Inhibiting hypoxia-inducible factor 1 for cancer therapy

Beyond boundaries: unraveling innovative approaches to combat bone-metastatic cancers

Evidence demonstrated that bones, liver, and lungs are the most common metastasis sites in some human malignancies, especially in prostate and breast cancers. Bone is the third most frequent target for spreading tumor cells among these organs and tissues. Patients with bone-metastatic cancers face a grim prognosis characterized by short median survival time. Current treatments have proven insufficient, as they can only inhibit metastasis or tumor progression within the bone tissues rather than providing a curative solution. Gaining a more profound comprehension of the interplay between tumor cells and the bone microenvironment (BME) is of utmost importance in tackling this issue. This knowledge will pave the way for developing innovative diagnostic and therapeutic approaches. This review summarizes the mechanisms underlying bone metastasis and discusses the clinical aspects of this pathologic condition. Additionally, it highlights emerging therapeutic interventions aimed at enhancing the quality of life for patients affected by bone-metastatic cancers. By synthesizing current research, this review seeks to shed light on the complexities of bone metastasis and offer insights for future advancements in patient care.

Intermittent hypoxia inhibits anti-tumor immune response via regulating PD-L1 expression in lung cancer cells and tumor-associated macrophages

Accumulating evidence has shown an increased tumor incidence and reduced survival rate in cancer patients with obstructive sleep apnea (OSA). Although intermittent hypoxia is known to play a crucial role, the molecular mechanism by which intermittent hypoxia accelerates lung cancer progression remains to be elucidated.A lung cancer xenograft mouse model was established by subcutaneously injecting LLC cells into C57BL/6 mice. The tumor-bearing mice were exposed to either normoxia or intermittent hypoxia and received either IgG2a, anti-programmed death ligand-1 (PD-L1), PX-478, or anti-PD-L1 + PX-478 treatment.A significant upregulation of tumor associated macrophages (TAMs) papulation and PD-L1 levels was observed in lung adenocarcinoma patients with OSA. We further confirmed that hypoxia-inducible factor-1 alpha (HIF-1α) regulates PD-L1 at transcriptional levels, mainly through binding to the hypoxia response element 4. Using a lung cancer xenograft mouse model, we observed that intermittent hypoxia exposed tumors grew faster and bigger with upregulated HIF-1α and PD-L1 expression, enhanced TAMs and Treg populations, and reduced cytotoxic T cells and cytokine secretion. Finally, we found a combination of PX-478 and anti-PD-L1 exerted an encouraging tumor inhibition effect compared to single treatment. Combination therapies based on HIF-1α and PD-L1 blockade might serve as a promising strategy to treat lung cancer patients with OSA.

Differential Expression of HIF1A, EPAS1, and VEGF Genes in Benign and Malignant Ovarian Neoplasia

Simple Summary

Ovarian cancer (OC) has the highest mortality rate of all gynecological malignancies. Moreover, at the time of the first clinical manifestation, most patients have an advanced stage of the disease. Our study examined differences in mRNA levels of hypoxia-inducible factor 1-alpha (HIF1A); endothelial PAS domain protein 1, also known as hypoxia-inducible factor 2-alpha (HIF2A/EPAS1); and vascular endothelial growth factor A (VEGFA) between cancerous tissue, benign hyperplastic changes in the ovary, and normal tissue. We found that gene expression changes were visible not only in the case-control study, but also along with changes in severity. We observed disturbances in the expression levels of interdependent genes. Our findings suggest that mutual association in the expression of both HIF1A and HIF2A/EPAS1 with VEGFA has prognostic importance for patients with OC. Our observations may help identify patients for clinical trials aimed at inhibiting the hypoxia-induced neovascularization-dependent pathways.

Abstract

Ovarian cancer (OC) has the highest mortality rate of all gynecological malignancies. Moreover, at the time of the first clinical manifestation, most patients have an advanced stage of the disease. Our study examined differences in mRNA levels of hypoxia-inducible factor 1-alpha (HIF1A); endothelial PAS domain protein 1, also known as hypoxia-inducible factor 2-alpha (HIF2A/EPAS1); and vascular endothelial growth factor A (VEGFA) between cancerous tissue, benign hyperplastic changes in the ovary, and normal tissue. Our cohorts consisted of 52 patients diagnosed with OC (n = 55), benign non-cancerous changes (n = 21), and normal tissue samples (n = 38). The mRNA expression level was evaluated using RT-qPCR. We found that gene expression changes were visible not only in the case-control study, but also along with changes in severity. Additionally, the gene expression was differentiated in age, BMI, menopausal status, and the number of comorbidy-related groups. Furthermore, our findings demonstrate that analyzing the correlation between genes is essential. In a case-to-case and case-to-control study, we observed disturbances in the expression levels of interdependent genes. Our findings suggest that mutual association in the expression of both HIF1A and HIF2A/EPAS1 with VEGFA has prognostic importance for patients with OC. Our observations may help identify patients for clinical trials aimed at inhibiting the hypoxia-induced neovascularization-dependent pathways.

HIF-1α Is Associated with Resistance to Hypoxia-Induced Apoptosis in Ameloblastoma

Background

Ameloblastoma (AMB) is a benign odontogenic tumour, with an aggressive local behaviour and a high rate of recurrence. Previous studies have demonstrated that hypoxia-induced factor alpha 1 (HIF-1α) and activated caspase-3 contribute to tumour invasiveness and cytogenesis in ameloblastoma. Hypoxia increases HIF-1α levels, which triggers a number of signalling pathways. This paper aimed to present data in the study of hypoxia-activated signalling pathways that modulate proapoptotic and antiapoptotic events in AMB.

Methods

Twenty cases of AMB and ten cases of dental follicle (DF) were used to analyse the immunoexpression of HIF-1α, p53, BNIP3, Bcl-2, IAP-2, GLUT1, and Bax. To contribute to the study, an analysis of expression and genetic interaction was performed using the cell line AME-1.

Results

AMB and DF expressed the studied proteins. These proteins showed significantly greater immunoexpression in AMB compared with the DF (p < 0.05). HIF-1α showed an important association with GLUT1, and a positive correlation was observed among p53, Bcl-2, and IAP-2. Transcriptomic analysis showed the significant expression of the studied proteins, and the network generated showed a direct association of HIF-1αF with GLUT1 (SLC2A1), TP53, and LDHA. Interestingly, GLUT1 also exhibited direct interaction with TP53 and LDHA.

Conclusion

In AMB tumorigenesis, hypoxia is possibly related to antiapoptotic events, which suggests an important role for HIF-1α, GLUT1, Bcl-2, IAP-2, and possibly p53.

MITOCHONDRIAL CHOLESTEROL AND CANCER

Cholesterol is a crucial component of membrane bilayers that determines their physical and functional properties. Cells largely satisfy their need for cholesterol through the novo synthesis from acetyl-CoA and this demand is particularly critical for cancer cells to sustain dysregulated cell proliferation. However, the association between serum or tissue cholesterol levels and cancer development is not well established as epidemiologic data do not consistently support this link. While most preclinical studies focused on the role of total celular cholesterol, the specific contribution of the mitochondrial cholesterol pool to alterations in cancer cell biology has been less explored. Although low compared to other bilayers, the mitochondrial cholesterol content plays an important physiological function in the synthesis of steroid hormones in steroidogenic tissues or bile acids in the liver and controls mitochondrial function. In addition, mitochondrial cholesterol metabolism generates oxysterols, which in turn, regulate multiple pathways, including cholesterol and lipid metabolism as well as cell proliferation. In the present review, we summarize the regulation of mitochondrial cholesterol, including its role in mitochondrial routine performance, cell death and chemotherapy resistance, highlighting its potential contribution to cancer. Of particular relevance is hepatocellular carcinoma, whose incidence in Western countries had tripled in the past decades due to the obesity and type II diabetes epidemic. A better understanding of the role of mitochondrial cholesterol in cancer development may open up novel opportunities for cancer therapy.

