Regulation of vascular endothelial growth factor transcription by endothelial PAS domain protein 1 (EPAS1) and possible involvement of EPAS1 in the angiogenesis of renal cell carcinoma

Boosting Clear Cell Renal Carcinoma-Specific Drug Discovery Using a Deep Learning Algorithm and Single-Cell Analysis

Clear cell renal carcinoma (ccRCC), the most common subtype of renal cell carcinoma, has the high heterogeneity of a highly complex tumor microenvironment. Existing clinical intervention strategies, such as target therapy and immunotherapy, have failed to achieve good therapeutic effects. In this article, single-cell transcriptome sequencing (scRNA-seq) data from six patients downloaded from the GEO database were adopted to describe the tumor microenvironment (TME) of ccRCC, including its T cells, tumor-associated macrophages (TAMs), endothelial cells (ECs), and cancer-associated fibroblasts (CAFs). Based on the differential typing of the TME, we identified tumor cell-specific regulatory programs that are mediated by three key transcription factors (TFs), whilst the TF EPAS1/HIF-2α was identified via drug virtual screening through our analysis of ccRCC's protein structure. Then, a combined deep graph neural network and machine learning algorithm were used to select anti-ccRCC compounds from bioactive compound libraries, including the FDA-approved drug library, natural product library, and human endogenous metabolite compound library. Finally, five compounds were obtained, including two FDA-approved drugs (flufenamic acid and fludarabine), one endogenous metabolite, one immunology/inflammation-related compound, and one inhibitor of DNA methyltransferase (N4-methylcytidine, a cytosine nucleoside analogue that, like zebularine, has the mechanism of inhibiting DNA methyltransferase). Based on the tumor microenvironment characteristics of ccRCC, five ccRCC-specific compounds were identified, which would give direction of the clinical treatment for ccRCC patients.

Neonatal and adult cardiac fibroblasts exhibit inherent differences in cardiac regenerative capacity

Directly reprogramming fibroblasts into cardiomyocytes improves cardiac function in the infarcted heart. However, the low efficacy of this approach hinders clinical applications. Unlike the adult mammalian heart, the neonatal heart has an intrinsic regenerative capacity. Consequently, we hypothesized that birth imposes fundamental changes on cardiac fibroblasts which limit their regenerative capabilities. In support, we found that reprogramming efficacy in vitro was markedly lower with fibroblasts derived from adult mice versus those derived from neonatal mice. Notably, fibroblasts derived from adult mice expressed significantly higher levels of pro-angiogenic genes. Moreover, under conditions which promote angiogenesis, only fibroblasts derived from adult mice differentiated into tube-like structures. Targeted knockdown screening studies suggested a possible role for the transcription factor Epas1. Epas1 expression was higher in fibroblasts derived from adult mice and Epas1 knockdown improved reprogramming efficacy in cultured adult cardiac fibroblasts. Promoter activity assays indicated that Epas1 functions as both a transcription repressor and activator, inhibiting cardiomyocyte genes while activating angiogenic genes. Finally, the addition of an Epas1 targeting siRNA to the reprogramming cocktail markedly improved reprogramming efficacy in vivo with both the number of reprogramming events as well as cardiac function being markedly improved. Collectively, our results highlight differences between neonatal and adult cardiac fibroblasts and the dual transcriptional activities of Epas1 related to reprogramming efficacy.

A review on the design, synthesis, and structure-activity relationships of benzothiazole derivatives against hypoxic tumors

There has been a growing body of studies on benzothiazoles and benzothiazole derivatives as strong and effective antitumor agents against lung, liver, pancreas, breast, and brain tumors. Due to highly proliferative nature of the tumor cells, the oxygen levels get lower than that of a normal tissue in the tumor microenvironment. This situation is called as hypoxia and has been associated with increased ability for carcinogenesis. For the drug design and development strategies, hypoxic nature of the tumor tissues has been exploited more aggressively. Hypoxia itself acts as a signal initiating system to activate the pathways that eventually lead to the spread of the tumor cells into the different tissues, increases the rate of DNA damage and eventually ends up with more mutation levels that may increase the drug resistance. As one of the major mediators of hypoxic response, hypoxia inducible factors (HIFs) has been shown to activate to angiogenesis, metastasis, apoptosis resistance, and many other protumorigenic responses in cancer development. In the current review, we will be discussing the design, synthesis and structure-activity relationships of benzothiazole derivatives against hypoxic tumors such lung, liver, pancreas, breast and brain as potential anticancer drug candidates. The focus points of the study will be the biology behind carcinogenesis and how hypoxia contributes to the process, recent studies on benzothiazole and its derivatives as anti-cancer agents against hypoxic cancers, conclusions and future perspectives. We believe that this review will be useful for the researchers in the field of drug design during their studies to generate novel benzothiazole-containing hybrids against hypoxic tumors with higher efficacies.

Identification of novel mutations and functional impacts of EPAS1 in colorectal cancer

Endothelial PAS domain‐containing protein 1 (EPAS1) has implications in many cancers. However, the molecular behaviours, functional roles and mutational status of EPAS1 have never been studied in colorectal carcinoma (CRC). The study aims to examine the genetic alterations and functional roles of EPAS1 in CRC. In addition, the clinical impacts of EPAS1 in CRC were studied. Significant EPAS1 DNA amplification (63.4%; n = 52/82) and consequent mRNA overexpression (72%; n = 59/82) were noted in patients with CRC. In CRC, 16% (n = 13/82) of the patients had mutations in the EPAS1 coding sequence and most of the mutated samples exhibited aberrant DNA changes and mRNA overexpression. We have identified two novel variants, c.1084C>T; p.L362L and c.1121T>G; p.F374C in CRC. These EPAS1 aberrations in CRC were correlated with clinicopathological parameters, including tumour size, histological grade, T‐stages, cancer perforation as well as the presence of synchronous cancer. Also, reduced cell proliferation, wound healing, migration and invasion were noted in colon cancer cells followed by EPAS1 silencing. To conclude, the results obtained from the current study indicated that EPAS1 plays important role in colorectal carcinogenesis, thus, could be useful as a prognostic marker and as a target for therapy development.

