Cytoplasmic location of factor-inhibiting hypoxia-inducible factor is associated with an enhanced hypoxic response and a shorter survival in invasive breast cancer

Recent Advances and Therapeutic Implications of 2-Oxoglutarate-Dependent Dioxygenases in Ischemic Stroke

Ischemic stroke is a common disease with a high disability rate and mortality, which brings heavy pressure on families and medical insurance. Nowadays, the golden treatments for ischemic stroke in the acute phase mainly include endovascular therapy and intravenous thrombolysis. Some drugs are used to alleviate brain injury in patients with ischemic stroke, such as edaravone and 3-n-butylphthalide. However, no effective neuroprotective drug for ischemic stroke has been acknowledged. 2-Oxoglutarate-dependent dioxygenases (2OGDDs) are conserved and common dioxygenases whose activities depend on O2, Fe2+, and 2OG. Most 2OGDDs are expressed in the brain and are essential for the development and functions of the brain. Therefore, 2OGDDs likely play essential roles in ischemic brain injury. In this review, we briefly elucidate the functions of most 2OGDDs, particularly the effects of regulations of 2OGDDs on various cells in different phases after ischemic stroke. It would also provide promising potential therapeutic targets and directions of drug development for protecting the brain against ischemic injury and improving outcomes of ischemic stroke.

The Asparagine Hydroxylase FIH: A Unique Oxygen Sensor

Significance: Limited oxygen availability (hypoxia) commonly occurs in a range of physiological and pathophysiological conditions, including embryonic development, physical exercise, inflammation, and ischemia. It is thus vital for cells and tissues to monitor their local oxygen availability to be able to adjust in case the oxygen supply is decreased. The cellular oxygen sensor factor inhibiting hypoxia-inducible factor (FIH) is the only known asparagine hydroxylase with hypoxia sensitivity. FIH uniquely combines oxygen and peroxide sensitivity, serving as an oxygen and oxidant sensor. Recent Advances: FIH was first discovered in the hypoxia-inducible factor (HIF) pathway as a modulator of HIF transactivation activity. Several other FIH substrates have now been identified outside the HIF pathway. Moreover, FIH enzymatic activity is highly promiscuous and not limited to asparagine hydroxylation. This includes the FIH-mediated catalysis of an oxygen-dependent stable (likely covalent) bond formation between FIH and selected substrate proteins (called oxomers [oxygen-dependent stable protein oligomers]). Critical Issues: The (patho-)physiological function of FIH is only beginning to be understood and appears to be complex. Selective pharmacologic inhibition of FIH over other oxygen sensors is possible, opening new avenues for therapeutic targeting of hypoxia-associated diseases, increasing the interest in its (patho-)physiological relevance. Future Directions: The contribution of FIH enzymatic activity to disease development and progression should be analyzed in more detail, including the assessment of underlying molecular mechanisms and relevant FIH substrate proteins. Also, the molecular mechanism(s) involved in the physiological functions of FIH remain(s) to be determined. Furthermore, the therapeutic potential of recently developed FIH-selective pharmacologic inhibitors will need detailed assessment. Antioxid. Redox Signal. 37, 913-935.

Pseudohypoxic HIF pathway activation dysregulates collagen structure-function in human lung fibrosis

Extracellular matrix (ECM) stiffening with downstream activation of mechanosensitive pathways is strongly implicated in fibrosis. We previously reported that altered collagen nanoarchitecture is a key determinant of pathogenetic ECM structure-function in human fibrosis (Jones et al., 2018). Here, through human tissue, bioinformatic and ex vivo studies we provide evidence that hypoxia-inducible factor (HIF) pathway activation is a critical pathway for this process regardless of the oxygen status (pseudohypoxia). Whilst TGFβ increased the rate of fibrillar collagen synthesis, HIF pathway activation was required to dysregulate post-translational modification of fibrillar collagen, promoting pyridinoline cross-linking, altering collagen nanostructure, and increasing tissue stiffness. In vitro, knockdown of Factor Inhibiting HIF (FIH), which modulates HIF activity, or oxidative stress caused pseudohypoxic HIF activation in the normal fibroblasts. By contrast, endogenous FIH activity was reduced in fibroblasts from patients with lung fibrosis in association with significantly increased normoxic HIF pathway activation. In human lung fibrosis tissue, HIF-mediated signalling was increased at sites of active fibrogenesis whilst subpopulations of human lung fibrosis mesenchymal cells had increases in both HIF and oxidative stress scores. Our data demonstrate that oxidative stress can drive pseudohypoxic HIF pathway activation which is a critical regulator of pathogenetic collagen structure-function in fibrosis.

Hypoxia-mediated drug resistance in breast cancers

Tissue hypoxia in solid tumors is caused by several pathological changes associated with tumor growth, including altered microvasculature structure, increased diffusional distances, and tumor-associated anemia. As the oxygen tension decreases, tumor cells adapt to the limited oxygen supply. Previous studies have shown that such adaptation leads to an aggressive phenotype that is resistant to many anti-cancer therapies. Induction of hypoxia inducible factors (HIFs) mediates many proteomic and genomic changes associated with tumor hypoxia. In breast cancers, HIFs not only predict poor prognosis, but also promote metastasis and drug resistance. Several studies have proposed HIF-1α as a druggable target in drug-resistant breast cancers, leading to the synthesis and development of small molecule inhibitors. Disappointingly, however, none of these small molecule inhibitors have progressed to clinical use. In this review, we briefly discuss the role of HIF-1α in breast cancer drug resistance and summarize the current and future approaches to targeting this transcription factor in breast cancer treatment.

Polymorphisms in microRNA let-7 binding sites of the HIF1AN and CLDN12 genes can predict pathologic complete response to taxane- and platinum-based neoadjuvant chemotherapy in breast cancer

Background

Germline genetic polymorphisms in certain genes are associated with response to anthracycline- and taxane-based neoadjuvant chemotherapy in breast cancer (BC). Recent evidence has indicated that microRNA (miRNA) let-7 expression is associated with response to chemotherapeutics. This study aims to evaluate the potential role of let-7 miRNA-related single nucleotide polymorphisms (mirSNPs) in the prediction of pathologic complete response to taxane- and platinum-based neoadjuvant chemotherapy in locally advanced breast cancer (LABC).