Hypoxia-Induced Autophagy Enhances Cisplatin Resistance in Human Bladder Cancer Cells by Targeting Hypoxia-Inducible Factor-1α

Purpose

To investigate the effect of hypoxia on chemoresistance and the underlying mechanism in bladder cancer cells.

Methods

BIU-87 bladder cancer cell line was treated with cisplatin under hypoxic and normoxic conditions and tested using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blotting. All the data were expressed as mean ± standard error from three independent experiments and analyzed by multiple t-tests.

Results

Apoptosis of bladder cancer cells caused by cisplatin was attenuated in hypoxic conditions. Hypoxia enhanced autophagy caused by cisplatin. The autophagy inhibitor and HIF-1α inhibitor can reverse the chemoresistance in hypoxic condition. Apoptosis and autophagy of bladder cancer cells were downregulated by HIF-1α inhibitor YC-1. Hypoxia-induced autophagy enhanced chemoresistance to cisplatin via the HIF-1 signaling pathway.

Conclusion

Resistance to cisplatin in BIU-87 bladder cancer cells under hypoxic conditions can be explained by activation of autophagy, which is regulated by HIF-1α-associated signaling pathways. The hypoxia–autophagy pathway may be a target for improving the efficacy of cisplatin chemotherapy in bladder cancer.

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.

Molecular mechanisms and clinical management of cancer bone metastasis

As one of the most common metastatic sites of malignancies, bone has a unique microenvironment that allows metastatic tumor cells to grow and flourish. The fenestrated capillaries in the bone, bone matrix, and bone cells, including osteoblasts and osteoclasts, together maintain the homeostasis of the bone microenvironment. In contrast, tumor-derived factors act on bone components, leading to subsequent bone resorption or excessive bone formation. The various pathways involved also provide multiple targets for therapeutic strategies against bone metastases. In this review, we summarize the current understanding of the mechanism of bone metastases. Based on the general process of bone metastases, we specifically highlight the complex crosstalk between tumor cells and the bone microenvironment and the current management of cancer bone metastases.

Recent advances in strategies for overcoming hypoxia in photodynamic therapy of cancer

The selectivity of photodynamic therapy (PDT) derived from the tailored accumulation of photosensitizing drug (photosensitizer; PS) in the tumor microenvironment (TME), and from local irradiation, turns it into a "magic bullet" for the treatment of resistant tumors without sparing the healthy tissue and possible adverse effects. However, locally-induced hypoxia is one of the undesirable consequences of PDT, which may contribute to the emergence of resistance and significantly reduce therapeutic outcomes. Therefore, the development of strategies using new approaches in nanotechnology and molecular biology can offer an increased opportunity to eliminate the disadvantages of hypoxia. Emerging evidence indicates that wisely designed phototherapeutic procedures, including: (i) ROS-tunable photosensitizers, (ii) organelle targeting, (iii) nano-based photoactive drugs and/or PS delivery nanosystems, as well as (iv) combining them with other strategies (i.e. PTT, chemotherapy, theranostics or the design of dual anticancer drug and photosensitizers) can significantly improve the PDT efficacy and overcome the resistance. This mini-review addresses the role of hypoxia and hypoxia-related molecular mechanisms of the HIF-1α pathway in the regulation of PDT efficacy. It also discusses the most recent achievements as well as future perspectives and potential challenges of PDT application against hypoxic tumors.

Assessing predictors for new post translational modification sites: A case study on hydroxylation

Post-translational modification (PTM) sites have become popular for predictor development. However, with the exception of phosphorylation and a handful of other examples, PTMs suffer from a limited number of available training examples and sparsity in protein sequences. Here, proline hydroxylation is taken as an example to compare different methods and evaluate their performance on new experimentally determined sites. As a guide for effective experimental design, predictors require both high specificity and sensitivity. However, the self-reported performance may often not be indicative of prediction quality and detection of new sites is not guaranteed. We have benchmarked seven published hydroxylation site predictors on two newly constructed independent datasets. The self-reported performance is found to widely overestimate the real accuracy measured on independent datasets. No predictor performs better than random on new examples, indicating the refined models do not sufficiently generalize to detect new sites. The number of false positives is high and precision low, in particular for non-collagen proteins whose motifs are not conserved. As hydroxylation site predictors do not generalize for new data, caution is advised when using PTM predictors in the absence of independent evaluations, in particular for highly specific sites involved in signalling.

Machine learning methods are extensively used by biologists to design and interpret experiments. Predictors which take the only sequence as input are of particular interest due to the large amount of available sequence data and high self-reported performance. In this work, we evaluated post-translational modification (PTM) predictors for hydroxylation sites and found that they perform no better than random, in strong contrast to performances reported in their original publications. PTMs are chemical amino acid alterations providing the cell with conditional mechanisms to fine tune protein function, regulating complex biological processes such as signalling and cell cycle. Hydroxylation sites are a good PTM test case due to the availability of a range of predictors and an abundance of newly experimentally detected modification sites. Poor performances in our results highlight the overlooked problem of predicting PTMs when best practices are not followed and training data are likely incomplete. Experimentalists should be careful when using PTM predictors blindly and more independent assessments are needed to establish their usefulness in practice.

SB365 induces apoptosis and suppresses proliferation of glioblastoma cells

CONTEXT:

Glioblastoma is a malignant brain tumor with limited treatment modalities due to its nature. SB365, Pulsatilla saponin D, is known to induce apoptosis and inhibit the growth of many cancer cells.

AIM:

We elucidated the anticancer effects of SB365 in glioblastoma cells.

METHODS:

We examined the antiproliferative activity of SB365 in human glioblastoma cell lines. Apoptosis was evaluated using the Hoechst assay, TUNEL assay, DAPI nuclear staining, and Western blotting analysis. To test the antimetastatic capacity of SB365, cell migration assay was conducted, and hypoxia-inducible factor-1 alpha (HIF-1α) expression and vascular endothelial growth factor (VEGF) level were determined under hypoxic conditions.

STATICAL ANALYSIS:

Significance of the results was confirmed by a one-way analysis of variance analysis.

RESULTS:

SB365 treatment suppressed the growth of glioblastoma cells and resulted in apoptotic morphological features such as nuclear condensation and fragmentation, enhancing the expression of cleaved poly (ADP-ribose) polymerase and caspase-3. It also significantly delayed cell migration and decreased the HIF-1α expression and VEGF secretion.

CONCLUSION:

Our findings thus demonstrate that SB365 induced apoptosis and delayed the growth and migration of human glioblastoma cells. It is considered that SB365 would be a promising therapeutic option for glioblastoma.

Anti-Tumor Drug-Loaded Oxygen Nanobubbles for the Degradation of HIF-1α and the Upregulation of Reactive Oxygen Species in Tumor Cells

Hypoxia is a key concern during the treatment of tumors, and hypoxia-inducible factor 1 alpha (HIF-1α) has been associated with increased tumor resistance to therapeutic modalities. In this study, doxorubicin-loaded oxygen nanobubbles (Dox/ONBs) were synthesized, and the effectiveness of drug delivery to MDA-MB-231 breast cancer and HeLa cells was evaluated. Dox/ONBs were characterized using optical and fluorescence microscopy, and size measurements were performed through nanoparticle tracking analysis (NTA). The working mechanism of Dox was evaluated using reactive oxygen species (ROS) assays, and cellular penetration was assessed with confocal microscopy. Hypoxic conditions were established to assess the effect of Dox/ONBs under hypoxic conditions compared with normoxic conditions. Our results indicate that Dox/ONBs are effective for drug delivery, enhancing oxygen levels, and ROS generation in tumor-derived cell lines.

