Targeting hypoxia cell signaling for cancer therapy

Oxygen Sensor-Guided Fine Needle Biopsy Studies of Human Cancer Xenografts in Mice

An oxygen sensor-mounted fine-needle biopsy tool was used for in vivo measurement of oxygen levels in tumor xenografts. The system provides a means of measuring the oxygen content in harvested tumor tissue from specific locations. Oxygen in human tumor xenografts in a murine model was observed for over 1 min. Tissues were mapped in relation to oxygen tension (pO2) readings and sampled for conventional cytological examination. Careful modeling of the pO2 readings over 60 seconds yielded a diffusion coefficient for oxygen at the sensor tip, providing additional diagnostic information about the tissue before sampling. Oxygen level measurement may provide a useful adjunct to the use of biomarkers in tumor diagnosis.

Mild exposure to fine particulate matter promotes angiogenesis in non-small cell lung carcinoma

Fine particulate matter (PM2.5) is associated with public health problems worldwide. Especially, PM2.5 induces epigenetic and microenvironmental changes in lung cancer. Angiogenesis is important for the development and growth of cancer and is mediated by angiogenic factors, including vascular endothelial growth factor. However, the effects of mild PM2.5 exposure on angiogenesis in lung cancer remain unclear. In this study, we examined angiogenic effects using relatively lower concentrations of PM2.5 than in other studies and found that PM2.5 increased angiogenic activities in both endothelial cells and non-small cell lung carcinoma cells. PM2.5 also promoted the growth and angiogenesis of lung cancer via the induction of hypoxia-inducible factor-1α (HIF-1α) in a xenograft mouse tumor model. Angiogenic factors, including vascular endothelial growth factor (VEGF), were highly expressed in lung cancer patients in countries with high PM2.5 levels in the atmosphere, and high expression of VEGF in lung cancer patients lowered the survival rate. Collectively, these results provide new insight into the mechanisms by which mild exposure to PM2.5 is involved in HIF-1α-mediated angiogenesis in lung cancer patients.

Expression of HIF-1α/PKM2 axis correlates to biological and clinical significance in papillary thyroid carcinoma

hypoxia inducible factor-1α (HIF-1α) and pyruvate kinase M2 (PKM2) are 2 key metabolic regulatory proteins, they could engage in a positive feedback loop and drive cancer growth by enhancing glycolysis. This study aimed to investigate the expression of HIF-1α and PKM2 in papillary thyroid carcinoma (PTC) and its correlation with the patients clinicopathological features and with tumor invasion and metastasis. Surgically resected PTC specimens from 60 patients were collected. The expression levels of HIF-1α and PKM2 in PTC tissues were examined by immunohistochemical staining. The full clinical records of all patients were collected to analyze the relevance between HIF-1α and PKM2 expressions and the clinical pathological features of PTC. The results showed that the positive expressions of HIF-1α, PKM2, and HIF-1α/PKM2 axis (HIF-1α+/PKM2+) were all significantly higher in PTC than those in normal thyroid follicular epithelium, and a positive correlation was found between HIF-1α and PKM2 in PTC. Further analysis showed that in PTC, the positive expression of HIF-1α and HIF-1α/PKM2 axis (HIF-1α+/PKM2+) were significantly associated with bigger tumor size, moreover, the positive expressions of HIF-1α, PKM2 and HIF-1α/PKM2 axis (HIF-1α+/PKM2+) were all correlated with capsular invasion and lymph node metastasis, while they were all not correlated with gender, sex and multicentricity of tumor. This study identified HIF-1a/PKM2 axis as potential molecular marker for predicting the invasion and progression of papillary thyroid carcinoma.

Research progress on tumor hypoxia-associative nanomedicine

Hypoxia at the solid tumor site is generally related to the unrestricted proliferation and metabolism of cancerous cells, which can cause tumor metastasis and aggravate tumor progression. Besides, hypoxia plays a substantial role in tumor treatment, and it is one of the main reasons that malignant tumors are difficult to cure and have a poor prognosis. On account of the tumor specific hypoxic environment, many hypoxia-associative nanomedicine have been proposed for tumor treatment. Considering the enhanced targeting effect, designing hypoxia-associative nanomedicine can not only minimize the adverse effects of drugs on normal tissues, but also achieve targeted therapy at the lesion site. Mostly, there can be three strategies for the treatment of hypoxic tumor, including improvement of hypoxic environment, hypoxia responsive drug release and hypoxia activated prodrug. The review describes the design principle and applications of tumor hypoxia-associative nanomedicine in recent years, and also explores its development trends in solid tumor treatment. Moreover, this review presents the current limitations of tumor hypoxia-associative nanomedicine in chemotherapy, radiotherapy, photodynamic therapy, sonodynamic therapy and immunotherapy, which may provide a reference for clinic translation of tumor hypoxia-associative nanomedicine.

Recent Developments in the Study of the Microenvironment of Cancer and Drug Delivery

Cancer is characterized by disrupted molecular variables caused by cells that deviate from regular signal transduction. The uncontrolled segment of such cancerous cells annihilates most of the tissues that contact them. Gene therapy, immunotherapy, and nanotechnology advancements have resulted in novel strategies for anticancer drug delivery. Furthermore, diverse dispersion of nanoparticles in normal stroma cells adversely affects the healthy cells and disrupts the crosstalk of tumour stroma. It can contribute to cancer cell progression inhibition and, conversely, to acquired resistance, enabling cancer cell metastasis and proliferation. The tumour's microenvironment is critical in controlling the dispersion and physiological activities of nano-chemotherapeutics which is one of the targeted drug therapy. As it is one of the methods of treating cancer that involves the use of medications or other substances to specifically target and kill off certain subsets of malignant cells. A targeted therapy may be administered alone or in addition to more conventional methods of care like surgery, chemotherapy, or radiation treatment. The tumour microenvironment, stromatogenesis, barriers and advancement in the drug delivery system across tumour tissue are summarised in this review.

Hypoxia signaling pathway: A central mediator in endocrine tumors

Adequate oxygen levels are essential for the functioning and maintenance of biological processes in virtually every cell, albeit based on specific need. Thus, any change in oxygen pressure leads to modulated activation of the hypoxia pathway, which affects numerous physiological and pathological processes, including hematopoiesis, inflammation, and tumor development. The Hypoxia Inducible Factors (HIFs) are essential transcription factors and the driving force of the hypoxia pathway; whereas, their inhibitors, HIF prolyl hydroxylase domain (PHDs) proteins are the true oxygen sensors that critically regulate this response. Recently, we and others have described the central role of the PHD/HIF axis in various compartments of the adrenal gland and its potential influence in associated tumors, including pheochromocytomas and paragangliomas. Here, we provide an overview of the most recent findings on the hypoxia signaling pathway in vivo, including its role in the endocrine system, especially in adrenal tumors.

