RESUMEN
The spatial heterogeneity of the oxygen tension (pO(2)) in human and experimental tumours has been studied extensively, whereas studies of the temporal heterogeneity in pO(2) are sparse. In the work reported here, pO(2) was measured continuously over periods of at least 60 min in A-07 human melanoma xenografts by using the OxyLite fibre-optic oxygen-sensing device. The main purpose of the work was to establish the usefulness of the OxyLite system in measuring the temporal heterogeneity in pO(2) in tissues and to characterise the fluctuations in tissue pO(2) in A-07 tumours. The OxyLite device was found to be suitable for studies of the temporal heterogeneity in pO(2) in tumours. However, potential pitfalls were identified, and reliable pO(2) measurements require that precautions are taken to avoid these pitfalls, that is, erroneous pO(2) readings caused by tissue trauma induced by the probe, probe movements induced by reflex actions of the host mouse and occasional probe drift. Significant fluctuations in pO(2) were detected in the majority of the 70 tumour regions subjected to measurement. The fluctuations in different regions of the same tumour were in general temporally independent, implying that they were caused primarily by redistribution of the tumour perfusion rather than fluctuations in global perfusion. Fourier analysis of the pO(2) traces showed that the pO(2) usually fluctuated at frequencies lower than 1.5-2.0 mHz, corresponding to less than 0.1 cycle min(-1). Haemodynamic effects may cause pO(2) fluctuations in this frequency range, and hence, the redistribution of the perfusion could have been caused by morphological abnormalities of the tumour microvasculature. Moreover, acute hypoxia, that is, pO(2) fluctuations around 10 or 5 mmHg, was detected in 20 of 70 regions, that is, 29% (10 mmHg), or 27 of 70 regions, that is, 39% (5 mmHg). The median fraction of the time these regions were acutely hypoxic was 73% (10 mmHg) or 53% (5 mmHg). Consequently, if A-07 tumours are adequate models of tumours in man, acute hypoxia may be a commonly occurring phenomenon in neoplastic tissues, and hence, acute hypoxia is likely to cause resistance to radiation therapy and promote tumour aggressiveness.
Asunto(s)
Hipoxia de la Célula , Melanoma/fisiopatología , Oxígeno/análisis , Neoplasias Cutáneas/fisiopatología , Animales , Femenino , Tecnología de Fibra Óptica , Hemodinámica , Humanos , Cinética , Ratones , Ratones Endogámicos BALB C , Oxígeno/metabolismo , Radioterapia , Trasplante HeterólogoRESUMEN
Intratumour heterogeneity in the uptake of blood-borne technetium-labelled human serum albumin ((99m)Tc-HSA) was studied in human melanoma xenografts in an attempt to identify transport barriers leading to inadequate and heterogeneous uptake of macromolecular therapeutic agents in tumours. The Bioscope imaging system, which can detect the distribution of (99m)Tc in 10-microm-thick tissue sections with a spatial resolution of just above 50 microm, was used to image the (99m)Tc-HSA uptake. Xenografted tumours of four human melanoma cell lines were included in the study. Significant intratumour heterogeneity in the uptake of (99m)Tc-HSA was detected. The heterogeneity had two distinctly different components, one random and one radial component. The uptake was lowest in the centre of the tumours and increased towards the tumour periphery. This radial heterogeneity was superimposed by a random heterogeneity, that is, spots with high uptake colocalised with spots with high vascular density and regions without significant uptake colocalised with necrotic regions. The magnitude of the heterogeneity did not change significantly with time after the administration of (99m)Tc-HSA. The tumours showed a random and a radial heterogeneity in blood perfusion similar to that in the uptake of (99m)Tc-HSA. The observations reported here suggest that the intratumour heterogeneity in the distribution of (99m)Tc-HSA was initiated primarily because of heterogeneity in the supply of (99m)Tc-HSA through the microvasculature, and that the presence of severe transport barriers in the tumour interstitium prevented significant equalisation of the initial heterogeneity with time. Consequently, strategies for improving the delivery of macromolecular therapeutic agents to tumours should focus on increasing the tumour blood perfusion to increase the total uptake and improving the diffusion conditions in the tumour interstitium to diminish the heterogeneity in the uptake.