Methods

We genotyped the SNPs that reside in and around miRNA let-7 binding sites of two target genes: hypoxia-inducible factor 1 subunit alpha inhibitor (HIF1AN) and claudin 12 (CLDN12). The distribution frequencies of the SNPs were genotyped in LABC patients who received taxane- and platinum-based neoadjuvant chemotherapy. Associations among tumour-relevant biomarkers, genotype and pathological complete response (pCR) were evaluated using Student's t-test for continuous variables and the chi-square or Fisher's exact tests for non-categorical variables. The modified odds ratios (ORs) with their 95% confidence intervals (CIs) were calculated by a multivariate logistic regression analysis to explore the association of genotype with pCR.

Results

For rs11292, which is located in the 3'-untranslated region (UTR) of HIF1AN, significant differences were detected in codominant, dominant and overdominant models between the patients who achieved pCR and those who did not (non-pCR) (P<0.05) in a multivariate analysis. For rs1017105, which is located in the 3'-UTR of CLDN12, significant differences were observed in the recessive model between the pCR and non-pCR patients with luminal-type BC.

Conclusions

Let-7-related mirSNPs could predict pathologic complete response to taxane- and platinum-based neoadjuvant chemotherapy in LABC, which suggests the potential role of variants of miRNA let-7-related gene networks as predictive markers in a clinical setting.

Single nucleotide polymorphisms of let-7-related genes increase susceptibility to breast cancer

BACKGROUND

Let-7 is a microRNA (miRNA) that targets the β2 adrenergic receptor (ADRB2), hypoxia inducible factor 1 subunit alpha inhibitor (HIF1AN), and claudin 12 (CLDN12) genes. Single nucleotide polymorphisms (SNPs) in the structural or regulatory regions of these miRNA let-7-related genes may be associated with breast cancer carcinogenesis and prognosis. Low let-7 expression may increase breast cancer risk. We investigated the effects of let-7-related gene SNP (mirSNPs) on breast cancer risk and clinical outcomes.

METHODS

The distribution frequencies of the three SNPs were genotyped in patients with breast cancer and controls. Multivariate logistic regression analysis was used to evaluate the association between the SNPs and susceptibility to breast cancer. We investigated the effects of these mirSNPs prospectively on disease-free survival (DFS) using the Kaplan-Meier method and the extended multivariate Cox model.

RESULTS

We found that rs1042713 in the ADRB2 gene and rs11292 in the 3'-UTR of the HIF1AN gene were associated with breast cancer susceptibility (P<0.05). The CLDN12 rs1017105 genotype was associated with estrogen receptor (P=0.031) and progesterone receptor status (P=0.007). The number of risk alleles was associated with estrogen receptor (P=0.034) status in breast cancer patients. In the survival analysis, the extended Cox model demonstrated that rs1042713 (P=0.000) and rs1017105 (P=0.004) were independent predictors of DFS. The number of risk alleles of the ADRB2, HIF1AN, and CLDN12 genes was an independent predictor of DFS (P<0.001).

CONCLUSION

Let-7-related mirSNPs might be associated with carcinogenesis and clinical outcome in breast cancer, suggesting that variants of miRNA let-7-related gene networks coregulate breast cancer characteristics.

Oxygen sensor FIH inhibits HACE1-dependent ubiquitination of Rac1 to enhance metastatic potential in breast cancer cells

Oxygen is an indispensable element for cell survival and maintenance. Eukaryotic cells are equipped with a series of signaling pathways that cope with hypoxia. The dioxygenase factor inhibiting HIF (FIH) is an oxygen sensor that regulates the transcriptional activity of hypoxia-inducible factor (HIF) through asparaginyl hydroxylation. Given that HACE1 was detected as an FIH-interacting protein in a previous proteomics study, we tested whether the E3 ubiquitin ligase HACE1 is a substrate for FIH. FIH interacted with HACE1, in cells and in vitro, and was determined to hydroxylate HACE1 at the N191 residue within the ankyrin repeat domain. Hydroxylation disrupted the physical association between HACE1 and its representative target, Rac1. Under hypoxic conditions, HACE1 is less hydroxylated due to the inactivation of FIH, and subsequently functions to ubiquitinate the active form of Rac1, leading to the proteasomal degradation of Rac1. Since Rac1 stimulates cell movement, HACE1 inhibits cell migration and invasion in breast cancer by removing active Rac1. Such an effect of HACE1 is reinforced under hypoxia because HACE1 escapes from FIH-mediated hydroxylation. In clinical datasets, HACE1 downregulation is associated with poor outcomes in patients with breast cancer. Taken together, FIH is likely to act as an oxygen sensor that determines oxygen-dependent cancer progression.

Nuclear entry and export of FIH are mediated by HIF1α and exportin1, respectively

Hypoxia plays a crucial role at cellular and physiological levels in all animals. The responses to chronic hypoxia are, at least substantially, orchestrated by activation of the hypoxia inducible transcription factors (HIFs), whose stability and subsequent transcriptional activation are regulated by HIF hydroxylases. Factor inhibiting HIF (FIH), initially isolated as a HIFα interacting protein following a yeast two-hybrid screen, is an asparaginyl hydroxylase that negatively regulates transcriptional activation by HIF. This study aimed to define the mechanisms that govern transitions of FIH between the nucleus and cytoplasm. We report that FIH accumulates in the nucleus within a short time window during hypoxia treatment. We provide evidence, based on the application of genetic interventions and small molecule inhibition of the HIF hydroxylases, that the nuclear localization of FIH is governed by two opposing processes: nuclear entry by 'coupling' with HIF1α for importin β1-mediated nuclear import and active export via a Leptomycin B-sensitive exportin1-dependent pathway.This article has an associated First Person interview with the first author of the paper.

