Expression of hypoxia-inducible factor-1 alpha in oligodendrogliomas: its impact on prognosis and on neoangiogenesis

Hypoxia: The Cornerstone of Glioblastoma

Glioblastoma is the most aggressive form of brain tumor in adults and is characterized by the presence of hypervascularization and necrosis, both caused by a hypoxic microenvironment. In this review, we highlight that hypoxia-induced factor 1 (HIF-1), the main factor activated by hypoxia, is an important driver of tumor progression in GB patients. HIF-1α is a transcription factor regulated by the presence or absence of O2. The expression of HIF-1 has been related to high-grade gliomas and aggressive tumor behavior. HIF-1 promotes tumor progression via the activation of angiogenesis, immunosuppression, and metabolic reprogramming, promoting cell invasion and survival. Moreover, in GB, HIF-1 is not solely modulated by oxygen but also by oncogenic signaling pathways, such as MAPK/ERK, p53, and PI3K/PTEN. Therefore, the inhibition of the hypoxia pathway could represent an important treatment alternative in a disease with very few therapy options. Here, we review the roles of HIF-1 in GB progression and the inhibitors that have been studied thus far, with the aim of shedding light on this devastating disease.

Correlation of 18F-FDG/PET SUVmax, SUVmean, MTV, and TLG with HIF-1α in Patients with Colorectal Cancer

Objectives:

Post-hypoxia hypoxia-inducible factor (HIF)-1α activation plays a vital role in colorectal cancer (CRC) angiogenesis. Although glucose metabolism is induced in some cancer types via HIF-1α, the prognostic significance of HIF-1α in CRC and its correlation with ¹⁸fluorinefluorodeoxyglucose (¹⁸F-FDG) uptake in positron emission tomography (PET) remain controversial. This study aims to investigate the association between ¹⁸F-FDG/PET parameters and HIF-1α expression in CRC.

Methods:

Thirty-six histopathologically confirmed patients with CRC who had ¹⁸F-FDG/PET scans before surgery were enrolled in the study. The correlations between the maximum standardized uptake value (SUV_max), SUV_mean, metabolic tumor volume (MTV), total lesion glycolysis, HIF-1α overexpression, and histopathological features were evaluated.

Results:

The tumor location, tumor diameter, perineural invasion, lymphovascular invasion, T and N stage were not significantly correlated with HIF-1α overexpression. In contrast, the tumor differentiation was negatively correlated with HIF-1α expression (r=-0.332, p=0.048). None of the ¹⁸F-FDG/PET parameters was significantly correlated with HIF-1α overexpression. A significant relationship was found between tumor differentiation, tumor necrosis percentage, and MTV (p=0.030, p=0.020).

Conclusion:

The expected association between HIF-1α overexpression and ¹⁸F-FDG/PET parameters was not found in this study. However, there was a relationship between MTV, tumor differentiation, and tumor necrosis percentage. Hence, further studies are required to predict the pathological and prognostic courses of CRC using a diagnostic ¹⁸F-FDG/PET evaluation.

Characterizing Endocrine Status, Tumor Hypoxia and Immunogenicity for Therapy Success in Epithelial Ovarian Cancer

Epithelial ovarian cancer is predominantly diagnosed at advanced stages which creates significant therapeutic challenges. As a result, the 5-year survival rate is low. Within ovarian cancer, significant tumor heterogeneity exists, and the tumor microenvironment is diverse. Tumor heterogeneity leads to diversity in therapy response within the tumor, which can lead to resistance or recurrence. Advancements in therapy development and tumor profiling have initiated a shift from a "one-size-fits-all" approach towards precision patient-based therapies. Here, we review aspects of ovarian tumor heterogeneity that facilitate tumorigenesis and contribute to treatment failure. These tumor characteristics should be considered when designing novel therapies or characterizing mechanisms of treatment resistance. Individual patients vary considerably in terms of age, fertility and contraceptive use which innately affects the endocrine milieu in the ovary. Similarly, individual tumors differ significantly in their immune profile, which can impact the efficacy of immunotherapies. Tumor size, presence of malignant ascites and vascular density further alters the tumor microenvironment, creating areas of significant hypoxia that is notorious for increasing tumorigenesis, resistance to standard of care therapies and promoting stemness and metastases. We further expand on strategies aimed at improving oxygenation status in tumors to dampen downstream effects of hypoxia and set the stage for better response to therapy.

Apigenin as Tumor Suppressor in Cancers: Biotherapeutic Activity, Nanodelivery, and Mechanisms With Emphasis on Pancreatic Cancer

Pancreatic cancer is the most lethal malignancy of the gastrointestinal tract. Due to its propensity for early local and distant spread, affected patients possess extremely poor prognosis. Currently applied treatments are not effective enough to eradicate all cancer cells, and minimize their migration. Besides, these treatments are associated with adverse effects on normal cells and organs. These therapies are not able to increase the overall survival rate of patients; hence, finding novel adjuvants or alternatives is so essential. Up to now, medicinal herbs were utilized for therapeutic goals. Herbal-based medicine, as traditional biotherapeutics, were employed for cancer treatment. Of them, apigenin, as a bioactive flavonoid that possesses numerous biological properties (e.g., anti-inflammatory and anti-oxidant effects), has shown substantial anticancer activity. It seems that apigenin is capable of suppressing the proliferation of cancer cells via the induction of cell cycle arrest and apoptosis. Besides, apigenin inhibits metastasis via down-regulation of matrix metalloproteinases and the Akt signaling pathway. In pancreatic cancer cells, apigenin sensitizes cells in chemotherapy, and affects molecular pathways such as the hypoxia inducible factor (HIF), vascular endothelial growth factor (VEGF), and glucose transporter-1 (GLUT-1). Herein, the biotherapeutic activity of apigenin and its mechanisms toward cancer cells are presented in the current review to shed some light on anti-tumor activity of apigenin in different cancers, with an emphasis on pancreatic cancer.

Hypoxia in bone metastasis and osteolysis

Hypoxia is a common feature in tumors, driving pathways that promote epithelial-to-mesenchymal transition, invasion, and metastasis. Clinically, high levels of hypoxia-inducible factor (HIF) expression and stabilization at the primary site in many cancer types is associated with poor patient outcomes. Experimental evidence suggests that HIF signaling in the primary tumor promotes their dissemination to the bone, as well as the release of factors such as LOX that act distantly on the bone to stimulate osteolysis and form a pre-metastatic niche. Additionally, the bone itself is a generally hypoxic organ, fueling the activation of HIF signaling in bone resident cells, promoting tumor cell homing to the bone as well as osteoclastogenesis. The hypoxic microenvironment of the bone also stimulates the vicious cycle of tumor-induced bone destruction, further fueling tumor cell growth and osteolysis. Furthermore, hypoxia appears to regulate key tumor dormancy factors. Thus, hypoxia acts both on the tumor cells as well as the metastatic site to promote tumor cell metastasis.

