The hypoxic tumour microenvironment, patient selection and hypoxia-modifying treatments

Assessment of Serum Hypoxia Biomarkers Pre- and Post-radiotherapy in Patients with Brain Tumors

Hypoxia is a prevalent hallmark of many malignant neoplasms. The aim was to assess the serum hypoxia biomarkers HIF-1α, VEGF, osteopontin, erythropoietin, caveolin-1, GLUT-1, and LDH pre- and post-radiotherapy in patients with brain tumors. The study was conducted on 120 subjects were divided into two groups: group I: 40 healthy volunteers as control group. Group II: 80 brain tumor patients were subdivided into glioblastoma subgroup: 40 glioblastoma patients, meningioma subgroup: 40 malignant meningioma patients. Two venous blood samples were collected from every patient prior to and following RT and one sample from controls. Biomarkers were assayed by ELISA. In glioblastoma subgroup, HIF-1α, VEGF, and LDH were significantly increased after RT. On the contrary, these biomarkers were significantly decreased after RT in malignant meningioma subgroup. Osteopontin was significantly increased after RT in both subgroups. Regarding erythropoietin, it was significantly decreased in both subgroups when compared to before RT. Caveolin-1 showed a significant increase in glioblastoma subgroup after RT comparing to before RT. GLUT-1 was significantly increased after RT in both subgroups comparing to before RT. Association of significant elevation of hypoxia biomarkers either pre- or post-RT with aggressive tumor such as glioblastoma indicates that, they are markers of malignancy and may have a role in tumor development and progression.

Hypoxia-induced CXC chemokine ligand 14 expression drives protumorigenic effects through activation of insulin-like growth factor-1 receptor signaling in glioblastoma

Hypoxic tumor microenvironment (HTM) promotes a more aggressive and malignant state in glioblastoma. However, little is known about the role and mechanism of CXC chemokine ligand 14 (CXCL14) in HTM-mediated glioblastoma progression. In this study, we report that CXCL14 expression correlated with poor outcomes, tumor grade, and hypoxia-inducible factor (HIF) expression in patients with glioblastoma. CXCL14 was upregulated in tumor cells within the hypoxic areas of glioblastoma. Hypoxia induced HIF-dependent expression of CXCL14, which promoted glioblastoma tumorigenicity and invasiveness in vitro and in vivo. Moreover, CXCL14 gain-of-function in glioblastoma cells activated insulin-like growth factor-1 receptor (IGF-1R) signal transduction to regulate the growth, invasiveness, and neurosphere formation of glioblastoma. Finally, systemic delivery of CXCL14 siRNA nanoparticles (NPs) with polysorbate 80 coating significantly suppressed tumor growth in vivo and extended the survival time in patient-derived glioblastoma xenografts. Together, these findings suggest that HIF-dependent CXCL14 expression contributes to HTM-promoted glioblastoma tumorigenicity and invasiveness through activation of the IGF-1R signaling pathway. CXCL14 siRNA NPs as an oligonucleotide drug can inhibit glioblastoma progression and constitute a translational path for the clinical treatment of glioblastoma patients.

Target Definition in MR-Guided Adaptive Radiotherapy for Head and Neck Cancer

In recent years, MRI-guided radiotherapy (MRgRT) has taken an increasingly important position in image-guided radiotherapy (IGRT). Magnetic resonance imaging (MRI) offers superior soft tissue contrast in anatomical imaging compared to computed tomography (CT), but also provides functional and dynamic information with selected sequences. Due to these benefits, in current clinical practice, MRI is already used for target delineation and response assessment in patients with head and neck squamous cell carcinoma (HNSCC). Because of the close proximity of target areas and radiosensitive organs at risk (OARs) during HNSCC treatment, MRgRT could provide a more accurate treatment in which OARs receive less radiation dose. With the introduction of several new radiotherapy techniques (i.e., adaptive MRgRT, proton therapy, adaptive cone beam computed tomography (CBCT) RT, (daily) adaptive radiotherapy ensures radiation dose is accurately delivered to the target areas. With the integration of a daily adaptive workflow, interfraction changes have become visible, which allows regular and fast adaptation of target areas. In proton therapy, adaptation is even more important in order to obtain high quality dosimetry, due to its susceptibility for density differences in relation to the range uncertainty of the protons. The question is which adaptations during radiotherapy treatment are oncology safe and at the same time provide better sparing of OARs. For an optimal use of all these new tools there is an urgent need for an update of the target definitions in case of adaptive treatment for HNSCC. This review will provide current state of evidence regarding adaptive target definition using MR during radiotherapy for HNSCC. Additionally, future perspectives for adaptive MR-guided radiotherapy will be discussed.

A study of evaluating specific tissue oxygen saturation values of gastrointestinal tumors by removing adherent substances in oxygen saturation imaging

OBJECTIVES

Oxygen saturation (OS) imaging is a new method of endoscopic imaging that has clinical applications in oncology which can directly measure tissue oxygen saturation (Sto2) of the surface of gastrointestinal tract without any additional drugs or devices. This imaging technology is expected to contribute to research into cancer biology which leads to clinical benefit such as prediction to efficacy of chemotherapy or radiotherapy. However, adherent substances on tumors such as blood and white coating, pose a challenge for accurate measurements of the StO2 values in tumors. The aim of this study was to develop algorithms for discriminating between the tumors and their adherent substances, and to investigate whether it is possible to evaluate the tumor specific StO2 values excluding adherent substances during OS imaging.

METHODS

We plotted areas of tumors and their adherent substances using white-light images of 50 upper digestive tumors: blood (68 plots); reddish tumor (83 plots); white coating (89 plots); and whitish tumor (79 plots). Scatter diagrams and discriminating algorithms using spectrum signal intensity values were constructed and verified using validation datasets. StO2 values were compared between the tumors and tumor adherent substances using OS images of gastrointestinal tumors.

RESULTS

The discriminating algorithms and their accuracy rates (AR) were as follows: blood vs. reddish tumor: Y> - 4.90X+7.13 (AR: 95.9%) and white coating vs. whitish tumor: Y< -0.52X+0.17 (AR: 96.0%). The StO2 values (median, [range]) were as follows: blood, 79.3% [37.8%-100.0%]; reddish tumor, 74.5% [62.0%-86.9%]; white coating, 73.8% [42.1%-100.0%]; and whitish tumor, 65.7% [53.0%-76.3%].

CONCLUSIONS

OS imaging is strongly influenced by adherent substances for evaluating the specific StO2 value of tumors; therefore, it is important to eliminate the information of adherent substances for clinical application of OS imaging.