Prolyl hydroxylase domain protein 3 and asparaginyl hydroxylase factor inhibiting HIF-1 levels are predictive of tumoral behavior and prognosis in hepatocellular carcinoma

Hypoxia-inducible factors (HIFs) are key regulators in oxygen homeostasis. Their stabilization and activity are regulated by prolyl hydroxylase domain (PHD)-1, -2, -3 and factor inhibiting HIF (FIH). This study investigated the relation between these oxygen sensors and the clinical behaviors and prognosis of hepatocellular carcinoma (HCC). Tissue microarray and RT-PCR analysis of tumor tissues and adjacent non-tumor liver tissues revealed that mRNA and protein levels of both PHD3 and FIH were lower within tumors. The lower expression of PHD3 in tumor was associated with larger tumor size, incomplete tumor encapsulation, vascular invasion and higher Ki-67 LI (p < 0.05). The lower expression of FIH in tumor was associated with incomplete tumor encapsulation, vascular invasion, as well as higher TNM stage, BCLC stage, microvascular density and Ki-67 LI (p < 0.05). Patients with reduced expression of PHD3 or FIH had markedly shorter disease-free survival (DFS), lower overall survival (OS), or higher recurrence (p < 0.05), especially early recurrence. Patients with simultaneously reduced expression of PHD3 and FIH exhibited the least chance of forming tumor encapsulation, highest TNM stage (p < 0.0083), lowest OS and highest recurrence rate (p < 0.05). Multivariate analysis indicated that a lower expression of FIH independently predicted a poor prognosis in HCC. These findings indicate that downregulation of PHD3 and FIH in HCC is associated with more aggressive tumor behavior and a poor prognosis. PHD3 and FIH may be potential therapeutic targets for HCC treatment.

HIF1/2α mediates hypoxia-induced LDHA expression in human pancreatic cancer cells

Glycolysis is a typical conduit for energy metabolism in pancreatic cancer (PC) due to the hypoxic microenviroment. Lactate dehydrogenase A (LDHA) catalyzes the conversion of pyruvate to lactate and is considered to be a key checkpoint of anaerobic glycolysis. The aim of the present study was to explore the mechanism of interactions between hypoxia, HIF-1/2α and LDHA, and the function of LDHA on PC cells by analyzing 244 PC and paratumor specimens. It was found that LDHA was over-expressed and related to tumor stages. The result of in vitro study demonstrated that hypoxia induced LDHA expression. To explore the relationship between HIF and LDHA, chromatin immunoprecipitation assay and luciferase assay were performed. The result showed that HIF-1/2α bound to LDHA at 89bp under the hypoxic condition. Furthermore, knockdown of endogenous HIF-1α and HIF-2α decreased the LDHA expression even in the hypoxic condition, which was accompanied with a significant decrease in lactate production and glucose utilization (p < 0.01). Immunofluorescence in the 244 specimens showed that HIF-1/2α was over-expressed and associated with LDHA over-expression (p < 0.0001). Forced expression of LDHA promoted the growth and migration of PC cells, while knocking down the expression of LDHA inhibited the cell growth and migration markedly. In summary, the present study proved that HIF1/2α could activate LDHA expression in human PC cells, and high expression of LDHA promoted the growth and migration of PC cells.

Ankyrin Repeat Proteins of Orf Virus Influence the Cellular Hypoxia Response Pathway

Hypoxia-inducible factor (HIF) is a transcriptional activator with a central role in regulating cellular responses to hypoxia. It is also emerging as a major target for viral manipulation of the cellular environment. Under normoxic conditions, HIF is tightly suppressed by the activity of oxygen-dependent prolyl and asparaginyl hydroxylases. The asparaginyl hydroxylase active against HIF, factor inhibiting HIF (FIH), has also been shown to hydroxylate some ankyrin repeat (ANK) proteins. Using bioinformatic analysis, we identified the five ANK proteins of the parapoxvirus orf virus (ORFV) as potential substrates of FIH. Consistent with this prediction, coimmunoprecipitation of FIH was detected with each of the ORFV ANK proteins, and for one representative ORFV ANK protein, the interaction was shown to be dependent on the ANK domain. Immunofluorescence studies revealed colocalization of FIH and the viral ANK proteins. In addition, mass spectrometry confirmed that three of the five ORFV ANK proteins are efficiently hydroxylated by FIH in vitro While FIH levels were unaffected by ORFV infection, transient expression of each of the ORFV ANK proteins resulted in derepression of HIF-1α activity in reporter gene assays. Furthermore, ORFV-infected cells showed upregulated HIF target gene expression. Our data suggest that sequestration of FIH by ORFV ANK proteins leads to derepression of HIF activity. These findings reveal a previously unknown mechanism of viral activation of HIF that may extend to other members of the poxvirus family.

IMPORTANCE

The protein-protein binding motif formed from multiple repeats of the ankyrin motif is common among chordopoxviruses. However, information on the roles of these poxviral ankyrin repeat (ANK) proteins remains limited. Our data indicate that the parapoxvirus orf virus (ORFV) is able to upregulate hypoxia-inducible factor (HIF) target gene expression. This response is mediated by the viral ANK proteins, which sequester the HIF regulator FIH (factor inhibiting HIF). This is the first demonstration of any viral protein interacting directly with FIH. Our data reveal a new mechanism by which viruses reprogram HIF, a master regulator of cellular metabolism, and also show a new role for the ANK family of poxvirus proteins.

CA IX is upregulated in CoCl2-induced hypoxia and associated with cell invasive potential and a poor prognosis of breast cancer

Hypoxia, a common phenomenon during the development of malignant solid tumors including breast cancer, serves to propagate a cascade of molecular pathways triggered by hypoxia-inducible factor-1α (HIF-1α). Carbonic anhydrase IX (CA IX), one of the target genes of HIF-1α, has been reported to be involved in progression of malignant tumors. The objective of this study was to investigate the expression of HIF-1α and CA IX in hypoxia, involvement of CA IX in the regulation of migration and invasion/metastasis and its prognostic significance in breast cancer. We used cobalt chloride (CoCl2) as a hypoxia-mimetic agent and found that the expression of HIF-1α protein, CA IX mRNA and protein, is effectively upregulated, except for HIF-1α mRNA. Data showed that the elevated CA IX expression is closely related to in vitro cell migration and invasion, and the underlying mechanism of this process may be associated with epithelial-mesenchymal transition (EMT). The study of clinical tissue samples also demonstrated that CA IX is an independent prognostic marker that may serve as a useful clinical biomarker for predicting tumor progression and the invasion/metastasis of breast cancer. These results provide further insight into the role of CA IX in tumor progression and put forward further strong evidence as well as new consideration for CA IX target therapy.

