A common polymorphism in the oxygen-dependent degradation (ODD) domain of hypoxia inducible factor-1alpha (HIF-1alpha) does not impair Pro-564 hydroxylation

Idiopathic erythrocytosis: a germline disease?

Polycythemia Vera (PV) is typically caused by V617F or exon 12 JAK2 mutations. Little is known about Polycythemia cases where no JAK2 variants can be detected, and no other causes identified. This condition is defined as idiopathic erythrocytosis (IE). We evaluated clinical-laboratory parameters of a cohort of 56 IE patients and we determined their molecular profile at diagnosis with paired blood/buccal-DNA exome-sequencing coupled with a high-depth targeted OncoPanel to identify a possible underling germline or somatic cause. We demonstrated that most of our cohort (40/56: 71.4%) showed no evidence of clonal hematopoiesis, suggesting that IE is, in large part, a germline disorder. We identified 20 low mutation burden somatic variants (Variant allelic fraction, VAF, < 10%) in only 14 (25%) patients, principally involving DNMT3A and TET2. Only 2 patients presented high mutation burden somatic variants, involving DNMT3A, TET2, ASXL1 and WT1. We identified recurrent germline variants in 42 (75%) patients occurring mainly in JAK/STAT, Hypoxia and Iron metabolism pathways, among them: JAK3-V722I and HIF1A-P582S; a high fraction of patients (48.2%) resulted also mutated in homeostatic iron regulatory gene HFE-H63D or C282Y. By generating cellular models, we showed that JAK3-V722I causes activation of the JAK-STAT5 axis and upregulation of EPAS1/HIF2A, while HIF1A-P582S causes suppression of hepcidin mRNA synthesis, suggesting a major role for these variants in the onset of IE.

HIF-1α and NFIA-AS2 Polymorphisms as Potential Determinants of Total Hemoglobin Mass in Endurance Athletes

ABSTRACT

Malczewska-Lenczowska, J, Orysiak, J, Majorczyk, E, Sitkowski, D, Starczewski, M, and Żmijewski, P. HIF-1α and NFIA-AS2 polymorphisms as potential determinants of total hemoglobin mass in endurance athletes. J Strength Cond Res 36(6): 1596-1604, 2022-The aims of this study were to examine (1) the genotype distribution of rs11549465:C>T of the HIF-1α gene and rs1572312:C>A of the NFIA-AS2 gene; (2) the association between the genes and hematological status in endurance-oriented athletes; and (3) the association between the NFIA-AS2 gene and aerobic capacity in cyclists. Two hundred thirty-eight well-trained athletes (female n = 90, male n = 148) participated in the study. Total hemoglobin mass (tHbmass), blood morphology, intravascular volumes, i.e., erythrocyte volume (EV), blood volume (BV) and plasma volume (PV), and aerobic capacity indices, e.g., peak oxygen uptake (V̇o2peak), and power at anaerobic threshold (PAT) were determined. In both studied genes, the CC genotype was predominant. In the HIF-1α gene, there were no differences in genotype and allele distribution among athletes from different disciplines and between sexes. The distribution of genotypes and alleles of the NFIA-AS2 gene differed significantly in male athletes; the frequency of A allele carriers (CA + AA) was significantly higher in cyclists than in rowers and middle- and long-distance runners. The athletes with CC genotype of NF1A-AS2 had significantly higher relative values of: tHbmass (total female athletes, cyclists), PV, BV (cyclists), and EV (total male athletes, cyclists) and PAT (cyclists) than A allele carriers (CA + AA genotypes). In conclusion, our study indicates that NFIA-AS2 rs1572312:C>A polymorphism was associated with hematological status in endurance athletes, as well as aerobic capacity indices in male cyclists. It suggests that this polymorphism may be a determinant of quantity of hemoglobin and intrtavascular volumes, which in turn can have an impact on aerobic performance.

Integrative Map of HIF1A Regulatory Elements and Variations

Hypoxia-inducible factor (HIF) family of transcription factors (HIF1A, EPAS1, and HIF3A) are regulators of the cellular response to hypoxia. They have been shown to be involved in development of various diseases such as cancer, diabetes, and erythrocytosis. A complete map of connections between HIF family of genes with various omics types has not yet been developed. The main aim of the present analysis was to construct the integrative map of genomic elements associated with HIF1A gene and prioritize potentially deleterious variants. Various genomic databases and bioinformatics tools were used, including Ensembl, MirTarBase, STRING, Cytoscape, MethPrimer, CADD, SIFT, and UALCAN. Integrative HIF1A gene map was visualized and includes transcriptional and post-transcriptional regulators, downstream targets, and genetic variants. One CpG island overlaps transcription start site of the HIF1A gene. Out of over 450 missense variants, four have predicted deleterious effect on protein function by at least five bioinformatics tools. Currently there are 85 miRNAs reported to target HIF1A. HIF1A downstream targets include protein-coding genes, long noncoding RNAs, and microRNAs (hypoxamiRs). The study presents the first integration of heterogeneous molecular interactions associated with HIF1A gene enabling a holistic view of the gene and lays the groundwork for supplementing the data in the future.

Current Understanding of the HIF-1-Dependent Metabolism in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is the 10th most frequent human malignancy and is thus a global burden. Despite some progress in diagnosis and therapy, patients' overall survival rate, between 40 and 55%, has stagnated over the last four decades. Since the tumor node metastasis (TNM) system is not precise enough to predict the disease outcome, additive factors for diagnosis, prognosis, prediction and therapy resistance are urgently needed for OSCC. One promising candidate is the hypoxia inducible factor-1 (HIF-1), which functions as an early regulator of tumor aggressiveness and is a key promoter of energy adaptation. Other parameters comprise the composition of the tumor microenvironment, which determines the availability of nutrients and oxygen. In our opinion, these general processes are linked in the pathogenesis of OSCC. Based on this assumption, the review will summarize the major features of the HIF system-induced activities, its target proteins and related pathways of nutrient utilization and metabolism that are essential for the initiation, progression and therapeutic stratification of OSCC.

Genetic association of hypoxia inducible factor 1-alpha (HIF1A) Pro582Ser polymorphism with risk of diabetes and diabetic complications

Diabetes is an age-related chronic disease associated with a number of complications, emerging as one of the major causes of morbidity and mortality worldwide. Several studies indicated that hypoxia-inducible factor 1-alpha (HIF1A) genetic polymorphisms may be associated with diabetes and diabetic complications. However, this association remains ambiguous. Thus, we performed a meta-analysis to provide more precise conclusion on this issue. Odds ratios (OR) with corresponding 95% confidence intervals (CI) were applied to assess the strength of the relationships. There was a protective association between HIF1A Pro582Ser polymorphism and diabetes under the heterozygous genetic model (OR = 0.70, 95% CI = 0.55-0.91; P = 0.007). Similar associations were observed in diabetic complications risk under the allelic (OR = 0.69, 95% CI = 0.57-0.83; P < 0.001), homozygous (OR = 0.51, 95% CI = 0.30-0.87; P = 0.014), recessive (OR = 0.73, 95% CI = 0.59-0.90; P = 0.004) and dominant (OR = 0.40, 95% CI = 0.25-0.65; P < 0.001) genetic models. No effects of the HIF1A Ala588Thr polymorphism were found in risk of diabetes and diabetic complications. Taken together, these findings revealed the protective effect of HIF1A Pro582Ser polymorphism against diabetes and diabetic complications.