Asunto(s)
Melanoma Experimental/metabolismo , Neovascularización Patológica/patología , Agregado de Albúmina Marcado con Tecnecio Tc 99m/farmacocinética , Animales , Transporte Biológico , Femenino , Humanos , Sustancias Macromoleculares , Melanoma Experimental/patología , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Neovascularización Patológica/metabolismo , Trasplante HeterólogoRESUMEN
The aim of this study was to investigate whether tumour hypoxia and/or vascular hot spots promote the development of metastatic disease. The D-12 human melanoma xenograft line was used as a tumour model. Hypoxia and vascular hot spots were detected by immunohistochemistry using pimonidazole as a hypoxia marker and anti-CD31 antibody to visualize endothelial cells. Vascular hot spots were found to be induced in hypoxic foci, owing to hypoxia-induced up-regulation of angiogenesis stimulatory factors. This effect was mediated by interleukin 8 and possibly also by vascular endothelial growth factor. Interleukin 8 positive foci showed a high degree of co-localization with hypoxic foci, as revealed by immunohistochemistry. The incidence of spontaneous pulmonary metastases was associated with the density of hypoxic foci, the density of interleukin 8 positive foci and the density of vascular hot spots in the primary tumour. Treatment with neutralizing antibody against interleukin 8 and/or vascular endothelial growth factor resulted in hypoxia-induced necrosis rather than hypoxia-induced vascular hot spots and inhibited metastasis. Our study suggests a cause-effect relationship between hypoxia and metastasis in cancer and hence an elevated probability of metastatic disease in patients having primary tumours characterized by high densities of hypoxic foci and vascular hot spots.
Asunto(s)
Hipoxia/fisiopatología , Interleucina-8/biosíntesis , Neoplasias Pulmonares/secundario , Melanoma/patología , Metástasis de la Neoplasia/fisiopatología , Animales , Factores de Crecimiento Endotelial/biosíntesis , Factores de Crecimiento Endotelial/farmacología , Femenino , Humanos , Inmunohistoquímica , Interleucina-8/farmacología , Neoplasias Pulmonares/patología , Linfocinas/biosíntesis , Linfocinas/farmacología , Melanoma/irrigación sanguínea , Ratones , Ratones Endogámicos BALB C , Microcirculación , Flujo Sanguíneo Regional , Trasplante Heterólogo , Células Tumorales Cultivadas , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
Increased knowledge of the physiological basis behind the signal enhancement in tumors during dynamic contrast-enhanced magnetic resonance (MR) imaging may be useful in development of predictive assays based on this technique. In the present work, the relative signal intensity (RSI) increase in gadopentetate dimeglumine (Gd-DTPA)-enhanced MR images of patients with cervical carcinoma was related to tumor perfusion, vascular density, cell density, and oxygen tension (pO(2)). The patients were subjected to MR imaging before the start of treatment (N = 12) and after two weeks of radiotherapy (N = 8). Perfusion was determined from the kinetics of contrast agent in tumors and arteries, vascular density and cell density were determined from tumor biopsies, and pO(2) was determined by polarographic needle electrodes. The maximal RSI was correlated to perfusion (P = 0.002) and cell density (P = 0.004), but was not related to vascular density. There was also a correlation between pO(2) and perfusion (P < 0.001). Moreover, pO(2) tended to be correlated to cell density (P = 0.1), but was not related to vascular density. There was a significant correlation between RSI and pO(2), regardless of whether the median pO(2) (P < 0.001) or the fraction of pO(2) readings below 2.5 mmHg (P < 0.001), 5 mmHg (P < 0.0001), or 10 mmHg (P < 0.001) was considered. Our results suggest that the Gd-DTPA-induced signal enhancement in MR images of cervical tumors is influenced by both perfusion and cell density. These parameters are also of major importance for tumor oxygenation, leading to a correlation between signal enhancement and oxygenation. Dynamic contrast-enhanced MR imaging may therefore possibly be useful in prediction of treatment outcome.
Asunto(s)
Carcinoma de Células Escamosas/sangre , Carcinoma de Células Escamosas/patología , Medios de Contraste , Gadolinio DTPA , Imagen por Resonancia Magnética , Oxígeno/sangre , Neoplasias del Cuello Uterino/sangre , Neoplasias del Cuello Uterino/patología , Carcinoma de Células Escamosas/irrigación sanguínea , Femenino , Humanos , Aumento de la Imagen , Análisis de Regresión , Procesamiento de Señales Asistido por Computador , Neoplasias del Cuello Uterino/irrigación sanguíneaRESUMEN
Cancer therapy involving blood-borne macromolecular therapeutic agents often fails, owing to inadequate macromolecule uptake in malignant tissue. The transvascular and interstitial transport of a 19 kDa linear molecule (NC22181 or poly-[Gd-DTPA]-co-[1,6-diaminohexane]) was studied in the present work in an attempt to identify transport barriers limiting the delivery of macromolecules to tumors. Tumors of four human melanoma xenograft lines were included in the study. The uptake of NC22181 was measured by spoiled gradient recalled magnetic resonance imaging (MRI). The effective microvascular permeability constant and the interstitial influx constant of NC22181 were calculated from NC22181 uptake curves by using a three-compartment tissue model. The uptake of NC22181 was limited by the interstitial transport and not by the transvascular transport in all xenograft lines. If the melanoma xenografts used in this study are representative models of human cancer, our results suggest that strategies for increasing the delivery of macromolecular therapeutic agents to tumors should focus on improving the transport conditions in the interstitium, rather than enhancing the permeability of the microvascular wall.
