Relationship of hypoxia to metallothionein expression in murine tumors

Staining Hypoxic Areas of Frozen and FFPE Tissue Sections with Hypoxyprobe™

Hypoxia occurs due to inadequate levels of oxygen in tissue and has been implicated in numerous diseases such as cancer, diabetes, cardiovascular, and neurodegenerative diseases. Hypoxia activates hypoxia-inducible factors (HIF) which mediate the expression of several downstream genes. Within the context of cancer biology, these genes affect cellular processes including metabolism, proliferation, migration, invasion, and metastasis. Pimonidazole hydrochloride (HCl) is an exogenous marker that is reduced and binds to thiols under hypoxic conditions resulting in adducts that can be visualized using antibodies such as Hypoxyprobe™. This chapter describes a method for using Hypoxyprobe™ to detect hypoxic areas in frozen and FFPE mouse samples by immunofluorescence (IF) and immunohistochemistry (IHC) staining.

In Vivo Imaging of Tumor Hypoxia by Maintaining Green Fluorescence of 9-Aminoanthracene Under Hypoxic Conditions

In this study, 9-aminoanthracene (9AA) was used as a new fluorescence reagent for the in vivo imaging of tumor hypoxia by taking advantage of the maintenance of its green fluorescence under hypoxic conditions. As 9AA is insoluble in water, polyethylene glycol (PEG)-400 was used to dissolve 9AA in saline. Each organ was successfully stained with 9AA, as observed by green fluorescence using in vivo imaging, following intragastric administration of a 9AA PEG-saline solution in mice. Therefore, the intragastric administration of 9AA can be used for in vivo imaging of normal mice. Tumor hypoxia staining using the 9AA fluorescence method was evaluated by in vivo imaging of mice subcutaneously transplanted with Ehrlich ascites carcinoma cells and compared with conventional pimonidazole (PIMO) staining under hypoxic conditions. The tumor sections were stained with green fluorescence derived from 9AA and the same sections corresponded to hypoxic areas upon immunohistochemical staining with PIMO.

Neutrophil depletion enhanced the Clostridium novyi-NT therapy in mouse and rabbit tumor models

BACKGROUND

Hypoxia is a prominent feature of solid tumors and can function as fertile environment for oncolytic anaerobic bacteria such as Clostridium novyi-NT (C. novyi-NT) where it can induce tumor destruction in mice and patients. However, two major obstacles have limited its use, namely the host inflammatory response and the incomplete clearance of normoxic tumor areas.

METHODS

In this study, we first used a subcutaneous tumor model of a glioblastoma (GBM) cell line in immunocompetent mice to investigate the local distribution of tumor hypoxia, kinetics of C. novyi-NT germination and spread, and the local host immune response. We subsequently applied the acquired knowledge to develop a C. novyi-NT therapy in an orthotopic rabbit brain tumor model.

RESULTS

We found that local accumulation of granular leukocytes, mainly neutrophils, could impede the spread of bacteria through the tumor and prevent complete oncolysis. Depletion of neutrophils via anti-Ly6G antibody or bone marrow suppression using hydroxyurea significantly improved tumor clearance. We then applied this approach to rabbits implanted with an aggressive intracranial brain tumor and achieved long-term survival in majority of the animals without apparent toxicity.

CONCLUSION

These results indicated that depleting neutrophils can greatly enhance the safety and efficacy of C. novyi-NT cancer therapy for brain tumors.

Geminin overexpression-dependent recruitment and crosstalk with mesenchymal stem cells enhance aggressiveness in triple negative breast cancers

Resident mesenchymal stem cells (MSCs) promote cancer progression. However, pathways and mechanisms involved in recruiting MSCs into breast tumors remain largely undefined. Here we show that geminin-dependent acetylation releases HMGB1 from the chromatin to the cytoplasm and extracellular space. Extracellular acetylated HMGB1 (Ac-HMGB1) promotes geminin overexpressing (GemOE) cells survival by binding to RAGE and activating NF-κB signaling. Extracellular Ac-HMGB1 also triggers expression and activation of RAGE in the non-expressing MSCs. RAGE activation induces expression of CXCR4 in MSCs and directional migration towards SDF1 (aka CXCL12)-expressing GemOE cells in vitro and in vivo. These effects augmented by the necrotic and hypoxic environment in GemOE tumors, especially within their cores. Reciprocal interactions between newly recruited MSCs and GemOE tumor cells elevate tumor-initiating (TIC), basal and epithelial-to-mesenchymal transition (EMT) traits and enhance aggressiveness in vitro and in vivo in GemOE tumor cells. Indeed, faster, larger and more aggressive tumors develop when GemOE cells are co-injected with MSCs in orthotopic breast tumor model. Concurrently, inhibiting c-Abl (and thus geminin function), RAGE or CXCR4 prevented MSCs recruitment to GemOE cells in vitro and in vivo, and decreased the TIC, basal and EMT phenotypes in these tumor cells. Accordingly, we propose that GemOE tumor cells present within tumor cores represent metastatic precursors, and suppressing the GemOE→HMGB1/RAGE→SDF1/CXCR4 signaling circuit could be a valid target for therapies to inhibit GemOE tumors and their metastases.