Serum ROCK1 mRNA is of great diagnostic value for glioma patients

The study aimed to measure the presence of rho-associated protein kinase 1 (ROCK1) mRNA in serum samples collected from glioma and investigate its diagnostic significance in glioma.The presence of ROCK1 mRNA was examined by quantitative real-time polymerase chain reaction (qRT-PCR). The relationship between ROCK1 mRNA and clinical characteristics was analyzed via Chi-square test. The criteria of diagnosis evaluation, including sensitivity, specificity, optimal cutoff point, and area under the curve (AUC) were determined through the receiver operating characteristic (ROC) curve analysis.ROCK1 mRNA was significantly increased in serum samples collected from glioma patients compared to the controls (P <.05). Besides, high ROCK1 mRNA expression was tightly related with Karnofsky Performance Status (KPS) score (P = .024) and World Health Organization (WHO) grade (P = .029). However, there was no association between ROCK1 expression and gender, neurological disorders, family history and cigarette smoking (all, P >.05). In addition, the optimal cutoff point was 3.025, with the sensitivity and specificity of 88.89% and 79.25%, respectively. The AUC was 0.881, indicating that ROCK1 was a diagnostic biomarker for glioma patients (P <.0001, 95% CI = 0.829-0.933).Serum ROCK1 mRNA is significantly up-regulated in glioma cases compared to healthy controls. ROCK1 may be a potential diagnostic biomarker in glioma.

Selenium-Binding Protein 1 in Human Health and Disease

Selenium-binding protein 1 (SBP1) is a highly conserved protein that covalently binds selenium. SBP1 may play important roles in several fundamental physiological functions, including protein degradation, intra-Golgi transport, cell differentiation, cellular motility, redox modulation, and the metabolism of sulfur-containing molecules. SBP1 expression is often reduced in many cancer types compared to the corresponding normal tissues and low levels of SBP1 are frequently associated with poor clinical outcome. In this review, the transcriptional regulation of SBP1, the different physiological roles reported for SBP1, as well as the implications of SBP1 function in cancer and other diseases are presented.

Clinical imaging of hypoxia: Current status and future directions

Tissue hypoxia is a key feature of many important causes of morbidity and mortality. In pathologies such as stroke, peripheral vascular disease and ischaemic heart disease, hypoxia is largely a consequence of low blood flow induced ischaemia, hence perfusion imaging is often used as a surrogate for hypoxia to guide clinical diagnosis and treatment. Importantly, ischaemia and hypoxia are not synonymous conditions as it is not universally true that well perfused tissues are normoxic or that poorly perfused tissues are hypoxic. In pathologies such as cancer, for instance, perfusion imaging and oxygen concentration are less well correlated, and oxygen concentration is independently correlated to radiotherapy response and overall treatment outcomes. In addition, the progression of many diseases is intricately related to maladaptive responses to the hypoxia itself. Thus there is potentially great clinical and scientific utility in direct measurements of tissue oxygenation. Despite this, imaging assessment of hypoxia in patients is rarely performed in clinical settings. This review summarises some of the current methods used to clinically evaluate hypoxia, the barriers to the routine use of these methods and the newer agents and techniques being explored for the assessment of hypoxia in pathological processes.

Identification of a Prognostic Hypoxia-Associated Gene Set in IDH-Mutant Glioma

Glioma growth is often accompanied by a hypoxic microenvironment favorable for the induction and maintenance of the glioma stem cell (GSC) phenotype. Due to the paucity of cell models of Isocitrate Dehydrogenase 1 mutant (IDH1^mut) GSCs, biology under hypoxic conditions has not been sufficiently studied as compared to IDH1 wildtype (IDH1^wt) GSCs. We therefore grew well-characterized IDH1^mut (n = 4) and IDH1^wt (n = 4) GSC lines under normoxic (20%) and hypoxic (1.5%) culture conditions and harvested mRNA after 72 h. Transcriptome analyses were performed and hypoxia regulated genes were further analyzed using the expression and clinical data of the lower grade glioma cohort of The Cancer Genome Atlas (LGG TCGA) in a confirmatory approach and to test for possible survival associations. Results show that global expression changes were more pronounced in IDH1^wt than in IDH1^mut GSCs. However, when focusing on known hypoxia-regulated gene sets, enrichment analyses showed a comparable regulation in both IDH1^mut and IDH1^wt GSCs. Of 272 significantly up-regulated genes under hypoxic conditions in IDH1^mut GSCs a hypoxia-related survival score (HRS-score) of five genes (LYVE1, FAM162A, WNT6, OTP, PLOD1) was identified by the Least Absolute Shrinkage and Selection Operator (LASSO) algorithm which was able to predict survival independent of age, 1p19q co-deletion status and WHO grade (II vs. III) in the LGG TCGA cohort and in the Rembrandt dataset. Altogether, we were able to identify and validate a novel hypoxia-related survival score in IDH1^mut GSCs consisting of five hypoxia-regulated genes which was significantly associated with patient survival independent of known prognostic confounders.

Malignant Melanoma Metastatic to Oligodendroglioma: Case Report and Literature Review of Tumor-to-Tumor Metastasis to Gliomas

Tumor-to-tumor metastasis is an uncommon phenomenon, and a metastasis from an extracranial donor tumor to an intracranial recipient tumor is extremely rare. In particular, there are only 14 cases reported in the literature that describe a tumor-to-tumor metastasis involving a glioma. We present a rare case of an 83-year-old man with an 11-year history of lentigo maligna melanoma who presented with impaired balance and cognitive slowing and was found to have rapid progression of a previously known indolent right frontal brain mass. Pathologic examination of the tumor after resection revealed the presence of both malignant melanoma and an oligodendroglioma WHO grade II. To the best of our knowledge, this is the first reported case of malignant melanoma metastasizing to an oligodendroglioma that has been confirmed by immunohistochemistry and genetic analysis.