A reciprocal feedback loop between HIF-1α and HPIP controls phenotypic plasticity in breast cancer cells

While phenotypic plasticity is a critical factor contributing to tumor heterogeneity, molecular mechanisms underlying this process are largely unknown. Here we report that breast cancer cells display phenotypic diversity in response to hypoxia or normoxia microenvironments by operating a reciprocal positive feedback regulation of HPIP and HIF-1α. We show that under hypoxia, HIF-1α induces HPIP expression that establishes cell survival, and also promotes cell migration/invasion, EMT and metastatic phenotypes in breast cancer cells. Mechanistic studies revealed that HPIP interacts with SRP14, a component of signal recognition particle, and stimulates MMP9 synthesis under hypoxic stress. Whereas, in normoxia, HPIP stabilizes HIF-1α, causing the Warburg effect to support cell growth. Concurrently, mathematical modelling corroborates this reciprocal feedback loop in enabling cell-state transitions in cancer cells. Clinical data indicate that elevated levels of HPIP and HIF-1α correlate with unfavorable prognosis and shorter survival rates in breast cancer subjects. Together, this data shows a reciprocal positive feedback loop between HPIP and HIF-1α that was unknown hitherto. It unveils how the tumor microenvironment influences phenotypic plasticity that has an impact on tumor growth and metastasis and, further signifies considering this pathway as a potential therapeutic target in breast cancer.

β-arrestin 2 stimulates degradation of HIF-1α and modulates tumor progression of glioblastoma

The basic function of β-arrestin 2 (Arrb2) is to negatively regulate the G-protein-coupled receptor signaling pathway through facilitating receptor desensitization and internalization. Arrb2 has also been reported to play various roles in cancer pathology including the proliferation, migration, invasion, metastasis, and apoptosis of solid tumors. However, the molecular mechanisms underlying the tumorigenic capacities of Arrb2 have not been elucidated. Here, we show a novel function of Arrb2: Arrb2 facilitates the degradation of HIF-1α, which is a master regulator of oxygen homeostasis. We also demonstrate that Arrb2 interacts with HIF-1α and stimulates ubiquitin-mediated 26S proteasomal degradation of HIF-1α by recruiting PHD2 and pVHL. Overexpression of Arrb2 in human glioblastoma cells suppresses HIF-1α signaling, tumor growth, and angiogenesis. Consistent with this antitumorigenic effect of Arrb2, low Arrb2 expression levels correlate with high HIF-1α expression and poor glioblastoma patient survival. These results collectively reveal a novel function of Arrb2 in the oxygen-sensing mechanism that directly regulates HIF-1α stability in human cancers and suggest Arrb2 as a new potential therapeutic target for glioblastoma.

Modulating tumor-associated macrophages to enhance the efficacy of immune checkpoint inhibitors: A TAM-pting approach

Tumor-associated macrophages (TAM) plasticity and diversity are both essential hallmarks of the monocyte-macrophage lineage and the tumor-derived inflammation. TAM exemplify the perfect adaptable cell with dynamic phenotypic modifications that reflect changes in their functional polarization status. Under several tumor microenvironment (TME)-related cues, TAM shift their polarization, hence promoting or halting cancer progression. Immune checkpoint inhibitors (ICI) displayed unprecedented clinical responses in various refractory cancers; but only approximately a third of patients experienced durable responses. It is, therefore, crucial to enhance the response rate of immunotherapy. Several mechanisms of resistance to ICI have been elucidated including TAM role with its essential immunosuppressive functions that reduce both anti-tumor immunity and the subsequent ICI efficacy. In the past few years, thorough research has led to a better understanding of TAM biology and innovative approaches can now be adapted through targeting macrophages' recruitment axis as well as TAM activation and polarization status within the TME. Some of these therapeutic strategies are currently being evaluated in several clinical trials in association with ICI agents. This combination between TAM modulation and ICI allows targeting TAM intrinsic immunosuppressive functions and tumor-promoting factors as well as overcoming ICI resistance. Hence, such strategies, with a better understanding of the mechanisms driving TAM modulation, may have the potential to optimize ICI efficacy.

Multi-Layer Nanofibrous PCL Scaffold-Based Colon Cancer Cell Cultures to Mimic Hypoxic Tumor Microenvironment for Bioassay

Simple Summary

Multi-layer, nanofibrous poly(ε-caprolactone) (PCL) scaffold (pNFS)-based colon cancer cell cultures mimic the hypoxic tumor microenvironment. The simple procedure generates a 3D hypoxic tumor microenvironment comprising defined numbers and densities of colon cancer cells with easily controllable lateral dimensions and a thickness defined by pNFS. This pNFS-based multi-layered colon cancer cell culture system is useful for bioassays, for drug screening, and as a replacement for small animals in testing the effects of a hypoxic tumor microenvironment.

Abstract

Three-dimensional (3D) cancer cell culture systems have been developed to aid the study of molecular mechanisms in cancer development, identify therapeutic targets, and test drug candidates. In this study, we developed a strategy for mimicking the hypoxic tumor microenvironment in a 3D cancer cell culture system using multi-layer, nanofibrous poly(ε-caprolactone) (PCL) scaffold (pNFS)-based cancer cell cultures. We found that human colon cancer cells infiltrated pNFS within 3 days and could be cultured three-dimensionally within the NFS. When incubated in four stacks of 30 µm-thick pNFS for 3 days, colon cancer cells in layer three showed partially reduced entry into the S phase, whereas those in layer four, located farthest from the media, showed a marked reduction in S-phase entry. As a consequence, cells in layer four exhibited hypoxia-induced disorganization of F-actin on day 3, and those in layers three and four showed an increase in the expression of the hypoxia-induced transcription factor HIF-1α and its target genes, Glut1, CA9, VEGF, and LDHA. Consistent with these results, doxorubicin- and ionizing radiation-induced cell death was reduced in colon cancer cells cultured in layers three and four. These results suggest that pNFS-based multi-layer colon cancer cell cultures mimic the hypoxic tumor microenvironment and are useful for bioassays.