Asunto(s)
Medios de Contraste/farmacocinética , Imagen por Resonancia Magnética/métodos , Melanoma Experimental/patología , Animales , Transporte Biológico , Permeabilidad Capilar , Diaminas/farmacocinética , Gadolinio DTPA/análogos & derivados , Gadolinio DTPA/farmacocinética , Humanos , Sustancias Macromoleculares , Ratones , Ratones Endogámicos BALB C , Trasplante de Neoplasias , Trasplante HeterólogoRESUMEN
Some cancer patients show accelerated growth of pre-existing metastases after removal of the primary tumor. The purpose of this study was to investigate whether primary tumor-induced metastasis suppression can be mediated by thrombospondin-1 in melanoma. Human melanoma xenografts (D-12, R-18, and U-25) were used as models of melanoma in humans. Melanoma angiogenesis, lung colonization, and spontaneous pulmonary metastasis were inhibited in mice bearing D-12, U-25, or thrombospondin-1 overexpressing R-18 tumors, which showed high thrombospondin-1 expression and secreted large quantities of thrombospondin-1 into the blood, but not in mice bearing wild-type R-18 tumors, which were negative for thrombospondin-1. D-12 tumors suppressed the growth of their own spontaneous metastases. The anti-angiogenic and anti-metastatic effects of D-12 and U-25 tumors were blocked in mice treated with thrombospondin-1 neutralizing antibody. Dormant avascular microcolonies having an elevated apoptotic activity were seen in the lungs of mice bearing D-12 or U-25 tumors, whereas only neovascularized lung macrocolonies were seen in control and antibody-treated mice. This study suggests that some melanoma patients may benefit from combined local treatment and long-term anti-angiogenic therapy involving thrombospondin-1.
Asunto(s)
Neoplasias Pulmonares/prevención & control , Neoplasias Pulmonares/secundario , Melanoma/prevención & control , Melanoma/secundario , Neoplasias Cutáneas/patología , Trombospondina 1/fisiología , Animales , Anticuerpos Monoclonales/farmacología , Humanos , Pulmón/patología , Melanoma/irrigación sanguínea , Ratones , Trasplante de Neoplasias , Neovascularización Patológica/prevención & control , Neoplasias Cutáneas/irrigación sanguínea , Trombospondina 1/inmunología , Trasplante Heterólogo , Células Tumorales CultivadasRESUMEN
Several novel macromolecular anticancer agents have fallen short of expectations owing to inadequate and heterogeneous uptake in tumor tissue. In the present work, contrast-enhanced magnetic resonance imaging was used to measure the intertumor and intratumor heterogeneity in the effective microvascular permeability constant, P(eff), of an 82 kDa macromolecule in an attempt to identify possible causes of the inadequate and heterogeneous uptake. Tumors of two human melanoma xenograft lines (A-07 and R-18) were included in the study. Human serum albumin with 30 gadopentetate dimeglumine units per molecule was used as a model molecule of macromolecular therapeutic agents. P(eff) was measured in manually defined regions of interest, corresponding to a whole tumor (ROI(WHOLE)) or to subregions of a tumor (ROIs(SUB)). The P(eff) of the ROI(WHOLE) of individual tumors ranged from 1.4 x 10(-7) cm/s to 2.8 x 10(-7) cm/s (A-07) and from 7.7 x 10(-8) cm/s to 3.2 x 10(-7) cm/s (R-18). P(eff) decreased with increasing tumor volume in R-18, but was independent of tumor volume in A-07. The intratumor heterogeneity in P(eff) exceeded the intertumor heterogeneity in both tumor lines. Some ROIs(SUB) showed P(eff) values that were similar to or slightly higher than the P(eff) values of albumin in normal tissues. Our observations suggest that inadequate and heterogeneous uptake of macromolecular therapeutic agents in tumor tissue is partly a result of low and heterogeneous microvascular permeability. However, the microvascular wall is probably not the major transport barrier to macromolecules in A-07 and R-18 tumors, as most individual tumors and individual tumor subregions showed high P(eff) values, i.e. values that are up to 10-fold higher than those of normal tissues.