Expression of Hypoxia-Associated Protein HIF-1α in Follicular Thyroid Cancer is Associated with Distant Metastasis

Follicular thyroid carcinomas (FTCs) are the second most common malignant neoplasia of the thyroid and in general its prognosis is quite favorable. However, the occurrence of metastases or non-responsiveness to radioiodine therapy worsens the prognosis considerably. We evaluated immunohistochemically the expression of hypoxia-associated proteins by hypoxia-induced factor 1α (HIF-1α), the stroma-remodeling marker Tenascin C, as well as markers for the epithelial-mesenchymal transition (EMT), namely E-cadherin and slug in a series of 59 sporadic FTCs. In addition, various clinicopathologic parameters were assessed like TNM-staging, age, tumor size as well as tumor characteristics like desmoplasia, necrosis, and calcification. Overexpression of HIF-1α was seen in 29 of 59 tumors (49.2%) including 21 (35.6%) FTC with strong expression of tumor cell groups. HIF-1α correlated significantly with metastasis (p < 0.001; Mann-Whitney U test), degree of desmoplasia (p = 0.042, Kruskal-Wallis test), tenascin C expression (p = 0.042, Kruskal-Wallis test), calcification (p < 0.025, Kruskal-Wallis test), necrosis (p = 0.002), age (p = 0.011, Kruskal-Wallis test) and tumor stage UICC (p = 0.022, Kruskal-Wallis test). Furthermore, metastasis was associated with the degree of desmoplasia (p = 0.014; Fisher's exact test), calcification (p = 0.008, Fisher's exact test), necrosis (p = 0.042, Fisher's exact test), tumor size (p = 0.015, Mann-Whitney U test), and age (p = 0.001, Mann-Whitney U test). In a Cox proportional hazards model, only metastasis remained as an independent risk factor for overall survival (hazard rate: 10.2 [95% CI, 02.19 to 47.26]; p = 0.003). Our data suggest that HIF-1α plays a critical role in the remodeling of the extracellular matrix as well as metastasizing process of follicular thyroid carcinoma and targeting hypoxia-associated and -regulated proteins may be considered as potential targets for personalized medicine.

Doxorubicin and paclitaxel carried by methoxy poly(ethylene glycol)-poly(lactide-co-glycolide) is superior than traditional drug-delivery methods

AIM

To evaluate the advantages of nanomaterial methoxy poly(ethylene glycol)-poly(lactide-co-glycolide) (mPEG-PLGA) encapsulated doxorubicin (D/DOX) and paclitaxel (T/TAX; mPEG-PLGA-DT) over free form of DOX and TAX (DOX/TAX).

MATERIALS & METHODS

Metabonomics was conducted to characterize the systemic metabolic response of allograft breast cancer model mice to mPEG-PLGA-DT and DOX/TAX treatments.

RESULTS

Breast tumor growth induced metabolic reprogram in serum and multiple organs. DOX/TAX treatment could ameliorate the elevated energy and nucleotides demands in some organs while mPEG-PLGA-DT treatment showed outstanding therapeutic outcomes in restoring the metabolic phenotypes of serum and kidney from tumor-bearing mice to the healthy state.

CONCLUSION

This investigation proved the biological advantages of mPEG-PLGA-DT over DOX/TAX in molecular level through the comparison between their metabolic responses in vivo.

Lactate stimulates CA IX expression in normoxic cancer cells

Besides hypoxia, other factors and molecules such as lactate, succinate, and reactive oxygen species activate transcription factor hypoxia-inducible factor-1 (HIF-1) even in normoxia. One of the main target gene products of HIF-1 is carbonic anhydrase IX (CA IX). CA IX is overexpressed in many tumors and serves as prognostic factor for hypoxic, aggressive and malignant cancers. CA IX is also induced in normoxia in high cell density. In this study, we observed that lactate induces CA IX expression in normoxic cancer cells in vitro and in vivo. We further evidenced that participation of both HIF-1 and specificity protein 1 (SP1) transcription factors is crucial for lactate-driven normoxic induction of the CA9 gene. By inducing CA IX, lactate can facilitate the maintenance of cancer cell aggressive behavior in normoxia.

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY): an epileptogenic neoplasm with oligodendroglioma-like components, aberrant CD34 expression, and genetic alterations involving the MAP kinase pathway

Epileptogenic tumors affecting children and young adults are a morphologically diverse collection of neuroepithelial neoplasms that, as a group, exhibit varying levels of glial and/or neuronal differentiation. Recent advances in molecular profiling technology, including comprehensive DNA sequencing and methylation analysis, have enabled the application of more precise and biologically relevant classification schemes to these tumors. In this report, we describe a morphologically and molecularly distinct epileptogenic neoplasm, the polymorphous low-grade neuroepithelial tumor of the young (PLNTY), which likely accounts for a sizable portion of oligodendroglioma-like tumors affecting the pediatric population. Characteristic microscopic findings most notably include infiltrative growth, the invariable presence of oligodendroglioma-like cellular components, and intense immunolabeling for cluster of differentiation 34 (CD34). Moreover, integrative molecular profiling reveals a distinct DNA methylation signature for PLNTYs, along with frequent genetic abnormalities involving either B-Raf proto-oncogene (BRAF) or fibroblast growth factor receptors 2 and 3 (FGFR2, FGFR3). These findings suggest that PLNTY represents a distinct biological entity within the larger spectrum of pediatric, low-grade neuroepithelial tumors.

mRNA overexpression of the hypoxia inducible factor 1 alpha subunit gene (HIF1A): An independent predictor of poor overall survival in chronic lymphocytic leukemia

The hypoxia inducible factor 1 (HIF1) is a heterodimeric transcription factor that ultimately regulates cellular responses to changes in oxygen tension. In this study, we examined the potential diagnostic and prognostic potential of the mRNA expression of HIF1 regulatory α-subunit (HIF1A) in chronic lymphocytic leukemia (CLL). For this purpose, total RNA was isolated from peripheral blood mononuclear cells collected from 88 CLL patients and 33 non-leukemic blood donors, and poly(A)-RNA was reversely transcribed. HIF1A mRNA levels were quantified using real-time PCR. Kaplan-Meier survival analysis showed that high HIF1A mRNA expression predicts inferior overall survival for CLL patients (p=0.001). Bootstrap univariate Cox regression analysis confirmed that HIF1A mRNA overexpression is a significant unfavorable prognosticator in CLL (hazard ratio=3.75, bias-corrected and accelerated 95% confidence interval=1.43-24.36, bootstrap p<0.001), independent of other established prognostic factors, including CD38 expression, the mutational status of the immunoglobulin heavy chain variable region (IGHV), and the clinical stage (Binet or Rai stage) or risk group (p<0.001 in all cases). Interestingly, HIF1A mRNA positivity retains its unfavorable prognostic value in distinct subgroups of patients, stratified according to established prognostic factors. Thus, HIF1A mRNA overexpression can be regarded as a promising, independent molecular biomarker of unfavorable prognosis in CLL.

Therapeutic targeting of hypoxia and hypoxia-inducible factors in cancer

Insufficient tissue oxygenation, or hypoxia, contributes to tumor aggressiveness and has a profound impact on clinical outcomes in cancer patients. At decreased oxygen tensions, hypoxia-inducible factors (HIFs) 1 and 2 are stabilized and mediate a hypoxic response, primarily by acting as transcription factors. HIFs exert differential effects on tumor growth and affect important cancer hallmarks including cell proliferation, apoptosis, differentiation, vascularization/angiogenesis, genetic instability, tumor metabolism, tumor immune responses, and invasion and metastasis. As a consequence, HIFs mediate resistance to chemo- and radiotherapy and are associated with poor prognosis in cancer patients. Intriguingly, perivascular tumor cells can also express HIF-2α, thereby forming a "pseudohypoxic" phenotype that further contributes to tumor aggressiveness. Therefore, therapeutic targeting of HIFs in cancer has the potential to improve treatment efficacy. Different strategies to target hypoxic cancer cells and/or HIFs include hypoxia-activated prodrugs and inhibition of HIF dimerization, mRNA or protein expression, DNA binding capacity, and transcriptional activity. Here we review the functions of HIFs in the progression and treatment of malignant solid tumors. We also highlight how HIFs may be targeted to improve the management of patients with therapy-resistant and metastatic cancer.