Monitoring Tumor Hypoxia Using (18)F-FMISO PET and Pharmacokinetics Modeling after Photodynamic Therapy

Photodynamic therapy (PDT) is an efficacious treatment for some types of cancers. However, PDT-induced tumor hypoxia as a result of oxygen consumption and vascular damage can reduce the efficacy of this therapy. Measuring and monitoring intrinsic and PDT-induced tumor hypoxia in vivo during PDT is of high interest for prognostic and treatment evaluation. In the present study, static and dynamic (18)F-FMISO PET were performed with mice bearing either U87MG or MDA-MB-435 tumor xenografts immediately before and after PDT at different time points. Significant difference in tumor hypoxia in response to PDT over time was found between the U87MG and MDA-MB-435 tumors in both static and dynamic PET. Dynamic PET with pharmacokinetics modeling further monitored the kinetics of (18)F-FMISO retention to hypoxic sites after treatment. The Ki and k3 parametric analysis provided information on tumor hypoxia by distinction of the specific tracer retention in hypoxic sites from its non-specific distribution in tumor. Dynamic (18)F-FMISO PET with pharmacokinetics modeling, complementary to static PET analysis, provides a potential imaging tool for more detailed and more accurate quantification of tumor hypoxia during PDT.

Copper and hypoxia modulate transcriptional and mitochondrial functional-biochemical responses in warm acclimated rainbow trout (Oncorhynchus mykiss)

To survive in changing environments fish utilize a wide range of biological responses that require energy. We examined the effect of warm acclimation on the electron transport system (ETS) enzymes and transcriptional responses to hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperatures for 3 weeks followed by exposure to Cu, hypoxia or both for 24 h. Activities of ETS enzyme complexes I-IV (CI-CIV) were measured in liver and gill mitochondria. Analyses of transcripts encoding for proteins involved in mitochondrial respiration (cytochrome c oxidase subunits 4-1 and 2: COX4-1 and COX4-2), metal detoxification/stress response (metallothioneins A and B: MT-A and MT-B) and energy sensing (AMP-activated protein kinase α1: AMPKα1) were done in liver mitochondria, and in whole liver and gill tissues by RT-qPCR. Warm acclimation inhibited activities of ETS enzymes while effects of Cu and hypoxia depended on the enzyme and thermal acclimation status. The genes encoding for COX4-1, COX4-2, MT-A, MT-B and AMPKα1 were strongly and tissue-dependently altered by warm acclimation. While Cu and hypoxia clearly increased MT-A and MT-B transcript levels in all tissues, their effects on COX4-1, COX4-2 and AMPKα1 mRNA levels were less pronounced. Importantly, warm acclimation differentially altered COX4-2/COX4-1 ratio in liver mitochondria and gill tissue. The three stressors showed both independent and joint actions on activities of ETS enzymes and transcription of genes involved in energy metabolism, stress response and metals homeostasis. Overall, we unveiled novel interactive effects that should not be overlooked in real world situations wherein fish normally encounter multiple stress factors.

Behaviour of the oxidant scavenger metallothionein in hypoxia-induced neotropical fish

The pacu (Piaractus mesopotamicus) is a hypoxia-tolerant neotropical fish species. There is little or no information in this species regarding biochemical adaptations to waters with different oxygen concentrations, such as the production of reactive oxygen species and antioxidant scavengers, which might be of interest in the study of antioxidant defense mechanisms. Metallothioneins (MT) have been widely applied as biomarkers for metal exposure in fish liver, and, recently, in bile. These metalloproteins, however, have also been reported as free radical scavengers, although studies in this regard are scarce in fish. In this context, normoxic and hypoxic controlled experiments were conducted with pacu specimens and MT levels were quantified in both liver and bile. Reduced glutathione (GSH) indicative of oxidative stress, and thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation, were also determined in liver. The results demonstrate that hypoxic fish present significantly lower metallothionein levels in liver and bile and lower reduced glutathione levels in liver, whereas lipid peroxidation was not significantly different between hypoxic and normoxic fish. The results of the present study seem to suggest that metallothioneins may actively participate in redox regulation in hypoxic fish in both bile and liver. MT levels in these organs may be temporarily suppressed, supporting the notion that down-regulation of oxidant scavengers during the oxidative burst is important in defense signaling in these adapted organisms.

Dynamic (18) F-FDG PET for Assessment of Tumor Physiology in Two Breast Carcinoma Xenografts

PURPOSE

To compare dynamic 2-deoxy-2-[(18) F]fluoro-D-glucose positron emission tomography ((18) F-FDG PET) parameters in two selected human breast cancer xenografts and to evaluate associations with immunohistochemistry and histology.

