Biomedical subjects

Z Vujaskovic

Publications and source records attributed to Z Vujaskovic.

At least 19 recordsLinked to original sources

PubMed2006

Treatment with Imatinib in NSCLC is associated with decrease of phosphorylated PDGFR-beta and VEGF expression, decrease in interstitial fluid pressure and improvement of oxygenation.

Elevated intratumoral interstitial fluid pressure (IFP) and tumour hypoxia are independent predictive factors for poor survival and poor treatment response in cancer patients. However, the relationship between IFP and tumour hypoxia has not yet been clearly established. Preclinical studies have shown that lowering IFP improves treatment response to cytotoxic therapy. Interstitial fluid pressure can be reduced by inhibition of phosphorylated platelet-derived growth factor receptor-beta (p-PDGFR-beta), a tyrosine kinase receptor frequently overexpressed in cancer stroma, and/or by inhibition of VEGF, a growth factor commonly overexpressed in tumours overexpressing p-PDGFR-beta. We hypothesised that Imatinib, a specific PDGFR-beta inhibitor will, in addition to p-PDGFR-beta inhibition, downregulate VEGF, decrease IFP and improve tumour oxygenation. A549 human lung adenocarcinoma xenografts overexpressing PDGFR-beta were grown in nude mice. Tumour-bearing animals were randomised to control and treatment groups (Imatinib 50 mg kg(-1) via gavage for 4 days). Interstitial fluid pressure was measured in both groups before and after treatment. EF5, a hypoxia marker, was administered 3 h before being killed. Tumours were sectioned and stained for p-PDGFR-beta, VEGF and EF5 binding. Stained sections were viewed with a fluorescence microscope and image analysis was performed. Imatinib treatment resulted in significant reduction of p-PDGFR-beta, VEGF and IFP. Tumour oxygenation was also significantly improved. This study shows that p-PDGFR-beta-overexpressing tumours can be effectively treated with Imatinib to decrease tumour IFP. Importantly, this is the first study demonstrating that Imatinib treatment improves tumour oxygenation and downregulates tumour VEGF expression.

Adenocarcinoma↗

PubMed2006

ROS production and angiogenic regulation by macrophages in response to heat therapy.

PURPOSE: It has been well established that inadequate blood supply combined with high metabolic rates of oxygen consumption results in areas of low oxygen tension (<1%) within malignant tumours and that elevating tumour temperatures above 39 degrees Celsius results in significant improvement in tumour oxygenation. Macrophages play a dual role in tumour initiation and progression having both pro-tumour and anti-tumour effects. However, the response of macrophages to heat within a hypoxic environment has not yet been clearly defined. METHODS: Raw 264.7 murine macrophages were incubated under normoxia and chronic hypoxia at temperatures ranging from 37-43 degrees Celsius. Under normoxia at 41 degrees Celsius, macrophages start to release significant levels of superoxide. The combination of heat with hypoxia constitutes an additional stimulus leading to increased respiratory burst of macrophages. RESULTS: The high levels of superoxide were found to be associated with changes in macrophage production of pro-angiogenic cytokines. While hypoxia alone (37 degrees Celsius) increased levels of hypoxia inducible factor-1alpha (HIF-1alpha) in macrophages, the combination of hypoxia and mild hyperthermia (39-41 degrees Celsius) induced a strong reduction in HIF-1alpha expression. The HIF-regulated vascular endothelial growth factor (VEGF) decreased simultaneously, revealing that heat inhibits both HIF-1alpha stabilization and transcriptional activity. CONCLUSION: The data suggest that temperatures which are readily achievable in the clinic (39-41 degrees Celsius) might be optimal for maximizing hyperthermic response. At higher temperatures, these effects are reversed, thereby limiting the therapeutic benefits of more severe hyperthermic exposure.

Animals↗

PubMed2005

Human recombinant erythropoietin (rEpo) has no effect on tumour growth or angiogenesis.