MicroRNA-155-5p/EPAS1/interleukin 6 pathway participated in the protection function of sphingosylphosphorylcholine to ischemic cardiomyocytes

AIM

Previous research in our laboratory found that a biologically active sphingomyelin metabolite, sphingosylphosphorylcholine (SPC), can inhibit myocardial cell apoptosis caused by ischemia with an unknown mechanism. Here, we aimed to study the possible participation of EPAS1 in the protection process of SPC.

METHODS

The rat cardiomyocytes deprived of serum were used to mimic ischemic-caused apoptosis, then treated with or without SPC. The expression and nuclear shift of EPAS1 were detected by western blot and immunofluorescence, and its function was studied using its siRNA.

KEY FINDING

Our research shows that SPC inhibited serum starvation caused cardiomyocyte apoptosis, accompanied by the up-regulation and nucleus translocation of EPAS1. EPAS1 levels did not change when its transcript was blocked by Actinomycin D, which prompted us to search for a post-transcription mechanism for its increased expression, and finally found that miR-155-5p, regulated by STAT3, was a new post-transcription regulator to EPAS1. Further investigation found that EPAS1 participated in the protective effect of SPC is mainly achieved by activating the downstream target gene, interleukin-6 (IL-6).

SIGNIFICANCE

Our results expand our understanding of the biological functions of SPC, and bring a new pathway as a potential therapeutic target to the treatment of cardiovascular diseases caused by myocardial apoptosis.

HIF-1α Metabolic Pathways in Human Cancer

Oxygen is directly involved in many key pathophysiological processes. Oxygen deficiency, also known as hypoxia, could have adverse effects on mammalian cells, with ischemia in vital tissues being the most significant (Michiels C. Physiological and pathological responses to hypoxia. Am J Pathol 164(6): 1875-1882, 2004); therefore, timely adaptive responses to variations in oxygen availability are essential for cellular homeostasis and survival. The most critical molecular event in hypoxic response is the activation and stabilization of a transcriptional factor termed hypoxia-induced factor-1 (HIF-1) that is responsible for the upregulation of many downstream effector genes, collectively known as hypoxia-responsive genes. Multiple key biological pathways such as proliferation, energy metabolism, invasion, and metastasis are governed by these genes; thus, HIF-1-mediated pathways are equally pivotal in both physiology and pathology.As we gain knowledge on the molecular mechanisms underlying the regulation of HIF-1, a great focus has been placed on elucidating the cellular function of HIF-1, particularly the role of HIF-1 in cancer pathogenesis pathways such as proliferation, invasion, angiogenesis, and metastasis. In cancer, HIF-1 is directly involved in the shift of cancer tissues from oxidative phosphorylation to aerobic glycolysis, a phenomenon known as the Warburg effect. Although targeting HIF-1 as a cancer therapy seems like an extremely rational approach, owing to the complex network of its downstream effector genes, the development of specific HIF-1 inhibitors with fewer side effects and more specificity has not been achieved. Therefore, in this review, we provide a brief background about the function of HIF proteins in hypoxia response with a special emphasis on the unique role played by HIF-1α in cancer growth and invasiveness, in the hypoxia response context.

Cross talk between oxidative stress and hypoxia via thioredoxin and HIF-2α drives metastasis of hepatocellular carcinoma

Oxidative stress and hypoxia are two opposite microenvironments involved in HCC metastasis. Thioredoxin (TXN) and hypoxia-inducible factor 2α (HIF-2α) are typical proteins involved in these two different microenvironments, respectively. How these two factors interact to influence the fate on tumor cells remains unknown. Hypoxia facilitated HCC cells withstood oxidative stress and eventually promoted HCC cells metastasis, in which TXN and HIF-2α were mostly involved. Upregulation of TXN/HIF-2α correlated with poor HCC prognosis and promoted HCC metastasis both in vitro and in vivo. Epithelial-mesenchymal transition (EMT) process was involved in TXN/HIF-2α-enhanced invasiveness of HCC cells. Additionally, the stability and activity of HIF-2α were precisely regulated by TXN via SUMOylation and acetylation, which contributed to HCC metastasis. Our data revealed that the redox protein TXN and HIF-2α are both associated with HCC metastasis, and the fine regulation of TXN on HIF-2α contributes essentially during the process of metastasis. Our study provides new insight into the interaction mechanism between hypoxia and oxidative stress and implies potential therapeutic benefits by targeting both TXN and HIF-2α in the treatment of HCC metastasis.

Retracted Article: FOXO4 overexpression suppresses hypoxia-induced-MCF-7 cell survival and promotes apoptosis through the HIF-2α/Bnip3 signal pathway

Transcriptional regulator forkhead box O (FOXO) has implications in many diverse carcinomas and often acts as a tumour suppressor. Evidence suggests that FOXO4 may play a role in cancer cell proliferation and apoptosis; however, the function and mechanism of FOXO4 on breast cancer cell growth are still unknown. FOXO4 can respond to hypoxia and in the current study, our aim is to investigate the function and molecular mechanism of FOXO4 in hypoxia-induced MCF-7 cells. We first observed that hypoxia treatment reduced FOXO4 mRNA and protein expression in MCF-7 cells. Moreover, FOXO4 overexpression reversed hypoxia-induced MCF-7 cell survival. Hypoxia treatment markedly impeded MCF-7 cell apoptosis and inhibited caspase-3 activity, whereas FOXO4 overexpression promoted apoptosis and increased caspase-3 activity in hypoxia-induced MCF-7 cells. Further studies indicated that FOXO4 overexpression inhibited hypoxia-induced HIF-2α and Bnip3 expression in MCF-7 cells; moreover, FOXO4 suppressed Bnip3 expression, which is dependent on the low level of HIF-2α. Finally, we demonstrated that Bnip3 overexpression reversed the effects of FOXO4 overexpression on cell survival and apoptosis in hypoxia-induced MCF-7 cells. In conclusion, the present study suggests that FOXO4 overexpression mediated the HIF-2α/Bnip3 signal pathway, which has implications in cell survival and apoptosis in hypoxia-induced MCF-7 cells.