Dual prognostic role of 2-oxoglutarate-dependent oxygenases in ten cancer types: implications for cell cycle regulation and cell adhesion maintenance

Background

Tumor hypoxia is associated with metastasis and resistance to chemotherapy and radiotherapy. Genes involved in oxygen-sensing are clinically relevant and have significant implications for prognosis. In this study, we examined the pan-cancer prognostic significance of oxygen-sensing genes from the 2-oxoglutarate-dependent oxygenase family.

Methods

A multi-cohort, retrospective study of transcriptional profiles of 20,752 samples of 25 types of cancer was performed to identify pan-cancer prognostic signatures of 2-oxoglutarate-dependent oxygenase gene family (a family of oxygen-dependent enzymes consisting of 61 genes). We defined minimal prognostic gene sets using three independent pancreatic cancer cohorts (n = 681). We identified two signatures, each consisting of 5 genes. The ability of the signatures in predicting survival was tested using Cox regression and receiver operating characteristic (ROC) curve analyses.

Results

Signature 1 (KDM8, KDM6B, P4HTM, ALKBH4, ALKBH7) and signature 2 (KDM3A, P4HA1, ASPH, PLOD1, PLOD2) were associated with good and poor prognosis. Signature 1 was prognostic in 8 cohorts representing 6 cancer types (n = 2627): bladder urothelial carcinoma (P = 0.039), renal papillary cell carcinoma (P = 0.013), liver cancer (P = 0.033 and P = 0.025), lung adenocarcinoma (P = 0.014), pancreatic adenocarcinoma (P < 0.001 and P = 0.040), and uterine corpus endometrial carcinoma (P < 0.001). Signature 2 was prognostic in 12 cohorts representing 9 cancer types (n = 4134): bladder urothelial carcinoma (P = 0.039), cervical squamous cell carcinoma and endocervical adenocarcinoma (P = 0.035), head and neck squamous cell carcinoma (P = 0.038), renal clear cell carcinoma (P = 0.012), renal papillary cell carcinoma (P = 0.002), liver cancer (P < 0.001, P < 0.001), lung adenocarcinoma (P = 0.011), pancreatic adenocarcinoma (P = 0.002, P = 0.018, P < 0.001), and gastric adenocarcinoma (P = 0.004). Multivariate Cox regression confirmed independent clinical relevance of the signatures in these cancers. ROC curve analyses confirmed superior performance of the signatures to current tumor staging benchmarks. KDM8 was a potential tumor suppressor down-regulated in liver and pancreatic cancers and an independent prognostic factor. KDM8 expression was negatively correlated with that of cell cycle regulators. Low KDM8 expression in tumors was associated with loss of cell adhesion phenotype through HNF4A signaling.

Conclusion

Two pan-cancer prognostic signatures of oxygen-sensing genes were identified. These genes can be used for risk stratification in ten diverse cancer types to reveal aggressive tumor subtypes.

Electronic supplementary material

The online version of this article (10.1186/s40880-019-0369-5) contains supplementary material, which is available to authorized users.

Correlation between tumor glucose metabolism and multiparametric functional MRI (IVIM and R2*) metrics in cervical carcinoma: Evidence from integrated 18 F-FDG PET/MR

BACKGROUND

Multiparameter, multimodality ¹⁸ F-FDG PET/MRI holds great potential for the diagnosis of cervical cancer based on the correlation between tumor glucose metabolism and imaging parameters.

PURPOSE

To characterize the heterogeneity of tumor glucose metabolism by evaluating the correlation between ¹⁸ F-FDG uptake parameters and multiparametric functional MRI metrics in cervical carcinoma.

STUDY TYPE

Retrospective.

POPULATION

Fifty-four patients with cervical carcinoma.

FIELD STRENGTH/SEQUENCE

Hybrid PET/MR (3T), multi-b DWI, and R2* mapping.

ASSESSMENT

The maximum and mean standardized uptake values (SUV_max and SUV_mean , respectively) from PET and functional MRI metrics (D, D*, f, and R2*) were obtained. Cervical carcinoma tissues also underwent HIF-1α, VEGF, and GLUT-1 immunohistochemical staining.

STATISTICAL TESTS

Single-factor Spearman rank and Pearson correlation analysis and multiple linear regression (MLR) analysis were applied.

RESULTS

R2*, D, and f have different degrees of correlation (moderate, weak, moderately strong correlation, respectively) with SUV_max and SUV_mean (r = 0.530 and 0.527, and P < 0.001 for R2*; r = -0.292 and -0.291, and P < 0.05 for D; r = 0.539 and 0.520, and P < 0.001 for f, respectively). Immunohistochemical staining showed that HIF-1α expression has a moderate degree of correlation with R2* (r = 0.491; P < 0.001); GLUT-1 expression was significantly correlated with SUV_max and SUV_mean (r = 0.633 and 0.622; P < 0.001), and VEGF expression had a moderately strong correlation with f (r = 0.457; P = 0.001). If SUV_max is the dependent variable, MLR yields an R-squared value after adjustment (adjusted R-squared) = 0.358, and F = 10.833 (P < 0.001), and the fitting linear equation is Y (SUV_max ) = 9.184 + 0.161X1 (R2*)+50.343X2 (f)-4.780 (D). Otherwise, MLR yields the adjusted R-squared = 0.342, and F = 10.187 (P < 0.001), and the linear regression equation is Y (SUV_mean ) = 5.925 + 0.102X1 (R2*)+28.029X2 (f)-2.907X3 (D).

DATA CONCLUSION

The functional MRI sequence parameters R2*, f, and D can provide information on the hypoxic condition, blood perfusion, and molecular diffusion of the tumor. ¹⁸ F-FDG PET/MR multi-imaging technique can be adopted to evaluate the heterogeneity of glucose metabolism in cervical carcinoma.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;49:1704-1712.

Oxygen-Carrying Micro/Nanobubbles: Composition, Synthesis Techniques and Potential Prospects in Photo-Triggered Theranostics

Microbubbles and nanobubbles (MNBs) can be prepared using various shells, such as phospholipids, polymers, proteins, and surfactants. MNBs contain gas cores due to which they are echogenic and can be used as contrast agents for ultrasonic and photoacoustic imaging. These bubbles can be engineered in various sizes as vehicles for gas and drug delivery applications with novel properties and flexible structures. Hypoxic areas in tumors develop owing to an imbalance of oxygen supply and demand. In tumors, hypoxic regions have shown more resistance to chemotherapy, radiotherapy, and photodynamic therapies. The efficacy of photodynamic therapy depends on the effective accumulation of photosensitizer drug in tumors and the availability of oxygen in the tumor to generate reactive oxygen species. MNBs have been shown to reverse hypoxic conditions, degradation of hypoxia inducible factor 1α protein, and increase tissue oxygen levels. This review summarizes the synthesis methods and shell compositions of micro/nanobubbles and methods deployed for oxygen delivery. Methods of functionalization of MNBs, their ability to deliver oxygen and drugs, incorporation of photosensitizers and potential application of photo-triggered theranostics, have also been discussed.

Engineering oxygen nanobubbles for the effective reversal of hypoxia

Hypoxia, which results from an inadequate supply of oxygen, is a major cause of concern in cancer therapy as it is associated with a reduction in the effectiveness of chemotherapy and radiotherapy in cancer treatment. Overexpression and stabilization of hypoxia-inducible factor 1α (HIF-1α) protein in tumours, due to hypoxia, results in poor prognosis and increased patient mortality. To increase oxygen tension in hypoxic areas, micro- and nanobubbles have been investigated by various researchers. In the present research, lipid-shelled oxygen nanobubbles (ONBs) were synthesized through a sonication method to reverse hypoxic conditions created in a custom-made hypoxic chamber. Release of oxygen gas from ONBs in deoxygenated water was evaluated by measuring dissolved oxygen. Hypoxic conditions were evaluated by performing in vitro experiments on MDA-MB231 breast cancer cells through the expression of HIF-1α and the fluorescence of image-iT™ hypoxia reagent. The results indicated the degradation of HIF-1α after the introduction of ONBs. We propose that ONBs are successful in reversing hypoxia, downregulating HIF-1α, and improving cellular conditions, leading to further medical applications.