PROCEDURES

Dynamic (18) F-FDG PET of luminal-like MAS98.06 and basal-like MAS98.12 xenografts was performed, and the compartmental transfer rates (k 1 ,k 2 ,k 3 ), blood volume fraction (v B ) and metabolic rate of (18) F-FDG(MR FDG ) were estimated from pharmacokinetic model analysis. After sacrifice, analyses of hypoxia (pimonidazole), proliferation (Ki-67), vascularization (CD31), glucose transport receptor (GLUT1) and necrosis (HE) was performed. The level of hexokinase 2 (HK2) was estimated from Western blot analysis.

RESULTS

The (18) F-FDG uptake curves for the two xenografts were significantly different (p < 0.05). k 1 and v B were higher for MAS98.12 (p < 0.01), while k 3 was higher for MAS98.06 (p < 0.01). MAS98.12 had a higher fraction of stromal tissue and higher microvessel density (MVD), and it was less necrotic and hypoxic than MAS98.06. MAS98.12 had stronger positive GLUT1 staining and lower Ki-67 than MAS98.06. In both models significant correlations were found between k 1 and the GLUT1 score, between k 3 and the level of HK2, and between v B and MVD.

CONCLUSIONS

Significant differences in dynamic (18) F-FDG parameters between the two human breast cancer xenografts were found. The differences could be explained by underlying histological and physiological characteristics.

Gamma secretase inhibition promotes hypoxic necrosis in mouse pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a highly lethal disease that is refractory to medical intervention. Notch pathway antagonism has been shown to prevent pancreatic preneoplasia progression in mouse models, but potential benefits in the setting of an established PDA tumor have not been established. We demonstrate that the gamma secretase inhibitor MRK003 effectively inhibits intratumoral Notch signaling in the KPC mouse model of advanced PDA. Although MRK003 monotherapy fails to extend the lifespan of KPC mice, the combination of MRK003 with the chemotherapeutic gemcitabine prolongs survival. Combination treatment kills tumor endothelial cells and synergistically promotes widespread hypoxic necrosis. These results indicate that the paucivascular nature of PDA can be exploited as a therapeutic vulnerability, and the dual targeting of the tumor endothelium and neoplastic cells by gamma secretase inhibition constitutes a rationale for clinical translation.

EPAS1 Is Required for Spermatogenesis in the Postnatal Mouse Testis

Spermatogenesis, a process involving the differentiation of spermatogonial stem cells into mature spermatozoa, takes place throughout masculine life. A complex system in the testis, including endocrine signaling, physical interactions between germ and somatic cells, spermatocyte meiosis, and timely release of spermatozoa, controls this cycle. We demonstrate herein that decreased O(2) levels and Epas1 activation are critical components of spermatogenesis. Postnatal Epas1 ablation leads to male infertility, with reduced testis size and weight. While immature spermatogonia and spermatocytes are present in Epas1(Delta/Delta) testes, spermatid and spermatozoan numbers are dramatically reduced. This is not due to germ cell-intrinsic defects. Rather, Epas(Delta/Delta) Sertoli cells exhibit decreased ability to form tight junctions, thereby disrupting the blood-testis barrier necessary for proper spermatogenesis. Reduced numbers of tight junction complexes are due to decreased expression of multiple genes encoding tight junction proteins, including TJP1 (ZO1), TJP2 (ZO2), and occludin. Furthermore, Epas1(Delta/Delta) testes exhibit disrupted basement membranes surrounding the seminiferous tubules, causing the premature release of incompletely differentiated germ cells. We conclude that low O(2) levels in the male gonad regulate germ cell homeostasis in this organ via EPAS1.

Preliminary study on the effect of trauma-induced secondary cellular hypoxia in brain injury

Secondary cerebral hypoxia has recently been shown to play an important role in the outcome of patients suffering from traumatic brain injury (TBI). However, the precise mechanisms underlying secondary cerebral hypoxia are complex and interrelated. In this study, we investigate the effect of hypoxia within a rat model of trauma-induced late cerebral cortex injury. Using the hypoxia marker pimonidazole, we verified and isolated areas of the cortex that had suffered hypoxic damage. Using subsequent reverse-transcriptase PCR analyses, we found that the expressions of both transforming growth factor beta1 (TGF-beta1) and hypoxia-inducible factor-1alpha (HIF-1alpha) increased significantly under hypoxic conditions induced by TBI compared with uninjured control animals. In addition, the maximum mRNA expression of TGF-beta1 and HIF-1alpha was found at 3 days and 12h after TBI, respectively. Our data suggest that secondary cerebral hypoxia injury involves various cytokines including TGF-beta1 and HIF-1alpha. Furthermore, upon immunohistochemical analysis, both TGF-beta1 and HIF-1alpha expression were almost localized in the same types of cells by using immunohistochemical study. These results may have important implications in the understanding of trauma-induced secondary cerebral hypoxia injury.

Intrinsic susceptibility MR imaging of chemically induced rat mammary tumors: relationship to histologic assessment of hypoxia and fibrosis

PURPOSE

To investigate relationships between magnetic resonance (MR) imaging measurements of R2* and carbogen-induced DeltaR2* in vivo with subsequent histologic assessment of grade, hypoxia, fibrosis, and necrosis in a chemically induced rat mammary tumor model.

