Intra-individual comparison of therapeutic responses to vascular disrupting agent CA4P between rodent primary and secondary liver cancers

AIM

To compare therapeutic responses of a vascular-disrupting-agent, combretastatin-A4-phosphate (CA4P), among hepatocellular carcinomas (HCCs) and implanted rhabdomyosarcoma (R1) in the same rats by magnetic-resonance-imaging (MRI), microangiography and histopathology.

METHODS

Thirty-six HCCs were created by diethylnitrosamine gavage in 14 rats that were also intrahepatically implanted with one R1 per rat as monitored by T2-/T1-weighted images (T2WI/T1WI) on a 3.0T clinical MRI-scanner. Vascular response and tumoral necrosis were detected by dynamic contrast-enhanced (DCE-) and CE-MRI before, 1 h after and 12 h after CA4P iv at 10 mg/kg (treatment group n = 7) or phosphate-buffered saline at 1.0 mL/kg (control group n = 7). Tumor blood supply was calculated by a semiquantitative DCE parameter of area under the time signal intensity curve (AUC30). In vivo MRI findings were verified by postmortem techniques.

RESULTS

On CE-T1WIs, unlike the negative response in all tumors of control animals, in treatment group CA4P caused rapid extensive vascular shutdown in all R1-tumors, but mildly or spottily in HCCs at 1 h. Consequently, tumor necrosis occurred massively in R1-tumors but patchily in HCCs at 12 h. AUC30 revealed vascular closure (66%) in R1-tumors at 1 h (P < 0.05), followed by further perfusion decrease at 12 h (P < 0.01), while less significant vascular clogging occurred in HCCs. Histomorphologically, CA4P induced more extensive necrosis in R1-tumors (92.6%) than in HCCs (50.2%) (P < 0.01); tumor vascularity heterogeneously scored +~+++ in HCCs but homogeneously scored ++ in R1-tumors.

CONCLUSION

This study suggests superior performance of CA4P in metastatic over primary liver cancers, which could guide future clinical applications of vascular-disrupting-agents.​

Separate calculation of DW-MRI in assessing therapeutic effect in liver tumors in rats

AIM: To explore whether the antitumor effect of a vascular disrupting agent (VDA) would be enhanced by combining with an antiangiogenic agent, and whether such synergistic effects can be effectively evaluated with separate calculation of diffusion weighted magnetic resonance imaging (DW-MRI).

METHODS: Thirty-seven rats with implanted liver tumors were randomized into the following three groups: (1) ZD6126, a kind of VDA; (2) ZDTHA, ZD6126 in combination with an antiangiogenic, thalidomide; and (3) control. Morphological DW-MRI were performed and quantified before, 4 h and 2 d after treatment. The apparent diffusion coefficient (ADC) values were calculated separately for low b values (ADC_low), high b values (ADC_high) and all b values (ADC_all). The tissue perfusion contribution, ADC_perf, was calculated as ADC_low-ADC_high. Imaging findings were finally verified by histopathology.

RESULTS: The combination therapy with ZDTHA significantly delayed tumor growth due to synergistic effects by inducing cumulative tumor necrosis. In addition to delaying tumor growth, ZDTHA caused tumor necrosis in an additive manner, which was verified by HE staining. Although both ADC_high and ADC_all in the ZD6126 and ZDTHA groups were significantly higher compared to those in the control group on day 2, the entire tumor ADC_high of ZDTHA was even higher than that of ZD6126, but the significant difference was not observed for ADC_all between ZDTHA and ZD6126. This indicated that the perfusion insensitive ADC_high values calculated from high b value images performed significantly better than ADC_all for the monitoring of tumor necrosis on day 2. The perfusion sensitive ADC_perf derived from ADC_low by excluding high b value effects could better reflect the reduction of blood flow due to the vessel shutdown induced by ZD6126, compared to the ADC_low at 4 h. The ADC_perf could provide valuable perfusion information from DW-MRI data.

CONCLUSION: The separate calculation of ADC is more useful than conventional averaged ADC in evaluating the efficacy of combination therapy with ZD6126 and thalidomide for solid tumors.

Toward highly potent cancer agents by modulating the C-2 group of the arylthioindole class of tubulin polymerization inhibitors

New arylthioindole derivatives having different cyclic substituents at position 2 of the indole were synthesized as anticancer agents. Several compounds inhibited tubulin polymerization at submicromolar concentration and inhibited cell growth at low nanomolar concentrations. Compounds 18 and 57 were superior to the previously synthesized 5. Compound 18 was exceptionally potent as an inhibitor of cell growth: it showed IC₅₀ = 1.0 nM in MCF-7 cells, and it was uniformly active in the whole panel of cancer cells and superior to colchicine and combretastatin A-4. Compounds 18, 20, 55, and 57 were notably more potent than vinorelbine, vinblastine, and paclitaxel in the NCI/ADR-RES and Messa/Dx5 cell lines, which overexpress P-glycoprotein. Compounds 18 and 57 showed initial vascular disrupting effects in a tumor model of liver rhabdomyosarcomas at 15 mg/kg intravenous dosage. Derivative 18 showed water solubility and higher metabolic stability than 5 in human liver microsomes.

p21WAF1 expression induced by MEK/ERK pathway activation or inhibition correlates with growth arrest, myogenic differentiation and onco-phenotype reversal in rhabdomyosarcoma cells

Background

p21^WAF1, implicated in the cell cycle control of both normal and malignant cells, can be induced by p53-dependent and independent mechanisms. In some cells, MEKs/ERKs regulate p21^WAF1 transcriptionally, while in others they also affect the post-transcriptional processes. In myogenic differentiation, p21^WAF1 expression is also controlled by the myogenic transcription factor MyoD. We have previously demonstrated that the embryonal rhabdomyosarcoma cell line undergoes growth arrest and myogenic differentiation following treatments with TPA and the MEK inhibitor U0126, which respectively activate and inhibit the ERK pathway.

In this paper we attempt to clarify the mechanism of ERK-mediated and ERK-independent growth arrest and myogenic differentiation of embryonal and alveolar rhabdomyosarcoma cell lines, particularly as regards the expression of the cell cycle inhibitor p21^WAF1.

Results

p21^WAF1 expression and growth arrest are induced in both embryonal (RD) and alveolar (RH30) rhabdomyosarcoma cell lines following TPA or MEK/ERK inhibitor (U0126) treatments, whereas myogenic differentiation is induced in RD cells alone. Furthermore, the TPA-mediated post-transcriptional mechanism of p21^WAF1-enhanced expression in RD cells is due to activation of the MEK/ERK pathway, as shown by transfections with constitutively active MEK1 or MEK2, which induces p21^WAF1 expression, and with ERK1 and ERK2 siRNA, which prevents p21^WAF1 expression. By contrast, U0126-mediated p21^WAF1 expression is controlled transcriptionally by the p38 pathway. Similarly, myogenin and MyoD expression is induced both by U0126 and TPA and is prevented by p38 inhibition. Although MyoD and myogenin depletion by siRNA prevents U0126-mediated p21^WAF1 expression, the over-expression of these two transcription factors is insufficient to induce p21^WAF1. These data suggest that the transcriptional mechanism of p21^WAF1 expression in RD cells is rescued when MEK/ERK inhibition relieves the functions of myogenic transcription factors. Notably, the forced expression of p21^WAF1 in RD cells causes growth arrest and the reversion of anchorage-independent growth.

Conclusion

Our data provide evidence of the key role played by the MEK/ERK pathway in the growth arrest of Rhabdomyosarcoma cells. The results of this study suggest that the targeting of MEK/ERKs to rescue p21^WAF1 expression and myogenic transcription factor functions leads to the reversal of the Rhabdomyosarcoma phenotype.

Effect of vascular targeting agent in rat tumor model: dynamic contrast-enhanced versus diffusion-weighted MR imaging

PURPOSE

To compare dynamic contrast material-enhanced magnetic resonance (MR) imaging and diffusion-weighted MR imaging for noninvasive evaluation of early and late effects of a vascular targeting agent in a rat tumor model.