HIF1A gene polymorphisms and human diseases: Graphical review of 97 association studies

Hypoxia-inducible factors (HIFs) belong to a family of transcription factors (TF) responsive to a low O2 availability, which is often a characteristic feature of solid tumors. The alpha subunit of the HIF heterodimer is O2 -sensitive, and once stabilized in hypoxia, it functions as a master regulator of various genes involved in hypoxia pathway. Changes in the HIF1A (hypoxia inducible factor 1, alpha subunit) nucleotide sequence or expression has been shown to be associated with the development of several diseases. Because of increasing research interest in HIF1A gene a review of association studies was needed. We here reviewed published data on single nucleotide polymorphisms (SNPs) in HIF1A in various diseases; in total, 34 SNPs were tested for an association with 49 phenotypes, and the results were visualized using the Cytoscape software. Among all collected polymorphisms 16 SNPs showed significant associations with 40 different phenotypes, including six SNPs associated with 14 cancer types. Missense SNPs (rs11549465 and rs11549467) within the oxygen-dependent degradation domain were most frequently studied. The study provides a comprehensive tool for researchers working in this area and may contribute to more accurate disease diagnosis and identification of therapeutic targets.

Influencia del polimorfismo rs11549465 de HIF-1α en los niveles de hemoglobina y lactato en pacientes de cirugía cardiovascular

Introducción. La anemia perioperatoria es una complicación común de la cirugía cardiovascular. Pacientes con el alelo T del polimorfismo rs11549465 de HIF-1α podrían tener niveles alterados de hemoglobina y lactato antes, durante y después de la cirugía, en comparación con los del ancestral. Esto, por un aumento en la estabilidad de HIF-1α causado por este.Objetivo. Describir la frecuencia del alelo T en pacientes de cirugía cardiovascular programada y su relación con los niveles de hemoglobina y lactato.Materiales y métodos: Se aisló ADN de 84 pacientes de cirugía cardiovascular para genotipificación por secuenciación de Sanger y se recolectaron características demográficas y clínicas.Resultados. La frecuencia del alelo T fue 0.066 (IC95%: 0.037-0.114). No hubo diferencias significativas en los niveles de hemoglobina y lactato preoperatorios, intraoperatorios y posoperatorios entre pacientes con alelo T y aquellos con alelo ancestral.Conclusión. La frecuencia del alelo T fue menor que la esperada, de acuerdo con otros estudios en poblaciones similares de voluntarios sanos y no mostró diferencias significativas con algunas poblaciones asiáticas, ni con un grupo de pacientes con infarto agudo de miocardio. Parece que la genotipificación de rs11549465 en pacientes de cirugía cardiovascular no representó un método de estratificación de riesgo de anemia en este grupo.

Involvement of mTOR and Regulation by AMPK in Early Iodine Deficiency-Induced Thyroid Microvascular Activation

Iodine deficiency (ID) induces TSH-independent microvascular activation in the thyroid via the reactive oxygen species/nitric oxide-hypoxia-inducible factor-1α/vascular endothelial growth factor (VEGF) pathway. We hypothesized the additional involvement of mammalian target of rapamycin (mTOR) as a positive regulator of this pathway and AMP-activated protein kinase (AMPK) as a negative feedback regulator to explain the transient nature of ID-induced microvascular changes under nonmalignant conditions. mTOR and AMPK involvement was investigated using an in vitro model (human thyrocytes in primary cultures) and 2 murine models of goitrogenesis (normal NMRI and RET-PTC mice [a papillary thyroid cancer model]). In NMRI mice, ID had no effect on the phosphorylation of ribosomal S6 kinase (p70S6K), a downstream target of mTOR. However, rapamycin inhibited ID-induced thyroid blood flow and VEGF protein expression. In the RET-PTC model, ID strongly increased the phosphorylation of p70S6K, whereas rapamycin completely inhibited the ID-induced increase in p70S6K phosphorylation, thyroid blood flow, and VEGF-A expression. In vitro, although ID increased p70S6K phosphorylation, the ID-stimulated hypoxia-inducible factor/VEGF pathway was inhibited by rapamycin. Activation of AMPK by metformin inhibited ID effects both in vivo and in vitro. In AMPK-α1 knockout mice, the ID-induced increase in thyroid blood flow and VEGF-A protein expression persisted throughout the treatment, whereas both parameters returned to control values in wild-type mice after 4 days of ID. In conclusion, mTOR is required for early ID-induced thyroid microvascular activation. AMPK negatively regulates this pathway, which may account for the transient nature of ID-induced TSH-independent vascular effects under benign conditions.

SNP 1772 C > T of HIF-1α gene associates with breast cancer risk in a Taiwanese population

Background

Hypoxia inducible factor 1α (HIF-1α) is a stress-responsive transcription factor to hypoxia and its expression is correlated to tumor progression and angiogenesis. Several single nucleotide polymorphisms (SNPs) of HIF-1α gene in the oxygen-dependent degradation (ODD) domain was reportedly associated with increased HIF-1α activity.

Results

In this study, we focused on the relationship between SNP 1772 C > T (rs11549465) of HIF-1α gene and its breast cancer risk, as well as its correlation with HIF-1α expression and tumor angiogenesis. Ninety six breast cancer patients and 120 age-matched controls were enrolled. We found that 1772 T allele of HIF-1α gene was associated with increased breast cancer risk (adjusted OR = 14.51; 95% CI: 6.74-31.24). This SNP was not associated with clinicopathologic features of angiogenesis such as VEGF activity and the micro-vessel density and survival of breast cancer patients.

Conclusion

Taken together, the 1772 C > T of HIF-1α gene is a potential biomarker for breast cancer susceptibility.

The role of PHD2 mutations in the pathogenesis of erythrocytosis

The transcription of the erythropoietin (EPO) gene is tightly regulated by the hypoxia response pathway to maintain oxygen homeostasis. Elevations in serum EPO level may be reflected in an augmentation in the red cell mass, thereby causing erythrocytosis. Studies on erythrocytosis have provided insights into the function of the oxygen-sensing pathway and the critical proteins involved in the regulation of EPO transcription. The α subunits of the hypoxia-inducible transcription factor are hydroxylated by three prolyl hydroxylase domain (PHD) enzymes, which belong to the iron and 2-oxoglutarate-dependent oxygenase superfamily. Sequence analysis of the genes encoding the PHDs in patients with erythrocytosis has revealed heterozygous germline mutations only occurring in Egl nine homolog 1 (EGLN1, also known as PHD2), the gene that encodes PHD2. To date, 24 different EGLN1 mutations comprising missense, frameshift, and nonsense mutations have been described. The phenotypes associated with the patients carrying these mutations are fairly homogeneous and typically limited to erythrocytosis with normal to elevated EPO. However, exceptions exist; for example, there is one case with development of concurrent paraganglioma (PHD2-H374R). Analysis of the erythrocytosis-associated PHD2 missense mutations has shown heterogeneous results. Structural studies reveal that mutations can affect different domains of PHD2. Some are close to the hypoxia-inducible transcription factor α/2-oxoglutarate or the iron binding sites for PHD2. In silico studies demonstrate that the mutations do not always affect fully conserved residues. In vitro and in cellulo studies showed varying effects of the mutations, ranging from mild effects to severe loss of function. The exact mechanism of a potential tumor-suppressor role for PHD2 still needs to be elucidated. A knockin mouse model expressing the first reported PHD2-P317R mutation recapitulates the phenotype observed in humans (erythrocytosis with inappropriately normal serum EPO levels) and demonstrates that haploinsufficiency and partial deregulation of PHD2 is sufficient to cause erythrocytosis.