Peritumoral edema in breast cancer at preoperative MRI: an interpretative study with histopathological review toward understanding tumor microenvironment

Peritumoral edema (PE) of breast cancer at T2-weighted MR images is considered a poor prognostic sign and may represent the microenvironment surrounding the tumor; however, its histopathological mechanism remains unclear. The purpose of the study was to identify and describe detailed histopathological characteristics associated with PE at preoperative breast MRI in breast cancer patients. This retrospective study included breast cancer patients who had undergone preoperative MRI and surgery between January 2011 and December 2012. Two radiologists determined the presence of PE in consensus based on the signal intensity surrounding the tumor at T2-weighted images. The following detailed histopathological characteristics were reviewed by two breast pathologists using four-tiered grades; lymphovascular invasion, vessel ectasia, stromal fibrosis, growth pattern, and tumor budding. Tumor necrosis and tumor infiltrating lymphocytes were assessed using a percent scale. Baseline clinicopathological characteristics, including age and histologic grade, were collected. The associations between detailed histopathologic characteristics and PE were examined using multivariable logistic regression with odds ratio (OR) calculation. A total of 136 women (median age, 49 ± 9 years) were assessed; among them 34 (25.0%) had PE. After adjustment of baseline clinicopathological characteristics that were significantly associated with PE (age, T stage, N stage, histologic grade, and subtype, all Ps < 0.05), lymphovascular invasion (P = 0.009), vessel ectasia (P = 0.021), stromal fibrosis (P = 0.024), growth pattern (P = 0.036), and tumor necrosis (P < 0.001) were also associated with PE. In comparison with patients without PE, patients with PE were more likely to have a higher degree of lymphovascular invasion (OR, 2.9), vessel ectasia (OR, 3.3), stromal fibrosis (OR, 2.5), lesser degree of infiltrative growth pattern (OR, 0.4), and higher portion of tumor necrosis (OR, 1.4). PE of breast cancer at MRI is associated with detailed histopathological characteristics of lymphovascular invasion, vessel ectasia, stromal fibrosis, growth pattern, and tumor necrosis, suggesting a relevance for tumor microenvironment.

Anesthesia Medications and Interaction with Chemotherapeutic Agents

Cancer is now a leading health concern worldwide. In an effort to provide these patients with adequate care, coordination between anesthesiologists and surgeons is crucial. In cancer-related treatment, it is very clear that radio-chemotherapy and medical procedures are important. There are some obstacles to anesthesia when dealing with cancer treatment, such as physiological disturbances, tumor-related symptoms, and toxicity in traditional chemotherapy treatment. Therefore, it is important that a multisystemic, multidisciplinary and patient-centered approach is used to preserve perioperative homeostasis and immune function integrity. Adding adjuvants can help increase patient safety and satisfaction and improve clinical efficacy. Correctly paired anesthetic procedures and medications will reduce perioperative inflammatory and immune changes that could potentially contribute to improved results for future cancer patients. Further research into best practice strategies is required which will help to enhance the acute and long-term effects of cancer care in clinical practice.

Hypoxia-Activated Prodrug Enabling Synchronous Chemotherapy and HIF-1α Downregulation for Tumor Treatment

The overexpression of HIF-1α in solid tumors due to hypoxia is closely related to drug resistance and consequent treatment failure. Herein, we constructed a hypoxia-activated prodrug named as YC-Dox. This prodrug could be activated under hypoxic conditions and undergo self-immolation to release doxorubicin (Dox) and YC-1 hemisuccinate (YCH-1), which could execute chemotherapy and result in HIF-1α downregulation, respectively. This prodrug is capable of specifically releasing Dox and YCH-1 in response to hypoxia, leading to a substantial synergistic potency and a remarkable cytotoxic selectivity (>8-fold) for hypoxic cancer cells over normoxic healthy cells. The in vivo experiments reveal that this prodrug can selectively aim at hypoxic cancer cells and avoid undesired targeting of normal cells, leading to elevated therapeutic efficacy for tumor treatment and minimized adverse effects on normal tissues.

Design, synthesis of novel celastrol derivatives and study on their antitumor growth through HIF-1α pathway

Four series of hypoxia-inducible factor-1 alpha (HIF-1α) functioning derivatives stemming from modifications to the C-29 carboxyl group of celastrol were designed and synthesized, and their anticancer activities were evaluated. To address the structure and activity relationship of each derivative, extensive structural changes were made. HRE luciferase reporter assay demonstrated that 12 modified compounds showed superior HIF-1α inhibitory activity. Among them, compound C6 exhibited the best features: firstly, the strongest HIF-1α inhibitory activity (IC₅₀ = 0.05 μM, 5-fold higher than that of celastrol); secondly, lower cytotoxicity (22-fold lower, C6-16.85 μM vs celastrol-0.76 μM). Thus, the safety factor of C6 was about 112 times higher than that of celastrol. Western blot assay indicated that C6 may inhibit the expression of HIF-1α protein in cells. Additionally, C6 hindered tumor cell cloning, migration and induced cell apoptosis. It is worth mentioning that in the mouse tumor xenograft model, C6 (10 mg/kg) displayed good antitumor activity in vivo, showing a better inhibition rate (74.03%) than the reference compound 5-fluorouracil (inhibition rate, 59.58%). However, the celastrol treatment group experienced collective death after four doses of the drug. Moreover, C6 minimally affected the mouse weight, indicating that its application in vivo has little toxic effect. H&E staining experiments show that it could also exacerbate the degree of tumor cell damage. The results of water solubility experiment show that the solubility of C6 is increased by 1.36 times than that of celastrol. In conclusion, C6 is a promising antitumor agent through HIF-1α pathway.

Musa acuminata lectin exerts anti-cancer effects on HeLa and EAC cells via activation of caspase and inhibitions of Akt, Erk, and Jnk pathway expression and suppresses the neoangiogenesis in in-vivo models

In the present study aimed to purify the lectin from the sap of Musa acuminata pseudostem and elucidate the apoptotic and angiogenic molecular mechanism in both in-vitro and in-vivo model. Mannose specific lectin was purified by using mannose affinity column chromatography and analyzed by RP-HPLC, SDS-PAGE, and PAS staining method. Furthermore, the protein was identified by MALDI-MS/MS. MAL effectively agglutinates trypsinized RBCs and showed effective cytotoxicity against various human cancer cell lines. MAL mitigates the cell proliferation, colony formation, cell migration, arrest the cell cycle in the G2/M phase, and induce apoptosis by altering the expression of apoptotic proteins/mRNA level (Bax and Bcl-2) via caspase 8/9, 3 dependent pathway in both in-vitro and in-vivo. Supporting this, in-vivo EAC tumor mice models prove the efficacy of MAL by inducing cell death and inhibiting the neovessel formation by targeting the MVD, inhibition of VEGF secretion, suppressing the expression of MMPs, HIF-1α, Flt-1, Akt, Jnk, and Erk1/2. More importantly, the MAL treatment leads to effective inhibition of tumor growth and an increase in the survivability of EAC mice. Our study summarizes that the MAL having a significant anticancer potential expressively degenerates the tumor development by inducing apoptosis and suppressing neoangiogenesis.