MATERIALS AND METHODS

The study protocol was approved by the local ethics committee for animal care and use. Thirteen rats with one rhabdomyosarcoma in each flank (26 tumors) underwent dynamic contrast-enhanced imaging and diffusion-weighted echo-planar imaging in a 1.5-T MR unit before intraperitoneal injection of combretastatin A4 phosphate and at early (1 and 6 hours) and later (2 and 9 days) follow-up examinations after the injection. Histopathologic examination was performed at each time point. The apparent diffusion coefficient (ADC) of each tumor was calculated separately on the basis of diffusion-weighted images obtained with low b gradient values (ADC(low); b = 0, 50, and 100 sec/mm(2)) and high b gradient values (ADC(high); b = 500, 750, and 1000 sec/mm(2)). The difference between ADC(low) and ADC(high) was used as a surrogate measure of tissue perfusion (ADC(low) - ADC(high) = ADC(perf)). From the dynamic contrast-enhanced MR images, the volume transfer constant k and the initial slope of the contrast enhancement-time curve were calculated. For statistical analyses, a paired two-tailed Student t test and linear regression analysis were used.

RESULTS

Early after administration of combretastatin, all perfusion-related parameters (k, initial slope, and ADC(perf)) decreased significantly (P < .001); at 9 days after combretastatin administration, they increased significantly (P < .001). Changes in ADC(perf) were correlated with changes in k (R(2) = 0.46, P < .001) and the initial slope (R(2) = 0.67, P < .001).

CONCLUSION

Both dynamic contrast-enhanced MR imaging and diffusion-weighted MR imaging allow monitoring of perfusion changes induced by vascular targeting agents in tumors. Diffusion-weighted imaging provides additional information about intratumoral cell viability versus necrosis after administration of combretastatin.

Comprehensive model for simultaneous MRI determination of perfusion and permeability using a blood-pool agent in rats rhabdomyosarcoma

To present a new compartmental analysis model developed to simultaneously measure tissue perfusion and capillary permeability in a tumor using MRI and a macromolecular contrast medium. Rhadomyosarcomas were implanted subcutaneously in 20 rats and studied by 1.5-T MRI using a fast gradient echo sequence (2D fast SPGR TR/TE/alpha 13 ms/1.2 ms/60 degrees ) after injection of a macromolecular contrast medium. The left ventricle and tumor signal intensities were converted into concentrations and modeled using compartmental analysis, yielding tumor perfusion F, distribution volume Vdistribution, volume transfer constant Ktrans, rate constant of influx kpe, and initial extraction (fraction) E. Tumor perfusion was F=43+/-29 ml.min-1.100 g-1. The permeability study allowed the measurement of kpe=0.37+/-0.12 min-1 and Ktrans=0.01+/-0.0031 min-1. The blood volume could be assimilated to the distribution volume (Vdistribution=2.9+/-1.01%) since the capillary leakage was small. The simultaneous assessment of perfusion and permeability allowed quantification of the initial extraction (fraction) E=2.34+/-1.05%. Quantification of both tumor perfusion and capillary leakage is feasible using MRI using a macromolecular blood pool agent. The method should improve tumor characterization.

Tumor angiogenesis and its clinical significance in pediatric malignant liver tumor

AIM: To investigate the expression of vascular endothelial growth factor (VEGF) and microvascular density (MVD) count in pediatric malignant liver tumor and their clinical significances.

METHODS: Fourteen children with malignant liver tumors including seven hepatocellular carcinomas (HCCs), five hepatoblastomas, one malignant mesenchymoma and one rhabdomyosarcoma were studied. Twelve adult HCC samples served as control group. All samples were examined with streptavidin-biotin peroxidase (SP) immunohistochemical staining for VEGF expression and MVD count.

RESULTS: VEGF positive expression in all pediatric malignant liver tumors was significantly higher than that in adult HCC (0.4971±0.14 vs 0.4027±0.03, P<0.05). VEGF expression in pediatric HCC group was also markedly higher than that in adult HCC group (0.5665±0.10 vs 0.4027±0.03, P<0.01) and pediatric non-HCC group (0.5665±0.10 vs 0.4276±0.15, P<0.05). The mean value of MVD in pediatric malignant liver tumors was significantly higher than that in adult HCC (33.66±12.24 vs 26.52±4.38, P<0.05). Furthermore, MVD in pediatric HCC group was significantly higher compared to that in adult HCC group (36.94±9.28 vs 26.52±4.38, P<0.05), but there was no significant difference compared to the pediatric non-HCC group (36.94±9.28 vs 30.37±14.61, P>0.05). All 7 children in HCC group died within 2 years, whereas the prognosis in pediatric non-HCC group was better, in which two patients survived more than 5 years.

CONCLUSION: Children with malignant liver tumors, especially with HCC, may have extensive angiogenesis that induces a rapid tumor growth and leads to a poor prognosis.

Vascular targeting: a potential additional anti-cancer treatment

Our preclinical in vivo investigations were aimed to evaluate the potential of selectively targeting the tumour vasculature as an additional anti-cancer strategy. Using a clinical angiography method and the tumour growth delay assay, the efficacy of the vascular targeting compound combretastatin A-4 phosphate was demonstrated in rat rhabdomyosarcomas: specifically, an inverse efficacy as compared to radio- or chemotherapy was measured when comparing small and large tumours. The combination of this vascular targeting compound with ionising radiation indicated, depending on the timing and the sequence, a potential benefit. Within the limits of our experiments, no significant increase in tumour growth delay was measured when TNP-470 anti-angiogenesis was given after the combretastatin A-4 phosphate treatment. The use of the vascular targeting agent did advance the in vivo application of a non-apathogenic anaerobe Clostridium transfer system of therapeutic proteins. A strong improvement of the selective expression of cytosine deaminase in the tumour microenvironment was observed, even with very small tumours. In summary, the present preclinical results demonstrate several advantages from the introduction of vascular targeting next to classical and novel anti-cancer therapies.

[Microarray study of vasculogenic mimicry in bi-directional differentiation malignant tumor]

OBJECTIVE

To explore if vasculogenic mimicry (VM) exists in bi-directional differentiation malignant tumor.

METHODS

New sections were made from 158 paraffin sections of bi-directional malignant tumors, including malignant melanoma (n = 60), synoviosarcoma (n = 39), rhabdomyosarcoma (n = 29), malignant mesothelioma (n = 26), and epithelioid sarcoma (n = 4). The representative points in the paraffin sections were labeled and two tissue microarrays were made, one including 60 cases of malignant melanoma, and the other including the other tumors. Immunohistochemical staining of platelet-endothelial cell adhesion molecule (CD31 antigen) and periodic acid Schiff (PAS) staining were conducted. Microscopy was made and the areas of vessel-like channels consisted of CD31 antigen-positive tumor cells and of PAS positive material were calculated.

RESULTS

PAS positive material or CD31 positive material were observed in these bi-directional tumor cells. In the tumors vessel-like channels could be found, made of PAS positive material lined with CD31 negative tumor cells and red blood cells inside the channel, or made of tumor cells with CD31 positive material. The area of the former vessel-like channels was significantly smaller than that of the latter (P < 0.01). VM was found in 16 of the 39 cases of the highly malignant synoviosarcoma and acinar type rhabdomyosarcoma, a ratio higher than that among the cases of synoviosarcoma and acinar type rhabdomyosarcoma with lower malignancy (5/29) (P < 0.05).

CONCLUSION

VM exists in bi-directional differentiation malignant tumors.