MicroRNA-135b regulates ERα, AR and HIF1AN and affects breast and prostate cancer cell growth

MicroRNAs (miRNAs) regulate a wide range of cellular signaling pathways and biological processes in both physiological and pathological states such as cancer. We have previously identified miR-135b as a direct regulator of androgen receptor (AR) protein level in prostate cancer (PCa). We wanted to further explore the relationship of miR-135b to hormonal receptors, particularly estrogen receptor α (ERα). Here we show that miR-135b expression is lower in ERα-positive breast tumors as compared to ERα-negative samples in two independent breast cancer (BCa) patient cohorts (101 and 1302 samples). Additionally, the miR-135b expression is higher in AR-low PCa patient samples (47 samples). We identify ERα as a novel miR-135b target by demonstrating miR-135b binding to the 3'UTR of the ERα and decreased ERα protein and mRNA level upon miR-135b overexpression in BCa cells. MiR-135b reduces proliferation of ERα-positive BCa cells MCF-7 and BT-474 as well as AR-positive PCa cells LNCaP and 22Rv1 when grown in 2D. To identify other genes regulated by miR-135b we performed gene expression studies and found a link to the hypoxia inducible factor 1α (HIF1α) pathway. We show that miR-135b influences the protein level of the inhibitor for hypoxia inducible factor 1α (HIF1AN) and is able to bind to HIF1AN 3'UTR. Our study demonstrates that miR-135b regulates ERα, AR and HIF1AN protein levels through interaction with their 3'UTR regions, and proliferation in ERα-positive BCa and AR-positive PCa cells.

Value of dopachrome tautomerase detection in the assessment of melanocytic tumors

Dopachrome tautomerase (DCT) and tyrosinase (Tyr) are melanogenic enzymes and structurally related melanosomal proteins. The present study investigates DCT expression comparatively with Tyr, the most tested melanoma biomarker, aiming to evaluate DCT potential in the assessment of melanocytic tumors and gain insights into the molecular and pathological characterization of DCT-phenotype in tumor progression. DCT and Tyr are simultaneously analyzed in melanoma cell lines by semiquantitative RT-PCR, western blot, and N-glycan analysis, and in cell populations of melanocytic tumors by immunohistofluorescence using a novel anti-hDCT antibody against an extended sequence within DCT luminal domain. DCT, unlike Tyr, is fully processed along the secretory pathway in both pigmented and amelanotic melanoma cells. In 53 nevi and 116 primary malignant melanomas, 81% and 52%, respectively, are DCT+/Tyr+, showing that DCT is a stable antigen, retained by most tumors and partially expressed in Tyr-negative cell populations. The DCT/Tyr disjunction is a process correlated with melanocyte neoplastic transformation and malignant progression. A tumor architecture--DCT-phenotype-containing DCT+/Tyr- cell populations selected into the innermost dermis from double-positive cells is detected in 35% of DCT+/Tyr+ specimens. The DCT-phenotype is associated with enhanced neurotization in benign nevi and with ulceration in thin malignant melanomas. The intradermal DCT+/Tyr- clones in superficial melanomas acquire the expression and specific subcellular distribution of unfavorable prognostic markers. DCT assessment shows specific antigen patterns with potential significance in the outcome of melanocytic lesions, connecting DCT, a mediator of a melanoma stress-resistant pathway, and an antiapoptotic molecule to DCT- phenotypes that are possibly more stable and stress resistant.

Role of compartmentalization on HiF-1α degradation dynamics during changing oxygen conditions: a computational approach

HiF-1α is the central protein driving the cellular response to hypoxia. Its accumulation in cancer cells is linked to the appearance of chemoresistant and aggressive tumor phenotypes. As a consequence, understanding the regulation of HiF-1α dynamics is a major issue to design new anti-cancer therapies. In this paper, we propose a model of the hypoxia pathway, involving HiF-1α and its inhibitor pVHL. Based on data from the literature, we made the hypothesis that the regulation of HiF-1α involves two compartments (nucleus and cytoplasm) and a constitutive shuttle of the pVHL protein between them. We first show that this model captures correctly the main features of HiF-1α dynamics, including the bi-exponential degradation profile in normoxia, the kinetics of induction in hypoxia, and the switch-like accumulation. Second, we simulated the effects of a hypoxia/reoxygenation event, and show that it generates a strong instability of HiF-1α. The protein concentration rapidly increases 3 hours after the reoxygenation, and exhibits an oscillating pattern. This effect vanishes if we do not consider compartmentalization of HiF-1α. This result can explain various counter-intuitive observations about the specific molecular and cellular response to the reoxygenation process. Third, we simulated the HiF-1α dynamics in the tumor case. We considered different types of mutations associated with tumorigenesis, and we compared their consequences on HiF-1α dynamics. Then, we tested different therapeutics strategies. We show that a therapeutic decrease of HiF-1α nuclear level is not always correlated with an attenuation of reoxygenation-induced instabilities. Thus, it appears that the design of anti-HiF-1α therapies have to take into account these two aspects to maximize their efficiency.

Factor-inhibiting hypoxia-inducible factor expression in patients with high-risk locally advanced renal cell carcinoma and its relationship with tumor progression

Hypoxia-inducible factor (HIF) plays an important role in renal cell carcinoma (RCC) associated with angiogenesis. Factor-inhibiting HIF (FIH), which is the upstream mediator protein of HIF, is receiving more attention today. In the present study, the role of FIH expression in high-risk locally advanced renal cell carcinoma (LARCC) was explored. Eighty-eight high-risk LARCC cases were divided into two groups based on their prognosis. Using immunohistochemical staining, the correlations of FIH expression along with clinicopathological factors, progression-free survival (PFS), and overall survival (OS) were analyzed. FIH was mainly located in the cytoplasm (34/88) and nucleus (31/88) of the renal tumor cell. Nuclear negative expression or cytoplasmic positive expression of FIH were associated with an increased risk of disease progression (p = 0.007 and p < 0.001, respectively) and worse OS (p = 0.020 and p = 0.008, respectively). Using the group with nuclear and cytoplasmic FIH negative expression as reference, further stratified analysis found that the exclusive nuclear FIH expression group had a better PFS and OS [hazard ratio (HR) = 0.153, p = 0.07 and HR = 0, p = 0.961, respectively], and the exclusive cytoplasmic FIH positive group experienced the worst PFS and OS (HR = 2.876, p = 0.005 and HR = 2.799, p = 0.034, respectively). In addition, nuclear negative expression of FIH was associated with a significant negative predictive value for the effect of interferon-alpha (IFN-α) on PFS (p = 0.045). The nuclear negative and cytoplasmic positive expressions of FIH were identified not only as risk factors for disease progression in high-risk LARCC postoperative patients, but also to be associated with poor OS. Furthermore, the nuclear negative expression of FIH may be a promising biomarker for postoperative adjuvant therapy.