Tumour hypoxia has been shown to increase mutation rate, angiogenesis, and metastatic potential, and decrease response to conventional therapeutics. Improved tumour oxygenation should translate into increased treatment response. Exogenous recombinant erythropoietin (rEpo) has been recently shown to increase tumour oxygenation in a mammary carcinoma model. The mechanism of this action is not yet understood completely. The presence of Epo and its receptor (EpoR) have been demonstrated on several normal and neoplastic tissues, including blood vessels and various solid tumours. In addition, rEpo has been shown in two recent prospective, randomized clinical trials to negatively impact treatment outcome. In this study, we attempt to characterize the direct effects of rEpo on tumour growth and angiogenesis in two separate rodent carcinomas. The effect of rEpo on R3230 rat mammary adenocarcinomas, CT-26 mouse colon carcinomas, HCT-116 human colon carcinomas, and FaDu human head and neck tumours, all of which express EpoR, was examined. There were no differences in tumour growth or proliferation (measured by Ki-67) between placebo-treated and rEpo-treated tumours. In the mammary window chamber, vascular length density (VLD) measurements in serial images of both placebo-treated and Epo-treated rats revealed no difference in angiogenesis between the Epo-treated tumours and placebo-treated tumours at any time point. These experiments are important because they suggest that the recent clinical detriment seen with the use of Epo is not due to its tumour growth effects or angiogenesis. These studies also suggest that further preclinical studies need to examine rEpo's direct tumour effects in efforts to improve the therapeutic benefits of Epo in solid tumour patients.

Animals↗

PubMed2004

Physiological mechanisms underlying heat-induced radiosensitization.

The objective of this review is to evaluate hyperthermia related changes in tumor physiologic parameters and their relevance for tumor radiosensitization with particular emphases on tumor oxygenation. Elevation of temperature above the physiological level causes changes in blood flow, vascular permeability, metabolism, and tumor oxygenation. These changes in addition to the cellular effects such as direct cytotoxicity, inhibition of potentially lethal damage and sublethal damage repair, have an important influence on the efficacy of radiotherapy. There is now clear evidence that in a variety of rodent and canine, as well as human tumors, the changes in tumor oxygenation status caused by hyperthermia are temperature dependent and this relationship may greatly influence the response of tumors to thermoradiotherapy. The improvement of tumor oxygenation after mild hyperthermia, which often lasts for as long as 24-48 h after heating, may increase the likelihood of a positive response of tumors to radiation therapy. Furthermore, the activity of some chemotherapy drugs is also oxygen dependent, therefore, the heat-induced increase in tumor oxygenation may significantly increase the effectiveness of thermoradiotherapy in combination with certain chemotherapy drugs. Further investigations remain to be conducted to obtain clearer insights into the relationship between thermal parameters, oxygenation and response of human tumors to hyperthermia in combination with radiotherapy and/or chemotherapy.

Animals↗

PubMed2004

Effect of calcitonin gene related peptide vs sodium nitroprusside to increase temperature in spontaneous canine tumours during local hyperthermia.

The objectives of this study were to compare the effects of two vasodilators, sodium nitroprusside (SNP) and calcitonin gene-related peptide (CGRP) on mean arterial pressure (MAP), heart rate (HR) and temperatures in tumour and surrounding normal tissue during local hyperthermia treatment. Eleven tumour-bearing pet dogs with spontaneous soft tissue sarcomas were given SNP intravenously during local hyperthermia. The drug infusion rate was adjusted to maintain a 20% decrease in MAP. The median (95% CI) increase in the temperature distribution descriptors T(90) and T(50) was 0.2 degrees C (0.0-0.4 degrees C, p = 0.02) and 0.4 degrees C (0.1-0.7 degrees C, p = 0.02), respectively, in tumour. Normal subcutaneous tissue temperatures were mildly increased but remained below the threshold for thermal injury. The effects of CGRP were investigated in six tumour-bearing dogs following a protocol similar to that used for SNP. The median (interquartile (IQ) range) decrease in mean arterial pressure was 19% (15-26%) after CGRP administration and a significant increase was seen in tumour but not normal subcutaneous tissue temperatures. The median (95% CI) increase in the temperature distribution descriptors T(90) and T(50) was 0.5 degrees C (0.1-1.6 degrees C, p = 0.03) and 0.8 degrees C (0.1-1.6 degrees C, p = 0.13), respectively. Administration of SNP or CGRP did not result in local or systemic toxicity in tumour-bearing dogs. However, the magnitude of increase in tumour temperatures was not sufficient to improve the likelihood of increased response rates. Therefore, there is little justification for translation of this approach to human trials using conventional local hyperthermia.