VEGF-Trap: a VEGF blocker with potent antitumor effects

Vascular endothelial growth factor (VEGF) plays a critical role during normal embryonic angiogenesis and also in the pathological angiogenesis that occurs in a number of diseases, including cancer. Initial attempts to block VEGF by using a humanized monoclonal antibody are beginning to show promise in human cancer patients, underscoring the importance of optimizing VEGF blockade. Previous studies have found that one of the most effective ways to block the VEGF-signaling pathway is to prevent VEGF from binding to its normal receptors by administering decoy-soluble receptors. The highest-affinity VEGF blocker described to date is a soluble decoy receptor created by fusing the first three Ig domains of VEGF receptor 1 to an Ig constant region; however, this fusion protein has very poor in vivo pharmacokinetic properties. By determining the requirements to maintain high affinity while extending in vivo half life, we were able to engineer a very potent high-affinity VEGF blocker that has markedly enhanced pharmacokinetic properties. This VEGF-Trap effectively suppresses tumor growth and vascularization in vivo, resulting in stunted and almost completely avascular tumors. VEGF-Trap-mediated blockade may be superior to that achieved by other agents, such as monoclonal antibodies targeted against the VEGF receptor.

Combined anti-fetal liver kinase 1 monoclonal antibody and continuous low-dose doxorubicin inhibits angiogenesis and growth of human soft tissue sarcoma xenografts by induction of endothelial cell apoptosis

Vascular endothelial growth factor (VEGF) and VEGF receptor 2 [fetal liver kinase 1 (Flk-1)/kinase insert domain-containing receptor] have been shown to play a major role in tumor angiogenesis. In this study, we investigated whether anti-Flk-1 monoclonal antibody DC101 could therapeutically inhibit growth and angiogenesis of human soft tissue sarcoma, and we explored its capacity to enhance the tumoricidal effects of doxorubicin. Treatment of well-established leiomyosarcoma SKLMS-1 and rhabdomyosarcoma RD xenografts in severe combined immunodeficient mice with DC101 resulted in significant antitumor activity. In a parallel study, we compared tumor inhibition with continuous low-dose "antiangiogenic" schedule versus once-every-2-weeks high-dose standard schedule of doxorubicin. We found that continuous low-dose treatment inhibited the tumor growth of RD xenografts about 46.5% of that with standard-schedule treatment, but that continuous low-dose treatment did not inhibit the tumor growth of SKLMS-1 xenografts. Notably, combined DC101 and continuous low-dose doxorubicin resulted in more effective growth inhibition of SKLMS-1 and RD xenografts than has been observed with any agent alone in a long-term s.c. tumor xenograft model. The combination therapy was associated with no additional toxicity to the host animal compared with low-dose doxorubicin alone. Histological examination of xenografts showed significantly reduced microvessel counts in the tumors given combined therapy compared with the tumors given either agent alone. These results are consistent with an enhanced inhibition of angiogenesis in vivo by combined DC101 and doxorubicin using Matrigel plug assay. Additionally, DC101 plus doxorubicin directly exerted enhanced inhibitory effects on endothelial cell migration, proliferation, and tube-like formation in vitro. Furthermore, the combination induced an enhanced apoptosis of endothelial cells that was associated with an increase of capase-3 activity. Thus, the inhibition of angiogenesis and induction of endothelial cell apoptosis are likely important mechanisms for the antitumor activity of combined DC101 and doxorubicin. Collectively, our data suggested that anti-VEGF receptor 2 in combination with continuous low-dose doxorubicin may provide a new therapeutic approach for human soft tissue sarcoma in the clinic.

Effects of hyperbaric oxygen and normobaric carbogen on the radiation response of the rat rhabdomyosarcoma R1H

PURPOSE

Hypoxic tumor cells are an important factor of radioresistance. Hyperbaric oxygen (HBO) and normobaric carbogen (95% oxygen, 5% carbon dioxide) increase the oxygen delivery to tumors. This study was performed to explore changes of tumor oxygenation during a course of fractionated irradiation and to determine the effectiveness of normobaric carbogen and HBO during the final phase of the radiation treatment.

METHODS AND MATERIALS

Experiments were performed on the rhabdomyosarcoma R1H growing on WAG/Rij rats. After 20 X-ray fractions of 2 Gy within 4 weeks, oxygen partial pressure (pO2) was measured using the Eppendorf oxygen electrode under ambient conditions, with normobaric carbogen or HBO at a pressure of 240 kPa. Following the 4-week radiation course, a top-up dose of 10-50 Gy was applied in 2-10 fractions of 5 Gy with or without hyperoxygenation.

RESULTS

HBO but not carbogen significantly increased the median pO2 in irradiated tumors. The radiation doses to control 50% of tumors were 38.0 Gy, 29.5 Gy, and 25.0 Gy for air, carbogen, and HBO, respectively. Both high oxygen content gas inspirations led to significantly improved tumor responses with oxygen enhancement ratios (OERs) of 1.3 for normobaric carbogen and 1.5 for HBO (air vs. carbogen: p = 0.044; air vs. HBO: p = 0.02; carbogen vs. HBO: p = 0.048).

CONCLUSION

Both normobaric carbogen and HBO significantly improved the radiation response of R1H tumors. HBO appeared to be more effective than normobaric carbogen, both with regard to tumor oxygenation and response to irradiation.

[Comparison between the Eppendorf histograph and the Licox system for determination oxygen partial pressure in tumor tissue]

BACKGROUND

The oxygenation of a tumor is certainly one of the major facts influencing the response to treatment. pO2 measurement in tumor tissue can be done by using the Eppendorf-histograph. In recent years the Licox-system (GMS) was developed for oxygen tension measurement in tissues and fluids under clinical routine conditions and for research work. Aim of the present study was to assess the suitability of the Licox-system in drawing up histograms of pO2 values in tumor tissues.

METHOD

Histograms of the distribution of oxygen tension in twelve tumors were prepared with both measuring systems in parallel. Investigations were performed on rats with isotransplanted R1H rhabdomyosarcomas in continuous intravenous anesthesia with Fentanyl and Dormicum. Ventilation with a mixture of air and oxygen was applied through a tracheostoma. Arterial pressure and body temperature were analysed and balanced continuously.

RESULTS

No correspondence between data of both measuring methods could be found.

CONCLUSIONS

Because of constructional advantages the Eppendorf-histograph seems to be comparatively more suitable in drawing up histograms of oxygen tension tumor tissue.

Improvement of Clostridium tumour targeting vectors evaluated in rat rhabdomyosarcomas

Previous studies have demonstrated the feasibility of using apathogenic clostridia as a promising strategy for hypoxia-specific tumour targeting. The present study shows that the use of the vascular targeting compound combretastatin A-4 phosphate could significantly (P<0.001) increase the number of Clostridium vegetative cells in rat rhabdomyosarcomas with sizes between 0.2 cm(2) and 3 cm(2). Furthermore, this study showed that administration of metronidazole for a 9-day period was sufficient to eliminate systemically administered Clostridium from the tumour. Moreover, previous Clostridium spore administration did not effect tumour colonisation, regardless of the immune response status of the host.

In vivo antitumor effect of vascular targeting combined with either ionizing radiation or anti-angiogenesis treatment

PURPOSE

Interference with the tumor blood vessels through anti-angiogenesis or vascular targeting can indirectly suppress tumor growth. Vascular targeting of solid tumors, using tubulin-compromising agents, seems a promising and selective novel treatment. We aimed to evaluate the potential (hypothesis-based) benefit from combinations of vascular targeting using combretastatin A-4 phosphate (combreAp) with either ionizing radiation or anti-angiogenesis.

METHODS AND MATERIALS

Rhabdomyosarcoma tumor pieces were inplanted subcutaneously (s.c.) in the lower flank region of syngeneic adult WAG/Rij rats. Tumors were grown until different sizes and stratified for the various treatment groups: small (1-3 cm3), medium (3.1-7 cm3), and large (7.1-14 cm3). CombreAp was injected i.p.; injections of TNP-470 were s.c. in the neck area. Localized single-dose (8 Gy) irradiations of tumors were done under Nembutal anesthesia, always 1 day before a single combreAp (25 mg/kg) injection. The TNP-470 treatment (3 times 30 mg/kg in 1 week) started 1 day after a double (8 days interval between both) combreAp administration. Tumor responses were evaluated by the growth delay assay, and statistical significance of tumor growth change was computed.