Endothelial PAS domain protein 1 gene hypomethylation is associated with colorectal cancer in Han Chinese

Endothelial PAS domain-containing protein 1 (EPAS1) serves a role in angiogenesis, which is important for the development of tumors, including colorectal cancer (CRC). The current study aimed to estimate whether EPAS1 methylation was associated with CRC. A two-stage association study of EPAS1 methylation and CRC was conducted. In the first phase, EPAS1 methylation was evaluated in the tumor and adjacent non-tumor tissue samples from 41 patients with sporadic CRC in Jiangsu province, China. The diagnostic value of methylation of EPAS1 for CRC in the second phase was evaluated in 79 patients with sporadic CRC and 22 normal individuals in Zhejiang province, China. The methylation assay was performed using a quantitative methylation-specific polymerase chain reaction (qMSP) method. The percentage of methylated reference (PMR) was used to quantify the methylation level. The first-stage results indicated that EPAS1 promoter methylation was significantly lower in CRC tumor tissues compared with 5-cm-para-tumor tissues (median PMR, 0.59 vs. 1.22%; P=0.027) and 10-cm-para-tumor tissues (median PMR, 0.59 vs. 1.89%; P=0.001). In addition, the second-stage results indicated that EPAS1 promoter methylation was significantly lower in tumor tissues compared with 5-cm-para-tumor tissues (median PMR, 1.91 vs. 6.25%; P=3×10⁻⁷) and normal intestinal tissues from healthy controls (median PMR, 1.91 vs. 28.4%; P=5×10⁻⁷). Receiver Operating Characteristic curve analysis of the second-stage data indicated that the highest area under the curve of EPAS1 hypomethylation was 0.851 between Zhejiang CRC tissues and Zhejiang normal intestinal tissues (sensitivity, 95.5%; specificity, 60.8%).

Metastatic Renal Cell Carcinoma in a Hepatic Hemangioma

We report the case of 55-year-old female with biopsy-proven clear cell renal cell carcinoma with a suspicious lesion found in the liver who presented for right radical nephrectomy and partial hepatectomy. Histologic evaluation of the hepatic specimen demonstrated metastatic renal cell carcinoma within a hepatic hemangioma. Herein we provide a review of the literature for this uncommon scenario.

The role of hypoxia-inducible factor-2 in digestive system cancers

Hypoxia is an all but ubiquitous phenomenon in cancers. Two known hypoxia-inducible factors (HIFs), HIF-1α and HIF-2α, primarily mediate the transcriptional response to hypoxia. Despite the high homology between HIF-1α and HIF-2α, emerging evidence suggests differences between both molecules in terms of transcriptional targets as well as impact on multiple physiological pathways and tumorigenesis. To date, much progress has been made toward understanding the roles of HIF-2α in digestive system cancers. Indeed, HIF-2α has been shown to regulate multiple aspects of digestive system cancers, including cell proliferation, angiogenesis and apoptosis, metabolism, metastasis and resistance to chemotherapy. These findings make HIF-2α a critical regulator of this malignant phenotype. Here we summarize the function of HIF-2 during cancer development as well as its contribution to tumorigenesis in digestive system malignancies.

Genetic variability of VEGF pathway genes in six randomized phase III trials assessing the addition of bevacizumab to standard therapy

BACKGROUND

Despite extensive translational research, no validated biomarkers predictive of bevacizumab treatment outcome have been identified.

METHODS

We performed a meta-analysis of individual patient data from six randomized phase III trials in colorectal, pancreatic, lung, renal, breast, and gastric cancer to explore the potential relationships between 195 common genetic variants in the vascular endothelial growth factor (VEGF) pathway and bevacizumab treatment outcome.

RESULTS

The analysis included 1,402 patients (716 bevacizumab-treated and 686 placebo-treated). Twenty variants were associated (P < 0.05) with progression-free survival (PFS) in bevacizumab-treated patients. Of these, 4 variants in EPAS1 survived correction for multiple testing (q < 0.05). Genotype-by-treatment interaction tests revealed that, across these 20 variants, 3 variants in VEGF-C (rs12510099), EPAS1 (rs4953344), and IL8RA (rs2234671) were potentially predictive (P < 0.05), but not resistant to multiple testing (q > 0.05). A weak genotype-by-treatment interaction effect was also observed for rs699946 in VEGF-A, whereas Bayesian genewise analysis revealed that genetic variability in VHL was associated with PFS in the bevacizumab arm (q < 0.05). Variants in VEGF-A, EPAS1, and VHL were located in expression quantitative loci derived from lymphoblastoid cell lines, indicating that they affect the expression levels of their respective gene.

CONCLUSIONS

This large genetic analysis suggests that variants in VEGF-A, EPAS1, IL8RA, VHL, and VEGF-C have potential value in predicting bevacizumab treatment outcome across tumor types. Although these associations did not survive correction for multiple testing in a genotype-by-interaction analysis, they are among the strongest predictive effects reported to date for genetic variants and bevacizumab efficacy.

Interactions between vascular endothelial growth factor and neuroglobin

Vascular endothelial growth factor (VEGF) and neuroglobin (Ngb) participate in neuronal responses to hypoxia and ischemia, but the relationship between their effects, if any, is unknown. To address this issue, we measured Ngb levels in VEGF-treated mouse cerebrocortical cultures and VEGF levels in cerebrocortical cultures from Ngb-overexpressing transgenic mice. VEGF stimulated Ngb expression in a VEGFR2/Flk1 receptor-dependent manner, whereas Ngb overexpression suppressed expression of VEGF. These findings provide further insight into hypoxia-stimulated neuronal signaling pathways.

Transient ureteral obstruction prevents against kidney ischemia/reperfusion injury via hypoxia-inducible factor (HIF)-2α activation

Although the protective effect of transient ureteral obstruction (UO) prior to ischemia on subsequent renal ischemia/reperfusion (I/R) injury has been documented, the underlying molecular mechanism remains to be understood. We showed in the current study that 24 h of UO led to renal tubular hypoxia in the ipsilateral kidney in mice, with the accumulation of hypoxia-inducible factor (HIF)-2α, which lasted for a week after the release of UO. To address the functions of HIF-2α in UO-mediated protection of renal IRI, we utilized the Mx-Cre/loxP recombination system to knock out target genes. Inactivation of HIF-2α, but not HIF-1α blunted the renal protective effects of UO, as demonstrated by much higher serum creatinine level and severer histological damage. UO failed to prevent postischemic neutrophil infiltration and apoptosis induction in HIF-2α knockout mice, which also diminished the postobstructive up-regulation of the protective molecule, heat shock protein (HSP)-27. The renal protective effects of UO were associated with the improvement of the postischemic recovery of intra-renal microvascular blood flow, which was also dependent on the activation of HIF-2α. Our results demonstrated that UO protected the kidney via activation of HIF-2α, which reduced tubular damages via preservation of adequate renal microvascular perfusion after ischemia. Thus, preconditional HIF-2α activation might serve as a novel therapeutic strategy for the treatment of ischemic acute renal failure.