The potential of hypoxia markers as target for breast molecular imaging--a systematic review and meta-analysis of human marker expression

Background

Molecular imaging of breast cancer is a promising emerging technology, potentially able to improve clinical care. Valid imaging targets for molecular imaging tracer development are membrane-bound hypoxia-related proteins, expressed when tumor growth outpaces neo-angiogenesis. We performed a systematic literature review and meta-analysis of such hypoxia marker expression rates in human breast cancer to evaluate their potential as clinically relevant molecular imaging targets.

Methods

We searched MEDLINE and EMBASE for articles describing membrane-bound proteins that are related to hypoxia inducible factor 1α (HIF-1α), the key regulator of the hypoxia response. We extracted expression rates of carbonic anhydrase-IX (CAIX), glucose transporter-1 (GLUT1), C-X-C chemokine receptor type-4 (CXCR4), or insulin-like growth factor-1 receptor (IGF1R) in human breast disease, evaluated by immunohistochemistry. We pooled study results using random-effects models and applied meta-regression to identify associations with clinicopathological variables.

Results

Of 1,705 identified articles, 117 matched our selection criteria, totaling 30,216 immunohistochemistry results. We found substantial between-study variability in expression rates. Invasive cancer showed pooled expression rates of 35% for CAIX (95% confidence interval (CI): 26-46%), 51% for GLUT1 (CI: 40-61%), 46% for CXCR4 (CI: 33-59%), and 46% for IGF1R (CI: 35-70%). Expression rates increased with tumor grade for GLUT1, CAIX, and CXCR4 (all p < 0.001), but decreased for IGF1R (p < 0.001). GLUT1 showed the highest expression rate in grade III cancers with 58% (45-69%). CXCR4 showed the highest expression rate in small T1 tumors with 48% (CI: 28-69%), but associations with size were only significant for CAIX (p < 0.001; positive association) and IGF1R (p = 0.047; negative association). Although based on few studies, CAIX, GLUT1, and CXCR4 showed profound lower expression rates in normal breast tissue and benign breast disease (p < 0.001), and high rates in carcinoma in situ. Invasive lobular carcinoma consistently showed lower expression rates (p < 0.001).

Conclusions

Our results support the potential of hypoxia-related markers as breast cancer molecular imaging targets. Although specificity is promising, combining targets would be necessary for optimal sensitivity. These data could help guide the choice of imaging targets for tracer development depending on the envisioned clinical application.

HIF expression and the role of hypoxic microenvironments within primary tumours as protective sites driving cancer stem cell renewal and metastatic progression

Hypoxic microenvironments frequently exist in many solid tumours with oxygen levels fluctuating temporally and spatially from normoxia to hypoxia. The response to hypoxia in human cells is mainly regulated by hypoxia-inducible factors (HIFs), a family of transcription factors which orchestrate signalling events leading to angiogenesis and tumorigenesis. Several events conspire together to lead to the stabilization of HIF-α, commonly expressed in many cancer cell types. These events can result from low oxygen tensions occurring within the expanding tumour mass to produce hypoxic microenvironments or from mutations whereby the HIFs cause changes in expression of genes involved in several cellular functions. Hypoxia-mediated HIF-α regulation has gained significant prominence in tumour biology over recent years, and the hypoxic microenvironments have been shown to facilitate and trigger major molecular and immunological processes necessary to drive the progression of tumours to malignancy. More recently, it has been realized that the hypoxic microenvironments also play significant roles in shielding tumour cells from immune attack by promoting immune suppression. In addition, the hypoxic microenvironment promotes many other oncogenic events, such as the metabolic reconfiguration of tumour cells, neovascularization, epithelial to mesenchymal transition (EMT), and cancer stem cell renewal and accumulation. This article reviews the molecular mechanisms underlying tumour hypoxia and their pro-tumour contributions, such as immune suppression, development of nascent and more permeable tumour vasculature, selective cancer stem cell renewal, accumulation, mobilization and promotion of EMT leading to tumour cell metastasis.

Hypoxia inducible factor-1α is necessary for invasive phenotype in Vegf-deleted islet cell tumors

In the mouse model of pancreas endocrine tumor, loss of Vegf (VKO) results in dramatically decreased tumor progression; however, the residual microscopic lesions show increased invasion into surrounding exocrine tissue. Double KO mice of Vegf and hypoxia inducible factor-1α (Hif-1α) showed increased life span and suppressed tumor growth due to increased apoptosis. The increased invasiveness of tumors in VKO mice was diminished in DKO mice to the levels of wild-type mice. Compared to VKO mice, DKO mice also exhibited smaller changes in the expression levels of adhesion molecules, including E-cadherin, N-cadherin, and NCAM. These changes of adhesion molecules were not observed in the primary culture of the tumor cells under hypoxic conditions. Thus, the invasive phenotype observed under angiogenesis inhibition requires Hif-1α, but is not directly caused by acute hypoxia.

Subcellular FIH-1 expression patterns in invasive breast cancer in relation to HIF-1α expression

Background

Hypoxia Inducible Factor-1α (HIF-1α) expression in breast cancer is associated with a poor clinical outcome. HIF-1α shows two expression patterns: the canonical poor prognosis hypoxia-related perinecrotic pattern and a diffuse expression pattern that seems to have less downstream effects and is clearly associated with poor survival. Factor-inhibiting hypoxia-inducible factor 1 (FIH-1) inhibits HIF-1 activity by hydroxylating the C-terminal trans-activation domain of the HIF-1α subunit, thus preventing HIF-1 from recruiting co-activators CPB/p300, which are important for inducing the transcription of target genes. The aim of this study was to investigate the expression patterns of FIH-1 in breast cancer and evaluate the relationship between FIH-1 and HIF-1α expression in breast cancer as a possible explanation for apparently less downstream effects of diffuse HIF-1α expression.