Animals↗

PubMed2001

Radiation-induced hypoxia may perpetuate late normal tissue injury.

PURPOSE: The purpose of this study was to determine whether or not hypoxia develops in rat lung tissue after radiation. METHODS AND MATERIALS: Fisher-344 rats were irradiated to the right hemithorax using a single dose of 28 Gy. Pulmonary function was assessed by measuring the changes in respiratory rate every 2 weeks, for 6 months after irradiation. The hypoxia marker was administered 3 h before euthanasia. The tissues were harvested at 6 weeks and 6 months after irradiation and processed for immunohistochemistry. RESULTS: A moderate hypoxia was detected in the rat lungs at 6 weeks after irradiation, before the onset of functional or histopathologic changes. The more severe hypoxia, that developed at the later time points (6 months) after irradiation, was associated with a significant increase in macrophage activity, collagen deposition, lung fibrosis, and elevation in the respiratory rate. Immunohistochemistry studies revealed an increase in TGF-beta, VEGF, and CD-31 endothelial cell marker, suggesting a hypoxia-mediated activation of the profibrinogenic and proangiogenic pathways. CONCLUSION: A new paradigm of radiation-induced lung injury should consider postradiation hypoxia to be an important contributing factor mediating a continuous production of a number of inflammatory and fibrogenic cytokines.

Animals↗

PubMed2001

Comparison of three rat strains for development of radiation-induced lung injury after hemithoracic irradiation.

The purpose of this study is to define differences in radiation sensitivity among rat strains using breathing frequency and lung perfusion as end points of radiation-induced lung injury. The results have confirmed previous findings in mice showing that under stringently controlled iso-dose/volume irradiation conditions, substantial differences can be found in susceptibility to functional lung damage after radiation.

Animals↗

PubMed2000

Temperature-dependent changes in physiologic parameters of spontaneous canine soft tissue sarcomas after combined radiotherapy and hyperthermia treatment.

PURPOSE: The objectives of this study were to evaluate effects of hyperthermia on tumor oxygenation, extracellular pH (pHe), and blood flow in 13 dogs with spontaneous soft tissue sarcomas prior to and after local hyperthermia. METHODS AND MATERIALS: Tumor pO2 was measured using an Eppendorf polarographic device, pHe using interstitial electrodes, and blood flow using contrast-enhanced magnetic resonance imaging (MRI). RESULTS: There was an overall improvement in tumor oxygenation observed as an increase in median pO2 and decrease in hypoxic fraction (% of pO2 measurements <5 mm Hg) at 24-h post hyperthermia. These changes were most pronounced when the median temperature (T50) during hyperthermia treatment was less than 44 degrees C. Tumors with T50 > 44 degrees C were characterized by a decrease in median PO2 and an increase in hypoxic fraction. Similar thermal dose-related changes were observed in tumor perfusion. Perfusion was significantly higher after hyperthermia. Increases in perfusion were most evident in tumors with T50 < 44 degrees C. With T50 > 44 degrees C, there was no change in perfusion after hyperthermia. On average, pHe values declined in all animals after hyperthermia, with the greatest reduction seen for larger T50 values. CONCLUSION: This study suggests that hyperthermia has biphasic effects on tumor physiologic parameters. Lower temperatures tend to favor improved perfusion and oxygenation, whereas higher temperatures are more likely to cause vascular damage, thus leading to greater hypoxia. While it has long been recognized that such effects occur in rodent tumors, this is the first report to tie such changes to temperatures achieved during hyperthermia in the clinical setting. Furthermore, it suggests that the thermal threshold for vascular damage is higher in spontaneous tumors than in more rapidly growing rodent tumors.

