiogenesis defects, and immune response and oxidative metabolic gene downregulation, which induce oxidative stress. These results suggest that the endothelium of VHL patients is functionally compromised and more susceptible to tumor development. These findings contribute to shedding light on the vascular landscape of VHL patients preceding the second hit mutation in the VHL gene. This knowledge could be useful in searching for new therapies for these patients and other vascular diseases.

Sclareol Inhibits Hypoxia-Inducible Factor-1α Accumulation and Induces Apoptosis in Hypoxic Cancer Cells.

Purpose: The hypoxia in solid tumors is associated with the resistance to chemo/radiotherapy. Hypoxia-inducible factor-1 (HIF-1) plays a key role in cell remodeling to hypoxia. Therefore, the inhibition of HIF-1 accumulation is considered a hopeful strategy for the treatment of cancer. Here, we aimed to evaluate the geno- and cytotoxicity properties of sclareol, a natural bicyclic diterpene alcohol, on A549 cells in CoCl2-induced hypoxia. Methods: The cytotoxicity and apoptosis-inducing properties of sclareol on the A549 cell were evaluated using MTT assay and Annexin V/PI staining, respectively in hypoxia. DAPI staining, DNA ladder, and comet assay were used to evaluate the genotoxicity. Further, the qPCR technique was employed to assess the expression of HIF-1α, HIF-1β, and downstream target genes (GluT1, and Eno1). Finally, the level of HIF-1α protein was evaluated through Western blotting in sclareol-treated cells in hypoxia. Results: The inhibitory concentration (IC50) of sclareol against A549 cells was 8 μg/mL at 48 hours in hypoxia. The genotoxicity of sclareol was confirmed in the cells treated with sclareol in hypoxia. Sclareol induced ~46% apoptosis and also necrosis in the hypoxic condition. The qPCR analyses showed an enhanced suppression of HIF-1α, HIF-1β, GluT1, and Eno1 due to the sclareol treatment in the hypoxia. Moreover, protein quantification analysis showed dose-dependently degradation of HIF-1α in hypoxia upon treatment with sclareol. Conclusion: The results obtained here indicate that sclareol possesses dose-dependent cytotoxicity effects against A549 cells in hypoxia through inhibition of HIF-1α protein accumulation, increasing cell sensitivity to intracellular oxygen levels, and disruption of cell adaptation to hypoxia.

Detrimental effects of hypoxia on glomerular podocytes.

Hypoxia-inducible factor1 (HIF1) plays a pivotal role in ensuring cells adapt to low-oxygen conditions. Depletion of oxygen, a co-substrate during hydroxylation of prolyl (P402 and P564) residues of HIF1⍺, evades HIF1⍺ ubiquitination and enables its dimerization with HIF1β to mediate global transcriptional response to hypoxia. Though HIF1 is largely considered eliciting a protective role during physiological or pathological hypoxia or ischemia, elevated HIF1 during chronic hypoxia contributes to glomerular diseases' pathology and proteinuria. The glomerulus is responsible for renal permselectivity and excretion of ultra-filtrated urine. Podocytes are the glomerulus' major cell types and are instrumental for glomerular filtration, permselectivity, and glomerular basement membrane maintenance. Podocyte injury is expected to impair the efficiency of glomerular filtration and manifestation of glomerulosclerosis and proteinuria. Accumulated evidence suggests that podocytes are susceptible to various insults during chronic hypoxia, including podocyte EMT, slit-diaphragm dysfunction, foot process effacement, and cytoskeletal derangement due to accumulation of HIF1. This review discusses how hypoxia/HIF1 signaling regulates various features and function of podocytes during exposure to chronic hypoxia or inducing HIF1 by various chemical modulators.

TGF-β1 signaling protects retinal ganglion cells from oxidative stress via modulation of the HO-1/Nrf2 pathway

Oxidative stress provides a major contribution to the pathogenesis of glaucoma and may induce retinal ganglion cell (RGC) damage. Transforming growth factor β (TGF-β) has appeared as a neuroprotective protein in various indignities. However, the TGF-β mechanism of protective effects against oxidative stress damage in RGCs still undetermined. In our research, we investigated the regulatory mechanisms and potential effects of TGF-β1 & TGF-β2 in hydrogen peroxide (H2O2)-stimulated oxidative stress of RGCs in vitro. By a series of cell functional qualitative analysis, such as MTT cell viability assay, wound healing ability assay, apoptosis assay, intracellular ROS detection, immunoblot analysis, intracellular GSH content, and high-resolution respirometry, we illustrated the cell state in oxidative stress-induced injury. Results of protein expression showed that TGF-β1 & TGF-β2 was upregulated in RGCs after H2O2 stimulation. Cell functional assays resulted that knockdown of TGF-β1 & TGF-β2 reduced survival rate whereas enhanced apoptosis and accumulation of reactive oxygen species (ROS). Especially TGF-β1 upregulation promoted the protein expression of aldehyde dehydrogenase 3A1 (ALDH3A1) and increased the activity of antioxidant and neuroprotection pathways. Additionally, TGF-β1 & TGF-β2 on antioxidant signaling was related to activation of heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor (Nrf2), which are stress-response proteins. ROS accumulation followed by the accumulation of hypoxia-inducible factor (HIF-1α) caused mitochondrial damage and led to neurodegeneration. In summary, our results demonstrated that TGF-β1 preserves RGCs from free radicals-mediated injury by upregulating the activation of Nrf2 expression and HO-1 signaling balance HIF-1α upregulation, implying a prospective role of TGF-β1 in retinal neuroprotection-related therapies.