Human cytomegalovirus inhibits erythropoietin production

Anemia is a feature of CKD and a complication of renal transplantation, often caused by impaired production of erythropoietin. The kidney is a target organ for human cytomegalovirus (hCMV) in such patients, but it is not known whether hCMV effects erythropoietin production. We found that kidneys from patients with CKD were positive for hCMV protein and that blood levels of hCMV IgG inversely correlated with red blood cell count. In mice, systemic murine cytomegalovirus infection decreased serum erythropoietin levels. In human erythropoietin-producing cells, hCMV inhibited hypoxia-induced expression of erythropoietin mRNA and protein. hCMV early gene expression was responsible, as ultraviolet-inactivated virus had no effect and valganciclovir treatment showed that late gene expression was nonessential. Hypoxia-induced gene transcription is controlled by the transcription factors hypoxia-inducible transcription factor (HIF)-1α and HIF2α, which are constitutively produced but stable only under low oxygen conditions. We found that hCMV inhibited constitutive production of HIF2α mRNA. HIF2α is thought to be the master regulator of erythropoietin transcription. Single-cell analysis revealed that nuclear accumulation of HIF2α was inhibited in hCMV-infected cells, and the extent of inhibition correlated with hCMV protein expression. Our findings suggest that renal hCMV infection could induce or exacerbate anemia in patients.

Hypoxia-inducible factor-1α C1772T polymorphism and cancer risk: a meta-analysis including 18,334 subjects

Studies on HIF 1α C1772T (P582S) polymorphism revealed a genetic susceptibility to malignant tumors, however, the results were conflicting. We conducted a meta-analysis utilizing 29 eligible case-control studies to analyze the data concerning the association between the HIF-1α C1772T polymorphism and cancer risks. There was statistical association between the HIF-1α CT/TT genotype and cancer risk (OR = 1.28, 95% CI = 1.06-1.54, P(heterogeneity) < .00001). The stability of these observations was confirmed by a one-way sensitivity analysis. Our findings suggested that CT/TT genotype was associated with increased risks of prostate cancer. Besides, the HIF-1α C1772T polymorphism most likely contributes to susceptibility to malignant tumors, especially in American population.

VHL and HIF-1α: gene variations and prognosis in early-stage clear cell renal cell carcinoma

Von Hipple-Lindau gene (VHL) inactivation represents the most frequent abnormality in clear cell renal cell carcinoma (ccRCC). Hypoxia-inducible factor-1α (HIF-1α) expression is regulated by O2 level. In normal O2 conditions, VHL binds HIF-1α and allows HIF-1α proteasomal degradation. A single-nucleotide polymorphism (SNP) has been found located in the oxygen-dependent degradation domain at codon 582 (C1772T, rs11549465, Pro582Ser). In hypoxia, VHL/HIF-1α interaction is abolished and HIF-1α activates target genes in the nucleus. This study analyzes the impact of genetic alterations and protein expression of VHL and the C1772T SNP of HIF-1α gene (HIF-1α) on prognosis in early-stage ccRCC (pT1a, pT1b, and pT2). Mutational analysis of the entire VHL sequence and the genotyping of HIF-1α C1772T SNP were performed together with VHL promoter methylation analysis and loss of heterozygosis (LOH) analysis at (3p25) locus. Data obtained were correlated with VHL and HIF-1α protein expression and with tumor-specific survival (TSS). VHL mutations, methylation status, and LOH were detected in 51, 11, and 12% of cases, respectively. Our results support the association between biallelic alterations and/or VHL silencing with a worse TSS. Moreover, we found a significant association between the HIF-1α C1772C genotype and a worse TSS. The same association was found when testing the presence of HIF-1α protein in the nucleus. Our results highlight the role of VHL/HIF-1α pathway in RCC and support the molecular heterogeneity of early-stage ccRCC. More important, we show the involvement of HIF-1α C1772T SNP in ccRCC progression.

Hypoxia-inducible factor-1α polymorphisms link to coronary artery collateral development and clinical presentation of coronary artery disease

AIMS

This study aimed to investigate the association of Hypoxia-inducible factor-1α (HIF-1α) C1772T and G1790A single nucleotide polymorphisms (SNPs) with: incidence, clinical type, severity of coronary atherosclerosis and coronary collaterals of coronary artery disease (CAD).

METHODS

The clinical data and genomic DNA were gathered in 958 subjects, including 560 controls and 398 patients with CAD. CAD was confirmed with coronary angiography (CAG). The genotypes for two SNPs were determined by high resolution melting after PCR amplification.

RESULTS

Neither the HIF-1α C1772T nor the G1790A genotype was significantly associated with CAD and, no gene-gene or gene-environmental interactions were identified. However, both HIF-1α C1772T and G1790A (P<0.05) alleles were associated with clinical type and formation of coronary collaterals (P<0.05). Patients carrying genotype CT (P=0.019, OR=4.905,91, 95% CI: 1.355-17.761) and GA (P=0.026, OR=3.052, 95% CI: 1.180-7.892) had significantly higher stable angina pectoris (SAP) than unstable angina pectoris (UAP) and acute myocardial infarction (AMI). The presence of HIF-1 genotype CT (P=0.016, OR=13.373, 95% CI: 15.468-32.709) and GA (P=0.001, OR=19.741, 95% CI: 8.125-47.966) predicted lower collateral formation and severity of CAD secondary to the absence of collaterals (r=0.242, P<0.001).

CONCLUSIONS

We conclude that functional polymorphisms in the HIF-1α gene do not modify CAD risk but they are associated with the formation of coronary collaterals and clinical presentation of CAD.

Congenital erythrocytosis associated with gain-of-function HIF2A gene mutations and erythropoietin levels in the normal range

Hypoxia-inducible factor 2α (HIF-2α) plays a pivotal role in the balancing of oxygen requirements throughout the body. The protein is a transcription factor that modulates the expression of a wide array of genes and, in turn, controls several key processes including energy metabolism, erythropoiesis and angiogenesis. We describe here the identification of two cases of familial erythrocytosis associated with heterozygous HIF2A missense mutations, namely Ile533Val and Gly537Arg. Ile533Val is a novel mutation and represents the genetic HIF2A change nearest to Pro-531, the primary hydroxyl acceptor residue, so far identified. The Gly537Arg missense mutation has already been described in familial erythrocytosis. However, our patient is the only described case of a de novo HIF2A mutation associated with the development of congenital polycythemia. Functional in vivo studies, based on exogenous expression of hybrid HIF-2α transcription factors, indicated that these genetic alterations lead to the stabilization of HIF-2α protein. All the identified polycythemic subjects with HIF2A mutations show serum erythropoietin in the normal range, independently of the hematocrit values and phlebotomy frequency. The erythroid precursors obtained from the peripheral blood of patients showed an altered phenotype, including an increased rate of growth and a modified expression of some HIF-2α target genes. These results suggest the novel proposal that polycythemia observed in subjects with HIF2A mutations might also be due to primary changes in hematopoietic cells and not only secondary to increased erythropoietin levels.

