The effect of electromagnetic field and local inductive hyperthermia on nonlinear dynamics of the growth of transplanted animal tumors

AIM

To examine the effects of electromagnetic field with amplified magnetic component and local inductive hyperthermia (IH) on nonlinear dynamics of the growth of animal tumors.

MATERIALS AND METHODS

Guerin carcinoma, Lewis lung carcinoma, sarcoma 45, Walker 256 carcinosarcoma and Pliss lymphosarcoma were studied. The animal tumors were exposed inside of loop aerial, 3 cm in diameter locally for 30 min. Parameters of electromagnetic irradiation (EI): frequency 40 MHz, magnetic intensity 72 A/m, electric intensity 200 V/m and the output power 50 W. The temperature measured by immersion of thermocouple inside the center of the tumor didn't exceed 38.5-39.5 degrees C. Nonlinear dynamics of the growth of animal tumors was analyzed by autocatalytic equation. The heterogeneity of ultrasonic image of the tumor was analyzed by Moran spatial autocorrelation.

RESULTS

The strongest inhibition effect under the influence of EI was in Pliss lymphosarcoma and sarcoma 45. The growth stimulation of animal tumors after EI was recorded in Walker 256 carcinosarcoma. The use of mild IH increased the blood flow in the tumor of Guerin carcinoma.

CONCLUSION

These results are important for clinical application because they testify the necessity of optimization of schemes for local EI during anticancer neoadjuvant therapy with the use of drugs or magnetic nanoparticles. The use of mild IH as a basis for the monotherapy of malignant tumors is not expedient.

Photodynamic Therapy of Walker Tumors by Multiple Laser Irradiation

OBJECTIVE

Photodynamic therapy of Walker tumor after subcutaneous administration of 5-ALA solution using a multiple laser irradiation scheme was monitored by the fluorescence imaging technique to investigate the effectiveness of 5-ALA-PDT.

BACKGROUND DATA

Photodynamic therapy (PDT) is a localized cancer treatment based on the selective uptake and retention of photosensitizer at the tumoral level and on the activation of the photosensitizer by a specific wavelength of light, aiming to induce cytotoxic reactions. As a new photosensitizer, the heme precursor 5- aminolevulinic acid has been introduced recently for photodynamic therapy of tumors and precancerous lesions of the skin. It has been shown that the efficacy of topical 5-ALA-PDT is limited for deeper skin tumor by the depth of 5-ALA penetration through the skin. Oral or systemic administration of ALA or the use of different irradiation schemes may improve tumor response to PDT.

METHODS

Laser irradiation parameters used in this study were lambda = 635 nm, P = 3 mW, t(exp) = 300 sec, and three sessions. The fluorescence was excitated by monochromatic light of 405 nm. The temporal behavior of PpIX fluorescence was studied by processing and analyzing the fluorescence images acquired just after applying 5-ALA, just before and just after three laser irradiations.

RESULTS

The results demonstrate that PpIX is highly selective for tumors areas and a re-accumulation of PpIX appears between laser irradiations. During laser irradiation, the PpIX fluorescence intensity decreases rapidly, reflecting the photodegradation of PpIX.

CONCLUSIONS

In conclusion, the use of a multiple laser irradiation scheme, for the activation of reaccumulation of Pp IX (with three steps) is effective for photodynamic therapy of Walker tumor.

Biodistribution of 10B in a rat liver tumor model following intra-arterial administration of sodium borocaptate (BSH)/degradable starch microspheres (DSM) emulsion

We reported that intra-arterial administration of borocaptate sodium (BSH)/lipiodol emulsion provided selectively high (10)B concentrations (approximately 200 ppm 6 h after administration) in experimental liver tumors. In the present study, we investigated the pharmacokinetics of BSH following intra-arterial administration of BSH with other embolizing agent, degradable starch microspheres (DSM). The (10)B concentration in the tumor at 1 h after administration of BSH with DSM was 231 ppm. At 6 h, the (10)B concentration in the tumor in BSH with DSM group was 81.5 ppm. The (10)B concentration in the liver at 1 h after administration of BSH with DSM was 184 ppm. At 6 h, the(10)B concentration in the liver in BSH with DSM group was 78 ppm. The tumor/liver (10)B concentration ratios (T/L ratio) in the "BSH+DSM" group were significantly smaller than those in the "BSH+lipiodol" group at 1 h (1.4 vs. 3.6) and 6h (1.1 vs. 14.9). BSH/DSM-boron neutron capture therapy (BNCT) was not suitable for treatment of multiple liver tumors due to the low T/L (10)B concentration ratio. However, the high (10)B accumulation in the liver tumors following intra-arterial administration of BSH/DSM emulsion suggests that BSH/DSM-BNCT has the potential for application to malignant tumors in other sites.