Bi-functional oxidized dextran–based hydrogel inducing microtumors: An in vitro three-dimensional lung tumor model for drug toxicity assays

Cancer is a serious death causing disease having 8.2 million deaths in 2012. In the last decade, only about 10% of chemotherapeutic compounds showed productivity in drug screening. Two-dimensional culture assays are the most common in vitro drug screening models, which do not precisely model the in vivo condition for reliable preclinical drug screening. Three-dimensional scaffold–based cell cultures perhaps mimic tumor microenvironment and recapitulate physiologically more relevant tumor. This study was carried out to develop bi-functional oxidized dextran–based cell instructive hydrogel that provides three-dimensional environment to cancer cells for inducing microtumor. Oxidized dextran was blended with thiolated chitosan to fabricate an in situ self-gelable hydrogel (modified dextran–chitosan) in a one-step process. The hydrogels characterization revealed cross-linked network structure with highly porous structure and water absorption. The modified dextran–chitosan hydrogel showed reduced hydrophobicity and has reduced protein absorption, which resulted in changing the A549 cell adhesiveness, and encouraged them to form microtumor. The cells were proliferated in clusters having spherical morphology with randomly oriented stress fiber and large nucleus. Further microtumors were studied for hypoxia where reactive oxygen species generation demonstrated 15-fold increase as compared to monolayer culture. Drug-sensitivity results showed that microtumors generated on modified dextran–chitosan hydrogel showed resistance to doxorubicin with having 33%–58% increased growth than two-dimensional monolayer model at concentrations of 25–100 µM. In summary, the modified dextran–chitosan scaffold can provide surface chemistry that induces three-dimensional microtumors with physiologically relevant properties to in vivo tumor including growth, morphology, extracellular matrix production, hypoxic phenotype, and drug response. This model can be potentially utilized for drug toxicity studies and cancer disease modeling to understand tumor phenotype and progression.

The Impact of the "Yogic Lifestyle" on Cancer Prognosis and Survival: Can we Target Cancer Stem Cells with Yoga?

Cancer has recently been known to originate from stem cell-like cells, called cancer stem cells (CSCs). Their unique properties of self-duplication, multiplication, as well as migration give the CSC resistance over conventional cancer therapies. Newer therapies are in developmental stage to target these stem cell-like populations and become the vanguard of future treatments. Several complementary and alternative treatments have been used in cancer management as an adjunct to conventional therapy to improve the overall quality of life and reduce recurrence. Yoga stands as the third most popular of all complementary and alternative medicine treatments currently used in cancer patients today. Preliminary results show that yoga modulates neural, hormonal, and immune functions at a cellular level. The scope of this commentary is to discuss the current evidence-based medicine on yoga and its effect on CSCs.

Exploiting the cancer niche: Tumor-associated macrophages and hypoxia as promising synergistic targets for nano-based therapy

The tumor microenvironment has been widely exploited as an active participant in tumor progression. Extensive reports have defined the dual role of tumor-associated macrophages (TAMs) in tumor development. The protumoral effect exerted by the M2 phenotype has been correlated with a negative outcome in most solid tumors. The high infiltration of immune cells in the hypoxic cores of advanced solid tumors leads to a chain reaction of stimuli that enhances the expression of protumoral genes, thrives tumor malignancy, and leads to the emergence of drug resistance. Many studies have shown therapeutic targeting systems, solely to TAMs or tumor hypoxia, however, novel therapeutics that target both features are still warranted. In the present review, we discuss the role of hypoxia in tumor development and the clinical outcome of hypoxia-targeted therapeutics, such as hypoxia-inducible factor (HIF-1) inhibitors and hypoxia-activated prodrugs. Furthermore, we review the state-of-the-art of macrophage-based cancer therapy. We thoroughly discuss the development of novel therapeutics that simultaneously target TAMs and tumor hypoxia. Nano-based systems have been highlighted as interesting strategies for dual modality treatments, with somewhat improved tissue extravasation. Such approach could be seen as a promising strategy to overcome drug resistance and enhance the efficacy of chemotherapy in advanced solid and metastatic tumors, especially when exploiting cell-based nanotherapies. Finally, we provide an in-depth opinion on the importance of exploiting the tumor microenvironment in cancer therapy, and how this could be translated to clinical practice.

Advances in the targeting of HIF-1α and future therapeutic strategies for glioblastoma multiforme (Review)

Cell metabolism can be reprogrammed by tissue hypoxia leading to cell transformation and glioblastoma multiforme (GBM) progression. In response to hypoxia, GBM cells are able to express a transcription factor called hypoxia inducible factor-1 (HIF-1). HIF-1 belongs to a family of heterodimeric proteins that includes HIF-1α and HIF-1β subunits. HIF-1α has been reported to play a pivotal role in GBM development and progression. In the present review, we discuss the role of HIF-1α in glucose uptake, cancer proliferation, cell mobility and chemoresistance in GBM. Evidence from previous studies indicates that HIF-1α regulates angiogenesis, metabolic and transcriptional signaling pathways. Examples of such are the EGFR, PI3K/Akt and MAPK/ERK pathways. It affects cell migration and invasion by regulating glucose metabolism and growth in GBM cells. The present review focuses on the strategies through which to target HIF-1α and the related downstream genes highlighting their regulatory roles in angiogenesis, apoptosis, migration and glucose metabolism for the development of future GBM therapeutics. Combined treatment with inhibitors of HIF-1α and glycolysis may enhance antitumor effects in clinical settings.

Optical imaging probes in oncology

Cancer is a complex disease, characterized by alteration of different physiological molecular processes and cellular features. Keeping this in mind, the possibility of early identification and detection of specific tumor biomarkers by non-invasive approaches could improve early diagnosis and patient management.Different molecular imaging procedures provide powerful tools for detection and non-invasive characterization of oncological lesions. Clinical studies are mainly based on the use of computed tomography, nuclear-based imaging techniques and magnetic resonance imaging. Preclinical imaging in small animal models entails the use of dedicated instruments, and beyond the already cited imaging techniques, it includes also optical imaging studies. Optical imaging strategies are based on the use of luminescent or fluorescent reporter genes or injectable fluorescent or luminescent probes that provide the possibility to study tumor features even by means of fluorescence and luminescence imaging. Currently, most of these probes are used only in animal models, but the possibility of applying some of them also in the clinics is under evaluation.The importance of tumor imaging, the ease of use of optical imaging instruments, the commercial availability of a wide range of probes as well as the continuous description of newly developed probes, demonstrate the significance of these applications. The aim of this review is providing a complete description of the possible optical imaging procedures available for the non-invasive assessment of tumor features in oncological murine models. In particular, the characteristics of both commercially available and newly developed probes will be outlined and discussed.

Mitochondria, cholesterol and cancer cell metabolism

Given the role of mitochondria in oxygen consumption, metabolism and cell death regulation, alterations in mitochondrial function or dysregulation of cell death pathways contribute to the genesis and progression of cancer. Cancer cells exhibit an array of metabolic transformations induced by mutations leading to gain-of-function of oncogenes and loss-of-function of tumor suppressor genes that include increased glucose consumption, reduced mitochondrial respiration, increased reactive oxygen species generation and cell death resistance, all of which ensure cancer progression. Cholesterol metabolism is disturbed in cancer cells and supports uncontrolled cell growth. In particular, the accumulation of cholesterol in mitochondria emerges as a molecular component that orchestrates some of these metabolic alterations in cancer cells by impairing mitochondrial function. As a consequence, mitochondrial cholesterol loading in cancer cells may contribute, in part, to the Warburg effect stimulating aerobic glycolysis to meet the energetic demand of proliferating cells, while protecting cancer cells against mitochondrial apoptosis due to changes in mitochondrial membrane dynamics. Further understanding the complexity in the metabolic alterations of cancer cells, mediated largely through alterations in mitochondrial function, may pave the way to identify more efficient strategies for cancer treatment involving the use of small molecules targeting mitochondria, cholesterol homeostasis/trafficking and specific metabolic pathways.