MATERIALS AND METHODS

All experiments were performed in accordance with the local ethics review panel, the UK Home Office Animals Scientific Procedures Act of 1986, and the UK Co-ordinating Committee on Cancer Research guidelines. Of 30 rats injected with N-methyl-N-nitrosourea, 17 developed mammary tumors. Prior to MR imaging, rats were administered pimonidazole. Tumor R2* was then quantified while the host first breathed air and then carbogen (95% O(2), 5% CO(2); n = 16). Tumor sections were subsequently stained for pimonidazole, sirius red, cytokeratin 14, and hematoxylin-eosin for quantitative assessment of hypoxia, fibrosis, malignancy, and necrosis, respectively, and graded according to the Scarff-Bloom-Richardson scale. Linear regression analysis was used to identify any correlates of the MR imaging data with histologic data.

RESULTS

Tumors exhibited wide heterogeneity in the magnitude of carbogen-induced reduction in R2*, an emerging imaging biomarker of fractional blood volume. Significant correlations were found between pimonidazole adduct formation and both baseline tumor R2* (r = -0.54, P = .03) and carbogen-induced DeltaR2* (r = 0.56, P = .02), demonstrating that tumors with a larger fractional blood volume were less hypoxic. There was also a significant correlation between pimonidazole and sirius red staining (r = 0.76, P < .01), indicating that more fibrotic tumors were also more hypoxic. There were no correlations of R2* with grade.

CONCLUSION

In this model of breast cancer, baseline tumor R2* and carbogen-induced DeltaR2* are predictive imaging biomarkers for hypoxia and primarily determined by blood volume.

Discovery of fully human anti-MET monoclonal antibodies with antitumor activity against colon cancer tumor models in vivo

The receptor tyrosine kinase MET is a major component controlling the invasive growth program in embryonic development and in invasive malignancies. The discovery of therapeutic antibodies against MET has been difficult, and antibodies that compete with hepatocyte growth factor (HGF) act as agonists. By applying phage technology and cell-based panning strategies, we discovered two fully human antibodies against MET (R13 and R28), which synergistically inhibit HGF binding to MET and elicit antibody-dependent cellular cytotoxicity. Cell-based phosphorylation assays demonstrate that R13 and R28 abrogate HGF-induced activation of MET, AKT1, ERK1/2, and HGF-induced migration and proliferation. FACS experiments suggest that the inhibitory effect is mediated by "locking" MET receptor in a state with R13, which then increases avidity of R28 for the extracellular domain of MET, thus blocking HGF binding without activating the receptor. In vivo studies demonstrate that the combination of R13/28 significantly inhibited tumor growth in various colon tumor xenograft models. Inhibition of tumor growth was associated with induction of hypoxia. Global gene expression analysis shows that inhibition of HGF/MET pathway significantly upregulated the tumor suppressors KLF6, CEACAM1, and BMP2, the negative regulator of phosphatidylinositol-3-OH-kinase PIK3IP1, and significantly suppressed SCF and SERPINE2, both enhancers of proliferation and invasiveness. Moreover, in an experimental metastasis model, R13/28 increased survival by preventing the recurrence of otherwise lethal lung metastases. Taken together, these results underscore the utility of a dual-antibody approach for targeting MET and possibly other receptor tyrosine kinases. Our approach could be expanded to drug discovery efforts against other cell surface proteins.

Inhibition of transforming growth factor-beta, hypoxia-inducible factor-1alpha and vascular endothelial growth factor reduced late rectal injury induced by irradiation

Tumor hypoxia and angiogenesis associated with malignant progression have been studied widely. The efficacy of angiogenesis inhibition combined with radiotherapy has been demonstrated in cancer treatment. Here, we studied the effect of hypoxia and angiogenesis inhibition on radiation-induced late rectal injury. The rectum of C57BL/6N mice was irradiated locally with a single dose of 25 Gy. Radiation-induced histological changes were examined at 90 days after irradiation by hematoxylin-eosin (H.E.) staining and azan staining. Pimonidazole was administered and its distribution was assayed by immunohistochemistry staining. Expression of transforming growth factor beta1 (TGF-beta1), hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) was assessed on the fibrotic region using real-time PCR and immunohistochemistry. In addition, the effects of TGF-beta, VEGF and HIF-1alpha on radiation-induced injury were investigated by the administration of neutralizing antibody of TGF-beta, antibody of VEGF or YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole) which was developed as an agent for inhibiting HIF-1 expression after irradiation respectively. Fibrosis and uptake of pimonidazole were found 90 days after irradiation. The expression of TGF-beta1, HIF-1alpha and VEGF significantly increased with the formation of fibrosis induced by irradiation compared with unirradiated controls. In addition, treatment of neutralizing antibody of TGF-beta, antibody of VEGF or YC-1 reduced the development of radiation-induced injury. Our results suggested that radiation-induced hypoxia may play an important role in late rectal injury. Although the inhibition of HIF-1alpha and VEGF reduced the radiation induced late injury, the precise mechanism is still unclear.