Genetically heterogeneous origins of idiopathic erythrocytosis

The idiopathic erythrocytosis (IE) group of disorders is defined by an absolute increase in red cell mass and hematocrit without elevation of the megakaryocytic or granulocytic lineages. It is associated with a wide range of serum erythropoietin (Epo) levels and broadly falls into groups of raised/inappropriately normal or low/undetectable Epo levels. A spectrum of molecular defects has been described in association with IE, which reflects the heterogeneity of this disorder. To date the most common identified cause of IE has been mutations in the von Hippel Landau (VHL) protein, which results in aberrant oxygen sensing and dysregulated Epo production. Studying the molecular basis of IE will provide insights into the control of Epo synthesis and Epo-induced signaling pathways.

Hypoxia-inducible factor-1α(Pro-582-Ser) polymorphism prevents iron deprivation in healthy blood donors

BACKGROUND

Frequent blood loss induces progressive depletion of iron stores, leading to iron deficiency and, ultimately, to overt iron-deficient anaemia. The erythropoietin-mediated bone marrow response to anaemia is under the control of hypoxia-inducible factors (HIF), the master regulators of oxygen and iron homeostasis. Since the HIF-1α(Pro-582-Ser) variant is associated with elevated trans-activation capacity of hypoxia responsive elements of target genes, we investigated whether the HIF-1α(Pro-582-Ser) polymorphism might influence the response to repeated blood withdrawals.

MATERIALS AND METHODS

Using polymerase chain reaction analysis and DNA sequencing, we retrospectively investigated the presence of HIF-1α(Pro-582-Ser) in a series of 163 blood donors. Haematological findings, serum ferritin levels and frequency of donations were compared according to the mutational status of the HIF-1α gene.

RESULTS

We found that male carriers of the HIF-1α(Pro-582-Ser) polymorphism had higher haemoglobin and ferritin levels than individuals homozygous for the wild-type allele. Moreover, the HIF-1α(Pro-582-Ser) polymorphism protected regular blood donors from developing iron deficiency and anaemia and predicted uninterrupted donation activity.

DISCUSSION

These findings show for the first time that the HIF-1α(Pro-582-Ser) polymorphism significantly affects red blood cell and iron homeostasis after blood loss, conferring to male carriers a resistance to anaemia. Regarding the female gender, large series of individuals should be investigated to establish whether there is an effect of the HIF-1α(Pro-582-Ser) polymorphism in this population. Although these data need to be confirmed in prospective studies, they could have important implications in blood donor selection and donation procedures.

Impact of the hypoxia-inducible factor-1 α (HIF1A) Pro582Ser polymorphism on diabetes nephropathy

OBJECTIVE

Hypoxia plays a major pathogenic role in diabetic nephropathy (DN). We have investigated in this study the effect of hypoxia-inducible factor 1 α subunit (HIF1A) genetic polymorphisms on the development of DN.

RESEARCH DESIGN AND METHODS

In 1,165 American type 1 diabetic patients with and without DN selected from the Genetics of Kidneys in Diabetes (GoKinD) study, the HIF1A genetic polymorphisms were genotyped with TaqMan allelic discrimination. The regulation of HIF-1α in the kidneys of diabetic mice was appreciated by immunohistochemistry, and the effect HIF1A Pro582Ser polymorphism on HIF-1α sensitivity to glucose was evaluated in vitro.

RESULTS

We identified a protective association between HIF1A Pro582Ser polymorphism and DN in male subjects. We also provided mechanistic insights that HIF-1α is repressed in the medulla of diabetic mice despite hypoxia and that Pro582Ser polymorphism confers less sensitivity to the inhibitory effect of glucose during a hypoxic challenge.

CONCLUSIONS

The current study demonstrates for the first time that HIF1A Pro582Ser polymorphism has an effect on DN, possibly by conferring a relative resistance to the repressive effect of glucose on HIF-1α.

Hypoxia inducible factor-1α gene polymorphisms in Korean patients with pre-eclampsia

BACKGROUND

Placental hypoxia has been implicated in the pathogenesis of pre-eclampsia. Hypoxia inducible factor-1α (HIF-1α) is activated by low oxygen tension and is a key regulator of genes involved in the cellular responses to hypoxia.

AIM

We determined whether maternal blood c.1722C>T (Pro582Ser) and c.1790G>A (Ala588Thr) polymorphisms in exon 12 of the HIF-1α gene are associated with pre-eclampsia.

SUBJECTS AND METHODS

Subjects included 163 pre-eclamptic patients (48 mild and 115 severe preeclampsia) and 194 healthy pregnant women. Polymorphisms were genotyped by PCR and direct DNA sequencing.

RESULTS

There were no significant differences in genotype or allele frequencies of the c.1772C>T and c.1790G>A polymorphisms of the HIF-1α gene among the study groups. Moreover, subgroup analysis according to pre-eclampsia severity revealed no significant differences in genotype or allele frequencies of the HIF-1α c.1772C>T and c.1790G>A polymorphism in mild pre-eclamptic compared to severe pre-eclamptic group. In addition, there were no significant differences in the frequencies of 3 haplotypes (C-G,-G, T-G, and C-A) between the control and pre-eclamptic groups.

CONCLUSIONS

Our results suggest that the HIF-1α gene polymorphisms are not associated with the development of pre-eclampsia in the studied Korean women population.

Hypoxia-inducible factors in OSCC

Oral squamous cell carcinoma (OSCC) is a characteristic locally aggressive tumor in which hypoxia levels are very high, causing a low response to chemotherapy and providing basic resistance to anticancer drugs. Tumoral hypoxia directly depends on hypoxia-inducible factors (HIF). The goal of this paper is to describe HIF basic biology and tumor cells (HIF-1α, mainly), analyzing the effects of its expression in OSCC, study its relation with other molecules such as nitric oxide (NO), carbonic anhydrase (CA) or VEGF and assess the possibility of its manipulation as a therapeutic target.

The HIF pathway and erythrocytosis

Because of the central role that red blood cells play in the delivery of oxygen to tissues of the body, red blood cell mass must be controlled at precise levels. The glycoprotein hormone erythropoietin (EPO) regulates red blood cell mass. EPO transcription, in turn, is regulated by a distinctive oxygen-sensing mechanism. In this pathway, prolyl hydroxylase domain protein (PHD) site-specifically hydroxylates the α-subunit of the transcription factor hypoxia-inducible factor α (HIF-α), thereby targeting the latter for degradation by the von Hippel-Lindau tumor-suppressor protein (VHL). Under hypoxic conditions, this posttranslational modification of HIF-α is inhibited, which stabilizes it and promotes the transcriptional activation of genes, including that for EPO. Rare patients with erythrocytosis have mutations in the genes encoding for PHD2, HIF-2α, and VHL, which implicates these proteins as critical to the proper control of red blood cell mass in humans.