RESULTS

Large tumors responded better to combreAp treatment given alone than did the smaller ones, confirming our previous data with this tumor model. Combining irradiation with combreAp also resulted in a tumor size-dependent growth delay. With small and medium tumor volumes, a similar response was measured after the combination treatment when compared with irradiation only. Large tumors, however, showed a strong (at least additive) increase of the growth delay with the combined therapy; the difference in tumor growth between the two treatment groups was very significant (p < 0.0001). m When TNP-470 was combined with combreAp, no significant lengthening of the growth delay, irrespective of the tumor size, was present with the applied schedule.

CONCLUSION

The current data show a significant advantage in the combination of combreAp with irradiation in rhabdomyosarcomas having a large size (7-14 cm3) at treatment. Such a benefit in tumor response was not observed with the smaller tumors, seemingly because irradiation as such was very effective. No significant gain in growth delay for any tumor size was observed when TNP-470, showing efficacy on its own specifically with tumors measuring <7 cm3, was added to the combreAp treatment. This presumably reflects only little angiogenesis during the first week of rhabdomyosarcoma regrowth after the combreAp treatment.

Complete inhibition of rhabdomyosarcoma xenograft growth and neovascularization requires blockade of both tumor and host vascular endothelial growth factor

Growth of the human rhabdomyosarcoma A673 cell line in nude mice is substantially reduced but not completely suppressed after systemic administration of the antihuman vascular endothelial growth factor (VEGF) monoclonal antibody (Mab) A.4.6.1. Potentially, such escape might be attributable to incomplete local penetration of the antibody because of a diffusion barrier associated with tumor growth. Alternatively, it might reflect a compensatory up-regulation of murine VEGF, produced by the stroma of the host, or of other angiogenic factor genes. To test these potential mechanisms, systemic administration of Mab A.4.6.1, was performed in conjunction with intratumoral administration of an irrelevant antibody, an antihuman VEGF Fab or mFlt(1-3)-IgG that neutralizes both human and murine VEGF. Tumor growth in the systemic-plus-intratumoral anti-VEGF group was not different from that in the systemic anti-VEGF-plus-intratumoral-control antibody group, arguing against the possibility that bioavailability is the factor that limits the antitumor efficacy of Mab A.4.6.1. However, intratumoral mFlt(l-3)-IgG administration dramatically enhanced the activity of systemic anti-VEGF Mab and resulted in complete suppression of tumor growth, which indicated that host VEGF significantly contributes to tumor growth. Systemic administration of mFlt(1-3)-IgG alone replicated these findings. Histological analysis of residual tumor tissues revealed an almost complete absence of host-derived vasculature and massive tumor-cell necrosis in the mFlt(1-3)-IgG groups. Such extensive necrotic areas were not present in the other groups. Real-time reverse transcription-PCR analysis of total RNA derived from tumor tissues indicated strong up-regulation of both human and murine VEGF as well as other genes regulated by hypoxia. Our findings emphasize the need to completely block VEGF for maximal inhibition of tumor growth.

Vascular targeting of solid tumours: a major 'inverse' volume-response relationship following combretastatin A-4 phosphate treatment of rat rhabdomyosarcomas

Tumour-specific vascularisation may be therapeutically approached in two different ways: by antiangiogenic treatments specifically directed to dividing and migrating endothelial cells, or by agents that target principally the inadequate and ill-structured tumour vasculature. Combretastatin A-4 phosphate (combreAp), a recently synthesised prodrug (OXiGENE, Lund, Sweden), is a vascular targeting agent of the latter kind. We evaluated the effect of a single intraperitoneal (i.p.) combreAp injection on the growth of rhabdomyosarcomas syngeneic in WAG/Rij rats. Different tumour volume groups, ranging between 0.1 and 27 cm(3), were selected to assess the relationship between the size at treatment time and the response to combreAp. A double combreAp treatment (2x25 mg/kg) was investigated within the same overall aim: the relationship between growth delay and tumour size. Our results show that the systemic administration of combreAp induces a clear-cut differential growth delay in the solid rat rhabdomyosarcomas: with very large tumours (>/= 14 cm(3)), a 17.6-fold stronger effect was measured than with very small tumours (<1 cm(3)). This is the 'inverse' of the volume-response seen with the conventional therapeutic approaches (radiotherapy, chemotherapy or surgery). These combreAp antitumour responses were observed without treatment limiting systemic toxicity in the rats. With clinical digital subtraction angiography, using microsurgical cannulation of a major tumour draining vessel, and with histopathology, we demonstrate that growth delay is related to an early (within 3-6 h) and extensive breakdown of tumour blood vessels. The experiments involving a second injection also indicate a volume-dependent effect of combreAp in reducing the regrowth rate of small or large rhabdomyosarcomas. This significant differential volume-response obtained with 'selective' vascular targeting, stronger in larger tumours than smaller ones, suggests the potential of broadening the therapeutic window.

Tumor hypoxia--a confounding or exploitable factor in interstitial brachytherapy? Effects of tissue trauma in an experimental rat tumor model

PURPOSE

To evaluate the potential effects of tumor hypoxia induced by afterloading catheter implantation on the effectiveness of brachytherapy in a rat tumor model.

METHODS AND MATERIALS

Afterloading catheters (4) were implanted in subcutaneously growing R1M rhabdomyosarcoma in female Wag/Rij rats. A MicroSelectron (Nucletron) was used for interstitial high-dose-rate irradiation ((192)Ir). Tumor oxygenation, perfusion, and cell survival were assessed by pO(2) histography (Eppendorf), Tc-99m injection, and excision assay, respectively.

RESULTS

Tumor perfusion was markedly reduced at 1 h after catheter implantation (33.9 +/- 6.0% (SEM, n = 9) of control) and partly recovered after 5 h (61.5 +/- 12.2%). At 24 h, the perfusion level reached control values (100.6 +/- 25.7%), but was highly variable with some of the tumors showing hardly any recovery at all. Tumor oxygenation showed a similar pattern, but with less recovery. Median pO(2) readings were 13.5, 1.2, and 5.3 mm Hg before and at 1 and 24 h after implantation, respectively (7 tumors). The percentages of pO(2) readings </= 2.5 mm Hg were 18.9%, 55.6%, and 41.3% at these time points. The difference in cell survival after irradiation (10 Gy) at 1 or 24 h after implantation was compatible with a radiobiological oxygen effect.

CONCLUSION

Implantation of brachytherapy afterloading catheters induces an increased level of hypoxia for several hours by disrupting tumor perfusion, causing both a modest degree of direct cell kill and a significant reduction of the radiation effect. This transient hypoxia might be exploited by combining irradiation with properly timed treatments targeting hypoxic cells.

The influence of inspiratory hyperoxia on ischemia-reperfusion-induced tumour growth delay

We investigated the ischemia-reperfusion-induced tumour growth delay as a function of ischemic time, tumour temperature, and the amount of inspired oxygen during reperfusion. The rhabdomyosarcoma R1H growing on the right flank of male WAG/Rij rats was clamped for 2 or 4 h at 20 degrees C or 37 degrees C. Five minutes prior to and 10 min during reperfusion the animals respired air, pure oxygen or carbogen (95% O2, 5% CO2). Comparison of single treatment modalities with untreated controls revealed significant tumour growth delays after clamping times of 4 h at 37 degrees C for air and pure oxygen, but not for carbogen.

Microvascular and tumor cell alterations during continuous hyperfractionated irradiation: an electron microscopic investigation on the rat R1H rhabdomyosarcoma

PURPOSE

Conventionally fractionated y-irradiation results in severe damage of tumor capillaries associated with decreasing oxygen partial pressure within the tumor. The present study was undertaken to assess whether vasculo-connective changes are less pronounced after continuous hyperfractionated irradiation, implying better tumor oxygenation and improved radiosensitivity.