Identification of hypoxia-induced genes in human SGBS adipocytes by microarray analysis

Hypoxia in adipose tissue is suggested to be involved in the development of a chronic mild inflammation, which in obesity can further lead to insulin resistance. The effect of hypoxia on gene expression in adipocytes appears to play a central role in this inflammatory response observed in obesity. However, the global impact of hypoxia on transcriptional changes in human adipocytes is unclear. Therefore, we compared gene expression profiles of human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes under normoxic or hypoxic conditions to detect hypoxia-responsive genes in adipocytes by using whole human genome microarrays. Microarray analysis showed more than 500 significantly differentially regulated mRNAs after incubation of the cells under low oxygen levels. To gain further insight into the biological processes, hypoxia-regulated genes after 16 hours of hypoxia were classified according to their function. We identified an enrichment of genes involved in important biological processes such as glycolysis, response to hypoxia, regulation of cellular component movement, response to nutrient levels, regulation of cell migration, and transcription regulator activity. Real-time PCR confirmed eight genes to be consistently upregulated in response to 3, 6 and 16 hours of hypoxia. For adipocytes the hypoxia-induced regulation of these genes is shown here for the first time. Moreover in six of these eight genes we identified HIF response elements in the proximal promoters, specific for the HIF transcription factor family members HIF1A and HIF2A. In the present study, we demonstrated that hypoxia has an extensive effect on gene expression of SGBS adipocytes. In addition, the identified hypoxia-regulated genes are likely involved in the regulation of obesity, the incidence of type 2 diabetes, and the metabolic syndrome.

Occult renal cell carcinoma manifesting with epistaxis in a woman: a case report

Introduction

Metastatic disease in the sinonasal region occurs rarely and the primary site may be elusive. This case highlights the possibility of an occult renal tumor manifesting with nasal symptoms and the risk of severe bleeding following nasal biopsy.

Case presentation

We report the case of a 79-year-old Caucasian woman who presented with a six-week history of intermittent left-sided nosebleeds. She was fit, without previous surgery or anticoagulation. Nasal endoscopy and computed tomography showed a hemorrhagic mass occupying her left ethmoid cells and middle meatus. After a highly hemorrhagic biopsy, the lesion was histologically confirmed as clear cell carcinoma. Screening revealed a right kidney mass with widespread metastases. Palliative radiotherapy to the sinonasal metastasis and systemic treatment rendered her free of symptoms nine months after initial presentation.

Conclusions

General practitioners and ear, nose and throat (ENT) doctors are very often confronted with epistaxis. A small minority of patients with epistaxis show a primary or metastatic nasal mass. Detection of the origin of secondary sinonasal masses requires a high index of suspicion and examination of infraclavicular sites by a multidisciplinary team. Renal cell carcinoma metastases are prone to severe bleeding during any surgical intervention, therefore, preoperative embolization is recommended. Resection or radiotherapy to the sinonasal metastasis of renal origin is justified in order to prevent recurrent nosebleeds.

Genome-wide association study of renal cell carcinoma identifies two susceptibility loci on 2p21 and 11q13.3

We conducted a two-stage genome-wide association study of renal cell carcinoma (RCC) in 3,772 affected individuals (cases) and 8,505 controls of European background from 11 studies and followed up 6 SNPs in 3 replication studies of 2,198 cases and 4,918 controls. Two loci on the regions of 2p21 and 11q13.3 were associated with RCC susceptibility below genome-wide significance. Two correlated variants (r² = 0.99 in controls), rs11894252 (P = 1.8 × 10⁻⁸) and rs7579899 (P = 2.3 × 10⁻⁹), map to EPAS1 on 2p21, which encodes hypoxia-inducible-factor-2 alpha, a transcription factor previously implicated in RCC. The second locus, rs7105934, at 11q13.3, contains no characterized genes (P = 7.8 × 10⁻¹⁴). In addition, we observed a promising association on 12q24.31 for rs4765623, which maps to SCARB1, the scavenger receptor class B, member 1 gene (P = 2.6 × 10⁻⁸). Our study reports previously unidentified genomic regions associated with RCC risk that may lead to new etiological insights.

Microarray gene expression profiles of fasting induced changes in liver and adipose tissues of pigs expressing the melanocortin-4 receptor D298N variant

Transcriptional profiling coupled with blood metabolite analyses were used to identify porcine genes and pathways that respond to a fasting treatment or to a D298N missense mutation in the melanocortin-4 receptor (MC4R) gene. Gilts (12 homozygous for D298 and 12 homozygous for N298) were either fed ad libitum or fasted for 3 days. Fasting decreased body weight, backfat, and serum urea concentration and increased serum nonesterified fatty acid. In response to fasting, 7,029 genes in fat and 1,831 genes in liver were differentially expressed (DE). MC4R genotype did not significantly affect gene expression, body weight, backfat depth, or any measured serum metabolite concentration. Pathway analyses of fasting-induced DE genes indicated that lipid and steroid synthesis was downregulated in both liver and fat. Fasting increased expression of genes involved in glucose sparing pathways, such as oxidation of amino acids and fatty acids in liver, and in extracellular matrix pathways, such as cell adhesion and adherens junction in fat. Additionally, we identified DE transcription factors (TF) that regulate many DE genes. This confirms the involvement of TF, such as PPARG, SREBF1, and CEBPA, which are known to regulate the fasting response, and implicates additional TF, such as ESR1. Interestingly, ESR1 controls several fasting induced genes in fat that are involved in cell matrix morphogenesis. Our findings indicate a transcriptional response to fasting in two key metabolic tissues of pigs, which was corroborated by changes in blood metabolites, and the involvement of novel putative transcriptional regulators in the immediate adaptive response to fasting.