Asunto(s)
Antineoplásicos/farmacocinética , Permeabilidad Capilar/fisiología , Medios de Contraste/farmacocinética , Gadolinio DTPA/farmacocinética , Aumento de la Imagen , Imagen por Resonancia Magnética , Melanoma Experimental/irrigación sanguínea , Albúmina Sérica/metabolismo , Animales , Humanos , Ratones , Ratones Desnudos , Trasplante Heterólogo , Células Tumorales CultivadasRESUMEN
Knowledge of the intratumor heterogeneity in blood perfusion may lead to increased understanding of tumor response to treatment. In the present work, absolute perfusion values, in units of ml/g.min, were determined in 20 tumor subregions of patients with cervical cancer before treatment (n = 12) and after 2 weeks of radiotherapy (n = 8), by using a method based on contrast-enhanced magnetic resonance imaging. The aims were to evaluate the intratumor heterogeneity in perfusion in relation to the intertumor heterogeneity and to search for changes in the heterogeneities during the early phase of therapy. The intra- and intertumor heterogeneity in perfusion were estimated from components of one-way analyses of variance. The mean perfusion differed significantly among the patients before treatment, ranging from 0.044 to 0.12 ml/g x min. Large differences in perfusion were also observed within individual tumors. The heterogeneity was largest in the best perfused tumors, perfusion values ranging, e.g., from 0.055 to 0.29 ml/g x min were observed. The intratumor heterogeneity was similar to the intertumor heterogeneity. The mean perfusion generally increased or tended to increase during radiotherapy, ranging from 0.064 ml/g x min to 0.13 ml/g x min after 2 weeks of treatment. There was a tendency of increased intratumor heterogeneity in perfusion after therapy, consistent with the higher mean value; a difference in perfusion of more than a factor of 10 was seen within some tumors. These results suggest that cervix tumors contain a significant amount of poorly perfused subregions with high treatment resistance. Moreover, the perfusion and perfusion heterogeneity may increase during the early phase of radiotherapy and influence tumor response.
Asunto(s)
Carcinoma de Células Escamosas/irrigación sanguínea , Carcinoma de Células Escamosas/radioterapia , Neoplasias del Cuello Uterino/irrigación sanguínea , Neoplasias del Cuello Uterino/radioterapia , Carcinoma de Células Escamosas/tratamiento farmacológico , Femenino , Humanos , Neovascularización Patológica , Neoplasias del Cuello Uterino/tratamiento farmacológicoRESUMEN
The effective microvascular permeability of human melanoma xenografts to albumin-Evans blue was measured and related to tumor volumetric growth rate, rate of tumor angiogenesis, and expression of vascular endothelial growth factor (VEGF) in an attempt to identify mechanisms regulating the microvascular permeability of tumors to macromolecules. Three melanoma lines (A-07, R-18, and U-25) were included in the study. Effective microvascular permeability was assessed by using the indicator diffusion method. Intradermal and intratumor angiogenesis assays were used to measure the rate of tumor angiogenesis. VEGF expression was studied by ELISA, immunohistochemistry, Western blotting, and measurement of tumor-induced formation of ascitic fluid. The effective microvascular permeabilities of albumin-Evans blue were determined to be (1.5 +/- 0.2) x 10(-6) cm/s (A-07), (1.1 +/- 0.4) x 10(-6) cm/s (R-18), and (0.9 +/- 0.3) x 10(-6) cm/s (U-25). These values are high compared with those measured for other tumor lines and are not significantly different. Correlations between the effective microvascular permeability of albumin-Evans blue and tumor volumetric growth rate, rate of tumor angiogenesis, or VEGF expression were not found. The three last-mentioned parameters differed significantly among the melanoma lines and covered a broad range of values relative to those of other experimental tumors. Our study suggests that the effective microvascular permeability of macromolecules can be high even in slowly growing tumors, poorly angiogenic tumors, and tumors showing low VEGF expression.