MATERIALS AND METHODS

Twenty rats with an isotransplanted R1H rhabdomyosarcoma were irradiated for 12 days with 2 daily fractions of 2.5 Gy (delta t = 6 h). After 0, 15, 30, 45, and 60 Gy, tumor tissue of 4 rats each was analyzed histologically and electron-microscopically.

RESULTS

Untreated rhabdomyosarcomas were composed of spindle-shaped tumor cells with numerous mitoses. There were many apoptotic nuclei and a large central necrosis. Tumor capillaries showed a continuous lining of flattened endothelial cells with broad overlapping cell contacts overlying a delicate continuous basal lamina. During irradiation, mean tumor volume declined from 1.9 cm3 to 1.2 cm3. The number of atypical mitoses and apoptoses increased and numerous giant tumor cells appeared. The proportion occupied by necrotic tumor tissue rose from 30% to 60%. After 15 Gy (3 days), a marked vasodilatation was apparent accompanied by an interstitial edema. Occasionally, endothelial cells were rounded up and showed indented nuclei, with the underlying basal lamina disintegrated. These changes progressed with increasing radiation doses. After 30 Gy (6 days), leukocytes started to adhere to the endothelial wall. Electron-dense fine fibrillar and basal lamina-like deposits appeared in the perivascular space. Endothelial cell edema was only observed after 60 Gy (12 days). Cell contact areas were shortened, however, the endothelial lining was not interrupted. No signs of radiation fibrosis were observed.

CONCLUSION

Continuous hyperfractionated irradiation induces relatively discrete alterations of the vasculo-connective tumor tissue as compared to conventional irradiation. This may be an advantage with respect to tumor blood flow, oxygenation, and thus, radiosensitivity.

Insulin-like growth factor II and PAX3-FKHR cooperate in the oncogenesis of rhabdomyosarcoma

The mouse myoblast C2C12 cell line transfected singly with cDNA for Pax-3, PAX3-FKHR, or insulin-like growth factor (IGF) II or cotransfected with IGF-II plus Pax-3 or with IGF-II plus PAX3-FKHR genes showed an altered morphology, a lack of differentiation, and higher proliferation rates in vitro. On s.c. injection into nude mice, tumors grew from transfected cell lines but not from cells transfected with the empty vector. Tumors derived from IGF-II/PAX3-FKHR- and IGF-II-transfected cells grew most rapidly. Cotransfection of IGF-II plus Pax-3 induced tumors comprised highly differentiated striated muscle cells; Pax-3, PAX3-FKHR, or IGF-II transfection produced tumors at varying stages of differentiation. Tumors derived from IGF-II plus PAX3-FKHR-cotransfected cells were composed of undifferentiated cells. This was the only tumor type to infiltrate the underlying muscle. The most angiogenesis and the least apoptosis were observed in the latter tumors. These results support the hypothesis that PAX3-FKHR interacts with IGF-II to play a critical role in the oncogenesis of rhabdomyosarcoma.

Host microvasculature influence on tumor vascular morphology and endothelial gene expression

We have previously demonstrated that vascular endothelial growth factor-165 (VEGF), a tumor-secreted angiogenic factor, can acutely and chronically induce fenestrations in microvascular endothelium (Cancer Res 1997, 57:765-772). Because the morphology and function of microvascular endothelium differs from tissue to tissue, we undertook studies to examine whether the neovasculature in tumors also differed depending upon tumor location. Four tumor types implanted in the brain or subcutis in nude mice were studied: a murine rhabdomyosarcoma (M1S), a murine mammary carcinoma (EMT), and two human glioblastomas (U87 and U251). In addition, we studied Chinese hamster ovary cells stably transfected with human VEGF165. As previously reported, tumors grown in the subcutaneous space had a microvasculature that was fenestrated and had open endothelial gaps. The identical tumors when grown in the brain also had fenestrated endothelium and vessels with open endothelial gaps, but they were drastically reduced in occurrence. Open endothelial gaps were not seen in all tumors implanted in the brain (EMT and M1S), although fenestrated endothelium was always seen. VEGF and VEGF receptors were measured in tumors from both locations by immunoblotting and competitive polymerase chain reaction, respectively. VEGF amount was not significantly different between the tumor locations. Interestingly, total tumor vascular mRNA expression of both Flk-1 and Flt-1 was greater in tumor vessels derived from the brain compared with tumor vessels derived from subcutaneous tissues. These results demonstrate that the host microvascular environment determines the morphology and function of the tumor vasculature and that endothelia from different tissues vary in their ability to express the VEGF receptors given identical stimuli.

Blood flow, oxygenation, metabolic and energetic status in different clonal subpopulations of a rat rhabdomyosarcoma

Differentiation of a tumor plays an important role in terms of biological aggressiveness. The question arises as to whether this is reflected in differences in the metabolic and energetic status of solid tumors. The aim of this study was to analyze the influence of clonal tumor cell differentiation on the microenvironment of rat rhabdomyosarcomas. Two distinct lines of a rhabdomyosarcoma (BA-HAN-1) with different histomorphological properties were used (line F1, co-existence of mononuclear stellate cells and multinuclear myotube-like giant tumor cells; G8, polygonal, mononuclear tumor cells). Solid tumors were grown s.c. on the hind food dorsum of Lewis rats. Tumor oxygenation was measured using O2-sensitive needle electrodes. For determining tumor blood flow, the 133Xe clearance method was used. Global glucose and lactate concentrations were measured enzymatically, global ATP, ADP, and AMP were analyzed by HPLC. The regional distribution of metabolic and energetic parameters within the tumors was analyzed using quantitative bioluminescence and image analysis. Tumor growth rate was significantly different between the two lines. The volume doubling time was 2.5 days for the F1 and 3.0 days for G8 tumors. No differences in blood flow were seen between the two lines investigated, oxygenation was slightly poorer, glucose and ATP levels slightly higher, and lactate concentration somewhat lower in the F1 line as compared to the G8 line. From these differences - although marginal - it is concluded that the G8 line presumably relies on glycolysis whereas the F1 line seems to prefer oxidative glucose turnover. Despite these different metabolic profiles between the two tumor lines, the histopathology of the rhabdomyosarcomas seems to be only of limited significance for the tissue oxygenation status as already postulated for various tumors in the clinical setting.

Tumor devascularization by intratumoral ethanol injection during surgery. Technical note

Preoperative reduction in tumor vascularity has been accomplished previously by selective catheterization of tumor vessels and delivery of occlusive materials. The results of percutaneous infusion of vertebral hemangiomas and other vascular lesions led the authors to speculate that rapid devascularization of tumors by direct injection of ethanol (ETOH) could be used to reduce bleeding and facilitate resection during surgery. Thus, the use of intratumoral injection of ETOH and its effects on tumor hemostasis and resectability were examined. Four patients received direct injection of ETOH into either a spinal epidural (two renal cell carcinomas and one rhabdomyosarcoma) or a large cerebellar neoplasm (hemangioblastoma). Intraoperative perfusion of the tumors with ETOH produced immediate blanching and devascularization and enhanced visualization and resection. Incremental tumor devascularization is achieved by careful injection of small amounts of ETOH directly into the lesion, producing immediate and complete regional tumor devascularization. Use of this technique reduces intratumoral bleeding and enhances the ease and effectiveness of resection.

Humanization of an anti-vascular endothelial growth factor monoclonal antibody for the therapy of solid tumors and other disorders

Vascular endothelial growth factor (VEGF) is a major mediator of angiogenesis associated with tumors and other pathological conditions, including proliferative diabetic retinopathy and age-related macular degeneration. The murine anti-human VEGF monoclonal antibody (muMAb VEGF) A.4.6.1 has been shown to potently suppress angiogenesis and growth in a variety of human tumor cells lines transplanted in nude mice and also to inhibit neovascularization in a primate model of ischemic retinal disease. In this report, we describe the humanization of muMAb VEGF A.4.6.1. by site-directed mutagenesis of a human framework. Not only the residues involved in the six complementarity-determining regions but also several framework residues were changed from human to murine. Humanized anti-VEGF F(ab) and IgG1 variants bind VEGF with affinity very similar to that of the original murine antibody. Furthermore, recombinant humanized MAb VEGF inhibits VEGF-induced proliferation of endothelial cells in vitro and tumor growth in vivo with potency and efficacy very similar to those of muMAb VEGF A.4.6.1. Therefore, recombinant humanized MAb VEGF is suitable to test the hypothesis that inhibition of VEGF-induced angiogenesis is a valid strategy for the treatment of solid tumors and other disorders in humans.