Nutrient metabolism and cancer in the in vivo context: a metabolic game of give and take

Nutrients are indispensable resources that provide the macromolecular building blocks and energy requirements for sustaining cell growth and survival. Cancer cells require several key nutrients to fulfill their changing metabolic needs as they progress through stages of development. Moreover, both cell-intrinsic and microenvironment-influenced factors determine nutrient dependencies throughout cancer progression-for which a comprehensive characterization remains incomplete. In addition to the widely studied role of genetic alterations driving cancer metabolism, nutrient use in cancer tissue may be affected by several factors including the following: (i) diet, the primary source of bodily nutrients which influences circulating metabolite levels; (ii) tissue of origin, which can influence the tumor's reliance on specific nutrients to support cell metabolism and growth; (iii) local microenvironment, which dictates the accessibility of nutrients to tumor cells; (iv) tumor heterogeneity, which promotes metabolic plasticity and adaptation to nutrient demands; and (v) functional demand, which intensifies metabolic reprogramming to fuel the phenotypic changes required for invasion, growth, or survival. Here, we discuss the influence of these factors on nutrient metabolism and dependence during various steps of tumor development and progression.

Vestibular Schwannoma Tumor Size and Growth Rate Predict Response with Gamma Knife Stereotactic Radiosurgery

Objective The aim of this study is to determine if pretreatment growth of sporadic vestibular schwannomas (VS) predicts postradiosurgery response.

Methods This study was a retrospective chart review at a tertiary referral center of patients with VS that had at least two pretreatment magnetic resonance imaging (MRI) studies at least 6 months apart and underwent Gamma Knife radiosurgery with a minimum of 14 months postradiosurgery imaging surveillance. Tumor linear measurements and volumetric segmentation were assessed before and after radiosurgery. The main outcome measure was persistent enlargement following radiosurgery, defined as 2 mm enlargement in greatest axial diameter or 20% enlargement in volume without size regression.

Results Thirty-five patients met the inclusion criteria. Patients were observed for median pre- and posttreatment intervals of 29.5 and 40.6 months, respectively. Median dose to the tumor margin was 13 Gy. Postradiosurgery enlargement occurred in six (17.1%) and nine (25.7%) patients based on linear and volumetric enlargement definitions, respectively. Pseudoprogression—defined as tumor enlargement—followed by linear or volumetric regression that occurred in 34.3% of tumors, reaching a maximum size at a median time of 6.3 months (3.3–8.4) postradiosurgery. When controlling for age, gender, and radiation dose, preradiosurgery tumor volume less than 0.3 cm3 (odds ratio [OR]: 59.7, p = 0.012) and preradiosurgery tumor diameter growth rate greater than or equal to 2.5 mm/year (OR: 19.3, p = 0.045) were associated with persistent postradiosurgery tumor enlargement.

Conclusion Smaller pretreatment tumor volume and greater linear tumor growth rates were associated with postradiosurgery tumor enlargement when controlling for age, gender, and radiation dose.

Level of Evidence :This study indicates that the level of evidence is V.

Long-Term Survival Outcomes of Metabolically Supported Chemotherapy with Gemcitabine-Based or FOLFIRINOX Regimen Combined with Ketogenic Diet, Hyperthermia, and Hyperbaric Oxygen Therapy in Metastatic Pancreatic Cancer

BACKGROUND

Despite introduction of new chemotherapeutic agents, outcomes of patients with metastatic pancreatic cancer are still poor. Metabolically supported chemotherapy (MSCT) is a novel approach targeting dysregulated energy mechanism of the tumor cell.

OBJECTIVES

This study aimed to examine the efficacy of metabolically supported administration of chemotherapy combined with ketogenic diet, hyperthermia, and hyperbaric oxygen therapy (HBOT) in patients with metastatic pancreatic cancer.

METHOD

This retrospective observational study included 25 patients with metastatic pancreatic ductal carcinoma (stage IV) who received MSCT (either gemcitabine-based or FOLFIRINOX regimen administered concomitantly with induced hypoglycemia) plus ketogenic diet, hyperthermia, and HBOT combination. Survival outcomes were evaluated.

RESULTS

During the mean follow-up duration of 25.4 ± 19.3 months, median overall survival and median progression-free survival were 15.8 months (95% CI, 10.5-21.1) and 12.9 months (95% CI, 11.2-14.6), respectively. Age and gender did not have any effect on overall survival (p > 0.05 for all).

CONCLUSIONS

MSCT administered together with ketogenic diet, hyperthermia, and HBOT appears to be a viable option with the potential to improve survival outcomes in patients diagnosed with metastatic pancreatic cancer. Further research, particularly with larger comparative clinical trials, is warranted.

Simultaneous in vivo optical quantification of key metabolic and vascular endpoints reveals tumor metabolic diversity in murine breast tumor models

Therapeutically exploiting vascular and metabolic endpoints becomes critical to translational cancer studies because altered vascularity and deregulated metabolism are two important cancer hallmarks. The metabolic and vascular phenotypes of three sibling breast tumor lines with different metastatic potential are investigated in vivo with a newly developed quantitative spectroscopy system. All tumor lines have different metabolic and vascular characteristics compared to normal tissues, and there are strong positive correlations between metabolic (glucose uptake and mitochondrial membrane potential) and vascular (oxygen saturations and hemoglobin concentrations) parameters for metastatic (4T1) tumors but not for micrometastatic (4T07) and nonmetastatic (67NR) tumors. A longitudinal study shows that both vascular and metabolic endpoints of 4T1 tumors increased up to a specific tumor size threshold beyond which these parameters decreased. The synchronous changes between metabolic and vascular parameters, along with the strong positive correlations between these endpoints suggest that 4T1 tumors rely on strong oxidative phosphorylation in addition to glycolysis. This study illustrates the great potential of our optical technique to provide valuable dynamic information about the interplay between the metabolic and vascular status of tumors, with important implications for translational cancer investigations.

Reactive oxygen species and cancer: A complex interaction

Elevated levels of Reactive Oxygen Species (ROS), increased antioxidant ability and the maintenance of redox homeostasis can cumulatively contribute to tumor progression and metastasis. The sources and the role of ROS in a heterogeneous tumor microenvironment can vary at different stages of tumor: initiation, development, and progression, thus making it a complex subject. In this review, we have summarized the sources of ROS generation in cancer cells, its role in the tumor microenvironment, the possible functions of ROS and its important scavenger systems in tumor progression with special emphasis on solid tumors.

Normobaric hyperoxia inhibits the progression of lung cancer by inducing apoptosis