Hepatic HIF-2 regulates erythropoietic responses to hypoxia in renal anemia

The kidney is the main physiologic source of erythropoietin (EPO) in the adult and responds to decreases in tissue oxygenation with increased EPO production. Although studies in mice with liver-specific or global gene inactivation have shown that hypoxia-inducible factor 2 (Hif-2) plays a major role in the regulation of Epo during infancy and in the adult, respectively, the contribution of renal HIF-2 signaling to systemic EPO homeostasis and the role of extrarenal HIF-2 in erythropoiesis, in the absence of kidney EPO, have not been examined directly. Here, we used Cre-loxP recombination to ablate Hif-2α in the kidney, whereas Hif-2-mediated hypoxia responses in the liver and other Epo-producing tissues remained intact. We found that the hypoxic induction of renal Epo is completely Hif-2 dependent and that, in the absence of renal Hif-2, hepatic Hif-2 takes over as the main regulator of serum Epo levels. Furthermore, we provide evidence that hepatocyte-derived Hif-2 is involved in the regulation of iron metabolism genes, supporting a role for HIF-2 in the coordination of EPO synthesis with iron homeostasis.

Association of hypoxia inducible factor-1 alpha gene polymorphism with both type 1 and type 2 diabetes in a Caucasian (Hungarian) sample

Background

Hypoxia inducible factor-1 alpha (HIF-1α) is a transcription factor that plays an important role in neo-vascularisation, embryonic pancreas beta-cell mass development, and beta cell protection. Recently a non synonymous single nucleotide polymorphism (g.C45035T SNP, rs11549465) of HIF-1α gene, resulting in the p.P582S amino acid change has been shown to be associated with type 2 diabetes (T2DM) in a Japanese population. Our aim was to replicate these findings on a Caucasian (Hungarian) population, as well as to study whether this genetic effect is restricted to T2DM or can be expanded to diabetes in general.

Methods

A large Caucasian sample (N = 890) was recruited including 370 T2DM, 166 T1DM and 354 healthy subjects. Genotyping was validated by two independent methods: a restriction fragment analysis (RFLP) and a real time PCR using TaqMan probes. An overestimation of heterozygotes by RFLP was observed as a consequence of a nearby SNP (rs34005929). Therefore genotyping results of the justified TaqMan system were accepted. The measured genotype distribution corresponded to Hardy-Weinberg equilibrium (P = 0.740)

Results

As the TT genotype was extremely rare in the population (0.6% in clinical sample and 2.5% in controls), the genotypes were grouped as T absent (CC) and T present (CT and TT). Genotype-wise analysis showed a significant increase of T present group in controls (24.0%) as compared to patients (16.8%, P = 0.008). This genetic effect was demonstrated in the separated samples of type 1 (15.1%, P = 0.020), and also in type 2 (17.6%, P = 0.032) diabetes. Allele-wise analysis gave identical results showing a higher frequency of the T allele in the control sample (13.3%) than in the clinical sample (8.7%, P = 0.002) with similar results in type 1 (7.8%, P = 0.010) and type 2 (9.1%, P = 0.011) diabetes. The odds ratio for diabetes (either type 1 or 2) was 1.56 in the presence of the C allele.

Conclusion

We confirmed the protective effect of a rare genetic variant of HIF-1α gene against type 2 diabetes in a Caucasian sample. Moreover we demonstrated a genetic contribution of the same polymorphism in type 1 diabetes as well, supporting a possible overlap in pathomechanism for T2DM and a T1DM.

Association of the hypoxia inducible factor-1alpha gene polymorphisms with gastric cancer in Tibetans

To determine how single nucleotide polymorphisms (SNPs) in the hypoxia inducible factor-1alpha (HIF-1alpha) gene coding regions affect gastric cancer, the authors conducted an association study of the HIF-1alpha polymorphisms C1772T and G1790A for a Tibet population. DNA was extracted from peripheral blood of 87 gastric cancer patients and 106 controls and analyzed using the polymerase chain reaction/ligase detection reaction test for HIF-1alpha polymorphisms. There was a significant increase in the frequency of the GA 1790 genotype in patients with gastric cancer compared with healthy controls (OR 2.93; 95% CI 1.06-8.06). The genotype frequency of the HIF-1alpha G1790A allele A is higher in gastric cancer groups than in controls (OR 2.78; 95% CI 1.03-7.45). As for the C1772T polymorphism, no positive correlation was found between gastric cancer patients and controls (P = 0.06). Our results suggest that the HIF-1alpha G1790A polymorphism may be associated with gastric cancer in Tibetans.

Polymorphisms in the hypoxia inducible factor 1-alpha and the impact on the prognosis of early stages of oral cancer

BACKGROUND

Hypoxia-inducible factor-1 (HIF-1) is the key regulator of cellular responses to hypoxia and presumably plays a central role in the control of tumor growth. Polymorphisms or mutations increasing its activity and stability in vitro under normoxia have recently been identified. In this study, we aimed to investigate the effect of C1772T and G1790A single nucleotide polymorphisms (SNPs), located within the exon 12 of HIF-1alpha on the prognosis of early stages of oral squamous cell carcinoma (OSCC).

METHODS

The frequency of C1772T and G1790A polymorphisms was determined by PCR-RFLP in 139 DNA samples from healthy volunteers and 74 patients with surgically treated T1/2 N0 OSCC. The impact of HIF-1alpha SNPs on tumor size, invasive depth, pathological features, and histological grade was studied. Correlations between genotype and relapse and/or disease-specific survival were evaluated by Kaplan-Meier analysis and log-rank test.

RESULTS

Concerning G1790A SNP, the frequencies of GA heterozygous and AA variant homozygous genotypes were significantly higher in patients than in healthy volunteers (32.8% vs. 6.5% and 4.7% vs. none, respectively) (P < .0001). Also, the presence of the variant allele A was associated to disease-relapse (P = .02) and shorter disease-free survival (P = .04). The genotype distribution of C1772T did not diverge between patients and healthy subjects, and no differences were observed with respect to disease-free or overall survival.

CONCLUSIONS

Our results suggest that G1790A polymorphism in the HIF-1alpha gene might confer susceptibility to OSCC and could be a marker of disfavorable prognosis at early stages.

Genetic origins and clinical phenotype of familial and acquired erythrocytosis and thrombocytosis

Familial and acquired erythrocytosis and thrombocytosis are characterized by myeloid lineage hyperproliferation, which is either single or multi-lineage in origin. The single lineage disorders exhibit Mendelian inheritance with polyclonal hematopoiesis and often arise from a single genetic defect. In contrast, the multi-lineage disorders exhibit complex patterns of inheritance with multi-genetic origins and clonal hematopoiesis. They have the potential to acquire JAK2 somatic mutations, but this is not the primary event. Identification of the disease-causing genes will enable better classification of familial and acquired erythrocytosis and thrombocytosis. Furthermore, it will provide an insight into the mechanisms regulating myeloid cell proliferation.

Genetic causes of erythrocytosis and the oxygen-sensing pathway

Idiopathic erythrocytosis is an uncommon disease, and is defined by an increase in red blood cell mass. The differential diagnosis of erythrocytosis is extensive, and can be divided into primary and secondary forms. Primary erythrocytoses are due to intrinsic defects in erythroid precursor cells and are characterized by low erythropoietin levels. Secondary erythrocytoses are extrinsic to erythroid progenitors and are characterized by either high or inappropriately normal erythropoietin levels. A distinct subset of secondary erythrocytoses are due to genetic mutations in key proteins of the oxygen-sensing pathway. These proteins constitute the core molecular machinery of oxygen-sensing with respect to red blood cell control. Apart from assigning physiologic roles for these proteins, studies of these rare mutations have (i) revealed the exquisite sensitivity of this pathway to genetic perturbations, (ii) highlighted important functional regions of the proteins, and (iii) provided a basis for potentially targeting this pathway for therapeutic benefit.