Animals↗

PubMed2000

The physical parameters and molecular events associated with radiation-induced lung toxicity.

Radiation therapy (RT) is frequently used to treat patients with tumors in and around the thorax. Clinical radiation pneumonitis is a common side effect, occurring in 5% to 20% of patients. Efforts to identify patients at risk for pneumonitis have focused on physical factors, such as dose and volume. Recently, the underlying molecular biological mechanisms behind RT-induced lung injury have come under study. Improved knowledge of the molecular events associated with RT-induced lung injury may translate into a better ability to individualized therapy. This review discusses our current understanding of the physical and molecular factors contributing to RT-induced pulmonary injury.

Carcinoma, Non-Small-Cell Lung↗

PubMed2000

Volume and dose-response effects for severe symptomatic pneumonitis after fractionated irradiation of canine lung.

PURPOSE: To study the dose-related incidence of severe symptomatic pneumonitis following fractionated irradiation applied to three different volumes of lung in normal beagle dogs. MATERIALS AND METHODS: A three-dimensional treatment planning system was used to design mediastinal fields of increasing width to irradiate 33%, 67% or 100% of both lungs combined in 128 normal beagle dogs. Total doses, ranging from 27 to 72 Gy, were delivered in 1.5 Gy fractions over 6 weeks. RESULTS: No dogs irradiated to 33% of their total lung volume developed severe symptomatic pneumonitis. In the 67% volume group, logistic fit of the data showed a dose-response curve with a 50% probability of developing severe symptomatic pneumonitis (ED50) after a total dose of 56.0 Gy (52.2-66.0 Gy, 95% confidence interval, CI). The more clinically relevant ED5 for the first 6 months after irradiation of 67% of the lung was 48.1 Gy (18.5-52.0 Gy, 95% CI). The ED50 and ED5 values after irradiation of the whole lung (100%) were 44.1 Gy (41.2-53.5Gy, 95% CI) and 39.1 Gy (8.8-41.8 Gy, 95% CI) respectively. CONCLUSION: Severe symptomatic pneumonitis proved to be a very informative volume-effect endpoint, clearly demonstrating that irradiated lung volume is a critical parameter to be considered in assigning thoracic radiotherapy treatment parameters. Volume effects in lung are dependent on the compensatory capacity of the nonirradiated lung. Underlying pathophysiology of irradiated tissue, as well as decreased compensatory capacity of nonirradiated tissue may have a strong effect on the dose-volume response.

Animals↗

PubMed2000

TGF-beta, radiation-induced pulmonary injury and lung cancer.

PURPOSE: To determine whether changes in TGF-beta plasma levels during radiation therapy may be useful in predicting radiation-induced pulmonary injury and tumour response in non-small-cell lung cancer (NSCLC) patients. MATERIALS AND METHODS: Plasma TGF-beta was investigated in 27 patients with stage III NSCLC, who were treated with 60 Gy (2Gy/day) radiotherapy with or without carboplatin. TGF-beta was measured prior to beginning radiotherapy and weekly during treatment; evaluated as a ratio between TGF-beta levels obtained during treatment and the pretreatment TGF-beta level. The endpoints of the study were development of symptomatic radiation pneumonitis and tumour response. RESULTS: Nine of the 27 patients developed pneumonitis. The patients who developed pneumonitis had high persistent TGF-beta levels throughout the course of treatment (TGF-beta ratio>1), whereas the TGF-beta levels in patients who did not develop pneumonitis were unchanged or declined towards normal (TGF-beta ratio < 1). Patients who responded to treatment had low or normal TGF-beta levels during treatment compared with patients who failed to respond. Other parameters such as pretreatment TGF-beta values, carboplatin treatment or field size did not appear to have a significant effect, which is probably due to the small number of patients entered in the study. CONCLUSION: This pilot study, with a limited number of patients, suggests the hypothesis that elevated TGF-beta levels during radiotherapy may not only indicate patients with a higher risk of developing pulmonary toxicity but also patients with a higher risk of treatment failure. This remains to be tested in a larger clinical study.