Smart strategies to overcome tumor hypoxia toward the enhancement of cancer therapy

Hypoxia, as a typical factor in a tumor microenvironment, plays a vital role in tumor treatment resistance, tumor invasion and migration. Hypoxia inducible factor (HIF), as the vital response element of hypoxia, mediates these untoward effects through a series of downstream reactions. Cancer treatments such as photodynamic therapy (PDT), radiotherapy (RT) and chemotherapy are severely hindered by hypoxia and HIF, back, however, could be intelligently manipulated through nanocomposite materials for their great potentiality to combine different functions. Herein, we reviewed the smart strategies in emerging research studies to overcome hypoxia toward the enhancement of tumor therapy.

Pre-treatment with Bifidobacterium infantis and its specific antibodies enhance targeted radiosensitization in a murine model for lung cancer

PURPOSE

The hypoxic microenvironments of solid tumours are complex and reduce the susceptibility of cancer cells to chemo- and radiotherapy. Conventional radiosensitisers have poor specificity, unsatisfactory therapeutic effects, and significant side effects. Anaerobic bacteria colonise and destroy hypoxic areas of the tumour and consequently enhance the effects of radiation.

METHODS

In this study, we treated a Lewis lung carcinoma transplant mouse model with Bifidobacterium infantis (Bi) combined with its specific monoclonal antibody (mAb) and radiotherapy (RT) to investigate its ability to radiosensitise the tumour. The tumour metabolism and hypoxia in the tumour tissue were monitored by micro-¹⁸F-FDG and ¹⁸F-FMISO PET/CT imaging. Immunohistochemistry was used to detect phosphorylated histone (γ-H2AX), proliferation (Ki-67), platelet endothelial cell adhesion molecules (CD31), tumour necrosis factor-α (TNF-α), hypoxia-inducible factor-1α (HIF-1α), and glucose transporter 1 (Glut-1) levels.

RESULTS

Tumour growth was slowed and survival time was markedly prolonged in mice subjected to the combination of B. infantis, specific antibody, and radiotherapy. Levels of HIF-1α, Glut-1, Ki-67, and CD31 expression, as well as uptake of FDG and FMISO, were the lowest in the combination-treated mice. In contrast, γ-H2AX and TNF-α expression levels were elevated and hypoxia in tumour tissue was reduced compared with controls.

CONCLUSION

In conclusion, our data indicated that the curative effect of radiotherapy for lung cancer was enhanced by pre-treating mice with a combination of B. infantis and its specific monoclonal antibody.

Targeting the Redox Landscape in Cancer Therapy

Reactive oxygen species (ROS) are produced predominantly by the mitochondrial electron transport chain and by NADPH oxidases in peroxisomes and in the endoplasmic reticulum. The antioxidative defense counters overproduction of ROS with detoxifying enzymes and molecular scavengers, for instance, superoxide dismutase and glutathione, in order to restore redox homeostasis. Mutations in the redox landscape can induce carcinogenesis, whereas increased ROS production can perpetuate cancer development. Moreover, cancer cells can increase production of antioxidants, leading to resistance against chemo- or radiotherapy. Research has been developing pharmaceuticals to target the redox landscape in cancer. For instance, inhibition of key players in the redox landscape aims to modulate ROS production in order to prevent tumor development or to sensitize cancer cells in radiotherapy. Besides the redox landscape of a single cell, alternative strategies take aim at the multi-cellular level. Extracellular vesicles, such as exosomes, are crucial for the development of the hypoxic tumor microenvironment, and hence are explored as target and as drug delivery systems in cancer therapy. This review summarizes the current pharmaceutical and experimental interventions of the cancer redox landscape.

The VHL/HIF Axis in the Development and Treatment of Pheochromocytoma/Paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors originating from chromaffin cells in the adrenal medulla (PCCs) or extra-adrenal sympathetic or parasympathetic paraganglia (PGLs). About 40% of PPGLs result from germline mutations and therefore they are highly inheritable. Although dysfunction of any one of a panel of more than 20 genes can lead to PPGLs, mutations in genes involved in the VHL/HIF axis including PHD, VHL, HIF-2A (EPAS1), and SDHx are more frequently found in PPGLs. Multiple lines of evidence indicate that pseudohypoxia plays a crucial role in the tumorigenesis of PPGLs, and therefore PPGLs are also known as metabolic diseases. However, the interplay between VHL/HIF-mediated pseudohypoxia and metabolic disorder in PPGLs cells is not well-defined. In this review, we will first discuss the VHL/HIF axis and genetic alterations in this axis. Then, we will dissect the underlying mechanisms in VHL/HIF axis-driven PPGL pathogenesis, with special attention paid to the interplay between the VHL/HIF axis and cancer cell metabolism. Finally, we will summarize the currently available compounds/drugs targeting this axis which could be potentially used as PPGLs treatment, as well as their underlying pharmacological mechanisms. The overall goal of this review is to better understand the role of VHL/HIF axis in PPGLs development, to establish more accurate tools in PPGLs diagnosis, and to pave the road toward efficacious therapeutics against metastatic PPGLs.

Resveratrol Ameliorates the Malignant Progression of Pancreatic Cancer by Inhibiting Hypoxia-induced Pancreatic Stellate Cell Activation

Pancreatic cancer is characterized by a hypoxic tumor microenvironment, which is primarily caused by massive fibrosis with pancreatic stellate cells (PSCs) as a main component. Our previous studies have shown that resveratrol can significantly inhibit pancreatic cancer. However, whether resveratrol can inhibit hypoxia-induced cancer development remains unclear. The objective of this study was to explore whether PSCs and hypoxia synergistically mediate aggressiveness in pancreatic cancer and detect the potential pleiotropic protective effects of resveratrol on hypoxia-induced pancreatic cancer progression. Human PSCs were treated with vehicle or resveratrol under normoxic or hypoxic conditions (3% O2), and PSC activation was assessed by immunofluorescence staining. SiRNA was used to silence hypoxia-inducible factor 1 (HIF-1) expression. The invasive capacity of Panc-1 and Mia Paca-2 cells cocultured with conditioned medium from PSCs was assessed by Transwell assays. To examine tumor formation kinetics, KPC (LSL-KrasG12D/+, Trp53fl/+, and Pdx1-Cre) mice were sacrificed at different time points. To investigate the antitumor effects of resveratrol in vivo, 8-wk-old KPC mice were divided into two groups and treated daily with or without 50 mg/kg resveratrol. Our data indicate that hypoxia induces PSC activation via HIF-1 and that the interleukin 6, vascular endothelial growth factor A, and stromal cell-derived factor 1 derived from activated PSCs promote both invasion and the epithelial-mesenchymal transition and inhibit apoptosis in pancreatic cancer cells. However, resveratrol inhibits hypoxia-induced PSC activation, blocks the interplay between PSCs and pancreatic cancer cells, and suppresses the malignant progression of pancreatic cancer and stromal desmoplasia in a KPC mouse model. Our data highlight that activated PSCs and intratumoral hypoxia are essential targets for novel strategies to prevent tumor-microenvironment interactions. Furthermore, the polyphenolic compound resveratrol effectively ameliorates the malignant progression of pancreatic ductal adenocarcinoma.