Familial erythrocytosis arising from a gain-of-function mutation in the HIF2A gene of the oxygen sensing pathway

A mutation of HIF-2 alpha has been detected in three generations of a family with erythrocytosis and the mutation co-segregated with the erythrocytosis phenotype. Functional studies revealed that Gly537Trp mutation would significantly impair the function of HIF-2 alpha thus leading to increased synthesis of Epo. In addition to VHL and PHD2 a further member of the oxygen sensing pathway, namely HIF-2 alpha,can be a cause of erythrocytosis. Furthermore, HIF-2 alpha plays an important role in the regulation of Epo production. Continued study of idiopathic cases of erythrocytosis with raised serum Epo will reveal whether HIF-2 alpha will be a major cause of erythrocytosis on par with VHL.

Single nucleotide polymorphisms in the hypoxia-inducible factor-1alpha (HIF-1alpha) gene in human sporadic breast cancer

BACKGROUND

DNA sequence variations in hypoxia-inducible factor-1alpha (HIF-1alpha) gene, which have been demonstrated to be correlated with tumor angiogenesis, may yield changes both in the production outcomes and in the activities of the gene. In this study, we investigated the relationship between three single nucleotide polymorphisms (SNPs) [C1772T and G1790A in exon 12 and C111A in exon 2 of the HIF-1alpha gene] in the HIF-1alpha gene coding regions and development of sporadic breast cancer in the Turkish population. These three polymorphisms result in an amino acid change from proline 582 to serine, from alanine 588 to threonine and from serine 28 to tyrosine, respectively.

METHODS

Genomic DNA was isolated from 102 sporadic breast cancer patients and 102 healthy female controls. All three HIF-1alpha gene regions were amplified by PCR, and genotypes were determined by RFLP and DNA sequencing.

RESULTS

There were no significant differences between patients and controls in terms of the distribution of C1772T and G1790A polymorphisms of HIF-1 gene (p >0.05). As for HIF-1alpha C111A polymorphism, we did not find CA and AA variants of the gene in either controls or patients. Multivariable logistic regression analysis was performed between CC and CT + TT genotypes of C1772T polymorphism. No significant differences were found between these two genotypes in terms of clinicopathological characteristics of the patients including age at enrollment, age at menarche and first delivery, number of full-term pregnancies, body mass index, use of oral contraceptives and postmenopausal hormones, family history of breast and ovarian cancers, menopausal status, histopathological features, oophorectomy, smoking habits, and alcohol consumption (p >0.05).

CONCLUSIONS

Our results suggest that none of the polymorphisms studied in the HIF-1alpha gene influence susceptibility to sporadic breast cancer. The present study is the first case-control study that investigates the association of HIF-1alpha polymorphisms with sporadic breast cancer in the Turkish population.

Hypoxia-inducible factor-1alpha (HIF-1alpha) gene polymorphisms, circulating insulin-like growth factor binding protein (IGFBP)-3 levels and prostate cancer

BACKGROUND

The Hypoxia-inducible factor-1 (HIF-1) plays an important role in regulating angiogenesis in response to hypoxia. Two non-synonymous polymorphisms (P582S C-->T and A588T G-->A) in the coding region of the subunit 1alpha (HIF-1alpha) gene have been associated with enhanced stability of the protein and androgen-independent prostate cancer (CaP). Insulin-like growth factor binding protein (IGFBP)-3 mRNA is more abundantly expressed in hypoxia-related inflammatory angiogenesis and recent in vivo data suggest that IGFBP-3 has direct, IGF-independent inhibitory effects on angiogenesis.

METHODS

We examined the association of these polymorphisms with CaP among 1,072 incident cases and 1,271 controls, and further explored their joint associations with various prediagnostic plasma vascular endothelial growth factor (VEGF), IGF-I, and IGFBP-3 levels.

RESULTS

Neither the P582S nor the A588T polymorphism was associated with risk of overall or metastatic/fatal CaP. However, we found that, among men with the homozygous CC wild-type (but not CT/TT) of the HIF-1alpha P582S, higher IGFBP-3 levels (>/= vs. <median) were associated with a 28% (95% CI, 0.55-0.95; P(interaction) = 0.01) lower risk of overall CaP and a 53% (0.25-0.88; P(interaction) = 0.11) lower risk of metastatic and fatal CaP. The A588T polymorphism was too rare to assess interactions.

CONCLUSIONS

The two HIF-1alpha gene polymorphisms were not directly associated with CaP, but the interaction between the P582S polymorphism and IGFBP-3 merits further evaluation in mechanistic studies.

The homozygous P582S mutation in the oxygen-dependent degradation domain of HIF-1 alpha is associated with increased risk for prostate cancer

BACKGROUND

The heterodimeric transcription factor HIF-1 (hypoxia-inducible factor 1), consisting of a critically regulated HIF-1 alpha subunit and a constitutively expressed HIF-1 beta subunit, is a master regulator of genes involved in adaptation and survival under low-oxygen conditions. Increased levels of HIF-1 activity are associated with increased tumor aggressiveness, therapeutic resistance, and mortality.

METHODS

We studied 402 prostate cancer patients for the presence of the 1772C > T (P582S) and 1790G > A (A588T) mutations within the oxygen-dependent domain of HIF-1 alpha.

RESULTS

Homozygosity for the P582S mutation was fourfold greater among prostate cancer patients compared to controls (OR = 4.10 [C.I. 95% 1.11 < OR < 17.87], P = 0.018). The existence of this mutation in prostate cancer patients was not associated with any of the clinical or pathological characteristics of the disease. No significant differences were found between the frequencies of A588T mutation in prostate cancer patients and controls.

CONCLUSIONS

Our data suggest that homozygous HIF1A P582S mutation confers significant susceptibility to prostate cancer.

Radiation pneumonitis and fibrosis: Mechanisms underlying its pathogenesis and implications for future research

Radiation pneumonitis and subsequent radiation pulmonary fibrosis are the two main dose-limiting factors when irradiating the thorax that can have severe implications for patients' quality of life. In this article, the current concepts about the pathogenetic mechanisms underlying radiation pneumonitis and fibrosis are presented. The clinical course of fibrosis, a postulated acute inflammatory stage, and a late fibrotic and irreversible stage are discussed. The interplay of cells and the wide variety of molecules orchestrating the immunologic response to radiation, their interactions with specific receptors, and the cascade of events they trigger are elucidated. Finally, the implications of this knowledge with respect to the therapeutic interventions are critically presented.