Hypoxia response and VEGF-A expression in human proximal tubular epithelial cells in stable and progressive renal disease

Proteinuria, inflammation, chronic hypoxia, and rarefaction of peritubular capillaries contribute to the progression of renal disease by affecting proximal tubular epithelial cells (PTECs). To study the transcriptional response that separates patients with a stable course from those with a progressive course of disease, we isolated PTECs by laser capture microdissection from cryocut tissue sections of patients with proteinuric glomerulopathies (stable n=20, progressive n=11) with a median clinical follow-up of 26 months. Gene-expression profiling and a systems biology analysis identified activation of intracellular vascular endothelial growth factor (VEGF) signaling and hypoxia response pathways in progressive patients, which was associated with upregulation of hypoxia-inducible-factor (HIF)-1alpha and several HIF target genes, such as transferrin, transferrin-receptor, p21, and VEGF-receptor 1, but downregulation of VEGF-A. The inverse expression levels of HIF-1alpha and VEGF-A were significantly superior in predicting clinical outcome as compared with proteinuria, renal function, and degree of tubular atrophy and interstitial fibrosis at the time of biopsy. Interactome analysis showed the association of attenuated VEGF-A expression with the downregulation of genes that usually stimulate VEGF-A expression, such as epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), and HIF-2alpha. In vitro experiments confirmed the positive regulatory effect of EGF and IGF-1 on VEGF-A transcription in human proximal tubular cells. Thus, in progressive but not in stable proteinuric kidney disease, human PTECs show an attenuated VEGF-A expression despite an activation of intracellular hypoxia response and VEGF signaling pathways, which might be due to a reduced expression of positive coregulators, such as EGF and IGF-1.

Prognostic significance of HIF-2α/EPAS1 expression in hepatocellular carcinoma

AIM: To evaluate the prognostic significance of HIF-2α/EPAS1 expression in hepatocellular carcinoma (HCC).

METHODS: Surgical specimens from 315 patients with HCC as well as 196 adjacent noncancerous lesions and 22 cases of normal liver tissue were investigated by immunohistochemistry (IHC) for HIF-2α/EPAS1 using a standard detection system. Correlations with clinicopathological factors, VEGF, microvessel density (MVD), and prognosis were analyzed.

RESULTS: Immunoreactivity of HIF-2α/EPAS1 was positive in 69.5% of HCC, 55.6% of adjacent noncancerous tissue, and 0% of normal liver tissue. And it was significantly correlated with tumor grade, venous invasion, intrahepatic metastasis, necrosis, and capsule infiltration. Correlation analysis of HIF-2α/EPAS1 with angiogenic factor VEGF (P < 0.001), and MVD (P = 0.016) was also noted. HIF-2α/EPAS1 protein was less frequently expressed in low MVD cases, whereas a high rate of expression was noted in cases with both medium and high MVD (P = 0.042). By Kaplan-Meier analysis, strong HIF-2α/EPAS1 staining (> 50% of tumor cells) in HCC correlated with a shortened survival in patients (Cox's regression, P < 0.001, r = 3.699).

CONCLUSION: We conclude that HIF-2α/EPAS1 expression may play an important role in tumor progression and prognosis of HCC. Assessment of HIF-2α/EPAS1 expression in HCC may be used as a diagnostic tool and possibly a target in the treatment of HCC.

Suppression of VEGF transcription in renal cell carcinoma cells by pyrrole-imidazole hairpin polyamides targeting the hypoxia responsive element

Hypoxia inducible factor (HIF), a master regulator of critical genes for cell survival under hypoxic conditions, is known to be related to tumorigenesis and progression of renal cell carcinoma. N-methylpyrrole (Py)-N-methylimidazole (Im) hairpin polyamides are synthetic organic compounds that recognize and bind to the minor grooves of specific DNA sequences. We synthesized three Py-Im hairpin polyamides targeting the flanking sequences of hypoxia responsive element (HRE; a binding site of HIF) in the promoter region of the vascular endothelial growth factor (VEGF) gene. The effects of the polyamides on HIF-induced transcription were evaluated by a luciferase assay using a reporter plasmid containing a VEGF promoter. Real time reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay were performed to examine the effects of the polyamides on the transcription and secretion of VEGF in A498 renal cell carcinoma cells, which have a frame-shift mutation in the von Hippel-Lindau gene. A combination of three Py-Im hairpin polyamides suppressed HIF-induced transcription in reporter assays using 293 cells and successfully suppressed transcription and translation of the VEGF gene in A498 cells. Inhibition of the HIF-HRE interaction was confirmed by an electrophoresis mobility shift assay. An approach using Py-Im hairpin polyamides may be a new strategy for the treatment of renal cell carcinoma.

Genetic evidence for a tumor suppressor role of HIF-2alpha

The hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha are activated in hypoxic tumor regions. However, their role in tumorigenesis remains controversial, as tumor growth promoter and suppressor activities have been ascribed to HIF-1alpha, while the role of HIF-2alpha remains largely unknown. Here, we show that overexpression of HIF-2alpha in rat glioma tumors enhances angiogenesis but reduces growth of these tumors, in part by increasing tumor cell apoptosis. Moreover, siRNA knockdown of HIF-2alpha reduced apoptosis in hypoxic human malignant glioblastoma cells. Furthermore, inhibition of HIF by overexpression of a dominant-negative HIF transgene in glioma cells or HIF-2alpha deficiency in teratomas reduced vascularization but accelerated growth of these tumor types. These findings urge careful consideration of using HIF inhibitors as cancer therapeutic strategies.

Endothelium-Intrinsic Requirement for Hif-2 α During Vascular Development

Background— The development of the vascular system is a complex process that involves communications among multiple cell types. As such, it is important to understand whether a specific gene regulates vascular development directly from within the vascular system or indirectly from nonvascular cells. Hypoxia-inducible factor-2α (Hif-2α, or endothelial PAS protein-1 [EPAS-1]) is required for vascular development in mice, but it is not clear whether its requirement resides directly in endothelial cells.

Methods and Results— To address this issue, we expressed Hif-2 α cDNA in the vascular endothelium of Hif-2 α −/− embryos by an embryonic stem (ES) cell–mediated transgenic approach and assessed whether endothelium-specific reexpression of Hif-2 α could rescue vascular development. Here we report that although ES cell–derived Hif-2 α −/− embryos developed severe vascular defects by embryonic day (E) 11.5 and died in utero before E12.5, endothelium-specific expression of Hif-2 α cDNA restored normal vascular development at all stages examined (up to E14.5) and allowed Hif-2 α −/− embryos to survive at a frequency comparable to that of Hif-2 α +/− embryos. Furthermore, we found that Tie-2 expression was significantly reduced in Hif-2 α −/− mutants but was restored by Hif-2 α cDNA expression.