Role of Hypoxia and Metabolism in the Development of Neointimal Hyperplasia in Arteriovenous Fistulas

For patients with end-stage renal disease requiring hemodialysis, their vascular access is both their lifeline and their Achilles heel. Despite being recommended as primary vascular access, the arteriovenous fistula (AVF) shows sub-optimal results, with about 50% of patients needing a revision during the year following creation. After the AVF is created, the venous wall must adapt to new environment. While hemodynamic changes are responsible for the adaptation of the extracellular matrix and activation of the endothelium, surgical dissection and mobilization of the vein disrupt the vasa vasorum, causing wall ischemia and oxidative stress. As a consequence, migration and proliferation of vascular cells participate in venous wall thickening by a mechanism of neointimal hyperplasia (NH). When aggressive, NH causes stenosis and AVF dysfunction. In this review we show how hypoxia, metabolism, and flow parameters are intricate mechanisms responsible for the development of NH and stenosis during AVF maturation.

Fucoidan inhibits epithelial-to-mesenchymal transition via regulation of the HIF-1α pathway in mammary cancer cells under hypoxia

This study examined the effects of fucoidan on epithelial-to-mesenchymal transition (EMT) in a human triple-negative breast cancer (TNBC) cell line in a hypoxic microenvironment. Transwell and wound-healing assays were performed to analyze the invasion and migration of MDA-MB-231 human mammary cancer cells, respectively. The expression levels of EMT markers and hypoxia-inducible factor-1α (HIF-1α) were detected through western blotting. Under hypoxia, fucoidan treatment inhibited proliferation of breast cancer cells. Fucoidan also suppressed the invasion and migration of MDA-MB-231 cells. Western blotting revealed that fucoidan treatment significantly reduced the protein expression levels of HIF-1α and HIF-1 target genes. Furthermore, the nuclear translocation and activity of HIF-1α were reduced. Fucoidan treatment significantly downregulated the expression levels of mesenchymal markers (N-cadherin and vimentin), but upregulated the expression levels of the epithelial markers zonula occludens-1 and E-cadherin. In addition, overexpression of HIF1-α protected cells from fucoidan-mediated suppression of migration and invasion. These data suggested that fucoidan may inhibit EMT in human TNBC cells via downregulation of the HIF1-α signaling pathway.

Montelukast inhibits hypoxia inducible factor-1α translation in prostate cancer cells

Through regulating the expression of hundreds of genes, hypoxia-inducible factor -1(HIF-1) plays a critical role in hypoxic adaption of cancer cells and is considered as a target for cancer therapy. Here we show that montelukast, a clinical leukotriene receptor antagonist for the treatment of asthma, inhibits hypoxia or CoCl₂-induced HIF-1α activation and reduces its protein expression in prostate cancer cells. However, the other two leukotriene receptor antagonists, pranlukast and zafirlukast, cannot decrease HIF-1α protein, which indicates that montelukast-induced downregulation of HIF-1α is not mediated by leukotriene receptor. Neither proteasome inhibitor MG132 nor the lysosomal inhibitor chloroquine (CQ) can block montelukast-induced downregulation of HIF-1α protein. Interestingly, GSK2606414, a PKR-like endoplasmic reticulum kinase (PERK) inhibitor, abrogates montelukast-induced downregulation of HIF-1α under hypoxic conditions. However, montelukast increases phosphorylation of eIF-2α at Ser51. Moreover, montelukast inhibits the proliferation of prostate cancer cells, which can be reversed by overexpression of HIF-1α protein. In conclusion, we identify montelukast may be used as a novel agent for the treatment of prostate cancer by decreasing HIF-1α protein translation.

Novel hypoxia-targeting Pt(iv) prodrugs

Novel Pt(iv) prodrugs targeting hypoxia inducible factor HIF-1α were prepared for evaluating their antitumor activity on hypoxic cancer cells for the first time. The resulting Pt(iv) prodrug exhibited effective inhibition on tumor growth in the HCT-116 xenograft mouse model with low toxicity in vivo.

Baicalin induces cellular senescence in human colon cancer cells via upregulation of DEPP and the activation of Ras/Raf/MEK/ERK signaling

Baicalin is a natural flavonoid glycoside which has potent anti-tumor and antioxidant activity in cancer cells. In the present study, we found that baicalin treatment significantly induced senescence in colon cancer cells. Furthermore, baicalin upregulated the expression of decidual protein induced by progesterone (DEPP) in HCT116 colon cancer cells, which accompanied with the activation of Ras/Raf/MEK/ERK and p16^INK4A/Rb signaling pathways. Meanwhile, these phenomena also appeared under the anti-oxidation effect exerted by baicalin. In addition, ectopic expression of DEPP in HCT116 cells significantly induced the activity of senescence-associated β-galactosidase (SA-β-Gal) in tumor cells regulated by Ras/Raf/MEK/ERK signaling pathway. Knockdown of DEPP by RNA interference efficiently counteracted the baicalin-mediated growth inhibition, senescence and cell cycle arrest in cancer cells. Importantly, in a xenograft mouse model of human colon cancer, we further confirmed that baicalin treatment dramatically inhibited tumor growth, which was due to the induction of tumor cellular senescence via the upregulation of DEPP and the activation of Ras/Raf/MEK/ERK signaling in vivo. In addition to baicalin treatment, we found that the hypoxia-response protein DEPP functions as a positive regulator involving the regulations of Ras/Raf/MEK/ERK signaling pathway and inhibition of human colon cancer by other anti-oxidative drugs, such as curcumin and sulforaphane, resulting in tumor cellular senescence. These results collectively suggest that baicalin upregulates the expression of DEPP and activates its downstream Ras/Raf/MEK/ERK and p16^INK4A/Rb pathways by acting as an antioxidant, leading to senescence in colon cancer cells.