Hypoxia Stress Response Pathways: Modeling and Targeted Therapy

Hypoxia is a consequence of the decrease in the oxygen reaching the tissues of the body. It is a prominent feature of most solid tumors and is known to promote malignant progression, metastatic capacity, resistance to chemotherapy, and leads to poor patient prognosis. When a cell is under hypoxic stress, a cascade of cell signals is initiated through a family of transcription factors named as hypoxia inducible factors (HIFs). During hypoxia, HIF stabilizes and enters the nucleus and binds to the DNA via the hypoxia response element (HRE) and leads to the translation of downstream genes. The decision of adaptation or cell death depends on the extent of hypoxic stress faced by the cells. Proper understanding of hypoxic stress response is critical for understanding the mechanism of tumor cell adaptation to hypoxia and to develop efficient therapeutic interventions. In this paper, we develop a Boolean network model with targeted drug intervention in a cell that mimics persistent hypoxia. This hypoxic pathway is combined with pathways that help the cell adapt to the situation or undergo cell death. It is linked to apoptosis, cell survival, and energy production via the p53/Mdm2, PI3k/Akt/mTOR, and Glycolysis/TCA cycle pathways, respectively. In this model, we have incorporated eight known anticancer drugs that target these pathways. Through simulations, we have identified drug combinations that provided overall benefits to the cell in comparison to the no intervention case. Where applicable, the behavior predicted by this model is in agreement with experimental observations from the published literature.

Neutralizing S1P inhibits intratumoral hypoxia, induces vascular remodelling and sensitizes to chemotherapy in prostate cancer

Hypoxia promotes neovascularization, increased tumor growth, and therapeutic resistance. The transcription factor, hypoxia-inducible factor 1α (HIF-1α), has been reported as the master driver of adaptation to hypoxia. We previously identified the sphingosine kinase 1/sphingosine 1-phosphate (SphK1/S1P) pathway as a new modulator of HIF-1α under hypoxia. Taking advantage of a monoclonal antibody neutralizing extracellular S1P (sphingomab), we report that inhibition of S1P extracellular signaling blocks HIF-1α accumulation and activity in several cancer cell models exposed to hypoxia. In an orthotopic xenograft model of prostate cancer, we show that sphingomab reduces hypoxia and modifies vessel architecture within 5 days of treatment, leading to increased intratumoral blood perfusion. Supporting the notion that a transient vascular normalization of tumor vessels is the mechanism by which sphingomab exerts its effects, we demonstrate that administration of the antibody for 5 days before chemotherapy is more effective at local tumor control and metastatic dissemination than any other treatment scheduling. These findings validate sphingomab as a potential new normalization agent that could contribute to successful sensitization of hypoxic tumors to chemotherapy.

MicroRNA-454 regulates stromal cell derived factor-1 in the control of the growth of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant carcinoma with an extremely high lethality. We recently reported that hypoxia-inducible factor 1 (HIF-1) targets quiescin sulfhydryl oxidase 1 to facilitate PDAC cell growth and invasion. Here, we analyzed the control of another HIF-1 target, stromal cell derived factor-1 (SDF-1), in PDAC cells. We detected significantly more CD68+ macrophages in the PDAC, compared to normal human pancreas (NT). Since macrophages are recruited to the tissue through their expression of CXCR4 in response to SDF-1, we thus examined the SDF-1 levels in the PDAC specimens. Surprisingly, the SDF-1 protein but not mRNA significantly increased in PDAC, compared to NT. Moreover, a SDF-1-targeting microRNA, miR-454, was found to decrease in PDAC. Promoter luciferase assay confirmed that bindings of miR-454 to 3'-UTR of SDF-1 mRNAs inhibited SDF-1 protein translation. Co-culture of bone marrow derived macrophages and miR-454-modified PDAC cells in a transwell migration experiment showed that macrophages migrated less towards miR-454-overexpressing PDAC cells, and migrated more towards miR-454-depleted cells. Implanted miR-454-depleted PDAC cells grew significantly faster than control, while implanted miR-454-overexpressing PDAC cells grew significantly slower than control. Together, our data suggest that miR-454 may regulate SDF-1 in the control of the growth of PDAC.

Phenanthroindolizidine alkaloids from Tylophora atrofolliculata with hypoxia-inducible factor-1 (HIF-1) inhibitory activity

Phenanthroindolizidine alkaloids from T. atrofolliculata with potent HIF-1 inhibitory effects.

Macrophages play an essential role in the long effects of low-dose photodynamic therapy on vessel permeability

Low-dose photodynamic therapy (L-PDT) has been used to transiently increase the permeability of tumor vessels to improve the delivery of chemotherapeutic drugs to lung tumors. However, the effects of L-PDT in a long-term on delivery of chemotherapeutic drugs are unknown. In this study, we studied this question as well as the underlying mechanisms. We found that the effects of L-PDT on tumor vessel permeability appeared to be prolonged. Moreover, L-PDT significantly increased the number of tumor associated macrophages, and appeared to induce macrophage polarization to a M1 phenotype. Further analyses showed that L-PDT upregulated stromal cell-derived factor 1 (SDF-1) in tumor to recruit macrophages through a SDF-1/Chemokine (C-X-C Motif) Receptor 4 (CXCR4) axis, which accounted for the prolonged effects of L-PDT on vessel permeability. Application of a specific CXCR4 inhibitor significantly suppressed the L-PDT-induced macrophage recruitment, resulting in abolishment of the prolonged effects of L-PDT on vessel permeability. Furthermore, the inhibitory effects of Liporubicin™ on the growth of the implanted tumor in L-PDT-treated mice were significantly attenuated by CXCR4 inhibition. Thus, our data demonstrate a previously unappreciated long-lasting effect of L-PDT on vessel permeability, and suggest that this long-lasting effects of L-PDT treatment on vessel permeability may result from modulation of macrophage recruitment and polarization. Hence, L-PDT may be a promising method to assist chemotherapeutic approaches.

The expression level of the transcription factor Aryl hydrocarbon receptor nuclear translocator (ARNT) determines cellular survival after radiation treatment

Background

Tumour hypoxia promotes radioresistance and is associated with poor prognosis. The transcription factor Aryl hydrocarbon receptor nuclear translocator (ARNT), also designated as Hypoxia-inducible factor (HIF)-1β, is part of the HIF pathway which mediates cellular adaptations to oxygen deprivation and facilitates tumour progression.

The subunits HIF-1α and ARNT are key players within this pathway. HIF-1α is regulated in an oxygen-dependent manner whereas ARNT is considered to be constitutively expressed. However, there is mounting evidence that certain tumour cells are capable to elevate ARNT in hypoxia which suggests a survival benefit.

Therefore the objective of this study was to elucidate effects of an altered ARNT expression level on the cellular response to radiation.

Methods

Different human cell lines (Hep3B, MCF-7, 786-Owt, 786-Ovhl, RCC4wt and RCC4vhl) originating from various tumour entities (Hepatocellular carcinoma, breast cancer and renal cell carcinoma respectively) were X-irradiated using a conventional linear accelerator. Knockdown of ARNT expression was achieved by transient siRNA transfection. Complementary experiments were performed by forced ARNT overexpression using appropriate plasmids. Presence/absence of ARNT protein was confirmed by Western blot analysis. Clonogenic survival assays were performed in order to determine cellular survival post irradiation. Statistical comparison of two groups was achieved by the unpaired t-test.