Hypoxia is a critical characteristic of solid tumors with respect to cancer cell survival, angiogenesis, and metastasis. Hyperoxic treatment has been attempted to reverse hypoxia by enhancing the amount of dissolved oxygen in the plasma. In this study, we evaluated the effects of normobaric hyperoxia on the progression of lung cancer to determine whether oxygen toxicity can be used in cancer therapy. Following a tail vein injection of the Lewis lung carcinoma cells, C57BL/6J mice were exposed to a 24-h normobaric hyperoxia/normoxia cycle for two weeks. In addition, A549 lung cancer cells were incubated in a normobaric hyperoxia chamber for a 24-h period. As a result, the size and number of tumors in the lung decreased significantly with exposure to normobaric hyperoxia in the mouse model. Cell viability, colony-forming ability, migration, and invasion all decreased significantly in A549 cells exposed to normobaric hyperoxia and the normal control group exposed to normobaric hyperoxia showed no significant damage. Oxidative stress was more prominent with exposure to normobaric hyperoxia in cancer cells. A549 cells exposed to normobaric hyperoxia showed a significantly higher cell apoptosis ratio compared with A549 cells without normobaric hyperoxia exposure and normal human lung cells (BEAS-2B cells). The Bax/Bcl-2 mRNA expression ratio also increased significantly. Changes in the key regulators of apoptosis were similar between in vivo and in vitro conditions. The p-ERK level decreased, while the p-JNK level increased, after normobaric hyperoxia exposure in A549 cells. This study demonstrated the role of normobaric hyperoxia in inhibiting lung cancer. Normal tissue and cells showed no significant hyperoxic damage in our experimental setting. The anti-tumor effect of normobaric hyperoxia may due to the increased reactive oxygen species activity and apoptosis, which is related to the mitogen-activated protein kinase pathway. Impact statement Normobaric hyperoxia (NBO) is a feasible therapy for cancer with a low complication rate. Although NBO may be beneficial in cancer treatment, very few studies have been conducted; thus, the evidence is thin. This is the first study to clearly demonstrate morphological changes in lung cancer with NBO exposure and to investigate the underlying mechanisms both in vivo and in vitro. This study will arouse interest in NBO treatment and promote further research.

Near-simultaneous quantification of glucose uptake, mitochondrial membrane potential, and vascular parameters in murine flank tumors using quantitative diffuse reflectance and fluorescence spectroscopy

The shifting metabolic landscape of aggressive tumors, with fluctuating oxygenation conditions and temporal changes in glycolysis and mitochondrial metabolism, is a critical phenomenon to study in order to understand negative treatment outcomes. Recently, we have demonstrated near-simultaneous optical imaging of mitochondrial membrane potential (MMP) and glucose uptake in non-tumor window chambers, using the fluorescent probes tetramethylrhodamine ethyl ester (TMRE) and 2-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG). Here, we demonstrate a complementary technique to perform near-simultaneous in vivo optical spectroscopy of tissue vascular parameters, glucose uptake, and MMP in a solid tumor model that is most often used for therapeutic studies. Our study demonstrates the potential of optical spectroscopy as an effective tool to quantify the vascular and metabolic characteristics of a tumor, which is an important step towards understanding the mechanisms underlying cancer progression, metastasis, and resistance to therapies.

Noninvasive Glioblastoma Testing: Multimodal Approach to Monitoring and Predicting Treatment Response

Glioblastoma is the most aggressive adult primary brain tumor which is incurable despite intensive multimodal treatment. Inter- and intratumoral heterogeneity poses one of the biggest barriers in the diagnosis and treatment of glioblastoma, causing differences in treatment response and outcome. Noninvasive prognostic and predictive tests are highly needed to complement the current armamentarium. Noninvasive testing of glioblastoma uses multiple techniques that can capture the heterogeneity of glioblastoma. This set of diagnostic approaches comprises advanced MRI techniques, nuclear imaging, liquid biopsy, and new integrated approaches including radiogenomics and radiomics. New treatment options such as agents targeted at driver oncogenes and immunotherapy are currently being developed, but benefit for glioblastoma patients still has to be demonstrated. Understanding and unraveling tumor heterogeneity and microenvironment can help to create a treatment regime that is patient-tailored to these specific tumor characteristics. Improved noninvasive tests are crucial to this success. This review discusses multiple diagnostic approaches and their effect on predicting and monitoring treatment response in glioblastoma.

Next-Generation Hypoxic Cell Radiosensitizers: Nitroimidazole Alkylsulfonamides

Innovations in the field of radiotherapy such as stereotactic body radiotherapy, along with the advent of radio-immuno-oncology, herald new opportunities for classical oxygen-mimetic radiosensitizers. The role of hypoxic tumor cells in resistance to radiotherapy and in suppression of immune response continues to endorse tumor hypoxia as a bona fide, yet largely untapped, drug target. Only nimorazole is used clinically as a radiosensitizer, and there is a dearth of new radiosensitizers in development. Here we present a survey of novel nitroimidazole alkylsulfonamides and document their cytotoxicity and ability to radiosensitize anoxic tumor cells in vitro. We use a phosphate prodrug approach to increase aqueous solubility and to improve tumor drug delivery. A 2-nitroimidazole and a 5-nitroimidazole analogue demonstrated marked tumor radiosensitization in either ex vivo assays of surviving clonogens or tumor regrowth delay.

Accelerated electron paramagnetic resonance imaging using partial Fourier compressed sensing reconstruction

PURPOSE

Electron paramagnetic resonance (EPR) imaging has evolved as a promising tool to provide non-invasive assessment of tissue oxygenation levels. Due to the extremely short T₂ relaxation time of electrons, single point imaging (SPI) is used in EPRI, limiting achievable spatial and temporal resolution. This presents a problem when attempting to measure changes in hypoxic state. In order to capture oxygen variation in hypoxic tissues and localize cycling hypoxia regions, an accelerated EPRI imaging method with minimal loss of information is needed.

METHODS

We present an image acceleration technique, partial Fourier compressed sensing (PFCS), that combines compressed sensing (CS) and partial Fourier reconstruction. PFCS augments the original CS equation using conjugate symmetry information for missing measurements. To further improve image quality in order to reconstruct low-resolution EPRI images, a projection onto convex sets (POCS)-based phase map and a spherical-sampling mask are used in the reconstruction process. The PFCS technique was used in phantoms and in vivo SCC7 tumor mice to evaluate image quality and accuracy in estimating O₂ concentration.

RESULTS

In both phantom and in vivo experiments, PFCS demonstrated the ability to reconstruct images more accurately with at least a 4-fold acceleration compared to traditional CS. Meanwhile, PFCS is able to better preserve the distinct spatial pattern in a phantom with a spatial resolution of 0.6mm. On phantoms containing Oxo63 solution with different oxygen concentrations, PFCS reconstructed linewidth maps that were discriminative of different O₂ concentrations. Moreover, PFCS reconstruction of partially sampled data provided a better discrimination of hypoxic and oxygenated regions in a leg tumor compared to traditional CS reconstructed images.

CONCLUSIONS

EPR images with an acceleration factor of four are feasible using PFCS with reasonable assessment of tissue oxygenation. The technique can greatly enhance EPR applications and improve our understanding cycling hypoxia. Moreover this technique can be easily extended to various MRI applications.

Irradiation of Epithelial Carcinoma Cells Upregulates Calcium-Binding Proteins That Promote Survival under Hypoxic Conditions

Hypoxia is thought to promote tumor radio-resistance via effects on gene expression in cancer cells that modulate their metabolism, proliferation, and DNA repair pathways to enhance survival. Here we demonstrate for the first time that under hypoxic condition A431 epithelial carcinoma cells exhibit increased viability when exposed to low-dose γ-irradiation, indicating that radiotherapy can promote tumor cell survival when oxygen supply is limited. When assessed using iTRAQ quantitative proteomics and Western blotting, irradiated tumor cells were observed to significantly up-regulate the expression of calcium-binding proteins CALM1, CALU, and RCN1, suggesting important roles for these mediators in promoting tumor cell survival during hypoxia. Accordingly, shRNA-knockdown of CALM1, CALU, and RCN1 expression reduced hypoxic tumor cell resistance to low-dose radiation and increased apoptosis. These data indicate that γ-irradiation of hypoxic tumor cells induces up-regulation of calcium-binding proteins that promote cancer cell survival and may limit the efficacy of radiotherapy in the clinic.