Conclusions— These data demonstrate an intrinsic requirement for Hif-2α by endothelial cells and imply that hypoxia may control endothelial functions directly via Hif-2α–regulated Tie-2 expression.

Hypoxia Is Important in the Biology and Aggression of Human Glial Brain Tumors

We investigated whether increasing levels of tissue hypoxia, measured by the binding of EF5 [2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide] or by Eppendorf needle electrodes, were associated with tumor aggressiveness in patients with previously untreated glial brain tumors. We hypothesized that more extensive and severe hypoxia would be present in tumor cells from patients bearing more clinically aggressive tumors. Hypoxia was measured with the 2-nitroimidazole imaging agent EF5 in 18 patients with supratentorial glial neoplasms. In 12 patients, needle electrode measurements were made intraoperatively. Time to recurrence was used as an indicator of tumor aggression and was analyzed as a function of EF5 binding, electrode values and recursive partitioning analysis (RPA) classification. On the basis of EF5 binding, WHO grade 2 tumors were characterized by modest cellular hypoxia (pO2s approximately 10%) and grade 3 tumors by modest-to-moderate hypoxia (pO2s approximately 10%- 2.5%). Severe hypoxia (approximately 0.1% oxygen) was present in 5 of 12 grade 4 tumors. A correlation between more rapid tumor recurrence and hypoxia was demonstrated with EF5 binding, but this relationship was not predicted by Eppendorf measurements.

Down-regulation of vascular endothelial growth factor in renal cell carcinoma cells by glucocorticoids

Metastatic renal cell carcinomas (RCC) remain highly resistant to systemic therapy. RCCs are highly vascular tumors, which overproduce angiogenic peptides such as vascular endothelial growth factor (VEGF) even under normoxic conditions. A potential suggested role of antiangiogenic therapeutic strategies is the treatment of RCC by inhibiting VEGF production. The down-regulation of VEGF expression by glucocorticoids has recently been demonstrated in several cells. In this study, the direct effects of glucocorticoids on VEGF production by RCC cells were evaluated. Four RCC cell lines A498, RCC270, Caki1, and ACHN were treated with dexamethasone (DEX), hydrocortisone (HC), 5-alpha-dihydrotestosterone (DHT), or estradiol (E2). RU486 was used as a glucocorticoid receptor (GR) antagonist. Cell growth was studied with MTS assays. VEGF mRNA and protein were evaluated with quantitative real-time RT-PCR and ELISA, respectively, and GR expression was examined using RT-PCR and immunocytochemistry. All four RCC cell lines expressed GR. DEX at 100 nM down-regulated VEGF secretions by more than 50% in three lines (A498, RCC270, and Caki1) and had a weak inhibitory effect on ACHN cells. The effect of DEX on reducing VEGF mRNA levels in A498 cells was concentration-dependent and maximal at 100 nM (80% inhibition). HC had similar but weaker effects on VEGF production in the RCC cells, but E2 and DHT had no effect. RU486 reversed the effects of DEX. DEX at 1-1000 nM did not affect cell growth in any of the four RCC cell lines. This is the first study showing that glucocorticoids, at concentrations achievable in vivo by oral administration of low doses of DEX, have an inhibitory effect on VEGF mRNA expression and protein secretion of RCC cells possibly through the GR pathway. Furthermore, DEX might have a potential role in antiangiogenic therapeutic strategies by inhibiting VEGF production during metastatic RCC treatment.

Differential activation of vascular genes by hypoxia in primary endothelial cells

Changes in the local environment, such as reduced oxygen tension (hypoxia), elicit transcriptional activation of a variety of genes in mammalian cells. Here we have analyzed the effect of hypoxia in different vascular endothelial cells (ECs) with emphasis on hypoxia-regulated transcription factors and genes of importance for blood vessel dynamics. While hypoxia induced the transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha) in all endothelial cells tested, the closely related HIF-2alpha protein was markedly induced in microvascular/capillary endothelial cells, but only weakly or not at all in artery and vein endothelial cells. Furthermore, microvascular/capillary endothelial cells responded to hypoxia with increased number of transcripts encoding vascular endothelial growth factor-A (VEGF-A), VEGF receptor-2, the angiopoietin receptor Tie2, platelet-derived growth factor-B (PDGF-B), and inducible nitric oxide synthase (iNOS). In vein endothelial cells, hypoxia instead increased transcripts encoding lymphatic vascular components VEGF-C, -D, and VEGF receptor-3. Finally, reduced VEGF receptor levels and phosphorylation indicated establishment of a functional autocrine VEGF-A loop in hypoxic endothelial cells. Our results show that endothelial cells, derived from different vascular beds, mount different transcriptional responses to changes in oxygen tension.

Ephrin B2 expression in Kaposi sarcoma is induced by human herpesvirus type 8: phenotype switch from venous to arterial endothelium

Kaposi sarcoma (KS) is an angioproliferative tumor derived from endothelial cells in which tumor cells form aberrant vascular structures. Ephrin B2 and ephrin B4 (EphB4) are artery- and vein-specific proteins, respectively, with critical roles in vessel maturation. We investigated whether the disorganized KS vasculature was due to unbalanced expression of ephrin B2 and EphB4. Secondly, we wished to determine if human herpesvirus type 8 (HHV-8), the viral agent associated with KS, regulates ephrin B2 and EphB4. An arterial phenotype was observed in KS tissue and cell lines, as shown by abundant expression of ephrin B2 with little or no EphB4. Infection of venous endothelial cells with HHV-8 resulted in a phenotype switch from EphB4 to ephrin B2, similar to that seen with vascular endothelial growth factor (VEGF). The HHV-8 effect on ephrin B2 expression was reproduced with the HHV-8-specific viral G-protein-coupled receptor. We also showed that ephrin B2 expression is required for KS cell viability by knock down with siRNA. KS is the first example of a human tumor with a predominantly arterial phenotype. This predominance can be attributed to expression of HHV-8 proteins and their downstream effects. Ephrin B2 is thus an important novel factor in KS biology and a potential target for therapy.