Results

The results of this study indicate that ARNT depletion renders tumour cells susceptible to radiation whereas overexpression of this transcription factor confers radioresistance.

Conclusions

These findings provide evidence to consider ARNT as a drug target and as a predictive marker in clinical applications concerning the response to radiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-015-0539-9) contains supplementary material, which is available to authorized users.

Hypoxia-induced autophagy mediates cisplatin resistance in lung cancer cells

Hypoxia which commonly exists in solid tumors, leads to cancer cells chemoresistance via provoking adaptive responses including autophagy. Therefore, we sought to evaluate the role of autophagy and hypoxia as well as the underlying mechanism in the cisplatin resistance of lung cancer cells. Our study demonstrated that hypoxia significantly protected A549 and SPC-A1 cells from cisplatin-induced cell death in a Hif-1α- and Hif-2α- dependent manner. Moreover, compared with normoxia, cisplatin-induced apoptosis under hypoxia was markedly reduced. However, when autophagy was inhibited by 3-MA or siRNA targeted ATG5, this reduction was effectively attenuated, which means autophagy mediates cisplatin resisitance under hypoxia. In parallel, we showed that hypoxia robustly augmented cisplatin-induced autophagy activation, accompanying by suppressing cisplatin-induced BNIP3 death pathways, which was due to the more efficient autophagic process under hypoxia. Consequently, we proposed that autophagy was a protective mechanism after cisplatin incubation under both normoxia and hypoxia. However, under normoxia, autophagy activation ‘was unable to counteract the stress induced by cisplatin, therefore resulting in cell death, whereas under hypoxia, autophagy induction was augmented that solved the cisplatin-induced stress, allowing the cells to survival. In conclusion, augmented induction of autophagy by hypoxia decreased lung cancer cells susceptibility to cisplatin-induced apoptosis.

Andrographolide inhibits hypoxia-inducible factor-1 through phosphatidylinositol 3-kinase/AKT pathway and suppresses breast cancer growth

Hypoxia-inducible factor-1 (HIF-1) is a master regulator of the transcriptional response to hypoxia. HIF-1α is one of the most compelling anticancer targets. Andrographolide (Andro) was newly identified to inhibit HIF-1 in T47D cells (a half maximal effective concentration [EC₅₀] of 1.03×10⁻⁷ mol/L), by a dual-luciferase reporter assay. It suppressed HIF-1α protein and gene accumulation, which was dependent on the inhibition of upstream phosphatidylinositol 3-kinase (PI3K)/AKT pathway. It also abrogated the expression of HIF-1 target vascular endothelial growth factor (VEGF) gene and protein. Further, Andro inhibited T47D and MDA-MB-231 cell proliferation and colony formation. In addition, it exhibited significant in vivo efficacy and antitumor potential against the MDA-MB-231 xenograft in nude mice. In conclusion, these results highlighted the potential effects of Andro, which inhibits HIF-1, and hence may be developed as an antitumor agent for breast cancer therapy in future.

Hypoxic signature of microRNAs in glioblastoma: insights from small RNA deep sequencing

Background

Hypoxia is a critical aspect of the glioma microenvironment and has been associated with poor prognosis and resistance to various therapies. However, the mechanisms responsible for hypoxic survival of glioma cells remain unclear. Recent studies strongly suggest that microRNAs act as critical mediators of the hypoxic response. We thus hypothesized their prominent role in hypoxia resistance in glioblastoma (GBM) and aimed to identify those.

Results

With this study, we present the first detailed analysis of small RNA transcriptome of cell line U87MG, a grade IV glioma cell line, and its alteration under hypoxic condition. Based on deep sequencing and microarray data, we identify a set of hypoxia regulated microRNAs, with the miR-210-3p and its isomiRs showing highest induction in GBM cell lines U87MG and U251MG. We show miR-210-3p, miR-1275, miR-376c-3p, miR-23b-3p, miR-193a-3p and miR-145-5p to be up-regulated, while miR-92b-3p, miR-20a-5p, miR-10b-5p, miR-181a-2-3p and miR-185-5p are down-regulated by hypoxia. Interestingly, certain hypoxia-induced miRNAs are also known to be over-expressed in GBM tumors, suggesting that hypoxia may be one of the factors involved in establishing the miRNA signature of GBM. Transcription factor binding sites for Hypoxia inducible factor 1 A (HIF1A) were identified in the promoter region (5 kb upstream) of 30 hypoxia-induced miRNAs. HIF-1A over-expression and silencing studies show regulation of specific miRNAs, including miR-210-3p, to be HIF1A dependent. On the other hand, miR-210-3p leads to an increase in transcriptional activity of HIF and its target genes vascular endothelial growth factor (VEGF) and carbonic anhydrase 9 (CA9). MiR-210-3p levels were found to be high in GBM patient samples and showed good correlation with the known hypoxia markers CA9 and VEGF. We show that miR-210-3p promotes hypoxic survival and chemoresistance in GBM cells and targets a negative regulator of hypoxic response, HIF3A. Additionally, a total of 139 novel miRNAs were discovered by the analysis of deep sequencing data and three of these were found to be differentially expressed under hypoxia.

Conclusions

Overall, our study reveals a novel miRNA signature of hypoxia in GBM and suggests miR-210-3p to be an oncogenic player and a novel potential intrinsic marker of hypoxia in glioblastoma.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-686) contains supplementary material, which is available to authorized users.

Biological characteristics of prostate cancer cells are regulated by hypoxia-inducible factor 1α

Hypoxia-inducible factor (HIF)-1α has been reported to be associated with malignancy in a number of types of cancer. However, the role of HIF-1 α in the regulation of prostate cancer (PCa) growth has yet to be elucidated. The present study aimed to investigate the effect of HIF-1α on the biological characteristics of the PCa PC3 cell line. Full-length (fL) HIF-1α and dominant-negative (dn) HIF-1α were transfected into PC3 cells. The expression of HIF-1α and its downstream genes, including vascular endothelial growth factor (VEGF), erythropoietin (EPO) and CXC chemokine receptor 4 (CXCR4), were detected using western blot analysis. Cell proliferation, apoptosis and migration were assessed using MTT, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and Boyden chamber assays. The expression of VEGF, EPO and CXCR4 was found to be upregulated in the fL HIF-1α-transfected PC3 cells and downregulated in the dn HIF-1α-transfected PC3 cells. The overexpression of HIF-1α was observed to enhance cell proliferation and migration and decrease docetaxol-induced cell apoptosis. However, dn HIF-1α was found to attenuate cell proliferation and migration, and promote docetaxol-induced cell apoptosis. These findings indicate that HIF-1α regulates the proliferation, apoptosis and migration of PC3 cells, at least in part, by regulating the expression of its target genes, including VEGF, EPO and CXCR4. Thus, the use of HIF-1α inhibitors may be a promising therapy for the treatment of PCa.

Hypoxia-inducible aryl hydrocarbon receptor nuclear translocator (ARNT) (HIF-1β): is it a rare exception?

The aryl hydrocarbon receptor nuclear translocator (ARNT), also designated as hypoxia-inducible factor (HIF)-1β, plays a pivotal role in the adaptive responses to (micro-)environmental stresses such as dioxin exposure and oxygen deprivation (hypoxia). ARNT belongs to the group of basic helix-loop-helix (bHLH)-Per-ARNT-Sim (PAS) transcription factors, which act as heterodimers. ARNT serves as a common binding partner for the aryl hydrocarbon receptor (AhR) as well as HIF-α subunits. HIF-α proteins are regulated in an oxygen-dependent manner, whereas ARNT is generally regarded as constitutively expressed, meaning that neither the arnt mRNA nor the protein level is influenced by hypoxia (despite the name HIF-1β). However, there is emerging evidence that tumor cells derived from different entities are able to upregulate ARNT, especially under low oxygen tension in a cell-specific manner. The objective of this review is therefore to highlight and summarize current knowledge regarding the hypoxia-dependent upregulation of ARNT, which is in sharp contrast to the general point of view described in the literature. Elucidating the mechanism behind this rare cellular attribute will help us to gain new insights into HIF biology and might provide new strategies for anti-cancer therapeutics. In conclusion, putative treatment effects on ARNT should be taken into account while studying the HIF pathway. This step is of great importance when ARNT is intended to serve as a loading control or as a reference.