USP37 promotes deubiquitination of HIF2α in kidney cancer

Clear cell renal cell carcinoma (ccRCC) is characterized by loss of tumor suppressor Von Hippel Lindau (VHL) function, which leads to accumulation of hypoxia inducible factor α (including HIF1α and HIF2α). HIF2α was previously reported to be one of the major oncogenic drivers in ccRCC, however, its therapeutic targets remain challenging. Here we performed a deubiquitinase (DUB) complementary DNA (cDNA) library binding screen and discovered that ubiquitin-specific peptidase 37 (USP37) is a DUB that binds HIF2α and promotes HIF2α deubiquitination. As a result, USP37 promotes HIF2α protein stability in an enzymatically dependent manner, and depletion of USP37 leads to HIF2α down-regulation in ccRCC. Functionally, USP37 depletion causes decreased cell proliferation measured by MTS, two-dimensional (2D) colony formation as well as three-dimensional (3D) anchorage- independent growth. USP37 is also essential for maintaining kidney tumorigenesis in an orthotopic xenograft model and its depletion leads to both decreased primary kidney tumorigenesis and spontaneous lung metastasis. Our results suggest that USP37 is a potential therapeutic target in ccRCC.

Tectorigenin, an isoflavone aglycone from the rhizome of Belamcanda chinensis, induces neuronal expression of erythropoietin via accumulation of hypoxia-inducible factor-1α.

Traditional Chinese medicines (TCMs) have been demonstrated as an important source for potential drug discovery. Flavonoids are regarded as the most common active components in TCMs because of their beneficial functions in the brain and erythropoietic system. Erythropoietin (EPO), a glycoprotein hormone, has been well-studied for its neuroprotective function. The blood circulating EPO is not able to cross the blood brain barrier, and thus there is mounting demand to search for compounds that can induce endogenous cerebral EPO. Here, tectorigenin, an active compound in the rhizome of Belamcanda chinensis (L.) DC., significantly induced the expression of EPO mRNA via accumulation of hypoxia-inducible factor (HIF)-1α in cultured neuron-like NT2/D1 cells and rat cortical neurons. Furthermore, tectorigenin induced transcription of HIF-1α and reduced degradation of HIF-1α-OH, a hydroxylated form of HIF-1α, in the culture. Thus, the upregulation of HIF-1α was assumed to play a significant role in regulating EPO during the treatment of tectorigenin in cultured neurons. Hence, we reported the neuroprotective function of tectorigenin through upregulation of EPO in neurons, which could be a good candidate in developing drugs or food supplements for the treatment of brain disorders.

The Difference in Maternal Serum Hypoxia-Inducible Factors-1α Levels between Early Onset and Late-Onset Preeclampsia.

BACKGROUND:Preeclampsia can be divided into early (EOPE) and late (LOPE) onset preeclampsia. Preeclampsia is related to the failure of placentation. Accumulation of hypoxia-inducible factors (HIF)-1α is commonly an acute and beneficial respond to hypoxia, while chronically elevated is associated with preeclampsia.AIM:This study aims to evaluate the serum levels of HIF-1α in preeclampsia and normal pregnancy, and to compare the difference between early-onset and late-onset preeclampsia.METHODS:A cross-sectional comparative study was conducted among a total of 69 pregnant women at ≥ 20 weeks of gestation, were recruited at obstetrics and gynaecology department at Dr M. Djamil Padang Hospital, network hospitals, health centres. They were divided into three groups early-onset preeclampsia, late-onset preeclampsia, and normal pregnancy. Preeclampsia was diagnosed using International Guidelines. Data were analysed by SPSS 24 program; data are presented as median and range or as mean ± standard deviation. One-way ANOVA test was used to determine the relationship between HIF-1α levels with the onset of preeclampsia.RESULTS:The results showed that the mean maternal serum HIF-1α levels in early-onset preeclampsia (EOPE), late-onset preeclampsia (LOPE), and normal pregnancy were 1366.96 ± 733.40 pg/ml, 916.87 ± 466.06 pg/ml, and 716.77 ± 541.08 pg/ml. Serum HIF-1α levels were higher in early-onset preeclampsia (EOPE), and late-onset preeclampsia (LOPE) compared to normal pregnancy. Among preeclampsia patients, serum HIF-1α was higher in EOPE than LOPE women. Statistical analysis revealed a significant difference in mean maternal serum HIF-1α between early-onset preeclampsia, late-onset preeclampsia, and normal pregnancy (p < 0.05).CONCLUSION:This study concluded that there is a significantly different level of HIF-1α between in early-onset preeclampsia, late-onset preeclampsia and normal pregnancy. Early-onset preeclampsia is the highest levels of serum HIF-1α.