Hypoxia-Inducible Factor-1α Expression in Indonesian Laryngeal Squamous Cell Carcinoma Patients

Objectives. This research aimed to determine the association between hypoxia-inducible factor-1α (HIF-1α) expression and laryngeal squamous cell carcinoma clinical stage. Methods. We retrospectively analyzed paraffin-embedded tissue from 47 laryngeal squamous cell carcinoma (LSCC) patients from 2011 to 2014. HIF-1α expression was analyzed by immunohistochemistry using an anti-HIF-1α mouse monoclonal antibody. The association between HIF-1α expression and clinical stage was analyzed using the chi square test. Results. The glottis was the predominant site of laryngeal squamous cell carcinoma occurrence, and 43/47 (91.5%) patients presented at an advanced stage. Of the advanced stage patients, 27/43 stained positive for HIF-1α expression and 16/43 stained negative. Of the early stage patients, 2/4 stained positive for HIF-1α expression and 2/4 stained negative. Statistical analysis did not demonstrate significant association of HIF-1α expression. Conclusion. There was no statistically significant association between HIF-1α expression and the clinical stage or histological differentiation of LSCC.

Current relevance of hypoxia in head and neck cancer

Head and Neck cancer (HNC) is a complex mix of cancers and one of the more common cancers with a relatively poor prognosis. One of the factors that may assist us in predicting survival and allow us to adjust our treatment strategies is the presence of tumor hypoxia. In this overview we aim to evaluate the current evidence and potential clinical relevance of tumor hypoxia in head and neck cancer according to an extensive search of current literature.An abundance of evidence and often contradictory evidence is found in the literature. Even the contradictory evidence and comparisons are difficult to judge as criteria and methodologies differ greatly, furthermore few prospective observational studies exist for verification of the pre-clinical studies. Despite these discrepancies there is clear evidence of associations between prognosis and poor tumor oxygenation biomarkers such as HIF-1α, GLUT-1 and lactate, though these associations are not exclusive. The use of genetic markers is expanding and will probably lead to significantly more and complex evidence. The lack of oxygenation in head and neck tumors is of paramount importance for the prediction of treatment outcomes and prognosis. Despite the wide array of conflicting evidence, the drive towards non-invasive prediction of tumor hypoxia should continue.

Direct and Repeated Clinical Measurements of pO2 for Enhancing Cancer Therapy and Other Applications

The first systematic multi-center study of the clinical use of EPR oximetry has begun, with funding as a PPG from the NCI. Using particulate oxygen sensitive EPR, materials in three complementary forms (India Ink, "OxyChips", and implantable resonators) the clinical value of the technique will be evaluated. The aims include using repeated measurement of tumor pO2 to monitor the effects of treatments on tumor pO2, to use the measurements to select suitable subjects for the type of treatment including the use of hyperoxic techniques, and to provide data that will enable existing clinical techniques which provide data relevant to tumor pO2 but which cannot directly measure it to be enhanced by determining circumstances where they can give dependable information about tumor pO2.

The H19 Long non-coding RNA in cancer initiation, progression and metastasis - a proposed unifying theory

The imprinted oncofetal long non-coding RNA (lncRNA) H19 is expressed in the embryo, down-regulated at birth and then reappears in tumors. Its role in tumor initiation and progression has long been a subject of controversy, although accumulating data suggest that H19 is one of the major genes in cancer. It is actively involved in all stages of tumorigenesis and is expressed in almost every human cancer. In this review we delineate the various functions of H19 during the different stages in the complex process of tumor progression. H19 up-regulation allows cells to enter a "selfish" survival mode in response to stress conditions, such as destabilization of the genome and hypoxia, by accelerating their proliferation rate and increasing overall cellular resistance to stress. This response is tightly correlated with nullification, dysfunction or significant down-regulation of the master tumor suppressor gene P53. The growing evidence of H19's involvement in both proliferation and differentiation processes, together with its involvement in epithelial to mesenchymal transition (EMT) and also mesenchymal to epithelial transition (MET), has led us to conclude that some of the recent disputes and discrepancies arising from current research findings can be resolved from a viewpoint supporting the oncogenic properties of H19. According to a holistic approach, the versatile, seemingly contradictory functions of H19 are essential to, and differentially harnessed by, the tumor cell depending on its context within the process of tumor progression.

Non-Toxic Metabolic Management of Metastatic Cancer in VM Mice: Novel Combination of Ketogenic Diet, Ketone Supplementation, and Hyperbaric Oxygen Therapy

The Warburg effect and tumor hypoxia underlie a unique cancer metabolic phenotype characterized by glucose dependency and aerobic fermentation. We previously showed that two non-toxic metabolic therapies - the ketogenic diet with concurrent hyperbaric oxygen (KD+HBOT) and dietary ketone supplementation - could increase survival time in the VM-M3 mouse model of metastatic cancer. We hypothesized that combining these therapies could provide an even greater therapeutic benefit in this model. Mice receiving the combination therapy demonstrated a marked reduction in tumor growth rate and metastatic spread, and lived twice as long as control animals. To further understand the effects of these metabolic therapies, we characterized the effects of high glucose (control), low glucose (LG), ketone supplementation (βHB), hyperbaric oxygen (HBOT), or combination therapy (LG+βHB+HBOT) on VM-M3 cells. Individually and combined, these metabolic therapies significantly decreased VM-M3 cell proliferation and viability. HBOT, alone or in combination with LG and βHB, increased ROS production in VM-M3 cells. This study strongly supports further investigation into this metabolic therapy as a potential non-toxic treatment for late-stage metastatic cancers.

Can 111In-RGD2 monitor response to therapy in head and neck tumor xenografts?

RGD (arginylglycylaspartic acid)-based imaging tracers allow specific imaging of integrin αvβ3 expression, proteins overexpressed during angiogenesis; however, few studies have investigated the potential of these tracers to monitor responses of antiangiogenic or radiation therapy. In the studies presented here, (111)In-RGD2 was assessed for its potential as an imaging tool to monitor such responses to therapies.

METHODS

DOTA-E-[c(RGDfK)]2 was radiolabeled with (111)In ((111)In-RGD2), and biodistribution studies were performed in mice with subcutaneous FaDu or SK-RC-52 xenografts after treatment with either antiangiogenic therapy (bevacizumab or sorafenib) or tumor irradiation (10 Gy). Micro-SPECT imaging studies and subsequent quantitative analysis were also performed. The effect of bevacizumab, sorafenib, or radiation therapy on tumor growth was determined.