Changes in tumor oxygenation during a combined treatment with fractionated irradiation and hyperthermia: an experimental study

PURPOSE

To determine the influence of adjuvant hyperthermia on the oxygenation status of fractionated irradiated tumors.

METHODS AND MATERIALS

Oxygen partial pressure (pO2) in rat rhabdomyosarcomas (R1H) was measured sequentially at weekly intervals during a fractionated irradiation with 60Co-gamma-rays (60 Gy/20f/4 weeks) in combination with local hyperthermia (8 f(HT) at 43 degrees C, 1 h/4 weeks). Tumors were heated twice weekly with a 2450 MHz microwave device at 43 degrees C, 1 h starting 10 min after irradiation. The pO2 measurements (pO2-histograph, Eppendorf, Germany) were performed in anesthetized animals during mechanical ventilation and in hemodynamic steady state. All tumor pO2 measurements were correlated to measurements of the arterial oxygen partial pressure (paO2) determined by a blood gas analyzer.

RESULTS

The oxygenation status of R1H tumors decreased continuously from the start of the combined treatment, with increasing radiation dose and number of heat fractions. In untreated controls a median tumor pO2 of 23 +/- 2 mmHg (mean +/- SEM) was measured. Tumor pO2 decreased to 11 +/- 2 mmHg after 30 Gy + 4 HT (2 weeks), and to 6 +/- 2 mmHg after 60 Gy + 8HT (4 weeks). The increase in the frequency of pO2-values below 5 mmHg and the decrease in the range of the pO2 histograms [delta p(10/90)] further indicated that tumor hypoxia increased relatively rapidly from the start of combined treatment. After 60 Gy + 8HT 48 +/- 5% (mean +/- SEM) of the pO2-values recorded were below 5 mmHg.

CONCLUSIONS

These findings suggest that adjuvant hyperthermia to radiotherapy induces greater changes in tumor oxygenation than radiation alone [cf. (39)]. This might be of importance for the temporary application of hyperthermia in the course of a conventional radiation treatment.

Complete inhibition of angiogenesis and growth of microtumors by anti-vascular endothelial growth factor neutralizing antibody: novel concepts of angiostatic therapy from intravital videomicroscopy

In the present study, we evaluated the effects of a neutralizing antivascular endothelial growth factor (anti-VEGF) antibody on angiogenesis and growth of tumor spheroids using an intravital microscopic technique permitting noninvasive, in vivo and in situ study of tumor angiogenesis and tumor growth in conscious mice. Tumor spheroids of the human rhabdomyosarcoma cell line A673, with a diameter between 600 and 1000 microns, were implanted in dorsal skinfold chambers inserted on Beige nude/xid mice. Tumor cells were prelabeled with a fluorescent vital dye [(5-(and-6)-((4-chloromethyl)benzoyl)amino)tetramethylrhodamine], which allowed estimation of the growth of the implanted tumor spheroids. Treatment (i.p.) with the monoclonal antibody A4.6.1, specific for VEGF, completely inhibited neovascularization of the microtumors and suppressed their growth to the extent that tumors implanted in treated animals leveled off at a volume less than 1 mm3, i.e., the anti-VEGF antibody dramatically changed the growth characteristics of the tumor line from being a rapidly growing malignancy to a dormant microcolony.

Temporary vascular occlusion and glucose: effects on tumour and normal tissue pH in animal experiments

The relationship between duration of a period of vascular occlusion and magnitude of pH decrease in tumour and normal tissue was investigated in rats. To acidify tissue pH further, moderate dose glucose (2.4-3.0 g.kg(-1).hr(-1)) was administered intravenously through a catheter positioned in a tail vein, immediately after the clamp was released. This sequence of pH modifying modalities was chosen since it is employed in clinical regional isolation perfusion for recurrence of malignant melanoma of the limbs. Tumour pH in rat rhabdomyosarcoma BA1112 decreased more than normal tissue pH under 10, 20, 30 or 60 min of temporary vascular occlusion. Administration of glucose following any period of clamping always decreased tumour pH further. The largest pH decrease (0.29 pH units) was obtained after 30 min of clamping followed by 60 min glucose and 60 min saline infusion. In the clinic the combination of a maximum of 30 min of clamping followed by moderate dose glucose infusion, which can decrease tumour pH effectively, can be easily achieved in the setting of regional isolation perfusion. It can be used for treatment modalities that are known to be enhanced at lowered tissue pH, such as hyperthermia and certain chemotherapeutic drugs. These results form the basis for studying the therapeutic gain which can be obtained with this model.

Correlation between cell differentiation stage, types of invasion, and hematogenous metastasis in experimental rhabdomyosarcomas

Cancer malignancy is directly related to invasiveness and metastasis and inversely related to the degree of tumor differentiation. The relation between the stage of cell differentiation and the types of invasion leading to metastasis is not entirely clear. Intramuscularly transplanted rat rhabdomyosarcomas are good models to study cell differentiation, invasion, and metastasis. Rat rhabdomyosarcoma cell lines (SMF-Ai, SMF-Da, and RMS-B and its clones) with defined invasive and metastatic potentials have been established. The stage of myogenic differentiation was evaluated morphologically and by immunohistochemistry. Invasiveness was evaluated according to the infiltration of muscle fibers and basal lamina. The SMF-Ai line is highly invasive and metastatic. It is composed of premyoblasts that were involved in intercellular, translaminar, and transcellular invasion of muscle fibers. The SMF-Da line is noninvasive and nonmetastatic. It is composed of myoblasts. The RMS-B line and its clones were at different stages of differentiation and they differed in their invasiveness and metastatic potentials. In highly invasive and metastatic clones (RMS-Bg and RMS-Bc), premyoblasts were involved in translaminar invasion. Clones composed of myoblasts, rhabdomyoblasts, and myotubes only showing intercellular invasion did not present hematogenous metastasis. Our results demonstrate a correlation between premyoblastic stage of differentiation and translaminar invasion. The presence of translaminar invasion is directly related to hematogenous metastatic ability of rat rhabdomyosarcomas.

Flunarizine enhancement of melphalan activity against drug-sensitive/resistant rhabdomyosarcoma

Flunarizine, a diphenylpiperazine calcium channel blocker, is known to increase tumor blood flow. It also interferes with calmodulin function, repair of DNA damage and drug resistance associated with P-glycoprotein. Flunarizine was tested for its ability to modulate either cyclophosphamide- or melphalan-induced growth delay for a drug-resistant rhabdomyosarcoma xenograft (TE-671 MR) and the drug-sensitive parent line (TE-671), in which P-glycoprotein is not involved in the mechanism of drug resistance. Tumour blood flow was increased by 30% after a flunarizine dose of 4 mg kg-1, but no modification in growth delay was induced by melphalan (12 mg kg-1). In contrast, a 60 mg kg-1 dose of flunarizine had no effect on tumour blood flow, but the same dose created significant enhancement in melphalan-induced tumour regrowth delay in both tumour lines. The dose-modifying factor for flunarizine as an adjuvant to melphalan was approximately 2 for both tumour lines. Although blood flow measurements were not performed with the combination of flunarizine and melphalan, the results from flunarizine alone suggested that augmentation of melphalan cytotoxicity is not mediated by changes in blood flow. In contrast, flunarizine did not affect drug sensitivity to cyclophosphamide in groups of animals bearing the drug-sensitive parent tumour line. These results suggest that the mechanism of drug sensitivity modification by flunarizine is not related to modification of tumour blood flow, but may be mediated by modification of transport mechanisms that are differentially responsible for cellular uptake and retention of melphalan as compared with cyclophosphamide.