SIRT2 regulates tumour hypoxia response by promoting HIF-1α hydroxylation

Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that has a central role in the regulation of tumour metabolism under hypoxic conditions. HIF-1α stimulates glycolytic energy production and promotes tumour growth. Sirtuins are NAD(+)-dependent protein deacetylases that regulate cellular metabolism in response to stress; however, their involvement in the hypoxic response remains unclear. In this study, it is shown that SIRT2-mediated deacetylation of HIF-1α regulates its stability in tumour cells. SIRT2 overexpression destabilized HIF-1α under hypoxic conditions, whereas HIF-1α protein levels were high in SIRT2-deficient cells. SIRT2 directly interacted with HIF-1α and deacetylated Lys709 of HIF-1α. Deacetylation of HIF-1α by SIRT2 resulted in increased binding affinity for prolyl hydroxylase 2, a key regulator of HIF-1α stability, and increased HIF-1α hydroxylation and ubiquitination. Moreover, a pharmacological agent that increased the intracellular NAD(+)/NADH ratio led to the degradation of HIF-1α by increasing SIRT2-mediated deacetylation and subsequent hydroxylation. These findings suggest that SIRT2-mediated HIF-1α deacetylation is critical for the destablization of HIF-1α and the hypoxic response of tumour cells.

Paradoxical regulation of hypoxia inducible factor-1α (HIF-1α) by histone deacetylase inhibitor in diffuse large B-cell lymphoma

Hypoxia inducible factor (HIF) is important in cancer, as it regulates various oncogenic genes as well as genes involved in cell survival, proliferation, and migration. Elevated HIF-1 protein promotes a more aggressive tumor phenotype, and greater HIF-1 expression has been demonstrated to correlate with poorer prognosis, increased risk of metastasis and increased mortality. Recent reports suggest that HIF-1 activates autophagy, a lysosomal degradation pathway which may promote tumor cell survival. We show here that HIF-1α expression is constitutively active in multiple diffuse large B cell lymphoma (DLBCL) cell lines under normoxia and it is regulated by the PI3K/AKT pathway. PCI-24781, a pan histone deacetylase inhibitor (HDACI), enhanced accumulation of HIF-1α and induced autophagy initially, while extended incubation with the drug resulted in inhibition of HIF-1α. We tested the hypothesis that PCI-24781- induced autophagy is mediated by HIF-1α and that inhibition of HIF-1α in these cells results in attenuation of autophagy and decreased survival. We also provide evidence that autophagy serves as a survival pathway in DLBCL cells treated with PCI-24781 which suggests that the use of autophagy inhibitors such as chloroquine or 3-methyl adenine in combination with PCI-24781 may enhance apoptosis in lymphoma cells.

Neuronal cell fate decisions: O2 and CO2 sensing neurons require egl-13/Sox5

We recently conducted a study that aimed to describe the differentiation mechanisms used to generate O2 and CO2 sensing neurons in C. elegans. We identified egl-13/Sox5 to be required for the differentiation of both O2 and CO2 sensing neurons. We found that egl-13 functions cell autonomously to drive O2 and CO2 sensing neuron fate and is therefore essential for O2 and CO2 sensing-induced behaviors. Through systematic dissection of the egl-13 promoter we identified upstream regulators of egl-13 and proposed a model of how differentiation of O2 and CO2 sensing neurons is regulated. In this commentary we discuss our findings and open questions we wish to address in future studies.

A cyclic peptide inhibitor of HIF-1 heterodimerization that inhibits hypoxia signaling in cancer cells

Hypoxia inducible factor-1 (HIF-1) is a heterodimeric transcription factor that acts as the master regulator of cellular response to reduced oxygen levels, thus playing a key role in the adaptation, survival, and progression of tumors. Here we report cyclo-CLLFVY, identified from a library of 3.2 million cyclic hexapeptides using a genetically encoded high-throughput screening platform, as an inhibitor of the HIF-1α/HIF-1β protein–protein interaction in vitro and in cells. The identified compound inhibits HIF-1 dimerization and transcription activity by binding to the PAS-B domain of HIF-1α, reducing HIF-1-mediated hypoxia response signaling in a variety of cell lines, without affecting the function of the closely related HIF-2 isoform. The reported cyclic peptide demonstrates the utility of our high-throughput screening platform for the identification of protein–protein interaction inhibitors, and forms the starting point for the development of HIF-1 targeted cancer therapeutics.

Molecular-targeted therapy hypoxia in head and neck squamous cell carcinoma patients

Despite advances in surgical techniques, radiotherapy, and chemotherapy, 5-year survival in patients with late-stage head and neck squamous cell carcinoma (HNSCC) have not improved significantly over the past decades. HNSCC tumors are commonly associated with hypoxia, which is characterized by an acute and/or chronic decline in oxygen tension. Hypoxia is an important cancer-aggravating microenvironmental factor that contributes to malignant behaviors such as acquisition of antiapoptotic ability by cancer cells and tumor progression, invasion, metastasis, and resistance to chemotherapy and radiotherapy. Numerous studies have assessed tumor hypoxia and identified molecular markers that are promising therapeutic targets in HNSCC cases. Moreover, investigators have suggested a number of molecular strategies to target cell processes critical to hypoxia development in HNSCC patients via the direct or indirect regulation of hypoxia-inducible factor-1α expression in cancer cells. In this review, we described recent advances in the identification and development of molecular-targeted therapy targeting hypoxia in HNSCC patients.

Dual inhibition of plasminogen kringle 5 on angiogenesis and chemotaxis suppresses tumor metastasis by targeting HIF-1α pathway

We had demonstrated that plasminogen kringle 5 (K5), a potent angiogenic inhibitor, inhibited retinal neovascularization and hepatocellular carcinoma growth by anti-angiogenesis. The current study investigated the effects and the underlying mechanisms of K5 on both tumor growth and spontaneous pulmonary metastasis in Lewis lung carcinoma (LLC) implanted mouse model. Similarly, K5 could decrease expression of VEGF in LLC cells and grafted tissues and suppress tumor angiogenesis and growth. K5 had no direct effect on proliferation and apoptosis of LLC. However, K5 could significantly inhibit SDF-1α-induced chemotaxis movement of LLC cells and resulted in a great reduction of surface metastatic nodules and micrometastases in the lungs of LLC tumor-bearing mice. K5 also decreased expression of chemokine (C-X-C motif) receptor 4 (CXCR4) in LLC cells and grafted tissues. Furthermore, K5 down-regulated SDF-1α expression in metastatic lung tissues of LLC-bearing mice. Therefore, K5 may suppress tumor pulmonary metastasis through inhibiting SDF-1α-CXCR4 chemotaxis movement and down-regulation of VEGF. Moreover, the role of hypoxia inducible factor-1α (HIF-1α), a crucial transcriptional factor for both VEGF and CXCR4 expression, was evaluated. The siRNA of HIF-1α attenuated expression of VEGF and CXCR4 and inhibited LLC migration. K5 decreased HIF-1α protein level and impaired nuclear HIF-1α accumulation. These results showed for the first time that K5 inhibits LLC growth and metastasis via the dual effects of anti-angiogenesis and suppression of tumor cell motility by targeting the pivotal molecule, HIF-1α.