Intra-arterial administration of sodium borocaptate (BSH)/lipiodol emulsion delivers B-10 to liver tumors highly selectively for boron neutron capture therapy: experimental studies in the rat liver model

PURPOSE

Boron neutron capture therapy (BNCT) is particle radiotherapy with alpha ((4)He) particle and recoiled lithium nucleus ((7)Li) derived from a reaction of boron ((10)B) and thermal neutron. We investigated applying BNCT to malignant liver tumors. The purpose of the present study was to reveal the efficacy for administration of emulsion of a boron compound (sodium borocaptate; BSH) and lipiodol via a hepatic artery using a rat liver tumor model.

METHODS AND MATERIALS

Rat liver tumors were developed by direct injection of Walker 256 cells into the liver parenchyma. BSH (75 mg/kg)/lipiodol (0.3 mL/kg) emulsion was administered via the hepatic artery. Boron concentrations in the tumors, liver, and blood were measured at 1, 6, and 12 h after administration. Neutron capture radiography (NCR) was taken to confirm the selective accumulation of (10)B in the liver tumors.

RESULTS

Boron concentrations in the liver tumors and the tumor/liver (T/L) boron concentration ratio at 1, 6, and 12 h after administration of BSH/lipiodol emulsion (concentration: T/L ratio) were 479.2 ppm: 4.0, 197.3 ppm: 14.9, and 96.5 ppm: 6.6, respectively. Highly selective irradiation was clearly demonstrated by the NCR images.

CONCLUSIONS

Intra-arterial administration of BSH/lipiodol emulsion is effective method for delivering high concentration of (10)B selectively to the liver tumors.

[18F]Fluoroazomycinarabinofuranoside (18FAZA) and [18F]Fluoromisonidazole (18FMISO): a comparative study of their selective uptake in hypoxic cells and PET imaging in experimental rat tumors

The present study compares the uptake of [(18)F]Fluoroazomycinarabinofuranoside ((18)FAZA), a recently developed hypoxia tracer for PET imaging of tissue hypoxia, with an established tracer [(18)F]Fluoromisonidazole ((18)FMISO) both in vitro, using Walker 256 rat carcinosarcoma cells, and in vivo in experimental rat tumors eleven to twelve days after tumor cell implantation. In vitro studies indicated that hypoxia-selective uptake of both (18)FAZA and (18)FMISO in tumor cells, 20 and 100 minutes post-incubation was of the same magnitude (20 min: 1.24 +/- 0.4% ((18)FAZA); 1.19 +/- 0.7% ((18)FMISO); 100 min: 3.6 +/- 1.6% ((18)FAZA); 3.3 +/- 1.7% ((18)FMISO)). PET imaging reflected a similar radiotracer distribution in rat tumors for (18)FAZA and (18)FMISO one h after radiotracer injection. The concentration of (18)FAZA in the tumors as measured by PET, however, was lower in comparison to (18)FMISO (SUV(FAZA) = 0.61 +/- 0.2 vs. SUV(FMISO) = 0.92 +/- 0.3, p < 0.05) although the tumor to muscle ratios for (18)FAZA and (18)FMISO did not differ in the PET images that were obtained after one h (SUV(FAZA) = 2.5 +/- 0.5 vs. SUV(FMISO) = 2.9 +/- 0.7). A comparison of PET data three h post-injection (SUV(FAZA) = 3.0 +/- 0.5 vs. SUV(FMISO) = 4.6 +/- 1.8, p < 0.05) demonstrated a lower (18)FAZA uptake that indicates a lower sensitivity of (18)FAZA in comparison to (18)FMISO in detecting hypoxic regions at a longer time in this animal model. However, these data also show a faster elimination of (18)FAZA from blood, viscera and muscle tissue, via the renal system. This advantage of a faster reduction of unspecific binding, in light of similar or marginally lower tumor uptake, warrants further investigation of (18)FAZA as a marker of regional hypoxia in tumors.

[Inhibitory effect of samarium-153-labeled ethylenediaminetetramethylene phosphonate (EDTMP) on bone invasion and osteolysis in Walker 256 carcinoma bearing rats]

OBJECTIVE

To investigate the inhibitory effect of samarium-153 EDTMP on bone invasion and osteolysis in Walker 256 carcinoma bearing rats.