Methods

Tissue sections from 92 consecutive invasive breast carcinomas were stained by immunohistochemistry for FIH-1, HIF-1α, glucose transporter 1 (GLUT-1) and carbonic anhydrase IX (CAIX).

Results

45 cases overexpressed HIF-1α, 5 of which in a perinecrotic fashion while FIH-1 was positive in 73 of the 92 cases studied. Contrary to our expectations, three out of five cases with perinecrotic HIF-1α expression were also positive for FIH1. Cytoplasmic FIH-1 correlated with HIF-1α expression (P = 0.03) and tumor grade (P = 0.01). HIF-1α overexpression predicted poorer prognosis as usual (P = 0.02). FIH expression had no additional prognostic value to HIF-1α.

Conclusions

FIH1 is expressed in the majority of invasive breast carcinomas and shows distinct subcellular localization patterns. FIH-1 expression does not seem to explain the proposed functional differences between diffuse and perinecrotic HIF-1α expression in breast cancer.

Recruitment of regulatory T cells is correlated with hypoxia-induced CXCR4 expression, and is associated with poor prognosis in basal-like breast cancers

Introduction

Basal-like breast cancers behave more aggressively despite the presence of a dense lymphoid infiltrate. We hypothesised that immune suppression in this subtype may be due to T regulatory cells (Treg) recruitment driven by hypoxia-induced up-regulation of CXCR4 in Treg.

Methods

Immunoperoxidase staining for FOXP3 and CXCL12 was performed on tissue microarrays from 491 breast cancers. The hypoxia-associated marker carbonic anhydrase IX (CA9) and double FOXP3/CXCR4 staining were performed on sections from a subset of these cancers including 10 basal-like and 11 luminal cancers matched for tumour grade.

Results

High Treg infiltration correlated with tumour CXCL12 positivity (OR 1.89, 95% CI 1.22 to 2.94, P = 0.004) and basal phenotype (OR 3.14, 95% CI 1.08 to 9.17, P = 0.004) in univariate and multivariate analyses. CXCL12 positivity correlated with improved survival (P = 0.005), whereas high Treg correlated with shorter survival for all breast cancers (P = 0.001), luminal cancers (P < 0.001) and basal-like cancers (P = 0.040) that were confirmed in a multivariate analysis (OR 1.61, 95% CI 1.02 to 2.53, P = 0.042). In patients treated with hormone therapy, high Treg were associated with a shorter survival in a multivariate analysis (OR 1.78, 95% CI 1.01 to 3.15, P = 0.040). There was a tendency for luminal cancers to show CXCL12 expression (102/138, 74%) compared to basal-like cancers (16/27, 59%), which verged on statistical significance (P = 0.050). Up-regulation of CXCR4 in Treg correlated with the basal-like phenotype (P = 0.029) and tumour hypoxia, as indicated by CA9 expression (P = 0.049).

Conclusions

Our data show that in the setting of hypoxia and CXCR4 up-regulation in Treg, CXCL12 expression may have the negative consequence of enhancing Treg recruitment and suppressing the anti-tumour immune response.

Nuclear localization of factor inhibitor hypoxia-inducible factor in prostate cancer is associated with poor prognosis

PURPOSE

We determined the role of factor inhibiting hypoxia-inducible factor-1 in prostate cancer specimens.

MATERIALS AND METHODS

A tissue microarray of 152 prostate cancers was constructed and stained for factor inhibiting hypoxia-inducible factor-1, hypoxia-inducible factor-1α and 2α, and glucose transporter 1 as a prototypical downstream target of hypoxia-inducible factor-1α. Correlation analysis was done between these variables, and between factor inhibiting hypoxia-inducible factor-1, and clinical and pathological variables, including prostate specific antigen as a surrogate of recurrence.

RESULTS

Factor inhibiting hypoxia-inducible factor-1 was expressed in the cytoplasm and/or the nucleus in 86.5% of tumors, including exclusive cytoplasmic expression in 51.3% and exclusive nuclear expression in 5.3%. Any nuclear and exclusive expression of factor inhibiting hypoxia-inducible factor was associated with poor prognosis on univariate analysis (p = 0.007 and 0.042, respectively). On multivariate analysis men with nuclear expression in tumors were twice as likely to experience recurrence (p = 0.034).

CONCLUSIONS

Factor inhibiting hypoxia-inducible factor-1 is widely expressed in prostate tumors. Its differential subcellular expression suggests that regulation of its expression is an important factor in the activity of the hypoxia-inducible factor pathway. Its modulation may help treat hypoxia-inducible factor driven aggressive prostate cancer.

The expression of the ubiquitin ligase SIAH2 (seven in absentia homolog 2) is mediated through gene copy number in breast cancer and is associated with a basal-like phenotype and p53 expression

Introduction

The seven in absentia homolog 2 (SIAH2) protein plays a significant role in the hypoxic response by regulating the abundance of hypoxia-inducible factor-α; however, its role in breast carcinoma is unclear. We investigated the frequency and expression pattern of SIAH2 in two independent cohorts of sporadic breast cancers.

Methods

Immunohistochemical evaluation of SIAH2protein expression was conducted in normal breast tissues and in tissue microarrays comprising ductal carcinoma in situ (DCIS) and a cohort of invasive breast carcinomas. Correlation analysis was performed between SIAH2 and clinicopathological variables and intrinsic breast cancer subgroups and validated in a cohort of 293 invasive ductal carcinomas. Promoter methylation, gene copy number and mRNA expression of SIAH2 were determined in a panel of basal-like tumors and cell lines.