Synthesis and biological evaluation of 1,2-dithiol-3-thiones and pyrrolo[1,2-a]pyrazines as novel hypoxia inducible factor-1 (HIF-1) inhibitor

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor which is strongly associated with tumor survival, progression, and therapeutic resistance. Accordingly, it has been suggested that the inhibition of the HIF-1 pathway can suppress tumor, and it has become an important therapeutic target. In present study, oltipraz, its metabolite M2, and their derivatives were synthesized and evaluated as HIF-1α inhibitors. Among the synthesized, benzyl-substituted pyrrolo[1,2-a]pyrazine 2g most potently inhibited HIF-1α protein accumulation (81% at 10μM) and VEGF, GLUT-1 transcription (77% and 92% at 10μM, respectively).

Methyl 3-((6-methoxy-1,4-dihydroindeno[1,2-c]pyrazol-3-yl)amino)benzoate (GN39482) as a tubulin polymerization inhibitor identified by MorphoBase and ChemProteoBase profiling methods

A series of indenopyrazoles was synthesized from the corresponding indanones and phenyl isothiocyanates in two steps. Among the compounds synthesized, methyl 3-((6-methoxy-1,4-dihydroindeno[1,2-c]pyrazol-3-yl)amino)benzoate 6m (GN39482) was found to possess a promising antiproliferative activity toward human cancer cells without affecting any antimicrobial and antimalarial activities at 100 nM. Both a methoxy group at R(1) position and a methoxycarbonyl group at R(2) position of the anilinoquinazoline framework are essential for the high cell growth inhibition. Both MorphoBase and ChemProteoBase profiling analyses suggested that compound 6m was classified as a tubulin inhibitor. Indeed, compound 6m inhibited the acetylated tubulin accumulation and the microtubule formation and induced G2/M cell cycle arrest in HeLa cells, revealing that a promising antiproliferative activity of compound 6m toward human cancer cells is probably caused by the tubulin polymerization inhibition.

DNA-PKcs deficiency inhibits glioblastoma cell-derived angiogenesis after ionizing radiation

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) plays a critical role in non-homologous end-joining repair of DNA double-strand breaks (DSB) induced by ionizing radiation (IR). Little is known, however, regarding the relationship between DNA-PKcs and IR-induced angiogenesis; thus, in this study we aimed to further elucidate this relationship. Our findings revealed that lack of DNA-PKcs expression or activity sensitized glioma cells to radiation due to the defective DNA DSB repairs and inhibition of phosphorylated Akt(Ser473) . Moreover, DNA-PKcs deficiency apparently mitigated IR-induced migration, invasion and tube formation of human microvascular endothelial cell (HMEC-1) in conditioned media derived from irradiated DNA-PKcs mutant M059J glioma cells or M059K glioma cells that have inhibited DNA-PKcs kinase activity due to the specific inhibitor NU7026 or siRNA knockdown. Moreover, IR-elevated vascular endothelial growth factor (VEGF) secretion was abrogated by DNA-PKcs suppression. Supplemental VEGF antibody to irradiated-conditioned media was negated enhanced cell motility with a concomitant decrease in phosphorylation of the FAK(Try925) and Src(Try416) . Furthermore, DNA-PKcs suppression was markedly abrogated in IR-induced transcription factor hypoxia inducible factor-1α (HIF-1α) accumulation, which is related to activation of VEGF transcription. These findings, taken together, demonstrate that depletion of DNA-PKcs in glioblastoma cells at least partly suppressed IR-inflicted migration, invasion, and tube formation of HMEC-1 cells, which may be associated with the reduced HIF-1α level and VEGF secretion. Inhibition of DNA-PKcs may be a promising therapeutic approach to enhance radio-therapeutic efficacy for glioblastoma by hindering its angiogenesis.

Hypoxia provokes base excision repair changes and a repair-deficient, mutator phenotype in colorectal cancer cells

Regions of acute and chronic hypoxia exist within solid tumors and can lead to increased rates of mutagenesis and/or altered DNA damage and repair protein expression. Base excision repair (BER) is responsible for resolving small, non-helix-distorting lesions from the genome that potentially cause mutations by mispairing or promoting DNA breaks during replication. Germline and somatic mutations in BER genes, such as MutY Homolog (MUTYH/MYH) and DNA-directed polymerase (POLB), are associated with increased risk of colorectal cancer. However, very little is known about the expression and function of BER proteins under hypoxic stress. Using conditions of chronic hypoxia, decreased expression of BER proteins was observed because of a mechanism involving suppressed BER protein synthesis in multiple colorectal cancer cell lines. Functional BER was impaired as determined by MYH- and 8-oxoguanine (OGG1)-specific glycosylase assays. A formamidopyrimidine-DNA glycosylase (Fpg) Comet assay revealed elevated residual DNA base damage in hypoxic cells 24 hours after H2O2 treatment as compared with normoxic controls. Similarly, high-performance liquid chromatography analysis demonstrated that 8-oxo-2'-deoxyguanosine lesions were elevated in hypoxic cells 3 and 24 hours after potassium bromate (KBrO3) treatment when compared with aerobic cells. Correspondingly, decreased clonogenic survival was observed following exposure to the DNA base damaging agents H2O2 and MMS, but not to the microtubule interfering agent paclitaxel. Thus, a persistent downregulation of BER components by the microenvironment modifies and facilitates a mutator phenotype, driving genetic instability and cancer progression.

IMPLICATIONS

Aberrant BER is a contributing factor for the observed genetic instability in hypoxic tumor cells.

Prognostic potential of DNA methylation and transcript levels of HIF1A and EPAS1 in colorectal cancer

Hypoxic conditions during the formation of colorectal cancer may support the development of more aggressive tumors. Hypoxia-inducible factor (HIF) is a heterodimeric complex, composed of oxygen-induced HIFα and constitutively expressed HIFβ subunits, which mediates the primary transcriptional response to hypoxic stress. Among HIFα isoforms, HIF1α (HIF1A) and endothelial PAS domain-containing protein 1 (EPAS1) are able to robustly activate hypoxia-responsive gene signatures. Although posttranslational regulation of HIFα subunits is well described, less is known about their transcriptional regulation. Here, molecular analysis determined that EPAS1 mRNA was significantly reduced in primary colonic adenocarcinoma specimens compared with histopathologically nonneoplastic tissue from 120 patients. In contrast, no difference in HIF1A mRNA levels was observed between cancerous and noncancerous tissue. Bisulfite DNA sequencing and high-resolution melting analysis identified significant DNA hypermethylation in the EPAS1 regulatory region from cancerous tissue compared with nonneoplastic tissue. Importantly, multivariate Cox regression analysis revealed a high HR for patients with cancer with low EPAS1 transcript levels (HR, 4.91; 95% confidence interval, CI, 0.42-56.15; P = 0.047) and hypermethylated EPAS1 DNA (HR, 33.94; 95% CI, 2.84-405.95; P = 0.0054). Treatment with a DNA methyltransferase inhibitor, 5-Aza-2'-deoxycytidine (5-aza-dC/Decitabine), upregulated EPAS1 expression in hypoxic colorectal cancer cells that were associated with DNA demethylation of the EPAS1 regulatory region. In summary, EPAS1 is transcriptionally regulated by DNA methylation in colorectal cancer.