HIFs and tumors--causes and consequences

For most organisms oxygen is essential fo life. When oxygen levels drop below those required to maintain the minimum physiological oxygen requirement of an organism or tissue it is termed hypoxia. To counter act possible deleterious effects of such a state, an immediate molecular response is initiated causing adaptation responses aimed at cell survival. This response is mediated by the hypoxia-inducible factor-1 (HIF-1), which is a heterodimer consisting of an alpha- and a beta-subunit. HIF-1 alpha protein is stabilized under hypoxic conditions and therefore confers selectivity to this response. Hypoxia is characteristic of tumors, mainly because of impaired blood supply resulting from abnormal growth. Over the past few years enormous progress has been made in the attempt to understand how the activation of the physiological response to hypoxia influences neoplastic growth. In this review some aspects of HIF-1 pathway activation in tumors and the consequences for pathophysiology and treatment of neoplasia are discussed.

Prognostic significance of endothelial Per-Arnt-sim domain protein 1/hypoxia-inducible factor-2alpha expression in a subset of tumor associated macrophages in invasive bladder cancer

PURPOSE

Endothelial Per-Arnt-Sim domain protein 1 (EPAS1) is induced under hypoxia and it transactivates a series of genes involved in angiogenesis and energy metabolism. Recent studies showed that EPAS1 is expressed in tumor associated macrophages (TAMs), which have multifaceted roles in tumor progression. We hypothesized that EPAS1 expressed in TAMs may contribute to bladder cancer progression.

MATERIALS AND METHODS

Clinicopathological and followup data on 69 patients undergoing radical cystectomy for T1-4N0-2M0 high grade bladder urothelial carcinoma were reviewed. Quantitative immunohistochemical analysis of TAMs and EPAS1 was performed separately in invasive front and in other superficial parts of carcinoma tissues. TAM counts and EPAS1 positive cell counts were compared with pathological variables and cancer specific survival (CSS).

RESULTS

The 5-year CSS rate in the 69 patients was 69% at a median followup of 58 months (range 2 to 196). EPAS1 expression was restricted to a small subset of TAMs. Although TAM counts were not associated with T stage or lymph node metastasis, EPAS1 expressing TAM counts were significantly associated with higher T stage. On univariate and multivariate analyses higher EPAS1 expressing TAM counts in invasive front along with higher T stage and positive lymph node metastasis were significantly associated with shorter CSS, while total TAM counts or EPAS1 expressing TAM counts in other superficial parts did not.

CONCLUSIONS

Despite limited prognostic effects of total TAMs EPAS1 expressing TAMs were associated with a poor prognosis of invasive bladder cancer, suggesting that EPAS1 expressed in a subset of TAMs mediates bladder cancer progression.

Metastatic renal cell carcinoma presenting as epistaxis

Metastatic tumors in the nasal and paranasal sinuses are very rare. The origin of metastatic tumors in the nasal or paranasal sinuses is often renal cancer. Renal cell carcinomas are known for their tendency to early metastasis, and symptoms due to the metastatic lesion may be the only initial manifestation. In this paper we deal with the case of a 73-year-old patient who presented with recurrent epistaxis. The presence of a primary renal cell carcinoma was recognized only after surgical removal of the metastatic tumor. The presentation, difficulties in diagnosis and treatment of this tumor are discussed, with a review of the literature.

HIF-1alpha mRNA and protein upregulation involves Rho GTPase expression during hypoxia in renal cell carcinoma

The small G proteins of the Rho family are involved in reorganization of the actin cytoskeleton, cell migration and in the regulation of gene transcription. Hypoxia-induced ATP depletion results in the disruption of actin organization which could affect Rho functions. In solid tumors, regions with low oxygen tension stimulate angiogenesis in order to increase oxygen and nutrient supply. This process is mediated by stabilization of the transcriptional factor hypoxia inducible factor 1 (HIF-1), which increases vascular endothelial growth factor (VEGF) production. In this study, we investigated the activities of Rho proteins, which are key regulators of cytoskeleton organization during hypoxia in renal cell carcinoma. Caki-1 cells were exposed to hypoxia (1% O2) and exhibited increased Cdc42, Rac1 and RhoA protein expression. Immunoprecipitation of metabolically labelled RhoA showed that overexpression was at least due to neo-synthesis. The Rho GTPases overexpressed during hypoxia were mainly located at membranes and pull-down assays demonstrated that they were active since they bound GTP. RT-PCR analysis indicated that the increase in RhoA protein expression was also reflected at the mRNA level. Overexpression and activation of Rho proteins were downstream of, and dependent on, the production of reactive oxygen species (ROS) since, in the presence of an inhibitor, both the rise of ROS and upregulation of Rho proteins were abolished. Importantly, preincubation of cells with the toxin C3, which inhibits RhoA, reduced HIF-1alpha protein accumulation by 84% during hypoxia. Together, these results support a model where ROS upregulate Rho protein expression and where active RhoA is required for HIF-1alpha accumulation during hypoxia.

Prognostic significance of tumor oxygenation in humans

Low tissue oxygen concentration has been shown to be important in the response of human tumors to radiation therapy, chemotherapy and other treatment modalities. Hypoxia is also known to be a prognostic indicator, as hypoxic human tumors are more biologically aggressive and are more likely to recur locally and metastasize. Herein, we discuss and summarize the various methods under investigation to directly or indirectly measure tissue oxygen in vivo. Secondly, we consider the advantages and disadvantages of each of these techniques. These considerations are made in light of our specific hypotheses that hypoxia should be measured as a continuum, not a binary measurement and that moderate, not severe hypoxia is of great biological consequence.

Widespread hypoxia-inducible expression of HIF-2alpha in distinct cell populations of different organs

Cellular responses to oxygen are increasingly recognized as critical in normal development and physiology, and are implicated in pathological processes. Many of these responses are mediated by the transcription factors HIF-1 and HIF-2. Their regulation occurs through oxygen-dependent proteolysis of the alpha subunits HIF-1alpha and HIF-2alpha, respectively. Both are stabilized in cell lines exposed to hypoxia, and recently HIF-1alpha was reported to be widely expressed in vivo. In contrast, regulation and sites of HIF-2alpha expression in vivo are unknown, although a specific role in endothelium was suggested. We therefore analyzed HIF-2alpha expression in control and hypoxic rats. Although HIF-2alpha was not detectable under baseline conditions, marked hypoxic induction occurred in all organs investigated, including brain, heart, lung, kidney, liver, pancreas, and intestine. Time course and amplitude of induction varied between organs. Immunohistochemistry revealed nuclear accumulation in distinct cell populations of each tissue, which were exclusively non-parenchymal in some organs (kidney, pancreas, and brain), predominantly parenchymal in others (liver and intestine) or equally distributed (myocardium). These data indicate that HIF-2 plays an important role in the transcriptional response to hypoxia in vivo, which is not confined to the vasculature and is complementary to rather than redundant with HIF-1.