Etoposide-Bevacizumab a new strategy against human melanoma cells expressing stem-like traits

Tumors contain a sub-population of self-renewing and expanding cells known as cancer stem cells (CSCs). Putative CSCs were isolated from human melanoma cells of a different aggressiveness, Hs294T and A375 cell lines, grown under hypoxia using “sphere-forming assay”, CD133 surface expression and migration ability. We found that a cell sub-population enriched for P1 sphere-initiating ability and CD133 expression also express larger amount of VEGF-R2. Etoposide does not influence phenotype of this sub-population of melanoma cells, while a combined treatment with Etoposide and Bevacizumab significantly abolished P1 sphere-forming ability, an effect associated with apoptosis of this subset of cells. Hypoxic melanoma cells sorted for VEGF-R2/CD133 positivity also undergo apoptosis when exposed to Etoposide and Bevacizumab. When Etoposide and Bevacizumab-treated hypoxic cells were injected intravenously into immunodeficient mice revealed a reduced capacity to induce lung colonies, which also appear with a longer latency period. Hence, our study indicates that a combined exposure to Etoposide and Bevacizumab targets melanoma cells endowed with stem-like properties and might be considered a novel approach to treat cancer-initiating cells.

Hypoxia-Induced Signaling Promotes Prostate Cancer Progression: Exosomes Role as Messenger of Hypoxic Response in Tumor Microenvironment

Prostate cancer (PCA) is the leading malignancy in men and the second leading cause of cancer-related deaths. Hypoxia (low O2 condition) is considered an early event in prostate carcinogenesis associated with an aggressive phenotype. In fact, clinically, hypoxia and hypoxia-related biomarkers are associated with treatment failure and disease progression. Hypoxia-inducible factor 1 (HIF-1) is the key factor that is activated under hypoxia, and mediates adaptation of cells to hypoxic conditions through regulating the expression of genes associated with angiogenesis, epithelial-to-mesenchymal transition (EMT), metastasis, survival, proliferation, metabolism, sternness, hormone-refractory progression, and therapeutic resistance. Besides HIF-1, several other signaling pathways including PI3K/Akt/mTOR, NADPH oxidase (NOX), Wnt/b-catenin, and Hedgehog are activated in cancer cells under hypoxic conditions, and also contribute in hypoxia-induced biological effects in HIF-1-dependent and -independent manners. Hypoxic cancer cells cause extensive changes in the tumor microenvironment both local and distant, and recent studies have provided ample evidence supporting the crucial role of nanosized vesicles "exosomes" in mediating hypoxia-induced tumor microenvironment remodeling. Exosomes' role has been reported in hypoxia-induced angiogenesis, sternness, activation of cancer-associated fibroblasts (CAFs), and EMT. Together, existing literature suggests that hypoxia plays a predominant role in PCA growth and progression, and PCA could be effectively prevented and treated via targeting hypoxia/hypoxia-related signaling pathways.

Overexpression of hypoxia-inducible factor and metabolic pathways: possible targets of cancer

Cancer, the main cause of human deaths in the modern world is a group of diseases. Anticancer drug discovery is a challenge for scientists because of involvement of multiple survival pathways of cancer cells. An extensive study on the regulation of each step of these pathways may help find a potential cancer target. Up-regulated HIF-1 expression and altered metabolic pathways are two classical characteristics of cancer. Oxygen-dependent (through pVHL, PHDs, calcium-mediated) and independent (through growth factor signaling pathway, mdm2 pathway, HSP90) regulation of HIF-1α leads to angiogenesis, metastasis, and cell survival. The two subunits of HIF-1 regulates in the same fashion through different mechanisms. HIF-1α translation upregulates via mammalian target of rapamycin and mitogen-activated protein kinase signaling pathways, whereas HIF-1β through calmodulin kinase. Further, the stabilized interactions of these two subunits are important for proper functioning. Also, metabolic pathways crucial for the formation of building blocks (pentose phosphate pathway) and energy generation (glycolysis, TCA cycle and catabolism of glutamine) are altered in cancer cells to protect them from oxidative stress and to meet the reduced oxygen and nutrient supply. Up-regulated anaerobic metabolism occurs through enhanced expression of hexokinase, phosphofructokinase, triosephosphate isomerase, glucose 6-phosphate dehydrogenase and down-regulation of aerobic metabolism via pyruvate dehydrogenase kinase and lactate dehydrogenase which compensate energy requirements along with high glucose intake. Controlled expression of these two pathways through their common intermediate may serve as potent cancer target in future.

Protein S-glutathionylation induced by hypoxia increases hypoxia-inducible factor-1α in human colon cancer cells

Hypoxia is a common characteristic of many types of solid tumors. Intratumoral hypoxia selects for tumor cells that survive in a low oxygen environment, undergo epithelial-mesenchymal transition, are more motile and invasive, and show gene expression changes driven by hypoxia-inducible factor-1α (HIF-1α) activation. Therefore, targeting HIF-1α is an attractive strategy for disrupting multiple pathways crucial for tumor growth. In the present study, we demonstrated that hypoxia increases the S-glutathionylation of HIF-1α and its protein levels in colon cancer cells. This effect is significantly prevented by decreasing oxidized glutathione as well as glutathione depletion, indicating that S-glutathionylation and the formation of protein-glutathione mixed disulfides is related to HIF-1α protein levels. Moreover, colon cancer cells expressing glutaredoxin 1 are resistant to inducing HIF-1α and expressing hypoxia-responsive genes under hypoxic conditions. Therefore, S-glutathionylation of HIF-1α induced by tumor hypoxia may be a novel therapeutic target for the development of new drugs.

Combining anaerobic bacterial oncolysis with vaccination that blocks interleukin-10 signaling may achieve better outcomes for late stage cancer management

Late stage solid tumors cause significant cancer mortality rates worldwide and effective therapy remains a big challenge. Cancer therapeutic vaccines elicit tumor specific T cells that kill tumor cells yet often fail to result in tumor destruction because of the limited T cell response and the local immune-suppressive environment. Blocking interleukin 10 (IL-10) signaling at the time of therapeutic vaccination elicits much stronger T cell responses than vaccination without IL-10 blocking. Anaerobic oncolytic bacteria target hypoxic regions of the late stage tumor tissues which not only stops tumor growth but also provides a pro-inflammatory environment that may increase the effectiveness of a therapeutic vaccine by recruiting more effector T cells to tumor site. In this review, we argue that combining both bacterial and vaccine therapies may improve the efficiency of late stage cancer management.