IMPLICATIONS

DNA methylation and mRNA status of EPAS1 have novel prognostic potential for colorectal cancer.

The potential role of HIF on tumour progression and dissemination

Cancer is the second cause of mortality worldwide, primarily owing to failure to cure metastatic disease. The need to target the metastatic process to reduce mortality is clear and research over the past decade has shown hypoxia-inducible factor-1 (HIF-1) to be one of the promising targets. In order for metastatic disease to be established, multiple steps need to be taken whereby the tumour cells escape into the bloodstream and survive, disseminate and then establish at a premetastatic niche. HIF-1 mediates hypoxia-induced proangiogenic factors such as vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF), which promote extravasation and chemotaxis. The migration of tumour cells is mediated by loss of E-cadherin, which results in a more invasive phenotype; dissemination of the tumour cells by increased vascular permeability and survival in the bloodstream through resistance to apoptosis as well as adhesion at the premetastatic niche are all controlled by factors under the influence of HIF-1. The overexpression of HIF in many aggressive cancer types as well as its role in the establishment of metastatic disease and treatment resistance demonstrate its potential target in therapeutics. Taken together, the role of HIF-1 in cancer and metastatic disease is clear and the need for better treatment targeting metastases is paramount; more aggressive phenotypes with less response to treatment are associated with HIF-1 expression. Our research has shown promise but many questions still remain to be answered.

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.

Prognostic value and clinicopathological differences of HIFs in colorectal cancer: evidence from meta-analysis

Background

The prognostic value of HIFs in colorectal cancer was evaluated in a large number of studies, but the conclusions were inconclusive. Meanwhile, clinicopathologic differences of HIF-1α and HIF-2α were rarely compared in recent studies.

Methodology

Identical search strategies were used to search relevant literatures in the PubMed and Web of Science databases. The prognostic significances and clinicopathological differences of HIFs in CRC were analyzed.

Principal Findings

A total of 23studies comprising 2984 CRC patients met the inclusion criteria. The results indicated that overexpressed HIFs were significantly associated with increase of mortality risk, including overall survival (OS) (HR 2.06 95%CI 1.55–2.74) and disease free survival (HR 2.84, 95%CI 1.87–4.31). Subgroup analysis revealed that both overexpressed HIF-1α and HIF-2α had correlations with worse prognosis. The pooled HRs were 2.01 (95% CI: 1.55–2.6) and 2.07(95% CI: 1.01–4.26). Further subgroup analysis on HIF-1α was performed by study location, number of patients, quality score and cut-off value. The results showed that HIF-1α overexpression was significantly associated with poor OS, particularly in Asian countries (HR 2.3, 95% CI: 1.74–3.01), while not in European or other countries. In addition, overexpression of HIF-1α was closely related with these clinicopathological features, including Dukes' stages (OR 0.39, 95% CI: 0.17–0.89), UICC stages (OR 0.42 95% CI: 0.3–0.59), depth of invasion (OR 0.71, 95% CI: 0.51–0.99), lymphnode status (OR 0.49, 95% CI: 0.32–0.73) and metastasis (OR 0.29, 95% CI: 0.11–0.81). While overexpression of HIF-2α was only associated with grade of differentiation (OR 0.48, 95% CI: 0.29–0.81).

Conclusions

This study showed that both HIF-1α and HIF-2α overexpression were associated with an unfavorable prognosis. HIF-1α overexpression seemed to be associated with worse prognosis in Asian countries. Additionally, HIF-1α and HIF-2α indicated distinct clinicopathologic features.

Expression of hypoxia-inducible factor-1α and vascular density in mammary adenomas and adenocarcinomas in bitches

Background

The study aimed at examining hypoxia-inducible factor (HIF)1α expression in adenocarcinomas and adenomas in bitches in regard to tumour malignancy grade, proliferation, apoptosis and vascularisation. Therefore, paraffin sections of 15 adenomas and 64 adenocarcinomas sampled from 79 dogs aged 6 to 16 years were analysed.

Results

A significantly higher HIF-1α expression was noted in adenocarcinomas in comparison to adenomas (P < 0.0004). Moreover, HIF-1α expression in adenocarcinomas correlated positively with tumour malignancy grade (r = 0.59, P < 0.05), Ki-67 antigen expression (r = 0.43; P < 0.0005), TUNEL-positive cells (r = 0.62, P < 0001) and tumour vascularity measured by quantification of vessels characterized by the expression of von Willebrand Factor (r = 0.57, P < 0.05).

Conclusion

Results of this study indicate a similar biological role of HIF-1α in dogs and in humans, which may confirm suitability of the animal model in investigations on progression of tumours in humans.

Oxygen sensing, hypoxia-inducible factors, and disease pathophysiology

Hypoxia-inducible factors (HIFs) are transcriptional activators that function as master regulators of oxygen homeostasis, which is disrupted in disorders affecting the circulatory system and in cancer. The role of HIFs in these diseases has been elucidated by clinical studies and by analyses of mouse models. HIFs play a protective role in the pathophysiology of myocardial ischemia due to coronary artery disease, limb ischemia due to peripheral arterial disease, pressure-overload heart failure, wound healing, and chronic rejection of organ transplants. In contrast, HIFs contribute to the pathogenesis of pulmonary arterial hypertension, systemic hypertension associated with sleep apnea, ocular neovascularization, hereditary erythrocytosis, and cancer.

Hypoxia-inducible factors: mediators of cancer progression; prognostic and therapeutic targets in soft tissue sarcomas

Soft-tissue sarcomas remain aggressive tumors that result in death in greater than a third of patients due to either loco-regional recurrence or distant metastasis. Surgical resection remains the main choice of treatment for soft tissue sarcomas with pre- and/or post-operational radiation and neoadjuvant chemotherapy employed in more advanced stage disease. However, in recent decades, there has been little progress in the average five-year survival for the majority of patients with high-grade soft tissue sarcomas, highlighting the need for improved targeted therapeutic agents. Clinical and preclinical studies demonstrate that tumor hypoxia and up-regulation of hypoxia-inducible factors (HIFs) is associated with decreased survival, increased metastasis, and resistance to therapy in soft tissue sarcomas. HIF-mediated gene expression regulates many critical aspects of tumor biology, including cell survival, metabolic programming, angiogenesis, metastasis, and therapy resistance. In this review, we discuss HIFs and HIF-mediated genes as potential prognostic markers and therapeutic targets in sarcomas. Many pharmacological agents targeting hypoxia-related pathways are in development that may hold therapeutic potential for treating both primary and metastatic sarcomas that demonstrate increased HIF expression.