Association between ulcerative growth and hypoxia inducible factor-1alpha polymorphisms in colorectal cancer patients

The hypoxia inducible factor-1alpha (HIF-1alpha) has been found to be involved in several different physiological mechanisms, such as blood-vessel formation, apoptosis, and erythropoiesis. HIF-1alpha is hydroxylated at normoxia and rapidly degraded via the von Hippel-Lindau (VHL)/ubiquitin-proteasome degradation system to prevent angiogenesis. In a previous study, the C1772T (P582S) and the G1790A (A588T) polymorphisms were identified in the human HIF-1alpha gene, which was shown to have a higher transactivating capability in vitro compared to the wild type allele. However, the role for these polymorphisms in vivo is still unclear. In the present investigation, we have therefore studied the role of the two polymorphic variants in the development of colorectal cancer (CRC) with PCR/RFLP (restriction fragment length polymorphism), single strand conformation analysis (SSCA), and immunohistochemistry (IHC). A significant higher-risk was identified between patients heterozygous for the C1772T polymorphism and the more severe ulcerative growth pattern compared to homozygous C1772C wild type tumors (RR = 5.2; 95% CI 1.26-21.6; P = 0.006). This was also verified on the allelic level (RR = 6.5; 95% CI 1.58-26.8; P = 0.001). In addition, patients carrying one or more polymorphic alleles in either the HIF-1alpha C1772T or the G1790A polymorphisms display significant higher risk for the development of ulcerative CRCs (RR = 4.17; 95% CI = 1.33-13.08; P = 0.004). These results suggest that the HIF-1alpha polymorpisms are an important factor for development of a subset of ulcerative intestinal tumors. Future screening of the polymorphic HIF-1alpha allele may therefore be of importance in the selection of treatment strategies of CRC.

C2028T polymorphism in exon 12 and dinucleotide repeat polymorphism in intron 13 of the HIF-1alpha gene define HIF-1alpha protein expression in non-small cell lung cancer

OBJECTIVES

In this study, we investigated whether polymorphisms of the HIF-1alpha gene may account for the patterns of HIF-1alpha protein expression in non-small cell lung carcinomas (NSCLC) and the expression of HIF-1alpha down-stream proteins.

METHODS

Specific HIF-1alpha polymorphisms were assessed in a series of patients with NSCLC: (a) the C to T transition at nucleotide 1744 (position 2028 according to sequence with accession number , which gives rise to Pro/Ser variation at codon 582), (b) the G to A nucleotide substitution at point 1790 (position 2046 according to sequence with accession number , which gives rise to Ala/Thr variation at codon 588), and (c) the dinucleotide GT repeat polymorphism in intron 13. Immunohistochemistry for HIF-1alpha and down-stream proteins (VEGF, LDH-5, GLUT-1) was also performed in tumor material.

RESULTS

A strong association of the P582S polymorphism and of GT repeat polymorphism higher than 14/14 with increased HIF-1alpha expression was noted. HIF-1alpha polymorphism did not relate to the expression of the HIF-1alpha downstream proteins analysed, but significant association of HIF-1alpha expression with LDH-5 was confirmed (p=0.008).

CONCLUSIONS

HIF-1alpha polymorphisms may have an important impact on HIF-protein stability and, eventually, function.

Endogenous markers of hypoxia/anaerobic metabolism and anemia in primary colorectal cancer

Anemia has been implicated in the decreased oxygen tension noted within the tumor environment. In a series of 79 colorectal adenocarcinomas we investigated the role of anemia in activating molecular pathways regulated by hypoxia. Preoperative Hb levels were correlated with the immunohistochemical expression of HIF1alpha and HIF2alpha, LDH5, GLUT1, VEGF, DEC1 and BNIP3, and with angiogenesis and the cancer cell proliferation index. Upregulation of HIF1alpha and HIF2alpha proteins, found in 43% and 44.3% of cases, respectively, was not related to anemia (Hb < 10 g%). This is in agreement with other studies suggesting that HIF activation occurs for various reasons, such as poor or irregular vascularity, or oncogene activation. Nevertheless, low Hb levels (<10 g%) were linked to activated anaerobic metabolism (LDH5 overexpression) in a subset of tumors not expressing HIF1alpha (P < 0.01). Overexpression of HIFs, whether linked to anemia or not, was associated with a number of factors related to tumor aggressiveness (assessed as local invasion and nodal metastasis), anaerobic metabolism and intratumoral acidosis (LDH5, GLUT1; increased glucose metabolism to lactate), activation of genes related to necrosis (BNIP3) and angiogenesis (VEGF). Expression of BNIP3 emerged as the strongest independent factor related to transmural invasion and metastasis to lymph nodes. Identification of specific patterns of the hypoxia molecular cascade activated in cancer cells might help in developing specific therapeutic policies.

Gene expression profiling reveals the profound upregulation of hypoxia-responsive genes in primary human astrocytes

Oxygen is vital for the development and survival of mammals. In response to hypoxia, the brain initiates numerous adaptive responses at the organ level as well as at the molecular and cellular levels, including the alteration of gene expression. Astrocytes play critical roles in the proper functioning of the brain; thus the manner in which astrocytes respond to hypoxia is likely important in determining the outcome of brain hypoxia. Here, we used microarray gene expression profiling and data-analysis algorithms to identify and analyze hypoxia-responsive genes in primary human astrocytes. We also compared gene expression patterns in astrocytes with those in human HeLa cells and pulmonary artery endothelial cells (ECs). Remarkably, in astrocytes, five times as many genes were induced as suppressed, whereas in HeLa and pulmonary ECs, as many as or more genes were suppressed than induced. More genes encoding hypoxia-inducible functions, such as glycolytic enzymes and angiogenic growth factors, were strongly induced in astrocytes compared with HeLa cells. Furthermore, gene ontology and computational algorithms revealed that many target genes of the EGF and insulin signaling pathways and the transcriptional regulators Myc, Jun, and p53 were selectively altered by hypoxia in astrocytes. Indeed, Western blot analysis confirmed that two major signal transducers mediating insulin and EGF action, Akt and MEK1/2, were activated by hypoxia in astrocytes. These results provide a global view of the signaling and regulatory network mediating oxygen regulation in human astrocytes.

Oxygen sensing: recent insights from idiopathic erythrocytosis

Idiopathic erythrocytosis (IE) is a rare condition in which there is an increase in red cell mass and hematocrit. As it is typically driven by elevated or inappropriately normal erythropoietin (Epo) levels, it has the potential to reveal the identities of proteins involved in the oxygen sensing pathway that regulates the transcription factor, Hypoxia Inducible Factor (HIF), and hence Epo production in humans. One example of this is provided by Chuvash polycythemia, a form of erythrocytosis due to a mutation in the von Hippel Lindau tumor suppressor protein (VHL), a component of an E3 ubiquitin ligase complex that targets hydroxylated HIF for degradation. A recent report of familial erythrocytosis now implicates a different protein, Prolyl Hydroxylase Domain protein 2 (PHD2), which is an enzyme that hydroxylates HIF.

Common single nucleotide polymorphism of hypoxia-inducible factor-1alpha and its impact on the clinicopathological features of esophageal squamous cell carcinoma

OBJECTIVE

Angiogenesis is one of the most important molecular events in solid tumor development and growth, in which hypoxia-inducible factor (HIF)-1alpha is a key regulator and plays an important role. Studies have shown that a single nucleotide polymorphism (C1772T) in the HIF-1alpha gene exerts a large effect on the phenotype of human head and neck squamous cell carcinoma and renal cell carcinoma. But the impact of the C1772T polymorphism on the clinicopathological features of human esophageal squamous cell carcinoma (ESCC) remains unknown, and thus it is the main focus of our study.