Brusatol-Mediated Inhibition of c-Myc Increases HIF-1α Degradation and Causes Cell Death in Colorectal Cancer under Hypoxia

HIF-1 (hypoxia-inducible factor-1) regulates the expression of ~100 genes involved in angiogenesis, metastasis, tumor growth, chemoresistance and radioresistance, underscoring the growing interest in targeting HIF-1 for cancer control. In the present study, we investigated the molecular mechanisms underlying brusatol-induced HIF-1α degradation and cell death in colorectal cancer under hypoxia (0.5% O₂). Under hypoxia, pretreatment of cancer cells with brusatol increased HIF-1α degradation and cancer cell death in a dose-dependent manner. This effect was mediated by activation of prolyl hydroxylases (PHDs), as evidenced by the block of brusatol-induced HIF-1α degradation and cancer cell death by both pharmacological inhibition and siRNA-mediated knockdown of PHDs. In addition, a ferrous iron chelator (2,2'-bypyridyl) blocked brusatol-induced degradation of HIF-1α and cancer cell death in hypoxia by inhibiting PHD activation. We further found that brusatol inhibited c-Myc expression, and showed that overexpression of c-Myc prevented brusatol-induced degradation of HIF-1α and cancer cell death by increasing mitochondrial ROS production and subsequent ROS-mediated transition of ferrous iron to ferric iron. Consistent with these results, treatment of tumor-bearing mice with brusatol significantly suppressed tumor growth by promoting PHD-mediated HIF-1α degradation. Collectively, our results suggest that brusatol-mediated inhibition of c-Myc/ROS signaling pathway increases HIF-1α degradation by promoting PHD activity and induces cell death in colorectal cancer under hypoxia

MicroRNA‑21 promotes migration and invasion of glioma cells via activation of Sox2 and β‑catenin signaling

The expression of microRNA 21 (miR-21) has been reported to be upregulated in various types of cancer, including malignant gliomas. However, its functions and mechanisms in glioma remain to be fully elucidated. The present study established miRNA‑21 overexpression and knockdown cell lines using SRY‑box 2 (Sox2) small interfering RNA (siRNA) to knockdown expression and Sox2 cDNA was cloned into pcDNA 3.1 mammalian expression vector for ectopic expression. BIO and XAV‑939 were used for β‑catenin signaling activation and knockdown, respectively. Transwell chambers were used to assay the capacity of cells to migrate. The present study determined that increased expression of miR‑21 significantly promoted the migration and invasion of glioma cells, which was accompanied by an upregulated expression of the Sox2 protein. Sox2 overexpression also promoted glioma cell migration and invasion, whereas Sox2 siRNA markedly reduced the miR‑21‑enhanced migration and invasion of glioma cells, indicating Sox2 may act as a crucial mediator of miR‑21 function. Furthermore, miR‑21 also upregulated the protein expression level of β‑catenin, whereas anti‑miR‑21 and Sox2 knockdown significantly reduced β‑catenin expression. BIO, a β‑catenin specific agonist, enhanced migration and invasion of glioma cells. XAV‑939, an inhibitor of β‑catenin signaling, markedly inhibited the migration and invasion of glioma cells, suggesting that β‑catenin may be associated with miR‑21‑ and Sox2‑induced invasion of glioma cells. Notably, BIO restored the migration and invasion potential of glioma cells, which were inhibited by Sox2 siRNA and anti‑miR‑21. These findings indicated that β‑catenin may be an important downstream mediator of miR‑21 and Sox2. Therefore, the present study identified the miR‑21/Sox2/β‑catenin signaling pathway, which may regulate the migration and invasion of human glioma cells.

NQO1 inhibits proteasome-mediated degradation of HIF-1α

Overexpression of NQO1 is associated with poor prognosis in human cancers including breast, colon, cervix, lung and pancreas. Yet, the molecular mechanisms underlying the pro-tumorigenic capacities of NQO1 have not been fully elucidated. Here we show a previously undescribed function for NQO1 in stabilizing HIF-1α, a master transcription factor of oxygen homeostasis that has been implicated in the survival, proliferation and malignant progression of cancers. We demonstrate that NQO1 directly binds to the oxygen-dependent domain of HIF-1α and inhibits the proteasome-mediated degradation of HIF-1α by preventing PHDs from interacting with HIF-1α. NQO1 knockdown in human colorectal and breast cancer cell lines suppresses HIF-1 signalling and tumour growth. Consistent with this pro-tumorigenic function for NQO1, high NQO1 expression levels correlate with increased HIF-1α expression and poor colorectal cancer patient survival. These results collectively reveal a function of NQO1 in the oxygen-sensing mechanism that regulates HIF-1α stability in cancers.

Phase II study of irinotecan in combination with bevacizumab in recurrent ovarian cancer

OBJECTIVES

To evaluate the efficacy and safety of irinotecan and bevacizumab in recurrent ovarian cancer. The primary objective was to estimate the progression free survival (PFS) rate at 6months. Secondary objectives included estimation of overall survival (OS), objective response rate (ORR), duration of response, and an evaluation of toxicity.

METHODS

Recurrent ovarian cancer patients with no limit on prior treatments were eligible. Irinotecan 250mg/m2 (amended to 175mg/m2 after toxicity assessment in first 6 patients) and bevacizumab 15mg/kg were administered every 3weeks until progression or toxicity. Response was assessed by RECIST or CA-125 criteria every 2cycles.

RESULTS

Twenty nine patients enrolled (10 were platinum-sensitive and 19 were platinum-resistant). The median number of prior regimens was 5 (range 1-12); 13 patients had prior bevacizumab and 11 prior topotecan. The PFS rate at 6months was 55.2% (95% CI: 40%-77%). The median number of study cycles given was 7 (range 1-34). Median PFS was 6.8months (95% CI: 5.1-12.1months); median OS was 15.4months (95% CI: 11.9-20.4months). In this study, no complete response (CR) was observed. The objective response rate (ORR; PR or CR) for all patients entered was 27.6% (95% CI: 12.7%-47.2%) and the clinical benefit rate (CR+PR+SD) was 72.4% (95% CI: 52.8%-87.3%); twelve patients experienced duration of response longer than 6months. In the 24 patients with measurable disease, a partial response (PR) was documented in 8 (30%) patients; 13 patients maintained stable disease (SD) at first assessment. The most common grade 3/4 toxicity was diarrhea. No treatment-related deaths were observed.

CONCLUSIONS

Irinotecan and bevacizumab has activity in heavily pre-treated patients with recurrent ovarian cancer, including those with prior bevacizumab and topoisomerase inhibitor use.

Hypoxia: A Double-Edged Sword in Cancer Therapy

Hypoxia is a common feature of malignant tumors. There is an interactive connection between hypoxia and chemoresistance, radioresistance, invasiveness, and angiogenesis. Therefore, tumor hypoxia has been considered as a validated target for treating cancer. This review focuses on the role of hypoxia on chemoresistance and radioresistance. In addition, we address several approaches targeting tumor hypoxia, known as hypoxia-targeted therapy.