Bacterial delivery of a novel cytolysin to hypoxic areas of solid tumors

The efficacy of current anti-cancer gene therapies is limited by the inability of gene vectors to penetrate the poorly vascularized, hypoxic regions of tumors, leaving these sites untreated. We describe a new approach for targeting gene therapy to these sites, which employs an attenuated strain of the non-pathogenic bacterium, Salmonella typhimurium, carrying an exogenous (that is, reporter or therapeutic) gene under the regulation of a new, highly hypoxia-inducible promoter (FF+20(*)). This bacterial vector was seen to rapidly migrate into, and thrive in, hypoxic areas of both mammary tumor spheroids grown in vitro and orthotopic mammary tumors after systemic injection. Using the reporter gene construct, FF+20(*)-lacZ, we show that bacterial expression of high levels of beta-galactosidase occurred only in hypoxic/necrotic sites of spheroids and tumors. We then replaced the reporter gene with one encoding a novel cytotoxic protein (HlyE) and showed that this was also expressed by bacteria only in hypoxic regions of murine mammary tumors. This resulted in a marked increase in tumor necrosis and reduced tumor growth. Our system represents a promising new strategy for delivering gene therapy to poorly vascularized regions of tumors and shows, for the first time, the efficacy of HlyE as an anti-tumor agent.

Anticoagulation and inhibition of nitric oxide synthase influence hepatic hypoxia after monocrotaline exposure

Monocrotaline (MCT) is a pyrrolizidine alkaloid plant toxin that produces hepatotoxicity in humans and animals. Administration of MCT to rats causes rapid sinusoidal endothelial cell (SEC) injury, hemorrhage, pooling of blood and fibrin deposition in centrilobular regions of liver. These events precede hepatic parenchymal cell (HPC) injury and produce marked changes in the microvasculature of the liver, which could interrupt blood flow and produce hypoxia in affected regions. To test the hypothesis that hypoxia occurs in liver after MCT exposure, rats were treated with 300mgMCT/kg, and hypoxia was detected immunohistochemically. MCT produced significant hypoxia in centrilobular regions of livers by 8h after treatment. Inasmuch as fibrin deposition can impair oxygen delivery by reducing blood flow, the effect of anticoagulant treatment on MCT-induced hypoxia was determined. Administration of warfarin to MCT-treated rats reduced hypoxia in the liver by approximately 70%, suggesting that fibrin deposition plays a causal role in the development of hypoxia in the liver. Conversely, administration of l-NAME, a nonspecific inhibitor of nitric oxide synthases (NOSs), enhanced MCT-induced hypoxia and HPC injury. l-NAME did not, however, affect SEC injury or coagulation system activation. Results from these studies show that hypoxia occurs in the liver after MCT exposure. Furthermore, hypoxia precedes HPC injury, and manipulations that modify hypoxia also modulate HPC injury.

Loss of Cited2 affects trophoblast formation and vascularization of the mouse placenta

Cited2 is widely expressed in the developing embryo and in extraembryonic tissues including the placenta. Gene expression can be induced by a number of factors; most notably by the hypoxia inducible transcription factor, HIF1, under low oxygen conditions. Cited2 encodes for a transcriptional co-factor that in vitro can act as both a positive and negative regulator of transcription. This function is due to its interaction with CBP/p300 and appears to depend on whether Cited2 enables CBP/p300 to interact with the basic transcriptional machinery, or if its binding prevents such an interaction from occurring. Here, we report a novel function for Cited2 in placenta formation, following gene deletion in mouse. In the absence of Cited2 the placenta and embryo are significantly small from 12.5 and 14.5 dpc respectively, and death occurs in utero. Cited2 null placentas have fewer differentiated trophoblast cell types; specifically there is a reduction in trophoblast giant cells, spongiotrophoblasts and glycogen cells. In addition, the fetal vasculature of the placenta is disorganised and there are fewer anastomosing capillaries. Given that Cited2 is expressed in both trophoblasts and the fetal vasculature, the observed defects fit well with the sites of gene expression. We conclude that Cited2 is required for normal placental development and vascularisation, and hence for embryo viability.

Cadmium induced MTs synthesis via oxidative stress in yeast Saccharomyces cerevisiae

Yeast, Saccharomyces cerevisiae, exposed to CdCl2 for 17 h was analysed with reference to survival, MTs and oxidative stress biomarkers. An enhanced accumulation of MDA and the increased activities of SOD and GPx in the Cd-treated yeasts under aerobic condition indicated CdCl2-caused oxidative stress in S. cerevisiae. MTs were significantly induced by CdCl2 under aerobic condition and the induced MTs contents were positively correlated with the accumulation of MDA in this study. However, MTs induction can be prominently inhibited by coincubation with NAC or anaerobic culture via eliminating ROS. This oxidative stress reduction was reflected by the decreases in MDA level and SOD and GPx activities. The results suggest that MTs inductive activity of cadmium in yeast cells was mediated by oxidative stress. In addition, increase of MTs contents was observed in cells untreated with CdCl2 under anaerobic conditions or coincubation with NAC, suggesting MTs are also susceptive to reductive stress.