50 years of renal cell carcinoma

In the past 50 years, many knowledge gaps regarding renal cell carcinoma (RCC) have been closed. A pathological tumour classification has been developed and different histological subtypes are known today. In clear cell RCC, the (mutated) von Hippel-Lindau gene located on chromosome 3 is highly important. Operative therapy of non-metastatic RCC has evolved from radical nephrectomy to less radical techniques including procedures sparing the adrenal gland as well as nephron-sparing surgery. Surgical procedures are increasingly performed using laparoscopic or robot-assisted approaches. Even less invasive techniques such as cryoablation, radiofrequency ablation or active surveillance are applied for small renal masses, if indicated. Metastatic RCC is most commonly treated by systemic therapy. Chemotherapy has no effect in RCC. For more than 20years, cytokine therapy was the standard of care for metastatic RCC. Mutations of the von Hippel-Lindau gene associated with accumulation of hypoxia-inducible factor, followed by increased transcription of vascular endothelial growth factor, provided the scientific rationale for the successful use of tyrosine kinase inhibitors, mTOR inhibitors, and anti-VEGF antibodies introduced in 2006. The development of checkpoint inhibitors has changed the systemic treatment of RCC in yet another relevant manner.

Impact of tivozanib on patient outcomes in treatment of advanced renal cell carcinoma.

Renal cell carcinoma (RCC) is the most common type of kidney malignancy, and the clear-cell subtype represents the majority of RCCs. RCC is a heterogeneous disease in terms of genetic and histological features which determine the behavior of the disease. The von Hippel–Lindau (VHL) is a tumor suppressor gene and mutations of this gene are seen in 95% of clear-cell RCCs. Inactivation of VHL causes the accumulation of hypoxia-inducible factor-1 (HIF-1), and in turn, accumulation of HIF-1 induces overexpression of vascular endothelial growth factor (VEGF); the increase in VEGF expression makes RCC a highly vascularized tumor, and forms the rationale for antiVEGF treatment. In the past decade, improvement in the survival of RCC patients has been observed due to new effective therapies, such as antiVEGF and mammalian target of rapamycin (mTOR) targeting agents and immune checkpoint inhibitors. The majority of VEGF targeted agents are not just selective to VEGF receptors, but usually also have inhibitory effects on other kinases, such as c-KIT and FLT3. Tivozanib is an extremely potent and selective tyrosine kinase inhibitor (TKI) of VEGFR-1, 2, and 3, with a relatively long half-life, that is approved by the European Commission for the treatment of advanced/metastatic RCC. Tivozanib, at very low serum concentration can inhibit phosphorylation of VEGFR −1, −2, and −3 tyrosine kinase activity. This article summarizes the clinical data on tivozanib in the treatment of advanced/metastatic RCC.

Functional Interaction of Hypoxia-Inducible Factor 2-Alpha and Autophagy Mediates Drug Resistance in Colon Cancer Cells.

Hypoxia and the accumulation of hypoxia-inducible factors (HIFs) in tumors have been associated with therapeutic resistance and with autophagy establishment. We examined the effects of stable knockdown of HIF-1α or HIF-2α expression on autophagy and drug resistance in colon cancer cells. We found that under normoxic conditions, malignant cells exhibit increased basal levels of autophagy, compared with non-malignant cells, in addition to the previously reported coexpression of HIF-1α and HIF-2α. Knockdown of HIF-1α or HIF-2α expression resulted in increased autophagic and apoptotic cell death, indicating that the survival of cells is HIF-dependent. Cytotoxic-induced cell death was significantly increased by knockdown of HIFs but not by autophagy inhibition. Strikingly, although malignancy-resistant cells were sensitized to death by nutrient stress, the combination with HIF-2α depletion, but not with HIF-1α depletion, induced severe cell death. Oxidative stress levels were significantly increased as a result of HIF-2α specific inhibition or silencing suggesting that this may contribute to sensitize cells to death. The in vitro results were confirmed in vivo using a xenograft mouse model. We found that coordinated autophagy and mTOR inhibition enhanced cell death and induced tumor remission only in HIF-2α-silenced cells. Finally, using a specific HIF-2α inhibitor alone or in combination with drugs in patient-derived primary colon cancer cells, overcame their resistance to 5-FU or CCI-779, thus emphasizing the crucial role played by HIF-2α in promoting resistance and cell survival.