Anti-cancer effect of pristimerin by inhibition of HIF-1α involves the SPHK-1 pathway in hypoxic prostate cancer cells

BACKGROUND

Hypoxia is a typical character of locally advanced solid tumours. The transcription factor hypoxia-inducible factor 1α (HIF-1α) is the main regulator under the hypoxic environment. HIF-1α regulates various genes to enhance tumour progression, angiogenesis, and metastasis. Sphingosine kinase 1 (SPHK-1) is a modulator of HIF-1α.

METHODS

To investigate the molecular mechanisms of pristimerin in association with SPHK-1 pathways in hypoxic PC-3 cancer cells. Vascular endothelial growth factor (VEGF) production, cell cycles, and SPHK-1 activity were measured, and western blotting, an MTT assay, and an RNA interference assay were performed.

RESULTS

Pristimerin inhibited HIF-1α accumulation in a concentration- and-time-dependent manner in hypoxic PC-3 cells. Pristimerin suppressed the expression of HIF-1α by inhibiting SPHK-1. Moreover, inhibiting SPHK-1 with a sphingosine kinase inhibitor enhanced the suppression of HIF-1α, phosphorylation AKT, and glycogen synthase kinase-3β (GSK-3β) by pristimerin under hypoxia. Furthermore, a reactive oxygen species (ROS) scavenger enhanced the inhibition of HIF-1α and SPHK-1 by pristimerin.

CONCLUSION

Taken together, these findings suggest that pristimerin can exert an anti-cancer activity by inhibiting HIF-1α through the SPHK-1 pathway.

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.

Anticancer efficacy of the hypoxia-activated prodrug evofosfamide (TH-302) in osteolytic breast cancer murine models

Tumor hypoxia is a major cause of treatment failure for a variety of malignancies. However, hypoxia offers treatment opportunities, exemplified by the development of compounds that target hypoxic regions within tumors. Evofosfamide (TH‐302) is a prodrug created by the conjugation of 2‐nitroimidazole to bromo‐isophosphoramide mustard (Br‐IPM). When evofosfamide is delivered to hypoxic regions, the DNA cross‐linking effector, Br‐IPM, is released. This study assessed the cytotoxic activity of evofosfamide in vitro and its antitumor activity against osteolytic breast cancer either alone or in combination with paclitaxel in vivo. A panel of human breast cancer cell lines were treated with evofosfamide under hypoxia and assessed for cell viability. Osteolytic MDA‐MB‐231‐TXSA cells were transplanted into the mammary fat pad, or into tibiae of mice, allowed to establish and treated with evofosfamide, paclitaxel, or both. Tumor burden was monitored using bioluminescence, and cancer‐induced bone destruction was measured using micro‐CT. In vitro, evofosfamide was selectively cytotoxic under hypoxic conditions. In vivo evofosfamide was tumor suppressive as a single agent and cooperated with paclitaxel to reduce mammary tumor growth. Breast cancer cells transplanted into the tibiae of mice developed osteolytic lesions. In contrast, treatment with evofosfamide or paclitaxel resulted in a significant delay in tumor growth and an overall reduction in tumor burden in bone, whereas combined treatment resulted in a significantly greater reduction in tumor burden in the tibia of mice. Evofosfamide cooperates with paclitaxel and exhibits potent tumor suppressive activity against breast cancer growth in the mammary gland and in bone.

Hypoxia-Targeted Drug Q6 Induces G2-M Arrest and Apoptosis via Poisoning Topoisomerase II under Hypoxia

In spite of the tremendous efforts dedicated to developing hypoxia-activated prodrugs, no agents yet have been approved for clinical therapy. In the present study, the hypoxic selective anti-cancer activity as well as the cellular target of a novel tirapazamine (TPZ) analogue, 7-methyl-3-(3-chlorophenyl)-quinoxaline-2-carbonitrile 1,4-dioxide (Q6) were investigated. Q6 implemented anti-cancer effects via poisoning topoisomerase II (topo II) under hypoxia. Modified trapped in agarose DNA immunostaining (TARDIS) assay showed more topo II-DNA cleavage complexes trapped by Q6 than TPZ at even lower concentration. In addition, by introducing ataxia-telangiectasia-mutated (ATM) kinase inhibitors caffeine and KU-60019, we displayed that Q6-triggered apoptosis was attributed, at least partially, to DNA double-strand breaks generated by the topo II-targeting effect. Collectively, Q6 stood out for its better hypoxia-selectivity and topo II-poisoning than the parental compound TPZ. All these data shed light on the research of Q6 as a promising hypoxia-activated prodrug candidate for human hepatocellular carcinoma therapy.

Hypoxia-Targeted Drug Q6 Induces G2-M Arrest and Apoptosis via Poisoning Topoisomerase II under Hypoxia

In spite of the tremendous efforts dedicated to developing hypoxia-activated prodrugs, no agents yet have been approved for clinical therapy. In the present study, the hypoxic selective anti-cancer activity as well as the cellular target of a novel tirapazamine (TPZ) analogue, 7-methyl-3-(3-chlorophenyl)-quinoxaline-2-carbonitrile 1,4-dioxide (Q6) were investigated. Q6 implemented anti-cancer effects via poisoning topoisomerase II (topo II) under hypoxia. Modified trapped in agarose DNA immunostaining (TARDIS) assay showed more topo II–DNA cleavage complexes trapped by Q6 than TPZ at even lower concentration. In addition, by introducing ataxia-telangiectasia-mutated (ATM) kinase inhibitors caffeine and KU-60019, we displayed that Q6-triggered apoptosis was attributed, at least partially, to DNA double-strand breaks generated by the topo II-targeting effect. Collectively, Q6 stood out for its better hypoxia-selectivity and topo II-poisoning than the parental compound TPZ. All these data shed light on the research of Q6 as a promising hypoxia-activated prodrug candidate for human hepatocellular carcinoma therapy.

Structure Elucidation of Verucopeptin, a HIF-1 Inhibitory Polyketide-Hexapeptide Hybrid Metabolite from an Actinomycete

The transcriptional factor, hypoxia inducible factor-1 (HIF-1), is a promising target for cancer chemotherapy. From an actinomycete, verucopeptin (1) was identified as a HIF-1 signaling inhibitor. By a combination of chemical degradation and spectroscopic analyses, the absolute stereochemistry of metabolite 1 was determined to be 10R, 15S, 16S, 23S, 27S, 28R, 31S, 33S, 35R. Moreover, metabolite 1 was revealed to attenuate the HIF-1α and mTORC1 pathway, indicating that verucopeptin (1) would be a potent lead compound for anticancer chemotherapy.