Asunto(s)
Permeabilidad Capilar , Factores de Crecimiento Endotelial/biosíntesis , Linfocinas/biosíntesis , Melanoma Experimental/irrigación sanguínea , Melanoma Experimental/fisiopatología , Neovascularización Patológica , Animales , Factores de Crecimiento Endotelial/metabolismo , Azul de Evans/farmacocinética , Femenino , Humanos , Linfocinas/metabolismo , Melanoma Experimental/patología , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Trasplante de Neoplasias , Albúmina Sérica/metabolismo , Trasplante Heterólogo , Células Tumorales Cultivadas , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularAsunto(s)
Melanoma Experimental/sangre , Melanoma Experimental/irrigación sanguínea , Microcirculación/metabolismo , Oxígeno/metabolismo , Oxihemoglobinas/metabolismo , Animales , Femenino , Humanos , Melanoma Experimental/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Trasplante de Neoplasias , Trasplante Heterólogo , Células Tumorales CultivadasRESUMEN
The aim of the present study was to examine intratumour heterogeneity in microvessel oxyhaemoglobin (HbO2) saturations in human melanoma xenografts. The HbO2 saturations, measured with a cryospectrophotometric micromethod, were found to vary substantially within single tumours. All tumours showed a decrease in overall HbO2 saturation from the periphery towards the centre, although the profiles could vary substantially between individual tumours. Local differences could be large, and many tumours had HbO2 saturations spanning from 0 to 100% in peripheral regions. In central tumour regions, low saturations were prevailing although subregions of intermediate and high saturations could also be found.
Asunto(s)
Melanoma/irrigación sanguínea , Oxihemoglobinas/metabolismo , Animales , Femenino , Humanos , Melanoma/metabolismo , Ratones , Ratones Endogámicos BALB C , Trasplante de Neoplasias , Espectrofotometría , Trasplante HeterólogoRESUMEN
The perfusion in tumors shows substantial spatial heterogeneity compared to that in normal tissues. The aim of the present study was to evaluate the intratumor heterogeneity in perfusion in tumors of two amelanotic human melanoma xenograft lines, A-07 and R-18, grown intradermally in Balb/c nu/nu mice. A non-invasive contrast-enhanced magnetic resonance imaging method yielding results in absolute values was applied. The perfusion was determined in manually defined regions of interest, corresponding to a whole tumor or to subregions of a tumor. The mean perfusion and the intertumor heterogeneity in perfusion were similar for the two tumor lines. For whole A-07 tumors, the perfusion ranged from 0.089 mL/(g . min) to 0.20 mL/(g . min) [mean: 0.15 mL/(g . min)], and for whole R-18 tumors, from 0.030 mL/(g . min) to 0.17 mL/(g . min) [mean: 0.13 mL/(g . min)]. The intratumor heterogeneity, on the other hand, was estimated to be 6.4 times larger in A-07 tumors than in R-18 tumors. The highest perfusion values, up to 0.69 mL/(g . min), were found in subregions of A-07 tumors. The intratumor heterogeneity was substantially larger than the intertumor heterogeneity in A-07 tumors, whereas in R-18 tumors, the intratumor heterogeneity was similar to the intertumor heterogeneity. These observations imply that measurements of mean tumor perfusion may have limited value as a predictive assay for outcome of treatment.
Asunto(s)
Imagen por Resonancia Magnética/métodos , Melanoma Amelanótico/irrigación sanguínea , Melanoma Experimental/irrigación sanguínea , Adenocarcinoma/irrigación sanguínea , Animales , Cricetinae , Femenino , Fibrosarcoma/irrigación sanguínea , Humanos , Aumento de la Imagen , Neoplasias Mamarias Experimentales/irrigación sanguínea , Melanoma Amelanótico/terapia , Melanoma Experimental/terapia , Ratones , Ratones Endogámicos BALB C , Microcirculación , Modelos Teóricos , Trasplante de Neoplasias , Neoplasias Experimentales/irrigación sanguínea , Pronóstico , Ratas , Sarcoma Experimental/irrigación sanguínea , Trasplante Heterólogo , Resultado del Tratamiento , Células Tumorales CultivadasRESUMEN
Angiogenesis is a significant prognostic factor in melanoma, but the angiogenic factors controlling the neovascularization are not well defined. The purpose of this study was to investigate whether the angiogenesis and metastasis of melanoma are promoted by vascular endothelial growth factor (VEGF), interleukin 8 (IL-8), platelet-derived endothelial cell growth factor (PD-ECGF), and/or basic fibroblast growth factor (bFGF). Cells from human melanoma lines (A-07, D-12, R-18, and U-25) transplanted to BALB/c nu/nu mice were used as tumor models. Expression of angiogenic factors was studied by ELISA, Western blotting, and immunohistochemistry. Angiogenesis was assessed by using an intradermal angiogenesis assay. Lung colonization and spontaneous lung metastasis were determined after i.v. and intradermal inoculation of tumor cells, respectively. The specific roles of VEGF, IL-8, PD-ECGF, and bFGF in tumor angiogenesis, lung colonization, and spontaneous metastasis were assessed in mice treated with neutralizing antibody. The melanoma lines expressed multiple angiogenic factors, and each line showed a unique expression pattern. Multiple angiogenic factors promoted angiogenesis in the most angiogenic melanoma lines, whereas angiogenesis in the least angiogenic melanoma lines was possibly promoted solely by VEGF. Tumor growth, lung colonization, and spontaneous metastasis were controlled by the rate of angiogenesis and hence by the angiogenic factors promoting the angiogenesis. Lung colonization and spontaneous metastasis in A-07 were inhibited by treatment with neutralizing antibody against VEGF, IL-8, PD-ECGF, or bFGF. Each of these angiogenic factors may promote metastasis in melanoma, because inhibition of one of them could not be compensated for by the others. Our observations suggest that efficient antiangiogenic treatment of melanoma may require identification and blocking of common functional features of several angiogenic factors.