Hypoxia downregulates the expression of cell surface MICA without increasing soluble MICA in osteosarcoma cells in a HIF-1α-dependent manner

Tumor cells express NKG2D ligands on their cell surface, which are the ligands of the activating receptor, NKG2D, that is expressed on the surface of NK cells. The binding of NK cells to tumor cells through the interaction of NKG2D and its ligands induces the cytolysis of the tumor cells. In the present study, we investigated the effects of hypoxia on the expression of NKG2D ligands on the surface of human osteosarcoma cells using three cell lines. To produce hypoxic and normoxic conditions, the osteosarcoma cell lines were cultured under 1 and 20% O2 conditions, respectively. The osteosarcoma cells expressed NKG2D ligands such as MHC class I-related chain molecules A and B (MICA and MICB) and the UL16-binding proteins 1, 2 and 3 (ULBP 1, 2 and 3). MICA was the most frequently expressed NKG2D ligand in the osteosarcoma cells. Hypoxia decreased the expression of cell surface MICA only without increasing the secretion of soluble MICA, which is produced by proteolytic cleavage of cell surface MICA. Hypoxia consistently decreased the susceptibility of the osteosarcoma cells to the cytotoxicity of the NK cells. Hypoxia induced the expression of hypoxia-inducible factor-1α (HIF-1α), and knockdown of the expression of HIF-1α using small interfering RNA increased the expression of cell surface MICA and concomitantly increased the level of soluble MICA. Hypoxia decreased the production of nitric oxide (NO) metabolites (nitrite and nitrate), thus, indicating a decreasing effect on NO production. However, a NO donor, NOC18, decreased the expression of cell surface MICA without any apparent effects on the expression of HIF-1α under both hypoxic and normoxic conditions. The present results indicate that hypoxia downregulates the expression of cell surface MICA without increasing the level of soluble MICA in a HIF-1α-dependent manner and suggest that the effects of hypoxia are not linked to the hypoxia-induced reduction of NO production.

Dietary administration of scallion extract effectively inhibits colorectal tumor growth: cellular and molecular mechanisms in mice

Colorectal cancer is a common malignancy and a leading cause of cancer death worldwide. Diet is known to play an important role in the etiology of colon cancer and dietary chemoprevention is receiving increasing attention for prevention and/or alternative treatment of colon cancers. Allium fistulosum L., commonly known as scallion, is popularly used as a spice or vegetable worldwide, and as a traditional medicine in Asian cultures for treating a variety of diseases. In this study we evaluated the possible beneficial effects of dietary scallion on chemoprevention of colon cancer using a mouse model of colon carcinoma (CT-26 cells subcutaneously inoculated into BALB/c mice). Tumor lysates were subjected to western blotting for analysis of key inflammatory markers, ELISA for analysis of cytokines, and immunohistochemistry for analysis of inflammatory markers. Metabolite profiles of scallion extracts were analyzed by LC-MS/MS. Scallion extracts, particularly hot-water extract, orally fed to mice at 50 mg (dry weight)/kg body weight resulted in significant suppression of tumor growth and enhanced the survival rate of test mice. At the molecular level, scallion extracts inhibited the key inflammatory markers COX-2 and iNOS, and suppressed the expression of various cellular markers known to be involved in tumor apoptosis (apoptosis index), proliferation (cyclin D1 and c-Myc), angiogenesis (VEGF and HIF-1α), and tumor invasion (MMP-9 and ICAM-1) when compared with vehicle control-treated mice. Our findings may warrant further investigation of the use of common scallion as a chemopreventive dietary agent to lower the risk of colon cancer.

Role of the VEGF/VEGFR axis in cancer biology and therapy

New vessel formation (angiogenesis) is an essential physiological process for embryologic development, normal growth, and tissue repair. Angiogenesis is tightly regulated at the molecular level; however, this process is dysregulated in several pathological conditions such as cancer. The imbalance between pro- and antiangiogenic signaling molecules within tumors creates an abnormal vascular network that is characterized by dilated, tortuous, and leaky vessels. The pathophysiological consequences of these vascular abnormalities include temporal and spatial heterogeneity in tumor blood flow, oxygenation, and increased tumor interstitial fluid pressure. The resultant microenvironment deeply impacts on tumor progression, and also leads to a reduction in therapy efficacy. The discovery of vascular endothelial growth factor (VEGF) as a major driver of tumor angiogenesis has led to efforts to develop novel therapeutics aimed at inhibiting its activity. Anti-VEGF therapy has become an important option for the management of several human malignancies; however, a significant number of patients do not respond to anti-VEGF therapy when used either as single agent or in combination with chemotherapy. In addition, the benefit of antiangiogenic therapy is relatively short lived and the majority of patients relapse and progress. An increasing amount of reports suggest several potential mechanisms of resistance to antiangiogenic therapy including, but not limited to, tumor hypoxia. This chapter discusses the role of the VEGF axis in tumor biology and highlights the clinical application of anti-VEGF therapies elaborating on pitfalls and strategies to improve clinical outcome.

Design and in vitro activities of N-alkyl-N-[(8-R-2,2-dimethyl-2H-chromen-6-yl)methyl]heteroarylsulfonamides, novel, small-molecule hypoxia inducible factor-1 pathway inhibitors and anticancer agents

The hypoxia inducible factor (HIF) pathway is an attractive target for cancer, as it controls tumor adaptation to growth under hypoxia and mediates chemotherapy and radiation resistance. We previously discovered 3,4-dimethoxy-N-[(2,2-dimethyl-2H-chromen-6-yl)methyl]-N-phenylbenzenesulfonamide as a novel, small-molecule HIF-1 pathway inhibitor in a high-throughput cell-based assay, but its in vivo delivery is hampered by poor aqueous solubility (0.009 μM in water; log P(7.4) = 3.7). Here we describe the synthesis of 12 N-alkyl-N-[(8-R-2,2-dimethyl-2H-chromen-6-yl)methyl]heteroarylsulfonamides, which were designed to possess optimal lipophilicities and aqueous solubilities by in silico calculations. Experimental log P(7.4) values of 8 of the 12 new analogs ranged from 1.2-3.1. Aqueous solubilities of three analogs were measured, among which the most soluble N-[(8-methoxy-2,2-dimethyl-2H-chromen-6-yl)methyl]-N-(propan-2-yl)pyridine-2-sulfonamide had an aqueous solubility of 80 μM, e.g., a solubility improvement of ∼9000-fold. The pharmacological optimization had limited impact on drug efficacy as the compounds retained IC(50) values at or below 5 μM in our HIF-dependent reporter assay.

Overcoming disappointing results with antiangiogenic therapy by targeting hypoxia

Cancer cells rely on angiogenesis to fulfil their need for oxygen and nutrients; hence, agents targeting angiogenic pathways and mediators have been investigated as potential cancer drugs. Although this strategy has demonstrated delayed tumour progression--leading to progression-free survival and overall survival benefits compared with standard therapy--in some patients, the results are more modest than predicted. A significant number of patients either do not respond to antiangiogenic agents or fairly rapidly develop resistance to them, which raises questions about how resistance develops and how it can be overcome. Furthermore, whether cancers, once they develop resistance, become more invasive or lead to metastatic disease remains unclear. Several mechanisms of resistance have been recently proposed and emerging evidence indicates that, under certain experimental conditions, antiangiogenic agents increase intratumour hypoxia by promoting vessel pruning and inhibiting neoangiogenesis. Indeed, several studies have highlighted the possibility that inhibitors of VEGF (and its receptors) can promote an invasive metastatic switch, in part by creating an increasingly hypoxic tumour microenvironment. As a potential remedy, a number of therapeutic approaches have been investigated that target the hypoxic tumour compartment to improve the clinical outcome of antiangiogenic therapy.