METHODS

Invasion and resorption of tibia by Walker 256 carcinoma in rats were evaluated by X-ray and histological examination.

RESULTS

Intravenous administration of 153Sm-EDTMP at a dose of 74 or 148 MBq/kg, the rat numbers with tibia invasion and bone resorption were reduced by fifty percent. 153Sm-EDTMP at a dose of 37 MBq/kg still exhibited inhibitory effect on bone invasion and osteolysis as compared with the control group. However, there was no indication of change in the weight of primary tumor even at the highest dose utilized.

CONCLUSION

Samarium-153 EDTMP can inhibit bone invasion and osteolysis by Walker 256 carcinoma in rats, but it has no effect on the growth of the transplanted tumor. Therefore, that the effect of 153Sm-EDTMP is due to a reduction in tumor growth leading to decreased bone invasion and osteolysis can be reasonably ruled out.

Effect of recombinant human granulocyte colony-stimulating factor on efficacy of radiation therapy in tumor-bearing rats

The effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on radiation-induced neutropenia and on growth of transplanted tumors treated by irradiation was investigated using tumor-bearing rats as a model for radiation therapy. In a preliminary study using normal rats, neutropenia induced by upper hemi-body irradiation at 3 Gy/day 5 times a week for 3 weeks was prevented by consecutive subcutaneous injections of rhG-CSF at 100 micrograms/kg/day. Rats bearing Walker-256, a mammary tumor, were scheduled to receive upper hemibody irradiation at 3 Gy/day for 15 times in 3 weeks if white blood cell (WBC) counts were maintained above 3,000/microliters. In control tumor-bearing rats not receiving rhG-CSF, irradiation was often withheld because of the decrease in WBC counts below 3,000/microliters. In contrast, a decrease in WBC counts below 3,000/microliters was rarely found in tumor-bearing rats injected daily with rhG-CSF. The average number of radiation treatments in control rats and rats treated with rhG-CSF was about 8 and 14, respectively, out of the scheduled 15 treatments in 3 weeks. Treatment with rhG-CSF made it possible to complete the radiation therapy regimen and thus inhibit the growth of the transplanted tumor more effectively. These results suggest that rhG-CSF may be useful to ensure radiation therapy on schedule in cancer patients.

[Combined effect of hyperglycemia and chemo- and radiation action on the status of metabolic processes in certain experimental sarcomas in rats]

A number of metabolic parametres were studied in subcellular fractions of rat sarcoma 45, M-1 and carcinosarcoma Worker 256. Administration of high doses of glucose amplified some effects of chemotherapeutic drugs and X-ray therapy, which were manifested as follows: a decrease in glycolysis rate, alteration in the rate of redox reactions, shifts in the ratio between glycolysis and biological oxidation in mitochondria. These alterations were determined by the type of sarcoma, by sequence of operations in the procedure and by cytostatic used. The most effective procedure proved to be simultaneous administration of drugs and X-ray therapy followed by hyperglycemia. Distinct inhibition of glycolysis defected under these conditions may contribute to inhibition of energy metabolism during the sarcoma growth and regression.

Polarography of Walker Tumor Submitted to Radiotherapy

A Polarographic study of oxigen was done in 57 rats inoculated with Walker 256 tumor and platinum electrode implanted in muscle and in tumor. The goal of the research was the study of oxygen in tumor before and after irradiation. Tumor growth caused a decrease in tumoral oxygen. Oxygen was always lower in the tumor than in the muscle. Radiotherapy with 2000 rad (but not with 1000 rad) increased oxygen in the tumor.

Tumor oxygenation using direct injection of oxygenated saline

Direct injection of oxygen into an in-vivo tumor system was performed using saline lavage through a double-lumen catheter inserted into a Walker 256 carcinoma implanted in the flank of a rat. Ten extremely hypoxic tumors (core pO2 0 to 1 mm Hg) were examined. The mean pO2 in these tumors increased from 66 to 112 mm Hg after 5 minutes of lavage with oxygenated saline. These results indicate a substantial increase in tumor pO2 can be obtained with this system, possibly resulting in improved radioresponsiveness. More general applications of this system may also be feasible.