RESULTS

The uptake of (111)In-RGD2 in tumors, as determined from biodistribution studies, correlated well with that quantified from micro-SPECT images, and both showed that 15 d after irradiation (111)In-RGD2 uptake was enhanced. Specific or nonspecific uptake of (111)In-RGD2 in FaDu or SK-RC-52 xenografts was not affected after antiangiogenic therapy, except in head and neck squamous cell carcinoma 19 d after the start of sorafenib therapy (P < 0.05). The uptake of (111)In-RGD2 followed tumor volume in studies featuring antiangiogenic therapy. However, the uptake of (111)In-RGD2 in FaDu xenografts was decreased as early as 4 h after tumor irradiation, despite nonspecific uptake remaining unaltered. Tumor growth was inhibited after antiangiogenic or radiation therapy.

CONCLUSION

Here, it is suggested that (111)In-RGD2 could allow in vivo monitoring of angiogenic responses after radiotherapy and may therefore prove a good clinical tool to monitor angiogenic responses early after the start of radiotherapy in patients with head and neck squamous cell carcinoma. Despite clear antitumor efficacy, antiangiogenic therapy did not alter tumor uptake of (111)In-RGD2, indicating that integrin expression was not altered.

Head and neck tumor hypoxia imaging by 18F-fluoroazomycin-arabinoside (18F-FAZA)-PET: a review

Tumor hypoxia is known to be associated with poor clinical outcome; therefore, patients with hypoxic tumors might benefit from more intensive treatment approaches. This is particularly true for patients with head and neck cancer. Pretreatment assessment of hypoxia in tumors would be desirable, not only to predict prognosis but also to select patients for more aggressive treatment.As an alternative to the invasive polarographic needle electrode method, there is the possibility of using PET with radiopharmaceuticals visualizing hypoxia. Most hypoxia imaging studies on head and cancer have been performed using F-labeled fluoromisonidazole (F-FMISO). A chemically related molecule, F-fluoroazomycin-arabinoside (F-FAZA), seems to have superior kinetic properties and may therefore be the radiopharmaceutical of choice.This minireview summarizes the published literature on animal and human F-FAZA PET studies. Furthermore, future perspectives on how individualized treatment could be applied in patients with hypoxic head and neck tumors are discussed, for instance, the use of hypoxia sensitizers or special intensity-modulated radiation therapy techniques achieving tumor subvolume dose escalation.

Synergistic antitumor effect of combining metronomic chemotherapy with adoptive cell immunotherapy in nude mice

Adoptive cell immunotherapy with cytokine-induced killer cell (CIK cell) represents a promising non-toxic anticancer therapy. However, the clinical efficacy of CIK cells is limited because of abnormal tumor vasculature. Metronomic chemotherapy shows promising anticancer activity by its potential antiangiogenic effect and reduced toxicity. We hypothesized that metronomic chemotherapy with paclitaxel could improve the antitumor effect of adoptive CIK cell immunotherapy. Mice health status was analyzed by measuring mice weight and observing mice behavior. Immunohistochemistry was used to investigate the recruitment of CIK cells, the expression of endothelial cell molecules, as well as the hypoxic tumor area. Metronomic paclitaxel synergized with adoptive CIK cell immunotherapy to inhibit the growth of non-small cell lung cancer (NSCLC). Metronomic paclitaxel reduced hypoxic tumor area and increased CIK cell infiltration. Hypoxia impeded the adhesion of CIK cells and reduced the expression of endothelial cell adhesion molecules. In vivo studies demonstrated that more CIK cells were found in endothelial cell adhesion molecules high expressed area. Our study provides a new rationale for combining metronomic chemotherapy with adoptive cell immunotherapy in the treatment of xenograft NSCLC tumors in immunodeficient mice. Further clinical trials integrating translational research are necessary to better evaluate the clinical benefit of this promising approach.

Tumor hypoxia as a driving force in genetic instability

Sub-regions of hypoxia exist within all tumors and the presence of intratumoral hypoxia has an adverse impact on patient prognosis. Tumor hypoxia can increase metastatic capacity and lead to resistance to chemotherapy and radiotherapy. Hypoxia also leads to altered transcription and translation of a number of DNA damage response and repair genes. This can lead to inhibition of recombination-mediated repair of DNA double-strand breaks. Hypoxia can also increase the rate of mutation. Therefore, tumor cell adaptation to the hypoxic microenvironment can drive genetic instability and malignant progression. In this review, we focus on hypoxia-mediated genetic instability in the context of aberrant DNA damage signaling and DNA repair. Additionally, we discuss potential therapeutic approaches to specifically target repair-deficient hypoxic tumor cells.

Interaction of EGFR with the tumour microenvironment: implications for radiation treatment

Treatment failure through radioresistance of tumours is associated with activation of the epidermal growth factor receptor (EGFR). Tumour cell proliferation, DNA-repair, hypoxia and metastases-formation are four mechanisms in which EGFR signalling has an important role. In clinical trials, a correlation has been demonstrated between high EGFR expression in tumours and poor outcome after radiotherapy. Inhibition of EGFR signalling pathways improves the effectiveness of radiotherapy of head and neck cancers by overcoming these main mechanisms of radioresistance. The fact that only a minority of the patients respond to EGFR inhibitors reflects the complexity of interactions between EGFR-dependent signalling pathways and the tumour microenvironment. Furthermore, many components of the microenvironment are potential targets for therapeutic interventions. Characterisation of the interaction of EGFR signalling and the tumour microenvironment is therefore necessary to improve the effectiveness of combined modality treatment with radiotherapy and targeted agents. Here, the current status of knowledge is reviewed and directions for future research are discussed.

The ketogenic diet and hyperbaric oxygen therapy prolong survival in mice with systemic metastatic cancer

Introduction

Abnormal cancer metabolism creates a glycolytic-dependency which can be exploited by lowering glucose availability to the tumor. The ketogenic diet (KD) is a low carbohydrate, high fat diet which decreases blood glucose and elevates blood ketones and has been shown to slow cancer progression in animals and humans. Abnormal tumor vasculature creates hypoxic pockets which promote cancer progression and further increase the glycolytic-dependency of cancers. Hyperbaric oxygen therapy (HBO₂T) saturates tumors with oxygen, reversing the cancer promoting effects of tumor hypoxia. Since these non-toxic therapies exploit overlapping metabolic deficiencies of cancer, we tested their combined effects on cancer progression in a natural model of metastatic disease.

Methods

We used the firefly luciferase-tagged VM-M3 mouse model of metastatic cancer to compare tumor progression and survival in mice fed standard or KD ad libitum with or without HBO₂T (2.5 ATM absolute, 90 min, 3x/week). Tumor growth was monitored by in vivo bioluminescent imaging.

Results

KD alone significantly decreased blood glucose, slowed tumor growth, and increased mean survival time by 56.7% in mice with systemic metastatic cancer. While HBO₂T alone did not influence cancer progression, combining the KD with HBO₂T elicited a significant decrease in blood glucose, tumor growth rate, and 77.9% increase in mean survival time compared to controls.

Conclusions

KD and HBO₂T produce significant anti-cancer effects when combined in a natural model of systemic metastatic cancer. Our evidence suggests that these therapies should be further investigated as potential non-toxic treatments or adjuvant therapies to standard care for patients with systemic metastatic disease.