Adult↗

PubMed2000

Superior vena cava obstruction caused by radiation induced venous fibrosis.

Superior vena cava syndrome is most often caused by lung carcinoma. Two cases are described in whom venous obstruction in the superior mediastinum was caused by local vascular fibrosis due to radiotherapy five and seven years earlier. The development of radiation injury to greater vessels is discussed, together with the possibilities for treatment of superior vena cava syndrome.

Adult↗

PubMed2000

The relationship between intracellular and extracellular pH in spontaneous canine tumors.

Recently, it has been suggested that the cellular uptake of chemotherapeutic drugs may be dependent on the pH gradient between the intracellular (pHi) and extracellular (pHe) compartments. It has been demonstrated in murine tumor models that the extracellular environment is acidic, relative to the intracellular environment, thus favoring preferential accumulation of drugs that are weak acids into cells. However, concomitant measurements of pHi and pHe in spontaneous tumors have not been reported, so it is not certain how well the murine results translate to the clinical scenario. In this study, both types of measurements were performed in dogs with spontaneous malignant soft tissue tumors. On average, pHe was more acidic than pHi, with maintenance of a more physiologically balanced intracellular tumor environment. However, the magnitude of the gradient varied widely, and individual tumors had both positive and negative pH gradients (pHi - pHe). These data suggest that the magnitude and direction of the pH gradient may need to be measured for individual patient tumors and/or that manipulation of pHe may be required if exploitation of the pH gradient is to be achieved for tumor-selective augmentation of intracellular drug delivery.

Animals↗

PubMed1999

Effects of intraoperative irradiation (IORT) and intraoperative hyperthermia (IOHT) on canine sciatic nerve: histopathological and morphometric studies.

PURPOSE/OBJECTIVE: Peripheral neuropathies have emerged as the major dose-limiting complication reported after intraoperative radiation therapy (IORT). The combination of IORT with hyperthermia may further increase the risk of peripheral nerve injury. The objective of this study was to evaluate histopathological and histomorphometric changes in the sciatic nerve of dogs, after IORT with or without hyperthermia treatment. METHODS AND MATERIALS: Young adult beagle dogs were randomized into five groups of 3-5 dogs each to receive IORT doses of 16, 20, 24, 28, or 32 Gy. Six groups of 4-5 dogs each received IORT doses of 12, 16, 20, 24, or 28 Gy simultaneously with 44 degrees C of intraoperative hyperthermia (IOHT) for 60 min. One group of dogs acted as hyperthermia-alone controls. Two years after the treatment, dogs were euthanized, and histopathological and morphometric analyses were performed. RESULTS: Qualitative histological analysis showed prominent changes such as focal necrosis, mineralization, fibrosis, and severe fiber loss in dogs which received combined treatment. Histomorphometric results showed a significantly higher decrease in axon and myelin and small blood vessels, with a corresponding increase in connective tissue in dogs receiving IORT plus hyperthermia treatment. The effective dose for 50% of nerve fiber loss (ED50) in dogs exposed to IORT only was 25.3 Gy. The ED50 for nerve fiber loss in dogs exposed to IORT combined with IOHT was 14.8 Gy. The thermal enhancement ratio (TER) was 1.7. CONCLUSION: The probability of developing peripheral neuropathies in a large animal model is higher when IORT is combined with IOHT, when compared to IORT application alone. To minimize the risk of peripheral neuropathy, clinical treatment protocols for the combination of IORT and hyperthermia should not assume a thermal enhancement ratio (TER) to be lower than 1.5.

Animals↗

PubMed1999

TGF-beta and bFGF affect the differentiation of proliferating porcine fibroblasts into myofibroblasts in vitro.