Nitrogen-13 glutamate uptake and perfusion in Walker 256 carcinosarcoma before and after single-dose irradiation

Nitrogen-13 (13N) glutamate uptake was recorded in 18 anesthetized rats, both before and at least once after intervention. Each investigation was immediately followed by imaging of blood flow distribution using [11C]butanol. All animals had Walker 256 carcinosarcoma implants in one hind leg. Tumors were locally irradiated with a dose of 800 rad in 14 rats; in four rats, the vasoactive substance 5-hydroxytryptamine (5-HT) was administered. Prior to interventions, the [13N]glutamate tumor-to-muscle uptake showed a linear correlation with blood flow close to identity (y = 0.117 + 0.915x, r = 0.97). After irradiation, a discordant pattern was observed: blood flow tended to increase, while [13N]glutamate tumor-to-muscle uptake dropped from 4.30 +/- 0.66 (s.e.m.) to 3.06 +/- 0.36 (p less than 0.005) during 30 min and attained 4.04 +/- 0.67 2 days later. If [13N]glutamate tumor-to-muscle uptake was related to that of [11C] butanol in each individual animal, this index dropped from 0.93 +/- 0.03 (s.e.m.) to 0.62 +/- 0.04 (p less than 0.001) 30 min after irradiation and attained 0.90 +/- 0.09 after 2 days. In animals treated with 5-HT, [13N]glutamate and [11C]butanol showed a parallel drop from 6.60 +/- 0.84 to 2.10 +/- 0.60 (p less than 0.05) and from 6.8 +/- 0.78 to 2.08 +/- 0.74 (p less than 0.05), respectively. Thus, single-dose irradiation causes [13N]glutamate uptake to be uncoupled with respect to flow, while [13N]glutamate uptake in untreated tumors is flow-limited and responds together with flow on vasomotion.

Effect of dihydroxyanthraquinone on the response of a rat solid tumor to radiation therapy

Dihydroxyanthraquinone (DHAQ, NSC 279836, a new cancer chemotherapeutic agent presently in clinical trials) was tested, alone and in combination with radiation, for therapeutic effectiveness in a rat solid tumor model. The Walker 256 fibrosarcoma was implanted subcutaneously in the leg via trochar so as to yield palpable tumors within 7-11 days. When tumor diameters reached 1 cm, the animals were treated as follows: as controls; with DHAQ (3.0 mg/kg, i.p.); with 300 KVP x-rays (15 Gy to the tumor-burdened leg); or with a combination of DHAQ and radiation. Tumor diameters were measured three times a week to monitor the response to therapy. DHAQ alone had no effect on tumor growth rate. Radiation alone produced a delay in tumor growth. The combination of DHAQ and radiation resulted in a consistently better therapeutic response than did radiation only, but at only a marginal level of statistical significance (0.05 less than p less than 0.10). However, there were 3/10 long-term survivors (greater than 80 days post treatment) without evidence of tumor in the combination therapy group; whereas all animals in the radiation group died or were sacrificed because of progressive tumor growth by day 71. These results suggest that even though DHAQ is only minimally effective against this rat solid tumor when used alone, there may still be some added therapeutic benefit derived from a combination of DHAQ and radiation therapy.

[Irradiation of solid Walker carcino-sarcomas after synchronisation with hydroxyurea (author's transl)]

Sprague-Dawley rats with solid Walker carcino-sarcomas were synchronized with hydroxyurea (HU; 6 x 50 mg and 1 x 300 mg HU/kg body weight) and then irradiated at different time points (60Co). The synchronized tumors showed a significant delay of growth when irradiation was applied in the late G1 phase, at the transition G1/S and in the early S phase. The remaining phases of the cell cycle, especially the S phase showed the same sensitivity as the non-synchronized controls. Improvement of therapy by irradiation after HU application was largely due to the synchronization of tumor cells. Only the increased therapeutic effect of irradiation shortly after application of HU can be explained also by combination of both HU and irradiation.

[Influence of local hyperthermia induced by micro-waves and X-rays on the Walker carcinoma of the rat (author's transl)]

The authors studied the influence on the solid Walker carcinoma in the rat exerted by a slight local hyperthermia induced by micro-waves, which was applied alone and combined with X-ray irradiations. It could be demonstrated that the tumor has the same temperature as the sub-peritoneal region. Thus the final temperature reached by the treatment with micro-waves can be exactly controlled. Heating up to 41 degrees C for 30 minutes produces an increase of the survival rate of animals with tumors of 2 to 6 grams from 17% to 27%, whereas the healing rate is 57% after an X-ray irradiation with 1130 rad and 75% after the combined treatment. Each of the three therapy methods produces a significant prolongation of the survival time of the dying animals. The disadvantages of an anisologic tumor-host system are discussed on the basis of the results achieved.