Asunto(s)
Sustancias de Crecimiento/fisiología , Melanoma/irrigación sanguínea , Neovascularización Patológica/metabolismo , Animales , Factores de Crecimiento Endotelial/biosíntesis , Factores de Crecimiento Endotelial/fisiología , Femenino , Factor 2 de Crecimiento de Fibroblastos/biosíntesis , Factor 2 de Crecimiento de Fibroblastos/fisiología , Sustancias de Crecimiento/biosíntesis , Sustancias de Crecimiento/metabolismo , Humanos , Inmunohistoquímica , Interleucina-8/biosíntesis , Interleucina-8/metabolismo , Interleucina-8/fisiología , Linfocinas/biosíntesis , Linfocinas/fisiología , Melanoma/metabolismo , Melanoma/patología , Ratones , Ratones Endogámicos BALB C , Trasplante de Neoplasias , Timidina Fosforilasa/biosíntesis , Timidina Fosforilasa/metabolismo , Timidina Fosforilasa/fisiología , Trasplante Heterólogo , Células Tumorales Cultivadas , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
Poor outcome of treatment in advanced cervix carcinoma has been shown to be associated with poor oxygenation of the primary tumour. Hypoxia may cause radiation resistance and promote lymph-node metastasis. The purpose of the study reported here was to investigate whether hypoxia-induced treatment failure in advanced cervix carcinoma is primarily a result of hypoxia-induced radiation resistance or the presence of hypoxia-induced lymph-node metastases at the start of treatment. Thirty-two patients with squamous cell carcinoma of the uterine cervix were included in the study. Radiation therapy was given with curative intent as combined external irradiation and endocavitary brachytherapy. The oxygenation status of the primary tumour was measured prior to treatment using the Eppendorf PO2 Histograph. Pelvic and para-aortal lymph-node metastases were detected by magnetic resonance imaging at the time of initial diagnosis. The primary tumours of the patients with metastases (n = 18) were significantly more poorly oxygenated than those of the patients without metastases (n = 14). Multivariate Cox regression analyses involving biological and clinical parameters identified the tumour subvolume having PO2 values below 5 mmHg (HSV (pO2 < 5 mmHg) as the only significant, independent prognostic factor for locoregional control, disease-free survival and overall survival. The probabilities of locoregional control, disease-free survival and overall survival were significantly lower for the patients with HSV (PO2 < 5 mmHg) above the median value than for those with HSV (PO2 < 5 mmHg) below the median value. On the other hand, the outcome of treatment was not significantly different for the patients with metastases and the patients without metastases at the start of treatment, irrespective of clinical end-point. Consequently, treatment failure was primarily a result of hypoxia-induced radiation resistance rather than hypoxia-induced lymph-node metastasis, suggesting that novel treatment strategies aiming at improving tumour oxygenation or enhancing the radiation sensitivity of hypoxic tumour cells may prove beneficial in attempts to improve the radiation therapy of advanced cervix carcinoma.