Hypoxia potentiates transforming growth factor-beta expression of hepatocyte during the cirrhotic condition in rat liver

BACKGROUND/AIMS

Many studies have reported that hypoxia might be associated with angiogenesis and fibrogenesis, and the level of transforming growth factor-beta1 (TGF-beta1) was increased in fibrotic liver and maximal at cirrhosis. Therefore, we examined the expression of TGF-beta1, phosphorylated-Smad2/3 (p-Smad2/3) of the TGF-beta immediate down stream signaling system and hypoxic status during hepatic fibrogenesis.

METHODS

Fibrosis of rats was induced by carbon tetrachloride. Collagens were detected with Azan stain. Immunohistochemistry and immunoblotting was used.

RESULTS

TGF-beta1 was mainly produced by hypoxic hepatocytes at cirrhosis although myofibroblasts (MFBs) and macrophages producing TGF-beta1 were decreased. Moreover, distribution of p-Smad2/3 in hepatocytes was consistent with those of hypoxic hepatocytes regardless of MFBs. Furthermore, in recovery, most MFBs disappeared, whereas positive reactions of p-Smad2/3 still existed in the hepatocytes of hypoxic areas. Therefore, TGF-beta1 expression in hepatocytes might have been associated with hypoxia.

CONCLUSIONS

We put forward the hypothesis that TGF-beta1 is mainly produced by MFBs and macrophages at early and middle stages of fibrotic processes, but it is predominantly released by hypoxic hepatocytes in the last fibrotic stage or cirrhosis.

Regulation of malignant progression by the hypoxia-sensitive transcription factors HIF-1alpha and MTF-1

Solid tumors are known to develop microenvironmental hypoxia or anoxia due to malfunction and malformation of blood vessels and the energy demands of the highly proliferative tumor cells. Oxygen deprivation can cause aberrant modifications of signaling pathways and their downstream transcription factors that are believed to contribute to malignancy. Here, we review the latest studies related to the involvement of hypoxia-inducible transcription factor-1alpha (HIF-1alpha), the first known mammalian intracellular hypoxia sensor, in tumor development. We propose that a second far less studied protein, metal transcription factor-1 (MTF-1), acts as a more general oxygen sensor, responding to both hypoxia and oxidative stress, and is also intimately involved in malignant progression. Existing evidence suggests that activation of these two ubiquitous proteins, by hypoxia and genetic modifications, modulate the expression patterns of a number of important proteins involved in tumorigenesis.

Tumor-dependent kinetics of partial pressure of oxygen fluctuations during air and oxygen breathing

The primary purpose of this study was to examine the kinetics of partial pressure of oxygen (pO2) fluctuations in fibrosarcoma (FSA) and 9L tumors under air and O2 breathing conditions. The overall hypothesis was that key factors relating to oxygen tension fluctuations would vary between the two tumor types and as a function of the oxygen content of the breathing gas. To assist in the interpretation of the temporal data, spatial pO2 distributions were measured in 10 FSA and 8 9L tumors transplanted into the subcutis of the hind leg of Nembutal-anesthetized (50 mg/kg) Fischer 344 rats. Recessed-tip oxygen microelectrodes were inserted into the tumor, and linear pO2 measurements were recorded in 50-microm steps along a 3-mm path, and blood pressure was simultaneously measured via femoral arterial access. Additionally, pO2 was measured at a single location for 90 to 120 minutes in FSA (n=11) or 9L tumors (n=12). Rats were switched from air to 100% O2 breathing after 45 minutes. Temporal pO2 records were evaluated for their potential radiobiological significance by assessing the number of times they crossed a 10-mm-Hg threshold. In addition, the data were subjected to Fourier analysis for air and O2 breathing. FSA and 9L tumors had spatial median pO2 measurements of 4 and 1 mm Hg, respectively. 9L had more low pO2 measurements < or =2.5 mm Hg than did FSA, whereas between 2.5 and 10 mm Hg this pattern was reversed. Pimonidazole staining patterns in FSA and 9L tumors supported these results. Temporal pO2 instability was observed in all experiments during air and O2 breathing. Threshold analyses indicated that the 10 mm Hg threshold was crossed 2 to 5 times per hour, independent of tumor type. However, the magnitude of 9L pO2 fluctuations was approximately eight times greater than FSA fluctuations, as assessed with Fourier transform analysis (Wilcoxon, P < 0.005). O2 breathing significantly increased median pO2 in FSA from 3 to 8 mm Hg (P < 0.005) and caused a significant increase in frequency and magnitude of pO2 fluctuations. One hundred percent O2 breathing had no effect on 9L tumor pO2, and it decreased the magnitude of pO2 fluctuations with borderline significance. These results show that these two tumors differ significantly with respect to spatial and temporal oxygenation conditions under air and O2 breathing. Fluctuations of pO2 of the type reported herein are predicted to significantly affect radiotherapy response and could be a source for genetic instability, increased angiogenesis, and metastases.