Targeting hypoxia, HIF-1, and tumor glucose metabolism to improve radiotherapy efficacy

Radiotherapy, an important treatment modality in oncology, kills cells through induction of oxidative stress. However, malignant tumors vary in their response to irradiation as a consequence of resistance mechanisms taking place at the molecular level. It is important to understand these mechanisms of radioresistance, as counteracting them may improve the efficacy of radiotherapy. In this review, we describe how the hypoxia-inducible factor 1 (HIF-1) pathway has a profound effect on the response to radiotherapy. The main focus will be on HIF-1-controlled protection of the vasculature postirradiation and on HIF-1 regulation of glycolysis and the pentose phosphate pathway. This aberrant cellular metabolism increases the antioxidant capacity of tumors, thereby countering the oxidative stress caused by irradiation. From the results of translational studies and the first clinical phase I/II trials, it can be concluded that targeting HIF-1 and tumor glucose metabolism at several levels reduces the antioxidant capacity of tumors, affects the tumor microenvironment, and sensitizes various solid tumors to irradiation.

Distribution of residual cancer cells in the bowel wall after neoadjuvant chemoradiation in patients with rectal cancer

BACKGROUND

The standard treatment for locally advanced rectal cancer is preoperative chemoradiation and total mesorectal excision. After surgery, tumors are classified according to the depth of tumor invasion, nodal involvement, and tumor regression grade. However, these staging systems do not provide information about the distribution of residual cancer cells within the bowel wall.

OBJECTIVE

This study aimed to determine the distribution of residual cancer cells in each layer of the bowel wall in rectal cancer specimens.

DESIGN

This was a secondary analysis of data from a prospective phase II study.

SETTING

This study was performed in a multi-institutional setting.

PATIENTS

Included were 153 patients with stage II or stage III rectal cancer.

INTERVENTIONS

Patients were treated with chemoradiation and surgery. The surgical specimen tumor tissue was analyzed, and the distribution of residual cancer cells in each layer of the bowel wall was determined.

MAIN OUTCOME MEASURES

Statistical analysis was used to examine the correlation of residual cancer cells in each layer of the bowel wall with the clinical/pathologic stage and tumor regression grade.

RESULTS

Forty-two of 153 (27%) patients had complete response in the bowel wall (ypT0). Of the remaining 111 patients who had residual cancer cells, 5 (3%) were ypTis, 12 (8%) were ypT1, 41 (27%) were ypT2, 50 (33%) were ypT3, and 3 (2%) were ypT4. Of the 94 patients with ypT2-4 tumors, 12 (13%) had cancer cells in the mucosa, and 53 (56%) had cancer cells in the submucosa; 92 (98%) had cancer cells in the muscularis propria. Pretreatment cT correlated with the distribution of residual cancer cells. Tumor regression grade was not associated with the distribution of residual cancer cells after chemoradiation.

LIMITATIONS

: Patients received different chemotherapy regimens.

CONCLUSIONS

Residual cancer cells in rectal cancer specimens after chemoradiation are preferentially located close to the invasive front. This should be considered when designing strategies to diagnose complete pathologic response and when investigating the mechanisms of tumor resistance to chemoradiation.

NCI-RTOG translational program strategic guidelines for the early-stage development of radiosensitizers

The addition of chemotherapeutic agents to ionizing radiation has improved survival in many malignancies. Cure rates may be further improved by adding novel targeted agents to current radiotherapy or radiochemotherapy regimens. Despite promising laboratory data, progress in the clinical development of new drugs with radiation has been limited. To define and address the problems involved, a collaborative effort between individuals within the translational research program of the Radiation Oncology Therapy Group and the National Cancer Institute was established. We discerned challenges to drug development with radiation including: 1) the limited relevance of preclinical work, 2) the pharmaceutical industry's diminished interest, and 3) the important individual skills and institutional commitments required to ensure a successful program. The differences between early-phase trial designs with and without radiation are noted as substantial. The traditional endpoints for early-phase clinical trials-acute toxicity and maximum-tolerated dose-are of limited value when combining targeted agents with radiation. Furthermore, response rate is not a useful surrogate marker of activity in radiation combination trials.Consequently, a risk-stratified model for drug-dose escalation with radiation is proposed, based upon the known and estimated adverse effects. The guidelines discuss new clinical trial designs, such as the time-to-event continual reassessment method design for phase I trials, randomized phase II "screening" trials, and the use of surrogate endpoints, such as pathological response. It is hoped that by providing a clear pathway, this article will accelerate the rate of drug development with radiation.

Interstitial fluid pressure as an alternate regulator of angiogenesis independent of hypoxia driven HIF-1α in solid tumors

We previously showed that interstitial fluid pressure (IFP) may be an alternate regulator of angiogenesis in solid tumors. Given the accepted link between hypoxia-induced factor and angiogenesis this study investigated the effect of IFP on hypoxia-inducible factor (HIF-1α) and vascular endothelial growth factor (VEGF) in human osteosarcoma xenografts in SCID mice and in different hypoxic environments. Tumors were grown either at heterotopic (flank) or orthotopic (medullary canal of the proximal tibia) sites in the host animal. Microfluidic probes determined pH, O(2)-saturation, IFP, and peripheral blood flow perfusion continuously. We assessed tumor growth in the orthotopic site (n = 15) by softex radiographs weekly, 3D microCT, histological evaluation, and for molecular responses. An increased cytoplasmic immunohistostaining of cells for HIF-1α (p = 0.03) and VEGF-A (p = 0.004) on the outer periphery was noted compared to the tumor center, with VEGFR2 uniformly stained throughout. This paralleled a raised state of interstitial hypertension (p = 0.007) in the tumor center relative to the peripheral surface but was inconsistent with a state of hypoxia (p = 0.03) in the tumor center. In vitro culture of human osteosarcoma cell lines (HOS, U2OS) and a human osteoblast control at 0- and 20-mmHg of hydrostatic pressure revealed suppression of HIF-1α (p = 0.02) and VEGF-A (p = 0.02) gene expression when IFP was raised, while the effect on VEGFR1 was equivocal. This study proposes an alternative regulatory angiogenic pathway via the influence of IFP on cancer cell function. The identification of a mechanistic cellular link to the physical parameter becomes an important tool to evaluate cancer cell growth within solid tumors.

Value of three-dimensional power Doppler to predict clinical and histological response to neoadjuvant chemotherapy in locally advanced cervical carcinoma

OBJECTIVE

Platinum-based neoadjuvant chemotherapy followed by radical hysterectomy is an alternative therapeutic strategy for locally advanced cervical carcinoma but variables used to predict chemotherapy response are not well defined. We investigated the potential of three-dimensional (3D) power Doppler in predicting response to neoadjuvant chemotherapy.

METHODS

We enrolled 61 eligible patients with locally advanced cervical carcinoma who underwent neoadjuvant chemotherapy followed by surgery or radiation. Before the initial chemotherapy, we measured 3D power Doppler vascular indices, including vascularization index (VI), flow index (FI) and vascularization flow index (VFI), of the whole cervical carcinoma. We also measured two-dimensional (2D) hemodynamic parameters, such as resistance index and pulsatility index, at three random spots inside the tumor. The associations of all parameters with clinical and histological responses to chemotherapy were evaluated through univariable and multiple logistic regression analysis.