Asunto(s)
Carcinoma de Células Escamosas/radioterapia , Carcinoma de Células Escamosas/secundario , Hipoxia de la Célula/efectos de la radiación , Neoplasias del Cuello Uterino/patología , Neoplasias del Cuello Uterino/radioterapia , Braquiterapia , Carcinoma de Células Escamosas/metabolismo , Supervivencia sin Enfermedad , Femenino , Humanos , Metástasis Linfática , Oxígeno/metabolismo , Valor Predictivo de las Pruebas , Modelos de Riesgos Proporcionales , Radioterapia/métodos , Análisis de Supervivencia , Insuficiencia del Tratamiento , Neoplasias del Cuello Uterino/metabolismoRESUMEN
The uptake of albumin-Evans blue in human melanoma xenografts was studied and related to blood supply, vascular density, microvessel permeability and extracellular volume fraction in an attempt to identify transport barriers limiting the delivery of macromolecular therapeutic agents to tumours. Three melanoma lines (A-07, R-18, U-25) were included in the study. Tissue concentrations of albumin-Evans blue were determined by spectrophotometry. The [86Rb] uptake method was used to measure tumour blood supply. Vascular density was determined by stereological analysis of histological sections. Microvessel permeability was measured by using the indicator diffusion method. Contrast-enhanced magnetic resonance imaging was used to measure tumour extracellular volume fraction. The fractional volume of the extracellular space governed the uptake of albumin-Evans blue in the tumours. The uptake of albumin-Evans blue in the extracellular space was primarily limited by transport in the vasculature and not by transport across the microvascular wall or the transport through the interstitium. Our study thus suggests that novel strategies for improving the delivery of macromolecular therapeutic agents to tumours should focus on enhancing the tumour blood supply, increasing the half-life of the therapeutic agent in the blood plasma and/or enhancing the volume of the extracellular space available to macromolecules rather than on increasing the permeability of the microvascular wall or improving diffusion conditions in the tumour interstitium.
Asunto(s)
Albúminas/farmacocinética , Azul de Evans/farmacocinética , Melanoma/irrigación sanguínea , Melanoma/metabolismo , Animales , Permeabilidad Capilar , Humanos , Sustancias Macromoleculares , Ratones , Ratones Endogámicos BALB C , Microcirculación , Trasplante de Neoplasias , Trasplante HeterólogoRESUMEN
PURPOSE: To present and evaluate clinical data suggesting that cancer metastasis may be induced by the microenvironment of the primary tumour and to discuss possible mechanisms of microenvironment-induced metastasis, based on a critical review of relevant data from studies of experimental tumours and cells in culture. CONCLUSIONS: Low oxygen tension in the primary tumour is associated with metastasis in soft tissue sarcoma, cervix carcinoma and carcinoma of the head and neck. Multiple mechanisms may be involved in hypoxia-induced metastasis. Thus, hypoxia followed by reoxygenation may induce point mutations and DNA strand breakage leading to deletions, amplifications and genomic instability. Hypoxia may also provide a physiological pressure in tumours selecting for metastatic cell phenotypes. Moreover, hypoxia may induce a temporary increase in the expression of gene products involved in the metastatic cascade, either through gene amplifications or through normal physiological processes by activating oxygen sensors, hypoxia signal transduction pathways and DNA transcription factors. Low glucose concentration, high lactate concentration and low extracellular pH may induce metastasis by similar mechanisms as hypoxia. Tumour reoxygenation during radiation therapy may promote microenvironment-induced metastasis by rescuing hypoxic or nutritionally deprived metastatic cells from dying. Ionizing radiation can elicit a stress response in tumour cells similar to that elicited by hypoxia. Radiation therapy may therefore adversely affect the rate of metastasis in patients who do not achieve control of the primary tumour by enhancing the expression of gene products of importance in metastasis.
Asunto(s)
Metástasis de la Neoplasia , Neoplasias/irrigación sanguínea , Animales , Femenino , Humanos , Concentración de Iones de Hidrógeno , Hipoxia , Ratones , Trasplante de Neoplasias , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patología , Mutación Puntual , Radioterapia/efectos adversos , Factores de TiempoRESUMEN
The aim of this study was to investigate whether apparent diffusion coefficients (ADCs) could be used as measures of cell density and necrotic fraction of tumors. Tumors of four human melanoma xenograft lines were subjected to diffusion-weighted magnetic resonance imaging (DWI). ADCs were calculated from the images and related to cell density and necrotic fraction, as determined from histological sections. A significant correlation was found between the ADC of the viable tissue and cell density, regardless of whether tumors of different lines or different regions within individual tumors were considered. Necrosis was found in two of the lines. A single region of massive necrosis that could be differentiated from the viable tissue in ADC maps was found in one line, whereas a number of smaller necrotic regions that could not be identified in ADC maps were found in the other line. Tumor ADC was significantly correlated with the necrotic fraction of the former, but not of the latter line. Our results suggest that ADCs can be used as measures of cell density and necrotic fraction of some but not of all tumors, depending on whether the individual necrotic regions are large enough to be differentiated from the viable tissue with the obtained spatial resolution of the DW images. Magn Reson Med 43:828-836, 2000.