Angiogenesis and vascular architecture in pheochromocytomas: distinctive traits in malignant tumors

Angiogenesis is a critical step in tumor growth and metastatic invasion. We here report the study of the vascular status of 10 benign and 9 malignant pheochromocytomas. We examined the vascular architecture after immunostaining endothelial cells (CD34) and vascular smooth muscle cells (alpha-actin) and identified a vascular pattern characteristic of malignant lesions. To define a gene expression profile indicative of the invasive phenotype, we studied by in situ hybridization the expression of genes encoding several pro- and anti-angiogenic factors [hypoxia-inducible factor (HIF-1 alpha), EPAS1, vascular endothelial growth factor (VEGF), VEGF receptors, angiopoietins and their receptor Tie2, five genes of the endothelin system, and thrombospondin 1]. A semiquantitative evaluation of the labeling revealed an induction of genes encoding EPAS1, VEGF, VEGFR-1, VEGFR-2, endothelin receptor, type B (ETB) and endothelin receptor, type A (ETA) in malignant pheochromocytomas as compared to benign tumors. These differences were observed in tumor cells, in endothelial cells, or in both. Quantification by real-time reverse-transcriptase polymerase chain reaction showed an increase of EPAS1, VEGF, and ETB transcripts of 4.5-, 3.5-, and 10-fold, respectively, in malignant versus benign tumors. Furthermore, we observed a strong correlation between the expression of EPAS1 and VEGF in tumoral tissue and between EPAS1 and ETB in endothelial cells. Altogether, our observations show that analysis of angiogenesis provides promising new criteria for the diagnosis of malignant pheochromocytomas.

Activation of vascular endothelial growth factor A transcription in tumorigenic glioblastoma cell lines by an enhancer with cell type-specific DNase I accessibility

Unregulated expression of vascular endothelial growth factor-A (VEGF-A) plays an important role in tumor growth. We have identified a cell type-specific enhancer, HS-1100, that contributes to VEGF-A transcriptional activation in tumorigenic glioblastoma cell lines. This enhancer exhibits increased accessibility to DNase I in glioblastoma cell lines that express high levels of VEGF-A but not in several other cell lines that express much lower levels of VEGF-A. HS-1100 contains a number of sequence elements that are highly conserved among human, mouse, and rat, including the hypoxia-response element (HRE). We show that the HRE contributes significantly to the cell type-specific enhancer activity of HS-1100 in U87MG glioblastoma cells. We use chromatin immunoprecipitation assays to show that endothelial PAS domain protein 1 (EPAS1) can efficiently bind to the endogenous HRE in U87MG cells but not in HEK293 cells in which the chromosomal HS-1100 is not accessible to DNase I. A dominant negative EPAS1 significantly reduces HS-1100 enhancer activity and VEGF-A levels in U87MG cells. Our results provide insight into the molecular mechanisms of VEGF-A up-regulation during cancer development.

Positive expression of HIF-2alpha/EPAS1 in invasive bladder cancer

OBJECTIVES

To investigate the expression of hypoxia-inducible factor (HIF)-2alpha/endothelial PAS domain protein 1 (EPAS1) in bladder cancer.

METHODS

Two bladder cancer cell lines (T24, EJ-1) were examined for the expression of HIF-2alpha/EPAS1 mRNA by reverse transcriptase-polymerase chain reaction and HIF-2alpha/EPAS1 protein by Western blot analysis, respectively. Expression of HIF-2alpha/EPAS1 protein was also investigated immunohistochemically on paraffin-embedded sections from 24 patients with bladder cancer.

RESULTS

HIF-2alpha/EPAS1 mRNA and protein could be detected in the two bladder cell lines under normoxia. The normal urothelium and all 7 superficial cases (pTis-pTa) were negative for HIF-2alpha/EPAS1. Five of the 8 pT1 cases (62.5%) and all 9 muscle-invasive cases were positive. The invasive compartment showed stronger HIF-2alpha/EPAS1 immunoreactivity compared with the superficial compartment. All the tumor clusters infiltrating to the interstitial tissue among muscle fibers showed moderate to strong positive staining.

CONCLUSIONS

HIF-2alpha/EPAS1 is mostly expressed in invasive bladder cancer, which indicates a possible role for HIF-2alpha/EPAS1 in the invasion of bladder cancer.

Dissecting hypoxia-dependent and hypoxia-independent steps in the HIF-1alpha activation cascade: implications for HIF-1alpha gene therapy

The heterodimeric hypoxia-inducible factor (HIF)-1 is a master transcriptional regulator of oxygen homeostasis and a possible target for gene therapy of ischemic disease. Although the role of oxygen concentration in HIF-1a protein stabilization is well established, it is less clear whether and how oxygen-regulated mechanisms contribute to HIF-1a protein modifications, nuclear translocation, heterodimerization with the b-subunit, recruitment of cofactors, and gene trans-activation. Because the HIF-1a protein is proteolytically degraded under normoxic conditions, we established two HeLa Tet-Off cell lines (HT42 and HT43), which inducibly overexpress high levels of HIF-1a under normoxic conditions, allowing to distinguish hypoxia-dependent from hypoxia-independent activation mechanisms. Using these cells, we found that normoxically induced HIF-1a is localized to the nucleus, binds DNA, and trans-activates reporter and endogenous target genes. The levels of p53 expression remained unaffected. The MAP kinase inhibitor PD98059 attenuated HIF-1a protein modifications and trans-activation ability but not protein stabilization and DNA-binding activity. Because overexpressed HIF-1a is fully localized to the nucleus but displays only partial DNA-binding and trans-activation activity, mitogen-activated protein kinase-dependent phosphorylation might be required for full HIF-1 activation. HIF-1a protein was also overexpressed in vivo, following the transplantation of HT42 cells into nude mice, demonstrating the feasibility of HIF-1a gene transfer.