Current issues in the utility of 19F nuclear magnetic resonance methodologies for the assessment of tumour hypoxia

It is now well established that uncontrolled proliferation of tumour cells together with the chaotic and poorly regulated blood supply of solid tumours result in tissue hypoxia, and that hypoxic regions of tumours are resistant to radiotherapy and chemotherapy. The development and application of non-invasive methods to rapidly determine the degree and extent of tumour hypoxia in an individual tumour would clearly enhance cancer treatment strategies. This review describes the current status of two (19)F nuclear magnetic resonance (NMR) methodologies that have been exploited to investigate tumour hypoxia, namely: (i) (19)F NMR oximetry following administration of perfluorocarbons, from which tumour p(O)(2) measurements can be made; and (ii) (19)F NMR measurements of the tumour retention of fluorinated 2-nitroimidazoles.

Evidence that involucrin, a marker for differentiation, is oxygen regulated in human squamous cell carcinomas

The majority of hypoxic cells in squamous cell carcinomas of the head and neck and cervix express involucrin, a molecular marker for differentiation. This raises the question of whether involucrin is an oxygen-regulated protein and, if so, whether it could serve as an endogenous marker for tumour hypoxia. Consistent with oxygen regulation, involucrin protein was found to increase with increasing hypoxia in confluent cultures of moderately differentiated human SCC9 cells. Cells harvested at the point of confluence and exposed to graded concentrations of oxygen revealed a K_m of approximately 15 mmHg for involucrin induction. This is similar to K_ms for HIF-1α, CAIX and VEGF. Involucrin induction showed a steep dependence on pO₂ with a transition from minimum to maximum expression occurring over less than an order of magnitude change in pO₂. In contrast to SCC9 cells, involucrin was not induced by hypoxia in poorly differentiated SCC4 cells. It is concluded that involucrin is an oxygen-regulated protein, but that differentiation modulates its transcription status with respect to hypoxia induction.

Tumor vasculature is targeted by the combination of combretastatin A-4 and hyperthermia

BACKGROUND AND PURPOSE

Combretastatin A-4 disodium phosphate (CA-4) enhances thermal damage in s.c. BT(4)An rat gliomas. We currently investigated how CA-4 and hyperthermia affect the tumor microenvironment and neovasculature to disclose how the two treatment modalities interact to produce tumor response.

METHODS

By confocal microscopy and immunostaining for von Willebrand factor, we examined the extent of vascular damage subsequent to CA-4 (50 mg/kg) and hyperthermia (waterbath 44 degrees C, 60 min). The influence on tumor oxygenation was assessed using interstitial pO(2)-probes (Licox system) and by immunostaining for pimonidazole. We examined the direct effect of CA-4 on the tumor cell population by flow cytometry (cell cycle distribution) and immunostaining for beta-tubulin (cytoskeletal damage).

RESULTS

Whereas slight vascular damage was produced by CA-4 in the BT(4)An tumors, local hyperthermia exhibited moderate anti-vascular activity. In tumors exposed to CA-4 3 h before hyperthermia, massive vascular damage ensued. CA-4 reduced the pO(2) from 36.1 to 17.6 mmHg (P=0.01) in the tumor base, and tumor hypoxia increased slightly in the tumor center (pimonidazole staining). Extensive tumor hypoxia developed subsequent to hyperthermia or combination therapy. Despite a profound influence on beta-tubulin organization in vitro, CA-4 had no significant effect on the cell cycle distribution in vivo.

CONCLUSION

Our results indicate that the anti-vascular activity exhibited by local hyperthermia can be augmented by previous exposure to CA-4.

Vinblastine and hyperthermia target the neovasculature in BT(4)AN rat gliomas: therapeutic implications of the vascular phenotype

PURPOSE

The antivascular and antitumor activity of vinblastine and hyperthermia at different tumor volumes were examined in the subcutaneous (s.c.) BT(4)An rat glioma model.

METHODS AND MATERIALS

The influence of vinblastine (3 mg/kg) and hyperthermia (44 degrees C/60 min) on tumor growth was assessed in small (100 mm(3)) and large (200 mm(3)) BT(4)An tumors. To disclose how vinblastine and hyperthermia interacted in the neoplasms, tumor blood flow and the extent of vascular damage, hypoxia, cell proliferation, and apoptosis were assessed after treatment. The content of smooth muscle cells/pericytes in the tumor vasculature was examined in small and large tumors to assess how the vascular phenotype changed during tumor growth.

RESULTS

In the large tumors, vinblastine reduced the blood flow, but the tumor growth was not affected. The combination of drug and local heating yielded massive vascular damage and a significant tumor response. The small neoplasms had a higher content of smooth muscle cells/pericytes in the vessel walls (host vasculature), and the tumor vasculature displayed a higher resistance to vascular damage than the large neoplasms. Yet, vinblastine alone exhibited a potent antiproliferative activity and induced massive apoptosis in the small tumors, and the drug significantly inhibited tumor growth. The addition of hyperthermia yielded no additional growth delay in the small tumors.

CONCLUSION

The antivascular properties of vinblastine and hyperthermia can be exploited to facilitate vascular damage in BT(4)An solid tumors with a low content of host vasculature.