Results

There was a significant increase in nuclear SIAH2 expression from normal breast tissues through to DCIS and progression to invasive cancers. A significant inverse correlation was apparent between SIAH2 and estrogen receptor and progesterone receptor and a positive association with tumor grade, HER2, p53 and an intrinsic basal-like subtype. Logistic regression analysis confirmed the significant positive association between SIAH2 expression and the basal-like phenotype. No SIAH2 promoter methylation was identified, yet there was a significant correlation between SIAH2 mRNA and gene copy number. SIAH2-positive tumors were associated with a shorter relapse-free survival in univariate but not multivariate analysis.

Conclusions

SIAH2 expression is upregulated in basal-like breast cancers via copy number changes and/or transcriptional activation by p53 and is likely to be partly responsible for the enhanced hypoxic drive through abrogation of the prolyl hydroxylases.

DNA methylation analysis of the HIF-1α prolyl hydroxylase domain genes PHD1, PHD2, PHD3 and the factor inhibiting HIF gene FIH in invasive breast carcinomas

AIMS

Hypoxia-inducible factor-1 (HIF-1) activity is regulated by prolyl hydroxylase (PHD1, PHD2, PHD3) and factor inhibiting HIF-1 (FIH) that target the α subunit of HIF-1 (HIF-1α) for proteosomal degradation. We hypothesised that the elevated HIF-1α level is due in some tumours to epigenetic silencing by DNA hypermethylation of the promoter region of one or more of the PHDs and FIH genes. The aims were to define the presence or absence of promoter methylation of PHDs and FIH in cell lines of various sources and breast carcinomas and, if present, determine its effect on mRNA and protein expression.

METHODS AND RESULTS

Tumour cell lines (n = 20) and primary invasive breast carcinomas (n = 168) were examined for promoter region DNA methylation using methylation-sensitive high-resolution melting. There was evidence of PHD3 but not of PHD1, PHD2 or FIH DNA methylation in breast cancer (SkBr3) and leukaemic (HL60 and CCRF-CEM) cell lines, but there was no evidence of methylation in any of 168 breast cancers. Only the high-level PHD3 methylation seen in leukaemic cell lines correlated with absent mRNA and protein expression.

CONCLUSIONS

Methylation-induced epigenetic silencing of PHD1, PHD2, PHD3 and FIH is unlikely to underlie up-regulated HIF-1α expression in human breast cancer but may play a role in other tumour types.

Expression of nuclear FIH independently predicts overall survival of clear cell renal cell carcinoma patients

AIM

The hypoxia inducible factor (HIF) pathway plays an important role in sporadic clear cell renal cell carcinoma (ccRCC) by stimulating processes of angiogenesis, cell proliferation, cell survival and metastases formation. Herein, we evaluate the significance of upstream proteins directly regulating the HIF pathway; the prolyl hydroxylases domain proteins (PHD)1, 2 and 3 and factor-inhibiting HIF (FIH), as prognostic markers for ccRCC.

METHODS

Immunohistochemical marker expression was examined on a tissue microarray containing tumour tissue derived from 100 patients who underwent nephrectomy for ccRCC. Expression levels of HIF, FIH and PHD1, 2 and 3 were correlated with overall survival (OS) and clinicopathological prognostic factors.

RESULTS

HIF-1α was positively correlated with HIF-2α (p<0.0001), PHD1 (p = 0.024), PHD2 (p<0.0001), PHD3 (p = 0.004), FIH (p<0.0001) and VHL (p = 0.031). HIF-2α levels were significantly associated with FIH (p<0.0001) and PHD2 (p = 0.0155). Mutations in the VHL gene, expression variations of HIF-1α, HIF-2α and PHD1, 2, 3 did not show a correlation to OS or clinicopathological prognostic factors. Tumour stage, grade, diameter, metastastic disease and intensity of nuclear FIH were significantly correlated to OS in univariable analysis (p = 0.023). Low nuclear FIH levels remained a strong independent prognostic factor in multivariable analysis (p = 0.009).

CONCLUSION

These results show that low nuclear expression of FIH is a strong independent prognostic factor for a poor overall survival in ccRCC.

A therapeutic role for targeting c-Myc/Hif-1-dependent signaling pathways

Deregulated c-Myc occurs in approximately 30% of human cancers. Similarly, hypoxia-inducible factor (HIF) is commonly overexpressed in a variety of human malignancies. Under physiologic conditions, HIF inhibits c-Myc activity; however, when deregulated oncogenic c-Myc collaborates with HIF in inducing the expression of VEGF, PDK1 and hexokinase 2. Most of the knowledge of HIF derives from studies investigating a role of HIF under hypoxic conditions, however, HIF-1alpha stabilization is also found in normoxic conditions. Specifically, under hypoxic conditions HIF-1-mediated regulation of oncogenic c-Myc plays a pivotal role in conferring metabolic advantages to tumor cells as well as adaptation to the tumorigenic micromilieu. In addition, our own results show that under normoxic conditions oncogenic c-Myc is required for constitutive high HIF-1 protein levels and activity in Multiple Myeloma (MM) cells, thereby influencing VEGF secretion and angiogenic activity within the bone marrow microenvironment. Further studies are needed to delineate the functional relevance of HIF, MYC, and the HIF-MYC collaboration in MM and other malignancies, also integrating the tumor microenvironment and the cellular context. Importantly, early studies already demonstrate promising preclinical of novel agents, predominantly small molecules, which target c-Myc, HIF or both.

miR-31 ablates expression of the HIF regulatory factor FIH to activate the HIF pathway in head and neck carcinoma

MicroRNAs (miRNA) are endogenously expressed noncoding RNAs with important biological and pathological functions that are yet to be fully defined. This study investigated alterations in miRNA expression in head and neck squamous cell carcinoma (HNSCC), the incidence of which is rising throughout the world. Initial screening and subsequent analysis identified a panel of aberrantly expressed miRNAs in HNSCC tissues, with miR-31 among the most markedly upregulated. Ectopic expression of miR-31 increased the oncogenic potential of HNSCC cells under normoxic conditions in cell culture or tumor xenografts. Conversely, blocking miR-31 expression reduced the growth of tumor xenografts. The in silico analysis suggested that miR-31 may target the 3' untranslated region (UTR) of factor-inhibiting hypoxia-inducible factor (FIH), a hypoxia-inducible factor (HIF) regulatory factor that inhibits the ability of HIF to act as a transcriptional regulator under normoxic conditions. In support of this likelihood, miR-31 expression repressed FIH expression and mutations within the predictive miR-31 target site in the FIH 3' UTR abrogated FIH repression. Furthermore, miR-31 expression increased HIF transactivation activity. We found that FIH suppressed oncogenic phenotypes under normoxic conditions and that this activity was abrogated by functional mutations. Lastly, increased miR-31 expression was correlated with decreased levels of FIH in tumor tissues. Our findings suggest that miR-31 contributes to the development of HNSCC by impeding FIH to activate HIF under normoxic conditions.