Impact of tumor stroma on expression of the tumor bed effect in R1H rat rhabdomyosarcoma

The impact of intratumoral stroma on the expression of the tumor bed effect was studied in R1H rat rhabdomyosarcoma. For this, either R1H tumors growing in subcutaneous tissues (in situ) were irradiated at median volumes of 40 mm3 with a single exposure of 15 Gy (200 kVp X rays), or fresh tumor fragments or cloned tumor cells cultured in vitro were transplanted into subcutaneous tissue 2 days after preirradiation with 15 Gy. The tumor bed effect was evaluated by the time necessary for experimental tumors to grow from 0.1 cm3 to 10 cm3. When irradiated in situ, R1H tumors expressed a clear-cut tumor bed effect. The growth rate was decreased by a factor of 1.8 +/- 0.2 compared to controls. A significant decrease in growth rate by a factor of 1.7 +/- 0.2 was also observed when cultured tumor cells were transplanted into preirradiated tissue. However, when tumor fragments were transplanted into preirradiated sites, no significant decrease in growth rate occurred in two independent experiments (1.0 +/- 0.1; 1.2 +/- 0.2). Our results indicate that vessels originating from the intratumoral stroma can modulate the expression of the tumor bed effect in R1H tumors.

Ultrastructural studies on tumor capillaries of a rat rhabdomyosarcoma during fractionated radiotherapy

Sequential morphological changes in tumor capillaries of istransplanted R1H rat rhabdomyosarcoma were observed weekly by transmission electron microscopy during fractionated radiotherapy (75 Gy/25 fractions/5 weeks). During the first 2 weeks of irradiation (up to 30 Gy), edema of the tumor capillary wall was induced. Swollen endothelial cells bulged into the vascular lumen and were surrounded by a widened subendothelial space with increase amounts of collagen fibrils (subendothelial edema). The endothelial lining was preserved up to the 3rd week of irradiation (45 Gy). Prolonged irradiation was associated with progressive destruction of the vascular wall including shrinkage, gradual loss of cell contacts, disappearance of the normal chromatin pattern, and increase of cytoplasmic vacuoles in endothelial cells as well as disruption of basal laminae. One week after the end of radiotherapy (75 Gy), the tumor capillaries showed complete necrosis. Progressive damage to tumor capillaries in the course of fractionated radiotherapy might have adverse effects on blood supply and thus on tumor oxygenation.

[Brain metastasis of rhabdomyosarcoma with intratumorous hemorrhage: a case report and literature review]

A 56-year-old male suffered from primary rhabdomyosarcoma on the left internal thoracic wall, which was treated by chemotherapy, and local irradiation following biopsy. Four months after the diagnosis, he suddenly complained of headache and left paresthesia occurred followed by generalized convulsion and left hemiplegia. CT scan revealed a high density mass in the right parietal lobe. The patient was referred to our department and underwent emergency evacuation of the hematoma together with tumor removal. The pathological specimen showed spindle or oval-like cells with hypercellularity and some mitotic figures. Immunohistochemical study demonstrated that many cells were positive for desmin and myoglobin, which is specific to myogenic tumor. These characteristics were compatible with those of the primary thoracic lesion, and a diagnosis of metastatic rhabdomyosarcoma was made. Five weeks after the craniotomy, the metastatic brain tumor recurred in the same site and also in the bilateral occipital lobes. Although radiotherapy to the brain decreased the tumor size, the patient died of respiratory failure eleven and a half months after the initial diagnosis. Sarcomas metastasizing to the brain are rare and only 16 cases of rhabdomyosarcoma metastasizing to the brain have been reported so far. Recent advances in chemotherapy, however, have been able to show the increased incidence of sarcoma metastasis to the brain. Therefore, the necessity of follow-up CT scan for sarcoma patients of long survival is to be stressed, even if the patient shows no neurological symptoms.

Tumor-secreted vascular permeability factor/vascular endothelial growth factor influences photosensitizer uptake

The role of vascular permeability in the preferential accumulation of photosensitizers in tumor tissue was investigated. Two murine tumors [experimental mammary tumor carcinoma (EMT-6) and methylcholanthrene-induced rhabdomyosarcoma (M1S)] and a human bladder carcinoma (EJ) were grown s.c. on the flank in athymic nude mice and analyzed for in vivo vessel permeability, vascular permeability factor (VPF) secretion, and accumulation of the photosensitizer, chloroaluminum sulfonated phthalocyanine. In vivo tumor vessel permeability and vascular volume were quantitated by measuring Evans blue extravasation and accumulation of a high molecular weight fluoresceinated dextran, respectively. VPF was isolated from serum-free tumor cell conditioned medium using heparin-Sepharose affinity chromatography. Dot and Western blots stained with anti-VPF antiserum positively identified VPF in samples from each tumor. Chloroaluminum sulfonated phthalocyanine pharmacokinetics in tumor-bearing mice were measured using a fiber-based spectrofluorometer. In vivo vessel permeability was found to be greatest in M1S tumors, next in EMT-6 tumors and finally in EJ tumors. Consistent with in vivo data, M1S and EMT-6 tumor cells in culture secrete significantly more VPF than EJ tumor cells. Chloroaluminum sulfonated phthalocyanine accumulation was approximately 2 times greater in M1S and EMT-6 tumors compared to EJ tumors. Our data present evidence that photosensitizer accumulation can be correlated to in vivo tumor vessel permeability and VPF secretion of that tumor. Taken together, the data support the hypothesis that vascular permeability differences among tumors play a significant role in the uptake and retention of photodynamic agents.

Malignant microvasculature in abdominal tumors in children: detection with Doppler US

Malignant tumors produce a network of microscopic, thin-walled vessels that invade the host and provide the blood supply essential for growth. This network, situated at the periphery of malignant tumors, gives rise to characteristic, high-velocity Doppler shifts at ultrasound (US) scanning and was sought in 54 children with abdominal masses. Characteristic high-frequency Doppler signals (greater than 2.5 kHz) were found in 27 of 35 malignant tumors. These signals disappeared during successful chemotherapy in three children with neuroblastoma in whom the signals had been documented initially. The signals were absent in three other children, who had undergone clinically successful therapy, and were present in two children with rapidly progressing tumors despite chemotherapy. In 14 children, none of the benign tumors showed high-frequency Doppler shifts. The search for malignant neovasculature with Doppler US scanning may provide insight into tumor behavior. The Doppler US examination, a noninvasive adjunct to routine US, may become useful at both the time of diagnosis of a mass and afterward to assess the effect of chemotherapy.

Vascular and cellular damage in a murine tumour during fractionated treatment with radiation and hyperthermia

Tissue reactions and vascular damage in rat tumours (rhabdomyosarcoma R1H) were studied with morphological methods during fractionated treatments with 60Co-gamma-irradiation of 75 Gy alone and in combination with ten fractions of microwave hyperthermia at 43 degrees C, 60 min for five weeks. The nature and time course of tissue and vascular damage change individually with the treatment applied. During radiation-heat treatment congestion, dilation and rupture of tumour blood vessels were observed. The cellular and vascular damage, especially in the central parts of the tumours, occurred earlier and were generally more intense during the combined treatment than found after irradiation alone. The enhanced tissue damage can be related to the local temperatures in the R1H tumours during the microwave heat treatments.