Discovery of Indenopyrazoles as a New Class of Hypoxia Inducible Factor (HIF)-1 Inhibitors

The indenopyrazole framework was investigated as a new class of HIF-1α inhibitors. Indenopyrazole 2l was found to most strongly inhibit the hypoxia-induced HIF-1α transcriptional activity (IC50 = 0.014 μM) among all of the known compounds having relatively simple structures, unlike manassantins. Indenopyrazole 2l suppressed HIF-1α transcriptional activity without affecting both HIF-1α protein accumulation and HIF-1α/HIF-1β heterodimerization in nuclei under the hypoxic conditions, suggesting that 2l probably affected the transcriptional pathway induced by the HIF-1α/HIF-1β heterodimer.

Proteomics analysis of tumor microenvironment: Implications of metabolic and oxidative stresses in tumorigenesis

Tumorigenesis is always concomitant with microenvironmental alterations. The tumor microenvironment is a heterogeneous and complex milieu, which exerts a variety of stresses on tumor cells for proliferation, survival, or death. Recently, accumulated evidence revealed that metabolic and oxidative stresses both play significant roles in tumor development and progression that converge on a common autophagic pathway. Tumor cells display increased metabolic autonomy, and the hallmark is the exploitation of aerobic glycolysis (termed Warburg effect), which increased glucose consumption and decreased oxidative phosphorylation to support growth and proliferation. This characteristic renders cancer cells more aggressive; they devour tremendous amounts of nutrients from microenvironment to result in an ever-growing appetite for new tumor vessel formation and the release of more "waste," including key determinants of cell fate like lactate and reactive oxygen species (ROS). The intracellular ROS level of cancer cells can also be modulated by a variety of stimuli in the tumor microenvironment, such as pro-growth and pro-inflammatory factors. The intracellular redox state serves as a double-edged sword in tumor development and progression: ROS overproduction results in cytotoxic effects and might lead to apoptotic cell death, whereas certain level of ROS can act as a second-messenger for regulation of such cellular processes as cell survival, proliferation, and metastasis. The molecular mechanisms for cancer cell responses to metabolic and oxidative stresses are complex and are likely to involve multiple molecules or signaling pathways. In addition, the expression and modification of these proteins after metabolic or oxidative stress challenge are diverse in different cancer cells and endow them with different functions. Therefore, MS-based high-throughput platforms, such as proteomics, are indispensable in the global analysis of cancer cell responses to metabolic and oxidative stress. Herein, we highlight recent advances in the understanding of the metabolic and oxidative stresses associated with tumor progression with proteomics-based systems biology approaches.

Biology, genetics and imaging of glial cell tumours

Despite advances in therapy, gliomas remain associated with poor prognosis. Clinical advances will be achieved through molecularly targeted biological therapies, for which knowledge of molecular genetic and gene expression characteristics in relation to histopathology and in vivo imaging are essential. Recent research supports the molecular classification of gliomas based on genetic alterations or gene expression profiles, and imaging data supports the concept that molecular subtypes of glioma may be distinguished through non-invasive anatomical, physiological and metabolic imaging techniques, suggesting differences in the baseline biology of genetic subtypes of infiltrating glioma. Furthermore, MRI signatures are now being associated with complex gene expression profiles and cellular signalling pathways through genome-wide microarray studies using samples obtained by image guidance which may be co-registered with clinical imaging. In this review we describe the pathobiology, molecular pathogenesis, stem cells and imaging characteristics of gliomas with emphasis on astrocytomas and oligodendroglial neoplasms.

Hypoxia-inducible factor-1-regulated protein expression and oligodendroglioma patient outcome: comparison with established biomarkers and preoperative UCSF low-grade scoring system

Methods for predicting outcome for patients with oligodendrogliomas and anaplastic oligodendrogliomas (AOs) are limited. Hypoxia-inducible factor-1α (HIF-1α) controls many proteins involved in glycolysis and angiogenesis including VEGF, Glut-1, and CA-IX. We examined whether expression of HIF-1α and other hypoxia-regulated molecules (HRM) can predict overall (OS) and progression-free (PFS) survival. We correlated these data with more established biomarkers and a published preoperative scoring system. We prospectively collected tissue samples and followed outcomes of 50 patients with oligodendrogliomas and 32 with AOs. Tumor tissues were stained for measures of proliferative index, microvascular density, IDH-1 mutational status, and HRMs. We retrospectively analyzed preoperative imaging and clinical data based on the UCSF Scoring System (good prognostic indicators: Karnofsky Performance Scale (KPS) score > 80, age < 50 years, tumor diameter < 4 cm, noneloquent tumor location) and correlated these with immunohistochemical markers, 1p19q chromosomal status, and compared both with patient PFS and OS. Mean follow-up was 85.6 ± 41.4 months. HRMs showed higher expression in AOs than in oligodendrogliomas. Both 1p19q codeletion and IDH-1 mutation predict outcome of patients with both oligodendroglioma and AO. The UCSF score is a strong predictor for oligodendrogliomas patient outcome and is strengthened by IDH-1 and 1p19q status. Glut-1 may be useful in predicting PFS in AOs. Proliferation index >5 for oligodendrogliomas and KPS ≤ 80 for AOs predict a worse prognosis. Immunohistochemical markers of HRMs show a significantly higher expression in anaplastic variants of oligodendrogliomas and may contribute to the prediction of survival in these patients.

Microregional antitumor activity of a small-molecule hypoxia-inducible factor 1 inhibitor

Hypoxia-inducible factor 1 (HIF-1) activates the transcription of genes that play crucial roles in the adaptation of cancer cells to hypoxia. HIF-1α overexpression has been associated with poor prognosis in patients with various types of cancer. Here, we describe ER-400583-00 as a novel HIF-1 inhibitor. ER-400583-00 suppressed the production of HIF-1α protein in response to hypoxia, with a half-maximal inhibitory concentration value of 3.7 nM in human U251 glioma cells. The oral administration of 100 mg/kg ER-400583-00 to mice bearing U251 tumor xenografts resulted in a rapid suppression of HIF-1α that persisted for 24 h. Immunohistochemical analysis revealed that ER-400583-00 suppressed the proliferation of cancer cells most prominently in areas distal to the region of blood perfusion, where HIF-1α-expressing hypoxic cancer cells were located. These hypoxic cancer cells were resistant to radiation therapy. ER-400583-00 showed a synergistic interaction with radiation therapy in terms of antitumor activity. These data suggest that HIF-1 blockade by small compounds may have therapeutic value in cancer, especially in combination with radiation therapy.