Asunto(s)
Imagen por Resonancia Magnética/métodos , Melanoma/diagnóstico , Neoplasias Cutáneas/diagnóstico , Animales , Recuento de Células , Muerte Celular , Modelos Animales de Enfermedad , Humanos , Aumento de la Imagen/métodos , Masculino , Melanoma/patología , Ratones , Ratones Endogámicos BALB C , Necrosis , Trasplante de Neoplasias , Probabilidad , Sensibilidad y Especificidad , Neoplasias Cutáneas/patología , Estadísticas no Paramétricas , Trasplante HeterólogoRESUMEN
Angiogenesis of tumours might develop as a result of environmental conditions, such as hypoxia, and/or as a result of genetic alterations specific for tumour cells. The relative contributions of these mechanisms were investigated by comparing the in vivo expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) to the hypoxic fraction, the angiogenic potential and the vascular density of four human melanoma lines (A-07, D-12, R-18, U-25) grown intradermally in Balb/c nu/nu mice. VEGF expression, bFGF expression and expression of pimonidazole, a marker of hypoxic cells, were investigated by immunohistochemistry. An association between high VEGF and bFGF expression and high angiogenic potential was detected, suggesting an important role for VEGF/bFGF in the angiogenesis of melanomas. High VEGF/bFGF expression was also related to low hypoxic fraction and high vascular density. Thus, the constitutive, genetically determined level of VEGF was probably more important than hypoxia-induced upregulation in the angiogenesis of the melanoma xenografts.
Asunto(s)
Hipoxia de la Célula , Factores de Crecimiento Endotelial/metabolismo , Linfocinas/metabolismo , Melanoma/irrigación sanguínea , Neovascularización Patológica , Regulación hacia Arriba , Animales , Humanos , Inmunohistoquímica , Ratones , Ratones Endogámicos BALB C , Trasplante de Neoplasias , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
Identification of biological parameters of major importance for the control of malignant diseases can be useful for the design of optimal treatment regimes for individual patients. Tumor oxygen tension (pO2), vascular density, cell density, and frequency of mitosis and apoptosis were measured before treatment (40 patients) and after 2 weeks of radiotherapy (22 patients) in patients with uterine cervical cancer. The aim was to investigate whether one of the parameters was more important for disease control than the others. Three sets of data were considered; the pretreatment parameters, the parameters measured after 2 weeks of radiation, and the changes in the parameters during this time. The pO2 was measured polarographically; the other parameters were determined by histological analyses of tumor biopsies. Hypoxic subvolume (HSV5), ie., the fraction of pO2 readings <5 mm Hg multiplied with tumor volume, showed the strongest correlation to control. Patients with a small HSVs before treatment had a higher control probability after a median follow-up time of 50 months than patients with a large HSV5 (P < 0.001). All other parameters or changes in parameters showed impaired correlation to control compared with pretreatment HSV5. The present results suggest that pretreatment oxygenation is more important for disease control of cervical cancer than the oxygenation after 2 weeks of radiotherapy or the changes in oxygenation during this time. Moreover, vascular density, cell density, and frequency of mitosis and apoptosis before treatment or after 2 weeks of therapy are probably not as important as pretreatment oxygenation as well. Although significant correlations between disease control and some of the parameters other than pretreatment oxygenation can occur in studies based on a large number of patients, the specificity of these parameters in the prediction of control is probably not as high as for oxygenation.
Asunto(s)
Carcinoma de Células Escamosas/radioterapia , Neoplasias del Cuello Uterino/radioterapia , Adulto , Anciano , Apoptosis/efectos de la radiación , Carcinoma de Células Escamosas/irrigación sanguínea , Carcinoma de Células Escamosas/patología , Recuento de Células/efectos de la radiación , Supervivencia sin Enfermedad , Femenino , Humanos , Persona de Mediana Edad , Mitosis/efectos de la radiación , Neovascularización Patológica , Oxígeno/metabolismo , Presión Parcial , Factores de Tiempo , Neoplasias del Cuello Uterino/irrigación sanguínea , Neoplasias del Cuello Uterino/patologíaRESUMEN
Poor outcome of treatment was found to be associated with low oxygen tension in the primary tumor and not with high intratumor microvessel density in 40 patients with advanced squamous cell carcinoma of the uterine cervix. Multivariate Cox regression analysis identified the total volume of the hypoxic tumor regions, i. e. the tumor subvolume having pO(2) values below 5 mmHg, as a significant prognostic factor for locoregional control, disease-free survival, and overall survival. Other important prognostic factors, identified by univariate Cox regression analysis, were tumor volume, the fraction of pO(2) readings giving pO(2) values below 5 mmHg, and tumor stage.