Hypoxia in human intraperitoneal and extremity sarcomas

PURPOSE

The presence of hypoxia, measured by needle electrodes, has been shown to be associated with poor patient outcome in several human tumor types, including soft tissue sarcomas. The present report emphasizes the evaluation of hypoxia in soft tissue sarcomas based upon the binding of the 2-nitroimidazole drug EF5 (2-[2-nitro-1H-imidazol-1-yl]-N-(2,2,3,3,3-pentafluoropropyl) acetamide). EF5 has previously been shown to be predictive of radiation response in animal tumors and in in vitro studies. We have also previously reported studies of EF5 binding in human squamous cell tumors. Using fluorescent immunohistochemical techniques, we provide data on the presence and distribution of EF5 binding, as a surrogate for hypoxia, in human spindle cell tumors.

METHODS AND MATERIALS

Patients with spindle cell tumors who were scheduled for tumor surgery were asked to participate in the Phase I trial of EF5. Approximately 48 h preoperatively, EF5 was administered i.v. at doses between 9 and 21 mg/kg. Binding in frozen sections of biopsied tissues was determined using monoclonal antibodies labeled with the green-excited, orange-emitting fluorescent dye, Cy3. Calibration studies were performed in vitro by incubating fresh tumor tissue cubes obtained from each patient with EF3 (an analog of EF5) under hypoxic conditions ("reference binding"). The goal of these calibration studies was to quantify the maximal binding levels possible in individual patient's tissues. The relationship between binding (in situ based on EF5 binding) and reference binding (in vitro based on EF3 binding) was determined.

RESULTS

Eight patients were studied; 3 of these patients had gastrointestinal stromal tumors (GIST). The incubation of tumor tissue cubes in EF3 under hypoxic conditions demonstrated that all tumors bound drug to a similar extent. Reference binding showed a 3.2-fold variation in median fluorescence (113-356) on an absolute fluorescence scale, calibrated by a Cy3 dye standard. In situ binding in the brightest tumor section varied by a factor of 25.4 between the lowest and highest binding tumor (7.5-190.2). Heterogeneity of highest binding was greater between tumors than within individual tumors. A correspondence between EF5 binding and Eppendorf needle electrode studies was seen in the 5 patients with non-GISTs.

CONCLUSION

Inter- and intratumoral heterogeneity of EF5 binding in spindle cell tumors has been documented. Patterns of binding consistent with diffusion limited hypoxia are present in human spindle cell neoplasms.

Semiquantitative immunohistochemical analysis for hypoxia in human tumors

OBJECTIVE

The goal of this study was to develop a semiquantitative scoring system for measuring hypoxia in human tumors by an immunohistochemical marker approach.

METHODS AND MATERIALS

Eighteen patients diagnosed with squamous cell carcinoma of the uterine cervix or head and neck were infused intravenously with a solution of pimonidazole hydrochloride at a dose of 0.5 gm/m2. Twenty-four hours later, four biopsies on average from each tumor were fixed in formalin, processed into paraffin blocks, and sectioned. Tissue sections were immunostained for the presence of pimonidazole adducts. Microscopic images (x200) of immunostaining were captured and quantitated by standard image analysis. Images with known amounts of hypoxia spanning ranges of > 0% to 5%, > 5% to 15%, > 15% to 30%, and >30% were assigned scores of +1, +2, +3, and +4, respectively. Three observers then used this calibrated scoring system to analyze hypoxia in tumor sections in a blinded fashion.

RESULTS

Excellent interobserver reproducibility was obtained with the calibrated, semiquantitative, immunohistochemical assay for hypoxia in squamous cell carcinomas.

CONCLUSION

The calibrated, semiquantitative assay shows promise as an approach to simplifying the quantitation of human tumor hypoxia by immunohistochemical techniques.

Estimation of oxygen distribution in RIF-1 tumors by diffusion model-based interpretation of pimonidazole hypoxia and eppendorf measurements

Numerical simulations of oxygen diffusion from the capillaries in tumor tissue were used to predict the capillary oxygen supply within and near hypoxic regions of the RIF-1 tumor. A finite element method to simulate the oxygen distribution from a histology section is presented, along with a method to iteratively estimate capillary oxygen concentrations. Pathological structural data for these simulations came from sections of the tumor stained with hematoxylin and eosin and were used to define the capillary positions and shapes, while overlapping regions of low oxygen concentration were defined by the hypoxia marker pimonidazole. These simulations were used to calculate spatial maps of the oxygen concentration and were tested for their ability to reproduce Eppendorf pO(2) histograms from the same tumor line. This simulation study predicted that capillary oxygen concentrations ranged from zero to above 20 microM, with a dominant peak in the hypoxic regions showing 78% of capillaries with less than 1 microM oxygen concentration, compared to only 12% in the non-hypoxic regions. The results were not highly sensitive to the metabolic oxygen consumption rate, within the range of 2 to 16 microM/s. This numerical method for oxygen capillary simulation is readily adaptable to histology sections and provides a method to examine the heterogeneity of oxygen within the capillaries and throughout the tumor tissue section being examined.