RESULTS

The clinical and histological response rates to chemotherapy were 70.5% and 70.7%, respectively. Univariable logistic regression analysis showed that VI, FI and VFI were significantly higher in clinical responders than in non-responders (P < 0.05), and that FI was significantly higher in histological responders (P = 0.012). Multiple logistic regression analysis showed that FI was the only significant factor associated with both clinical and histological responses. The best FI cut-off values were 35.3 and 37.3 for clinical response and histological response, respectively (with sensitivity 86.0% and 73.2%, and specificity 72.2% and 64.7%). Interestingly, none of the 2D hemodynamic parameters was significantly correlated with either response.

CONCLUSION

FI is a potential marker for predicting both clinical and histological responses to chemotherapy in patients with locally advanced cervical carcinoma.

Dynamic changes in oxygenation of intracranial tumor and contralateral brain during tumor growth and carbogen breathing: a multisite EPR oximetry with implantable resonators

INTRODUCTION

Several techniques currently exist for measuring tissue oxygen; however technical difficulties have limited their usefulness and general application. We report a recently developed electron paramagnetic resonance (EPR) oximetry approach with multiple probe implantable resonators (IRs) that allow repeated measurements of oxygen in tissue at depths of greater than 10mm.

METHODS

The EPR signal to noise (S/N) ratio of two probe IRs was compared with that of LiPc deposits. The feasibility of intracranial tissue pO(2) measurements by EPR oximetry using IRs was tested in normal rats and rats bearing intracerebral F98 tumors. The dynamic changes in the tissue pO(2) were assessed during repeated hyperoxia with carbogen breathing.

RESULTS

A 6-10 times increase in the S/N ratio was observed with IRs as compared to LiPc deposits. The mean brain pO(2) of normal rats was stable and increased significantly during carbogen inhalation in experiments repeated for 3months. The pO(2) of F98 glioma declined gradually, while the pO(2) of contralateral brain essentially remained the same. Although a significant increase in the glioma pO(2) was observed during carbogen inhalation, this effect declined in experiments repeated over days.

CONCLUSION

EPR oximetry with IRs provides a significant increase in S/N ratio. The ability to repeatedly assess orthotopic glioma pO(2) is likely to play a vital role in understanding the dynamics of tissue pO(2) during tumor growth and therapies designed to modulate tumor hypoxia. This information could then be used to optimize chemoradiation by scheduling treatments at times of increased glioma oxygenation.

Synthesis and evaluation of two novel 2-nitroimidazole derivatives as potential PET radioligands for tumor imaging

INTRODUCTION

Nitroimidazole (azomycin) derivatives labeled with radioisotopes have been developed as cancer imaging and radiotherapeutic agents based on the oncological hypoxic mechanism. By attaching nitroimidazole core with different functional groups, we synthesized new nitroimidazole derivatives and evaluated their potentiality as tumor imaging agents.

METHODS

Starting with commercially available 2-nitroimidazole, 2-fluoro-N-(2-(2-nitro-1H-imidazol-1-yl)ethyl)acetamide (NEFA, [(19)F]7) and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl 2-fluoroacetate (NEFT, [(19)F]8), as well as radiolabeling precursors, the bromo-substituted analogs were quickly synthesized through a three-step synthetic pathway. The precursors were radiolabeled with [(18)F]F(-)/18-crown-6/KHCO(3) in dimethyl sulfoxide at 90°C for 10 min followed by purification with an Oasis HLB cartridge. Biodistribution studies were carried out in EMT-6 tumor-bearing mice. The uptake (%ID/g) in tumors and normal tissues were measured at 30 min postinjection. Liquid chromatography-electrospray ionization mass spectrometry (LC/MS) was used to distinguish metabolites from parent drugs in urine and plasma of rat injected with "cold" NEFA ([(19)F]7) and NEFT ([(19)F]8).

RESULTS

Two radiotracers, [(18)F]NEFA ([(18)F]7) and [(18)F]NEFT ([(18)F]8), were prepared with average yields of 6%-7% and 9%-10% (not decay corrected). Radiochemical purity for both tracers was >95% as determined by HPLC. Biodistribution studies in EMT-6 tumor-bearing mice indicated that the tumor to blood and tumor to liver ratios of both [(18)F]7 (0.96, 0.61) and [(18)F]8 (0.98, 1.10) at 30 min were higher than those observed for [(18)F]FMISO (1) (0.91, 0.59), a well-investigated azomycin-type hypoxia radiotracer. Liquid chromatography-electrospray ionization mass spectrometry analysis demonstrated that fluoroacetate was the main in vivo metabolite for both NEFA ([(19)F]7) and NEFT ([(19)F]8).

CONCLUSIONS

In this research, two new fluorine-18 labeled 2-nitroimidazole derivatives, [(18)F]7 and [(18)F]8, both of which containing in vivo hydrolyzable group, were successfully prepared. Further biological evaluations are warranted to investigate their potential as PET radioligands for imaging tumor.

Hemoglobin level predicts outcome for vulvar cancer patients independent of GLUT-1 and CA-IX expression in tumor tissue

Intratumoral hypoxia has been associated with poor prognosis in several solid tumors. The aim of this study was to determine whether the hypoxia-associated markers glucose transporter (GLUT)-1 and carbonic anhydrase (CA)-IX expression and preoperative hemoglobin (Hb) levels correlate with presence of inguinofemoral or distant metastases, and disease-free survival (DSS) in vulvar squamous cell carcinoma (SCC) patients. Vulvar SCC (n = 103) were reviewed for histopathological characteristics by an expert gynecopathologist and stained for GLUT-1 and CA-IX. Clinical data and preoperative Hb levels were obtained from medical records. No significant correlations were observed between GLUT-1 or CA-IX expression patterns and preoperative Hb levels, presence of inguinofemoral or distant metastases and DSS. However, anemic patients (Hb < 11.2 g/dL) had significantly more inguinofemoral metastases and lower Hb level was an independent prognostic factor for a worse DSS (p < 0.001). The number of comorbidic conditions was inversely correlated with preoperative Hb level. Preoperative Hb levels are associated with poor DSS for vulvar SCC patients, whereas tumor hypoxia reflected by GLUT-1 and CA-IX expression does not have a predictive value. Because preoperative Hb levels inversely correlated with the number of comorbidic conditions and not with GLUT-1 or CA-IX expression, it is most likely that preoperative Hb levels represent overall physical condition.

Hypoxia induces differential translation of enolase/MBP-1

Background

Hypoxic microenvironments in tumors contribute to transformation, which may alter metabolism, growth, and therapeutic responsiveness. The α-enolase gene encodes both a glycolytic enzyme (α-enolase) and a DNA-binding tumor suppressor protein, c-myc binding protein (MBP-1). These divergent α-enolase gene products play central roles in glucose metabolism and growth regulation and their differential regulation may be critical for tumor adaptation to hypoxia. We have previously shown that MBP-1 and its binding to the c-myc P₂ promoter regulates the metabolic and cellular growth changes that occur in response to altered exogenous glucose concentrations.