Differences in the response of the microcirculation to hyperthermia in five different tumours

The response of the microcirculation in five different tumours, growing in 'sandwich' observation chambers in the back of the rat, to hyperthermia was investigated. The tumours investigated encompassed three human xenografted tumours, of which two were carcinomata of the colon and one of the lung, and two isologous rat tumours, the Rhabdomyosarcoma BA1112 and a rat mammary carcinoma. It was concluded (1) that the various tumours required significantly different exposure times for inducing 50% stoppage of the tumour microcirculation (ST50). This seems to indicate that differences in the characteristics of the tumour cells are more important for causing microcirculatory stoppage than is the sensitivity of the cells of the blood vessels. (2) An increase in surface (i.e. volume) was observed in all four tumours examined for this phenomenon. The rate of increase (usually 1-2% per hour at 42.5 degrees C) was, however, significantly different between the various tumours. This rate was higher exposure temperatures (43 and 43.5 degrees C), but this was only investigated for the Rhabdomyosarcoma BA1112. Extensive statistical analysis of this phenomenon of volume increase could not demonstrate a correlation with any of the circulation parameters. (3) The relative velocity of the erythrocytes in selected capillaries in the tumours decreases as a result of the hyperthermic treatment, and is probably related to the tumour-specific ST50. (4) A human colon carcinoma xenograft, one of the tumours investigated, showed strong fluctuations in the parameter 'erythrocyte velocity'. The appearance of such fluctuations did not seem to influence the heat-induced stoppage of the circulation. Probably the phenomenon of fluctuations in the velocities of the erythrocytes in the tumour capillaries is a tumour-specific phenomenon.

Computerised tomography in the evaluation of expansile lesions arising from the skull vault in childhood--a report of 5 cases

Expansile lesions of the skull vault are rare in childhood, and often present as relatively asymptomatic calvarial swellings. The cases of 5 children with expansile lesions of the skull vault due to both benign and malignant primary bone lesions are described. The value of computerised tomography in demonstrating that the "tumour" arises primarily from the skull vault as opposed to the underlying brain, and in demonstrating clinically unsuspected endocranial extension of the mass is described. The CT findings in 2 cases of aneurysmal bone cyst, including the significance of the presence of "fluid levels" in reaching a definitive diagnosis are discussed. The successful pre-operative embolisation in one case of aneurysmal bone cyst is reported.

Basic fibroblast growth factor in human rhabdomyosarcoma cells: implications for the proliferation and neovascularization of myoblast-derived tumors

Cultured human embryonal rhabdomyosarcoma cells express the basic fibroblast growth factor (bFGF) gene and they produce bFGF, which is apparently composed of two microheterogenous forms with Mrs of 16,500 and 17,200, respectively. bFGF derived from the rhabdomyosarcoma cells stimulates their own proliferation and that of human or bovine vascular endothelial cells. It is conceivable that the rhabdomyosarcoma-derived bFGF stimulates the growth and neovascularization of human rhabdomyosarcomas and that it may thereby contribute to the development of these tumors.

Human tumour pH and its variation

The variation in human tumour pH values is large. The aim of this study was to analyse the reasons for these large variations and to determine whether tumour pH can be predicted on the basis of any easily measured parameter. One hundred and five determinations of tumour pH were performed in various human tumours, using the Philips C 902S tissue pH electrode. No correlations were found between the tumour pH and the tumour histology, degree of differentiation, tumour size, patient age or treatment history, and whether or not the tumour was ulcerated. However, tumour pH was significantly lower in primary tumours than in lymph node metastases. Tumours at their primary site (primary, recurrent or residual) were also more acid than distant metastases. The vascular disruption caused by the measuring technique was found to be acceptable.

Time-temperature relationship for hyperthermia induced stoppage of the microcirculation in tumors

The time-temperature dependence for microcirculation stoppage was investigated for the Rhabdomyosarcoma BA1112 growing in observation chambers ("sandwich chambers"). The tumor microcirculation could be observed continuously during the treatment, and the condition of the microcirculation was recorded every 15 minutes as "flowing" or "stoppage". By using large numbers of tumors, the 50% stoppage time (ST50) could be derived for the four temperatures investigated: 42 degrees, 42.5 degrees, 43 degrees and 43.5 degrees C. The respective ST50 values were 226, 152, 101 and 70 minutes. The results can be expressed as a log-linear relationship with a slope value of 0.4551 +/- 0.03 (SD) per degree centigrade. This value probably does not differ significantly from the "t 1/2 for every degree C" rule that has been found for the thermal response of many biological systems.

Vascularization of experimental tumours

At first sight, experimental tumours in observation chambers seem to contain areas with wide vessels showing a sluggish circulation as well as ischaemic areas. Only by careful analysis on cleared specimens can neovascularization be discerned. This process probably occurs primarily in the perimeter of the tumour. It is quite possible that areas of intense vascularization and ischaemic areas in tumours may both result from differences in intensity between the angiogenic stimulus and local tissue pressure.

The influence of a heat pulse on the thermally induced damage to tumour microcirculation

The effect of an initial short period of higher-temperature heat application on the stoppage of the microcirculation in the experimental rhabdomyosarcoma BA1112 in 'sandwich' chambers was investigated. The treatment consisted of an initial heat pulse of 45 degrees C for 10 min which was followed by a continuous exposure at 42.5 degrees C for 3 hr. Using the 't1/2 per degrees C' rule, the time equivalent of the heat pulse was 94 min. Taking this contribution into account, the derived 50% stoppage time of 151 min is essentially the same as the 152 min observed for 42.5 degrees C only treatments. The data therefore indicate that the effect of a heat pulse in the treatment can be accounted for by the customary correction procedure of one time exposure doubling per degrees C. However, it appeared that the microcirculation in the surrounding tumour bed was impaired more than was expected by this treatment.

A revision of the Spalteholz method for visualizing blood vessels

A transparent embedding method is described which enables blood vessels to be visualized in the organs of experimental animals. The circulatory system is perfused with a mixture of fixatives, latices and a pigment. The tissue is embedded in a solid plastic with an appropriate refractory index. The method allows the scoring of blood vessel abnormalities in thick sections. It may also be of use for quantitative histology and the localization of electrodes in thick sections.

[Arterio-venous fistula of the liver. Computer tomographic diagnosis (author's transl)]

By using serial computer tomography, an arterio-venous fistula of the liver could be demonstrated in five cases. The computer tomographic findings which, previously, could only be obtained by angiography, are described. The value of the method as a diagnostic procedure is discussed and its limitations compared with angiography are documented.

Effects of single-dose irradiation in tumor blood flow studied by 15O decay after proton activation in situ

A noninvasive technique employing photon activation of tissue oxygen in situ and detection of subsequent 15O positron decay was used to study the effects of single-dose 60Co irradiation on capillary blood flow in transplanted rat rhabdomyosarcomas. Tumor blood flow was measured before irradiation with 16.5, 38.5, or 60.5 Gy and at several intervals afterward (0-72 hr.). Pre-irradiation values of volume-averaged blood flow in the tumor ranged from 7 to 44 ml/min./100 g. Several hours after irradiation, blood flow fell by up to 50% for 60.5 Gy and up to 35% for 16.5 Gy. However, 24 hours after irradiation, tumor blood flow had recovered completely in the 16.5-Gy group and substantially in the others. For smaller doses such as the fractions typically employed in radiotherapy, no changes in tumor blood flow were observed.

Photon activation-15O decay studies of tumor blood flow

A direct, noninvasive method for measuring absolute values of specific capillary blood flow in living tissue is described. The method is based on the photon activation, in situ, of tissue elements and the measurement of the subsequent decay of the positron activity induced, employing coincidence detection of the photon pairs produced in positron annihilation. Analysis of the time-dependent coincidence spectrum reveals the contribution to the total signal from the decay of 15O, from which the specific capillary blood flow in the imaged, activated volume is ultimately determined. By virtue of its introduction of the radioisotope of interest (15O) directly and uniformly into the tissue volume under investigation, the method described permits both the nonperfused and well perfused fractions of an activated volume to be estimated and hence, the average specific blood flow within imaged tumor volumes to be computed. The model employed to describe and analyze the data is discussed in detail. Results of application of the technique to measurement of specific blood flow in rhabdomyosarcoma tumors grown in WAG/Rij rats are presented and discussed. The method is shown to be reliable and well suited to studies designed to determined the effects of various agents, such as heat, radiation and drugs, on tumor blood flow.