Jian-Pi-Yi-Shen Decoction Relieves Renal Anemia in 5/6 Nephrectomized Rats: Production of Erythropoietin via Hypoxia Inducible Factor Signaling.

Jian-Pi-Yi-Shen (JPYS) is one of the herbal medicines for treatment of anemic patients with chronic kidney disease (CKD). However, less of scientific evidence to support JPYS involved in treating anemia has been revealed. Here, an animal study was performed to investigate its hematopoietic activities and the underlying mechanism. The 5/6 nephrectomized inductions of CKD anemic rats were randomly divided into two groups: CKD group and JPYS group. Sham-operated rats served as sham group. JPYS (1.36 g/kg/d) was administered orally to CKD rats daily for six consecutive weeks. Results showed that JPYS treatment notably improved renal function and pathological injury in CKD rats. JPYS also restored the hematological parameters, including red blood cells, hemoglobin, and hematocrit. In parallel, the reduction level of EPO was reversed by JPYS. Furthermore, JPYS induced the accumulation of hypoxia inducible factor (HIF)-α protein expression. Collectively, these results provide convincing evidence for JPYS decoction in ameliorating CKD-associated anemia, and its mechanism might be related to regulate EPO production via HIF signaling pathway.

Aqp-1 Gene Knockout Attenuates Hypoxic Pulmonary Hypertension of Mice.

Objective- Hypoxic pulmonary hypertension (HPH) is characterized by proliferative vascular remodeling. Abnormal pulmonary artery smooth muscle cells proliferation and endothelial dysfunction are the primary cellular bases of vascular remodeling. AQP1 (aquaporin-1) is regulated by oxygen level and has been observed to play a role in the proliferation and migration of pulmonary artery smooth muscle cells. The role of AQP1 in HPH pathogenesis has not been directly determined to date. To determine the possible roles of AQP1 in the pathogenesis of HPH and explore its possible mechanisms. Approach and Results- Aqp1 knockout mice were used, and HPH model was established in this study. Primary pulmonary artery smooth muscle cells, primary mouse lung endothelial cells, and lung tissue sections from HPH model were used. Immunohistochemistry, immunofluorescence and Western blot, cell cycle, apoptosis, and migration analysis were performed in this study. AQP1 expression was upregulated by chronic hypoxia exposure, both in pulmonary artery endothelia and medial smooth muscle layer of mice. Aqp1 deficiency attenuated the elevation of right ventricular systolic pressures and mitigated pulmonary vascular structure remodeling. AQP1 deletion reduced abnormal cell proliferation in pulmonary artery and accompanied with accumulation of HIF (hypoxia-inducible factor). In vitro, Aqp1 deletion reduced hypoxia-induced proliferation, apoptosis resistance, and migration ability of primary cultured pulmonary artery smooth muscle cells and repressed HIF-1α protein stability. Furthermore, Aqp1 deficiency protected lung endothelial cells from apoptosis in response to hypoxic injury. Conclusions- Our data showed that Aqp1 deficiency could attenuate hypoxia-induced vascular remodeling in the development of HPH. AQP1 may be a potential target for pulmonary hypertension treatment.

Expression and epigenetic regulatory mechanism of BNIP3 in clear cell renal cell carcinoma.

The majority of clear cell renal cell carcinomas (ccRCCs) are caused by an accumulation of hypoxia-inducible factor (HIF) and the overexpression of downstream genes in response to the von Hippel-Lindau (VHL) gene becoming inactivated. In the present study, our hypothesis was that BNIP3, a gene positioned downstream of HIF, would be expressed at a higher level in ccRCC; however, instead, lower levels of BNIP3 expression were identified in RCC tumor tissues compared with adjacent non-tumor tissues. These changes were associated with lower levels of VHL, and higher levels of HIF and vascular endothelial growth factor. BNIP3 was also undetectable in three investigated RCC cell lines (786-O, ACHN, A498) and GRC-1-1 cells. Methylation of the BNIP3 promoter was not detected, and neither did treatment with a methylation inhibitor cause cell proliferation. However, treatment with a histone deacetylation inhibitor, trichostatin A (TSA), inhibited cultured RCC cell proliferation, promoted apoptosis and restored BNIP3 expression. Furthermore, histone deacetylation of the BNIP3 promoter was identified in ACHN and 786-O cells, and the acetylation status was restored following TSA treatment. Taken together, the results of the present study suggest that histone deacetylation, but not methylation, is most likely to cause BNIP3 inactivation in RCC. The data also indicated that restoration of BNIP3 expression by a histone deacetylation inhibitor led to growth inhibition and apoptotic promotion in RCC.