METHODS

The C1772T genotype of 95 ESCC patients and 104 healthy controls were studied by using the polymerase chain reaction and restriction fragment length polymorphism. Mutations were confirmed by direct DNA sequencing. The impact of C1772T on tumor size, invasive depth, lymph node metastasis, distant metastasis, histological grade and TNM stage was also studied.

RESULTS

The genotype frequency observed in the patients and controls was 11.58% versus 10.58%, respectively, for genotype C/T (P > 0.05). Genotype T/T was not found in our study. Larger tumors and a higher rate of lymph node metastasis was found for the C/T group.

CONCLUSIONS

Although there is no significant difference of genotype distribution between ESCC patients and healthy controls, genotype C/T is associated with larger tumor and higher rate of lymph node metastasis.

Mutation analysis of the HIF-1alpha oxygen-dependent degradation domain in invasive breast cancer

Hypoxia inducible factor-1 (HIF-1) is an important transcription factor that stimulates tumor growth and metastases via several pathways. Activation of HIF-1 depends on the presence of its alpha-subunit. Hypoxia increases HIF-1alpha levels by inhibiting prolyl-hydroxylase--mediated hydroxylation and thereby preventing proteosome degradation. Various other mechanisms might also contribute to HIF-1alpha expression, such as mutation of the oxygen dependent degradation domain (ODD), which prevents binding of prolyl-hydroxylases. Therefore, the presence of ODD mutations was evaluated as a possible explanation for diffuse HIF-1alpha protein expression often seen in invasive breast cancer. From a group of 200 primary breast cancers, 24 strong diffusely HIF-1alpha-positive tumor samples were identified with HIF-1alpha immunohistochemistry. DNA from these tumors was extracted from microdissected paraffin material and, after nested polymerase chain reaction, sequence analysis was performed to detect hif-1alpha ODD mutations. Additionally, five perinecrotically HIF-1alpha-positive breast cancers were analyzed as controls. All 24 diffuse and perinecrotic HIF-1alpha-positive breast cancers showed wild-type DNA sequences in the ODD domain. No mutations seem to occur in the ODD of hif-1alpha in HIF-1alpha overexpressing invasive breast cancer, which rules ODD mutations out as a possible explanation for the diffuse HIF-1alpha expression pattern often seen in this cancer.

Hypoxia-inducible factor-1alpha polymorphisms and TSC1/2 mutations are complementary in head and neck cancers

Background

Polymorphisms or mutations in hypoxia inducible factor-1 alpha (HIF-1alpha) that increases its activity and stability under normoxia have recently been identified. Likewise, disruption of the TSC1/TSC2 complex through loss of TSC1 or TSC2 has been shown to result in abnormal accumulation of HIF-1α. Here, we investigate the novel polymorphisms in exon 12, that approximate the oxygen-dependent degradation domain of HIF-1alpha in five cell lines and 28 patients with oral squamous carcinomas. Moreover, we assess for the presence of polymorphisms and mutations in TSC1 and TSC2, to ascertain if dysregulation of such might complement HIF-1alpha expression.

Results

Denaturing high pressure liquid chromatography (DHPLC) analysis on PCR fragments in exon 12 of HIF-1alpha from 28 patients with OSCC revealed that 6 of 28 patients had mismatched heteroduplex patterns. Genomic DNA was extracted from peripheral blood leukocytes and direct sequencing showed that in 5 of the six cases these changes represented polymorphisms while, one case was a somatic mutation. Analyses of TSC1 and TSC2 revealed heteroduplexes in exons: TSC1 exon 17; TSC2 exons 36,40, and 41. The relative levels of HIF-1alpha were significantly greater for tumors possessing a HIF-1alpha polymorphism or mutation within exon 12, whereas tumors possessing a deletion or polymorphism in TSC1/TSC2 displayed a trend for higher levels of HIF-1alpha. Western blot analyses for HIF-1alpha, TSC1 and TSC2 in five SCC cell lines revealed high levels of HIF-1alpha in SCC cells possessing TSC1 and/or TSC2 mutations. Wild-type TSC2 cells targeted with siRNA to TSC2 exhibited increased levels of HIF-1alpha. Transfection of a HIF-1alpha mutant produced higher levels of HIF-1alpha in TSC1/TSC2 mutant cell lines than in wild type cells. TSC1/TSC2 mutant cell lines administered Rapamycin blocked S6 phorphorylation and diminished the levels of HIF-1alpha to those observed in cell lines with wild type TSC1/TSC2.

Conclusion

Dysregulation of the TSC1/TSC2 complex by mutation compliments HIF-1α polymorphisms in the expression of HIF-1alpha in SCC of the head and neck, and may provide biomarkers to predict responses to specific therapies and overall disease prognosis.

A family with erythrocytosis establishes a role for prolyl hydroxylase domain protein 2 in oxygen homeostasis

The number of red blood cells is normally tightly regulated by a classic homeostatic mechanism based on oxygen sensing in the kidney. Decreased oxygen delivery resulting from anemia induces the production of erythropoietin, which increases red cell production and hence oxygen delivery. Investigations of erythropoietin regulation identified the transcription factor hypoxia-inducible factor (HIF). HIF is now recognized as being a key regulator of genes that function in a comprehensive range of processes besides erythropoiesis, including energy metabolism and angiogenesis. HIF itself is regulated through the alpha-subunit, which is hydroxylated in the presence of oxygen by a family of three prolyl hydroxylase domain proteins (PHDs)/HIF prolyl hydroxylases/egg-laying-defective nine enzymes. Hydroxylation allows capture by the von Hippel-Lindau tumor suppressor gene product, ubiquitination, and destruction by the proteasome. Here we describe an inherited mutation in a mammalian PHD enzyme. We show that this mutation in PHD2 results in a marked decrease in enzyme activity and is associated with familial erythrocytosis, identifying a previously unrecognized cause of this condition. Our findings indicate that PHD2 is critical for normal regulation of HIF in humans.

Identification of hypoxia-inducible factor-1alpha (HIF-1alpha) polymorphism as a mutation in prostate cancer that prevents normoxia-induced degradation

BACKGROUND

Hypoxia-inducible factor-1alpha (HIF-1alpha) regulates cellular responses to hypoxia and is rapidly degraded under normoxia through von Hippel-Lindau (VHL) mediated ubiquitination. Although HIF-1alpha stabilization appears to be the molecular basis for VHL-associated cancers, stabilizing mutations in HIF-1alpha have not been reported.

METHODS

A series of 15 metastatic androgen independent prostate cancers were examined for mutations in the oxygen-dependent domain (ODD) of HIF-1alpha by PCR amplification and DNA sequencing.

RESULTS

A somatic proline to serine mutation in codon 582 (P582S) was identified in one sample. Transfection studies with a HIF-1alpha regulated reporter gene showed increased transcriptional activity that correlated with higher mutant HIF-1alpha protein expression. Increased expression of the P582S mutant induced by iron chelation, which blocks proline hydroxylation of wild-type HIF-1alpha, was markedly attenuated. The mutant also showed increased stability under normoxic versus hypoxic conditions.

CONCLUSION

The P582S HIF-1alpha is a stable variant and HIF-1alpha mutation is a mechanism for enhancing HIF-1alpha activity in human cancer. The recent identification of the identical P582S HIF-1alpha as a polymorphism suggests that this variant may increase tumor susceptibility or cause more aggressive biological behavior.