Results

To examine the regulation of α-enolase and MBP-1 by a hypoxic microenvironment in breast cancer, MCF-7 cells were grown in low, physiologic, or high glucose under 1% oxygen. Our results demonstrate that adaptation to hypoxia involves attenuation of MBP-1 translation and loss of MBP-1-mediated regulation of c-myc transcription, evidenced by decreased MBP-1 binding to the c-myc P₂ promoter. This allows for a robust increase in c-myc expression, "early c-myc response", which stimulates aerobic glycolysis resulting in tumor acclimation to oxidative stress. Increased α-enolase mRNA and preferential translation/post-translational modification may also allow for acclimatization to low oxygen, particularly under low glucose concentrations.

Conclusions

These results demonstrate that malignant cells adapt to hypoxia by modulating α-enolase/MBP-1 levels and suggest a mechanism for tumor cell induction of the hyperglycolytic state. This important "feedback" mechanism may help transformed cells to escape the apoptotic cascade, allowing for survival during limited glucose and oxygen availability.

Development of hypoxia in a preclinical model of tumor micrometastases

PURPOSE

Hypoxic regions have been shown to be a characteristic feature of a wide variety of human primary tumors, whereas the oxygenation status of subclinical micrometastases is in general unknown. The development of hypoxia in a xenograft model of microscopic metastases was investigated in this study.

METHODS AND MATERIALS

U-25-GFP human melanomas growing in dorsal window chamber preparations in BALB/c nu/nu mice were used as a preclinical model of micrometastases. Tumor blood supply time and morphologic parameters of the vascular network were determined from first-pass imaging movies and vascular maps recorded by use of 155-kDa tetramethylrhodamine isothiocyanate-labeled dextran as a vascular tracer. Tumor hypoxia was assessed from immunohistochemical preparations of the imaged tissue by use of pimonidazole as a hypoxia marker.

RESULTS

Nearly half of the tumors had developed hypoxic regions when they reached a diameter of 2 to 3 mm. Tumors with multiple hypoxic foci showed a low growth rate, low blood flow velocity, high vessel tortuosity, high vessel segment length, and high vascular density, whereas tumors with a single hypoxic region showed a high growth rate, high blood flow velocity, low vessel tortuosity, low vessel segment length, and low vascular density. The tumors with hypoxic regions did not differ from those without hypoxia in any single parameter.

CONCLUSIONS

U-25-GFP xenograft models of vascularized human tumor micrometastases may develop hypoxic regions as a consequence of two distinctly different morphologic abnormalities in the vascular network: high resistance against blood flow (i.e., high vessel tortuosity and high vessel segment length) or low vascular density.

Hyperoxia increases the uptake of 5-fluorouracil in mammary tumors independently of changes in interstitial fluid pressure and tumor stroma

Background

Hypoxia is associated with increased resistance to chemo- and radiation-therapy. Hyperoxic treatment (hyperbaric oxygen) has previously been shown to potentiate the effect of some forms of chemotherapy, and this has been ascribed to enhanced cytotoxicity or neovascularisation. The aim of this study was to elucidate whether hyperoxia also enhances any actual uptake of 5FU (5-fluorouracil) into the tumor tissue and if this can be explained by changes in the interstitium and extracellular matrix.

Methods

One group of tumor bearing rats was exposed to repeated hyperbaric oxygen (HBO) treatment (2 bar, pO₂ = 2 bar, 4 exposures à 90 min), whereas one group was exposed to one single identical HBO treatment. Animals housed under normal atmosphere (1 bar, pO₂ = 0.2 bar) served as controls. Three doses of 5FU were tested for dose response. Uptake of [³H]-5FU in the tumor was assessed, with special reference to factors that might have contributed, such as interstitial fluid pressure (P_if), collagen content, oxygen stress (measured as malondialdehyd levels), lymphatics and transcapillary transport in the tumors.

Results

The uptake of the cytostatic agent increases immediately after a single HBO treatment (more than 50%), but not 24 hours after the last repeated HBO treatment. Thus, the uptake is most likely related to the transient increase in oxygenation in the tumor tissue. Factors like tumor P_if and collagen content, which decreased significantly in the tumor interstitium after repeated HBO treatment, was without effect on the drug uptake.

Conclusion

We showed that hyperoxia increases the uptake of [³H]-5FU in DMBA-induced mammary tumors per se, independently of changes in P_if, oxygen stress, collagen fibril density, or transendothelial transport alone. The mechanism by which such an uptake occur is still not elucidated, but it is clearly stimulated by elevated pO₂.

The relevance of a hypoxic tumour microenvironment in prostate cancer

Research into the hypoxic tumour microenvironment is accelerating and the reversal of hypoxia is increasingly being suggested as a mechanism for improving cancer treatment. Recent studies have suggested that hypoxia is also a feature in prostate cancer and is associated with a poor prognosis. Hypoxia has been shown to cause radio-resistance and hence hamper one of the major treatments for prostate cancer. However, unlike other solid tumours, such as cervical and head-and-neck cancer, there are inconsistencies and unanswered questions about the relevance of hypoxia in prostate cancer. This review outlines the role of low-oxygen conditions in prostate cancer and the areas where further studies are required.

Usefulness of hexamethylenetetramine as an adjuvant to radiation and cisplatin in the treatment of solid tumors: its independency of p53 status

The usefulness of hexamethylenetetramine as an adjuvant to radiation and cisplatin in the treatment of solid tumors and its dependency on the p53 status of tumor cells were examined. Human head and neck squamous cell carcinoma cells transfected with mutant TP53 (SAS/mp53), or with neo vector as a control (SAS/neo), were inoculated subcutaneously into both the hind legs of Balb/cA nude mice. The tumor-bearing mice received 5-bromo-2'-deoxyuridine (BrdU) continuously to label all proliferating (P) cells in the tumors. Then, they received hexamethylenetetramine (HMTA), intraperitoneally or continuously, combined with or without gamma-ray irradiation or cisplatin treatment. Immediately after treatment following HMTA, the response of quiescent (Q) cells was assessed in terms of the micronucleus frequency using immunofluorescence staining for BrdU. The response of the total (= P + Q) tumor cells was determined from the BrdU non-treated tumors. A higher toxicity of HMTA to Q cells than total cells, especially in SAS/neo, was made less clear by continuous administration. There was no apparent difference in the radio- and cisplatin-sensitivity enhancing effects by HMTA combination between SAS/neo and SAS/mp53 tumors, with a slightly greater effect in SAS/mp53. In both SAS/neo and SAS/mp53 tumors, continuous HMTA administration produced higher radio- and cisplatin-sensitivity enhancing effects than intraperitoneal single administration. Therefore, the use of HMTA as an adjuvant to radiation or cisplatin might be promising in curing solid tumors with large fraction of hypoxic cells and also with frequent loss-of-function in p53.