Hypoxia and metastasis in breast cancer

In this review we summarize the evidence for a role for hypoxic response in the biology of metastasis, with a particular emphasis on the metastasis of breast cancer and the function of the hypoxia inducible factor (HIF).

BRCA1 tumours correlate with a HIF-1alpha phenotype and have a poor prognosis through modulation of hydroxylase enzyme profile expression

Background:

There are limited data regarding the hypoxia pathway in familial breast cancers. We therefore performed a study of hypoxic factors in BRCA1, BRCA2 and BRCAX breast cancers.

Methods:

Immunoperoxidase staining for HIF-1α, PHD1, PHD2, PHD3, VEGF and FIH was carried out in 125 (38 BRCA1, 33 BRCA2 and 54 BRCAX) breast carcinomas. These were correlated with clinicopathological parameters and the intrinsic breast cancer phenotypes.

Results:

BRCA1 tumours correlated with positivity for HIF-1α (P=0.008) and negativity for PHD3 (P=0.037). HIF-1α positivity (P=0.001), PHD3 negativity (P=0.037) and nuclear FIH negativity (P=0.011) was associated with basal phenotype. HIF-1α expression correlated with high tumour grade (P=0.009), negative oestrogen receptor (ER) status (P=0.001) and the absence of lymph node metastasis (P=0.028). Nuclear FIH expression and PHD3 correlated with positive ER expression (P=0.024 and P=0.035, respectively). BRCA1 cancers with positive HIF-1α or cytoplasmic FIH had a significantly shorter relapse-free survival (P=0.007 and P=0.049, respectively).

Conclusions:

The aggressive nature of BRCA1 and basal-type tumours may be partly explained by an enhanced hypoxic drive and hypoxia driven ER degradation because of suppressed PHD and aberrantly located FIH expression. This may have important implications, as these tumours may respond to compounds directed against HIF-1α or its downstream targets.

The key hypoxia regulated gene CAIX is upregulated in basal-like breast tumours and is associated with resistance to chemotherapy

Basal-like tumours account for 15% of invasive breast carcinomas and are associated with a poorer prognosis and resistance to therapy. We hypothesised that this aggressive phenotype is because of an intrinsically elevated hypoxic response. Microarrayed tumours from 188 patients were stained for hypoxia-inducible factor (HIF)-1α, prolyl hydroxylase (PHD)1, PHD2, PHD3 and factor inhibiting HIF (FIH)-1, and carbonic anhydrase (CA) IX stained in 456 breast tumours. Tumour subtypes were correlated with standard clincopathological parameters as well as hypoxic markers. Out of 456 tumours 62 (14%) tumours were basal-like. These tumours were positively correlated with high tumour grade (P<0.001) and were associated with a significantly worse disease-free survival compared with luminal tumours (P<0.001). Fifty percent of basal-like tumours expressed HIF-1α, and more than half expressed at least one of the PHD enzymes and FIH-1. Basal-like tumours were nine times more likely to be associated with CAIX expression (P<0.001) in a multivariate analysis. Carbonic anhydrase IX expression was positively correlated with tumour size (P=0.005), tumour grade (P<0.001) and oestrogen receptor (ER) negativity (P<0.001). Patients with any CAIX-positive breast tumour phenotype and in the basal tumour group had a significantly worse prognosis than CAIX-negative tumours when treated with chemotherapy (P<0.001 and P=0.03, respectively). The association between basal phenotype and CAIX suggests that the more aggressive behaviour of these tumours is partly due to an enhanced hypoxic response. Further, the association with chemoresistance in CAIX-positive breast tumours and basal-like tumours in particular raises the possibility that targeted therapy against HIF pathway or downstream genes such as CAs may be an approach to investigate for these patients.

Phosphorylated ERα, HIF-1α, and MAPK Signaling As Predictors of Primary Endocrine Treatment Response and Resistance in Patients With Breast Cancer

Purpose

We aimed to identify signaling pathways involved in the response and resistance to aromatase inhibitor therapy in patients with breast cancer.

Patients and Methods

One hundred fourteen women with T2-4 N0-1, estrogen receptor (ER) α–positive tumors were randomly assigned to neoadjuvant letrozole or letrozole plus metronomic cyclophosphamide. Twenty-four tumor proteins involved in apoptosis, cell survival, hypoxia, angiogenesis, growth factor, and hormone signaling were assessed by immunohistochemistry in pretreatment samples (eg, caspase 3, phospho- mammalian target of rapamycin, hypoxia-inducible factor 1α [HIF-1α], vascular endothelial growth factor, mitogen-activated protein kinase [MAPK], phosphorylated epidermal growth factor receptor, phosphorylated ERα [pERα]). A multivariate generalized linear regression approach was applied using a penalized least-square minimization to perform variable selection and regularization. Ten-fold cross-validation and iterative leave-one-out were employed to validate and test the model, respectively. Tumor size, nodal status, age, tumor grade, histological type, and treatment were included in the analysis.

Results

Ninety-one patients (81%) attained a disease response, 48 achieved a complete clinical response (43%) whereas 22 did not respond (19%). Increased pERα and decreased p44/42 MAPK were significant factors for complete response to treatment in all leave-one-out iterations. Increased p44/42 MAPK and HIF-1α were significant factors for treatment resistance in all leave-one-out iterations. There was no significant interaction between these variables and treatment.

Conclusion

Activated ERα form was an independent factor for sensitivity to chemoendocrine treatment, whereas HIF-1α and p44/42 MAPK were independent factors for resistance. Although further confirmatory analyses are needed, these findings have clear potential implications for future strategies in the management of clinical trials with aromatase inhibitors in the breast cancer.