Design and synthesis of novel small-molecule inhibitors of the hypoxia inducible factor pathway

Hypoxia, a reduction in partial oxygen pressure, is a salient property of solid tumors. Hypoxia drives malignant progression and metastasis in tumors and participates in tumor resistance to radio- and chemotherapies. Hypoxia activates the hypoxia-inducible factor (HIF) family of transcription factors, which induce target genes that regulate adaptive biological processes such as anaerobic metabolism, cell motility, and angiogenesis. Clinical evidence has demonstrated that expression of HIF-1 is strongly associated with poor patient prognosis and activation of HIF-1 contributes to malignant behavior and therapeutic resistance. Consequently, HIF-1 has become an important therapeutic target for inhibition by small molecules. Herein, we describe the design and synthesis of small molecules that inhibit the HIF-1 signaling pathway. Many of these compounds exhibit inhibitory activity in the nanomolar range. Separate mechanistic studies indicate that these inhibitors do not alter HIF-1 levels but interfere with the ability of HIF-1α/HIF-1β to interact with cofactors p300/CBP to form an active transcriptional complex.

Combination therapy for renal cell cancer: what are possible options?

Antiangiogenic therapy has shown promise in the treatment of patients with renal cell carcinoma (RCC). Two classes of antiangiogenic drugs, the anti-vascular endothelial growth factor antibody bevacizumab and the tyrosine kinase inhibitors sorafenib, sunitinib and pazopanib, have shown efficacy in patients with RCC and are approved by the US Food and Drug Administration for treatment of this cancer. In practice, the clinical benefit of antiangiogenic drugs in RCC has been heterogeneous, and in patients who do respond, benefits are modest and/or short-lived. To improve efficacy, combination targeted therapy has been attempted, but with either very limited additional efficacy or nontolerable toxicities. Recent advances in the molecular understanding of tumor angiogenesis and mechanism of resistance, along with the rapid development of targeted drug discovery, have made it possible to further explore novel combination therapy for RCC.

The three-layer concentric model of glioblastoma: cancer stem cells, microenvironmental regulation, and therapeutic implications

Tumors arising in the central nervous system are thought to originate from a sub-population of cells named cancer stem cells (CSCs) or tumor initiating cells (TICs) that possess an immature phenotype, combined with self-renewal and chemotherapy resistance capacity. Moreover, in the last years, these cells have been identified in particular brain tumor niches fundamental for supporting their characteristics. In this paper, we report studies from many authors demonstrating that hypoxia or the so called “hypoxic niche” plays a crucial role in controlling CSC molecular and phenotypic profile. We recently investigated the relationship existing between Glioblastoma (GBM) stem cells and their niche, defining the theory of three-concentric layers model for GBM mass. According to this model, GBM stem cells reside preferentially within the hypoxic core of the tumour mass, while more differentiated cells are mainly localized along the peripheral and vascularized part of the tumour. This GBM model provides explanation of the effects mediated by the tumour microenvironment on the phenotypic and molecular regulation of GBM stem cells, describing their spatial distribution in the tumor bulk. Moreover, we discuss the possible clinical implications of the creation of this model for future GBM patient management and novel therapeutic strategies development.

Suppression of HIF-1α expression and radiation resistance in acute hypoxic conditions

Recently, it has become clear that acute hypoxia affecting radioresistance exists widely in tumor tissues. Concurrently, hypoxia-inducible factor-1α (HIF-1α) is recognized as an essential transcriptional factor, enabling cells to survive through hypoxia. However, it is unclear as to whether HIF-1α plays a direct role in the radioresistance caused by acute hypoxia. Therefore, in this study, we investigated the in vitro response of the human lung adenocarcinoma cell line, A549, to ionizing radiation in an experimental model that imitates acute hypoxia in the presence and absence of HIF-1α expression, using the HIF-1α inhibitor 5-[1-(phenylmethyl)-1H-indazol-3-yl]-2-furanmethanol (YC-1). Cells were treated with or without 10 μM YC-1 for 2 h. Cells were exposed to either 95% N(2) and 5% CO(2) (hypoxic condition of <0.1 mmHg) or atmospheric air (normoxic condition) for 1 h, and irradiated with 2, 5 and 10 Gy. Western blot analysis revealed that, without YC-1, cells exposed to hypoxic conditions expressed increased levels of HIF-1α compared with those exposed to normoxic conditions. Under hypoxic conditions, HIF-1α expression was suppressed by YC-1 to the same extent as that observed in cells exposed to normoxic conditions without YC-1. Clonogenic survival assay revealed that under hypoxic conditions there was no significant difference between the surviving fraction of cells treated with YC-1 and without YC-1 at any dose point examined. The oxygen enhancement ratio at 10% surviving fraction was calculated as 2.7 and 2.6 in the presence and the absence of YC-1, respectively. These results indicate that HIF-1α itself is not an immediate cause of acute hypoxia-induced radioresistance in A549 cells.

Can we develop effective combination antiangiogenic therapy for patients with hepatocellular carcinoma?

Antiangiogenic therapy has shown promise in the treatment of patients with hepatocellular carcinoma (HCC). Bevacizumab, sorafenib, and sunitinib showed efficacy in patients with HCC; and sorafenib is approved by the FDA for treatment of this cancer. In practice, the clinical benefit of these agents has been heterogeneous; and in patients who do respond, the benefit is modest and/or short-lived. Recent advances in the molecular understanding of tumor angiogenesis along with the rapid development of targeted drug discovery have made it possible to explore novel combination therapy for HCC. We review the clinical trial results, discuss possible molecular mechanisms of resistance, and suggest novel combinations with antiangiogenic therapy.

Choline metabolism, proliferation, and angiogenesis in nonenhancing grades 2 and 3 astrocytoma

PURPOSE

To study choline metabolism in biopsies from nonenhancing Grade 2 (AS2) and Grade 3 (AS3) astrocytomas to determine whether (1) phosphocholine (PC) dominates in AS3, and (2) PC is associated with proliferation or angiogenesis. PC and glycerophosphocholine (GPC) are involved in phospholipid metabolism that accompanies mitosis. PC is the predominant peak in Grade 4 astrocytoma (GBM) while GPC dominates in AS2.

MATERIALS AND METHODS

We used high resolution magic angle spinning magnetic resonance spectroscopy to compare the concentrations of 10 metabolites in 41 biopsies (16 AS2 and 25 AS3) from 24 tumors. Immunohistochemistry was performed on paired biopsies to determine the cell density, Ki-67 proliferation index, and vascular endothelial growth factor (VEGF) angiogenic marker expression.

RESULTS

AS3 had higher PC than AS2; however, the PC:GPC was less than 1 in all cases irrespective of tumor grade. Within tumors, GPC increased with Ki-67 and PC and tCho increased with cell density. There was no association between any choline compound and VEGF.