Fibroblasts and myofibroblasts are involved in the foreign body reaction to biomaterials, especially in capsule formation. However, contraction or detachment of the capsule can lead to complications. Biocompatibility of biomaterials may be improved by the application of proteins regulating the differentiation or activation of (myo)fibroblasts. Myofibroblasts, differentiating from fibroblasts can be identified by the expression of alpha-smooth muscle actin (alpha-SM actin). We investigated the influence of proliferation and quiescence on the differentiation of porcine dermal cells and whether transforming growth factor-beta (TGF-beta) and basic fibroblast growth factor (bFGF) are involved in the differentiation of proliferating cells. Porcine cells were used because pigs increasingly function as in vivo models while little is known of the characteristics of their cells. Serum-free cultured, quiescent fibroblasts differentiated into myofibroblasts, while proliferating fibroblasts cultured in the presence of serum containing TGF-beta, formed alpha-SM actin-negative cell clusters. After reaching confluency, these clusters started to expressing alpha-SM actin. Moreover, these proliferating cells produced TGF-beta from day 4 onwards while bFGF did not. Differentiation into myofibroblasts was inhibited by bFGF and to an even greater extent by antibodies to TGF-beta. Further, two theories concerning the role of the myofibroblast in tissue contraction in view of two biomaterial application will be discussed.

Actins↗

PubMed1998

Induction of tumor necrosis factor-alpha as a cause of bleomycin-related toxicity.

BACKGROUND: The application of bleomycin is characterized by acute side effects, such as fever, chills, and sometimes hypotension and tachypnea. Furthermore, bleomycin is known to induce pneumonitis. There are several indications that the induction of cytokines by bleomycin is involved in the development of these side effects. METHODS: In this study, the authors determined the plasma levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and transforming growth factor-beta (TGF-beta) before and after bleomycin infusion in 14 patients treated for disseminated nonseminomatous germ cell tumor. RESULTS: Compared with the pretreatment value, TNF-alpha was significantly increased 3, 4.5, and 24 hours after bleomycin infusion. For IL-1beta and TGF-beta, no significant alterations were observed within 24 hours after administration of bleomycin. CONCLUSIONS: The increase in TNF-alpha after administration of bleomycin suggests a role for this cytokine in the development of the acute side effects and probably also in the occurrence of bleomycin-induced pulmonary toxicity. The involvement of IL-1beta and TGF-beta deserve further study.

Adolescent↗

PubMed1997

Quantification of transforming growth factor-beta in biological material using cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct.

Transforming growth factor-beta (TGF-beta), a multifunctional cytokine, can be quantified by a variety of bioassays or immunoassays. One of the disadvantages of these techniques is that they require sample purification to remove components that interfere with the TGF-beta signal. In the current study the feasibility of quantifying TGF-beta in complex biological fluids directly with a recently developed bioassay was examined. This assay is based on the ability of TGF-beta to induce plasminogen activator inhibitor-1 (PAI-1) expression. Mature TGF-beta binds to the receptors of mink lung epithelial cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct (PAI/L), resulting in a dose-dependent increase of luciferase activity. Specificity for TGF-beta was proven by treatment of the samples with neutralizing antibodies. The sensitivity and the intraassay precision are comparable to the ELISA. It is demonstrated, however, that, unlike the ELISA, a purification step by, e.g., acid-ethanol extraction prior to the PAI/L assay, is not required. This not only simplifies the assay but also reduces the minimal sample volume and allows to discriminate between latent and mature TGF-beta. The present study furthermore provides insight in the critical steps for accurate TGF-beta determination, which include careful blood collection and sample handling (storage and preparation). With this protocol TGF-beta has been quantified in human plasma, rat plasma, rat saliva, tissue extracts from rat lung, and in culture medium of TGF-beta-producing cells.

Animals↗

PubMed1997

Plasma TGFbeta level in rats after hemithoracic irradiation.

Changes in TGF-beta plasma levels were observed 18 weeks after hemithoracic irradiation in rats. This coincides with an increase in the breathing frequency. being most pronounced between 22 and 28 weeks after irradiation. The correlation suggests a potential role of the circulating TGF-beta in the monitoring of localized radiation-induced lung injury.

Animals↗