CONCLUSION

These data suggest that PC:GPC less than 1 is not unique to low grade glioma. Furthermore, the PC concentration that is a marker of aggressive glial tumors is not tightly linked to cell proliferation or angiogenesis in nonenhancing astrocytomas.

Molecular Imaging of Hypoxia: Strategies for Probe Design and Application

Tumor hypoxia is a negative prognostic factor and its precise imaging is of great relevance to therapy planning. The present review summarizes various strategies of probe design for imaging hypoxia with a variety of techniques such as PET, SPECT and fluorescence imaging. Synthesis of some important probes that are used for preclinical and clinical imaging and their mechanism of binding in hypoxia are also discussed.

The emerging role of hypoxia, HIF-1 and HIF-2 in multiple myeloma

Hypoxia is an imbalance between oxygen supply and demand, which deprives cells or tissues of sufficient oxygen. It is well-established that hypoxia triggers adaptive responses, which contribute to short- and long-term pathologies such as inflammation, cardiovascular disease and cancer. Induced by both microenvironmental hypoxia and genetic mutations, the elevated expression of the hypoxia-inducible transcription factor-1 (HIF-1) and HIF-2 is a key feature of many human cancers and has been shown to promote cellular processes, which facilitate tumor progression. In this review, we discuss the emerging role of hypoxia and the HIFs in the pathogenesis of multiple myeloma (MM), an incurable hematological malignancy of BM PCs, which reside within the hypoxic BM microenvironment. The need for current and future therapeutic interventions to target HIF-1 and HIF-2 in myeloma will also be discussed.

Effects of polynitrogen compounds on the activity of recombinant human HIF-1α prolyl hydroxylase 3 in E. coli

Hypoxia inducible factor 1α (HIF-1α) becomes an important regulation factor within the histiocyte when it is under the hypoxia condition. Recently, prolyl hydroxylases (PHDs) have been identified to inactivation HIF-lα by hydroxylation. In this study, polynitrogen compounds were screened as HIF-1α PHD3 inhibitors. The coding region of human PHD3 DNA was optimized by using synonymous codons according to the code bias of Escherichia coli. Soluble and active human PHD3 was expressed in the E. coli with a Trx fusion tag under a lower induction temperature of 25°C. Mass spectrometry analysis of the resultant peptide product indicated a mass increase of 16 daltons, consistent with hydroxylation of the proline residue in the HIF-1α (556-574) peptide substrate. Polynitrogen compounds (1-4) inhibited the enzymatic hydroxylation of HIF-1α peptide in a concentration-dependent manner, and the apparent IC(50) values were 29.5, 16.0, 12.8 and 60.4 μM respectively. Double reciprocal (1/V versus 1/[HIF-1α peptide]) plots showed that these compounds are noncompetitive inhibitors of the hydroxylation by recombinant human PHD3 with K(i) values of 67.0, 25.3, 67.3, and 82.1 μM respectively. On the other hand, the metal complexes of these polynitrogen compounds (1-4) cannot inhibit the catalytical activity of PHD3. We hypothesized that the inhibitory mechanism of PHD3 activity by polynitrogen compounds is due to their binding to iron to form stable coordination complexes. Our results in this study indicated that polynitrogen compounds (1-4) could be potential inhibitors of PHD3 to regulate the transcriptional activity of HIF-1α.

Apigenin down-regulates the hypoxia response genes: HIF-1α, GLUT-1, and VEGF in human pancreatic cancer cells

BACKGROUND

The flavonoid apigenin exhibits anti-proliferative and anti-angiogenic activities. Our objective was to evaluate the effect of apigenin on hypoxia responsive genes important in pancreatic cancer cell proliferation.

MATERIALS AND METHODS

Immunohistochemistry for GLUT-1 expression was conducted on human pancreatic cancer samples and adjacent controls. Real-time RT-PCR, Western blot analysis, and enzyme-linked immunosorbent assay (ELISA) were conducted on CD18 and S2-013 human pancreatic cancer cells treated with apigenin (0-50 μM) in normoxic and hypoxic conditions to evaluate HIF-1α, GLUT-1, and VEGF mRNA and protein expression and secretion.

RESULTS

GLUT-1 expression was significantly increased in pancreatic adenocarcinoma samples versus adjacent controls (P < 0.001). Hypoxic conditions induced HIF-1α, GLUT-1, and VEGF protein expression in both CD18 and S2-013 pancreatic cancer cells. Apigenin (50 μM) blocked hypoxia induced up-regulation of all three proteins in both cell lines. Apigenin also impeded hypoxia-mediated induction of GLUT-1 and VEGF mRNA in both cell lines (P < 0.05).

CONCLUSIONS

Apigenin inhibits HIF-1α, GLUT-1, and VEGF mRNA and protein expression in pancreatic cancer cells in both normoxic and hypoxic conditions. This may account for the mechanism of apigenin's anti-proliferative and anti-angiogenic effects and further supports the potential of apigenin as a future chemopreventive agent for pancreatic cancer.

HIF-1α inhibition by siRNA or chetomin in human malignant glioma cells: effects on hypoxic radioresistance and monitoring via CA9 expression

Background

Hypoxia induces activation of the HIF-1 pathway and is an essential characteristic of malignant gliomas. Hypoxia has been linked to tumor progression, therapy resistance and poor prognosis. However, little is known about the impact of HIF-1α inhibition on radioresistance of malignant glioma.

Methods

In this study, we investigated the effects of the inhibition of HIF-1α on cell survival and radiosensitivity in U251MG and U343MG glioma cells, using two different strategies. HIF-1α inhibition was achieved by siRNA targeting of HIF-1α or via chetomin, a disruptor of interactions between HIF-1α and p300. The inhibition of the HIF-1 pathway was monitored by quantitative real-time PCR and Western blot analyses of the expression levels of HIF-1α and CA9. CA9 expression was investigated as a potential indicator of the efficacy of HIF-1 inhibition and the resulting radiosensitivity of malignant glioma cell lines was determined by clonogenic assay after irradiation under normoxic (2-10 Gy) or hypoxic (2-15 Gy) conditions.

Results

Although siRNA and chetomin show distinct modes of action, both attenuated the hypoxia-induced radioresistance of malignant glioma cell lines U251MG (DMF₁₀: 1.35 and 1.18) and U343MG (DMF₁₀: 1.78 and 1.48). However, siRNA and chetomin showed diverse effects on radiosensitivity under normoxic conditions in U251MG (DMF₁₀: 0.86 and 1.35) and U343MG (DMF₁₀: 1.33 and 1.02) cells.

Conclusions

Results from this in vitro study suggest that inhibition of HIF-1α is a promising strategy to sensitize human malignant gliomas to radiotherapy and that CA9 could serve as an indicator of effective HIF-1-related radiosensitization.