Tumor reoxygenation and postirradiation vascular changes

Postirradiation reoxygenation kinetics of the Walker 256 carcinoma were examined and related to radiation-induced changes in tumor vascular functions. Changes in the hypoxic cell component of irradiated Walker tumors may occur by two mechanisms. Reoxygenation of previously hypoxic cells may be due to an increased rate of blood flow in some parts of the tumor. Hypoxic tumor cells may also be eliminated by cell death due to prolonged or severe hypoxia in other parts of the tumor as a result of substantial damage to the tumor vasculature as seen in radiation-induced changes in vascular volume and blood vessel permeability. Reoxygenation of experimental tumors following single, massive doses of radiation may be different from that occurring in human tumors during the course of multifraction radiotherapy.

[Effects and mechanism of a locally combined treatment with radiation and heat therapy (author's transl)]

An animal experimental study on solid Walker-tumors was undertaken to determine the therapeutic effects utilizing hyperthermy in the form of combined decimeter wave megavolt treatment. Noted was the superior effect of combination therapy as compared to exclusive use of radiation therapy. Hyperthermy therapy alone does inhibit tumor growth but not involution. This inhibiting characteristic of hyperthermy probably changes cellular mitotic rhythm in the form of cellular synchronisation. The indications for combined hyperthermy megavolt treatment is hypoxic malignant tumors of low radiation sensitivity, especially in superficial and shallow tissue regions. The above treatment is tolerated well and no serious side effects have been observed.

[The influencing of rat-tail tumors with and without irradiation]

In a collective of 200 Wistar rats, the influence of anticoagulants upon the rat tail tumor (Walker 256 carcinosarcoma) was checked with and without irradiation. After implantation of the tumor and development of a certain definite tumor volume, the animals were divided into four different groups of 50 rats each. The first one was the control group without any manipulation, the second received an one-stage X-irradiation with 2500 R SD directed to the tail tumor, the third was treated with an oral dose of Phenprocoumon which was added to the daily drinking quantity (0.1 mg/kg body weight), and the fourth group was given an one-stage X-irradiation together with the oral Phenprocoumon treatment. The influence of these different treatments on the growth of the primary tumor, on the incidence of metastases and on the death rate was checked up. The best therapeutical effect was observed with combined radiation and Phenprocoumon treatment. The therapy resulted in an almost complete growth rate depression of the primary tumor, in an early tendency of remission of the primary tumor, a 42 per cent decrease of the incidence of metastases to the lung, and a 42 per cent increase of the survival rate. With regard to the frequency of metastases and to the survival rate, treatment with Phenprocoumon alone showed significantly better results as sole radiation treatment.

[Effect of 5-fluorouracil and irradiation of the cell kinetics of Walker carcinoma and the small intestine in rats]

A therapeutic schedule of synchronizing cytostatical-radiological treatment often used in human medicine is applied to rats carrying a Walker tumor. The effect of this treatment on the kinetics of tumor cells and epithelium of small intestine is investigated. 1. 5-Fluorouracil, i.p. during 18 and 12 hours, brings about no changes in the mitotic index; however, in the curve of marked mitoses a small fraction of cells is represented which is considered to be a consequence of the synchronization of a very small portion of tumor cells. 2. If ten hours after 5-FU-injection the cells are irradiated with a single dose of 300 rd, there occurs a distinct G2-block and a lengthening of the S-phase. These changes are found both in the 5-FU ground and in the controls. 3. 5-FU-injection thrice alternated with irradiation likewise causes a G2-block. After solution of the block a delayed increase of mitoses in the controls is going on which cannot be detected in the 5-FU group. These findings are interpreted as an effect of 5-FU on the proliferation rate of tumor tissues.

Tumor-induced angiogenesis: lack of inhibition by irradiation

The effect of irradiation of tumors on their ability to induce vascular responses (angiogenesis) was studied. Rat Walker carcino-sarcoma 256, rabbit V2 carcinoma, mouse (C57B1) melanoma and mouse (129) teratoma (OTT 6050, 100K) were irradiated with up to 5000R, then grafted either to the chicken chorioallantoic membrane or intracorneally into adult rabbits to assess competence to provoke angiogenesis. For all tumors and both assay systems the results were similar: irradiation did not interfere with tumor-induced vascular responses.

Investigations of tritiated menadiol sodium diphosphate (T-MNDP) as a radioactive drug

An attempt has been made to develop tritiated derivatives of Synkavit (menadiol sodium diphosphate, MNDP) of high specific activity as a radioactive drug.This paper summarizes the preliminary biological and physical studies, with emphasis on approximate radiation dosimetry and the necessary preliminary testing, and then gives an account of the clinical investigations and the trials carried out so far, which correspond essentially to Phases I and II trials for a chemotherapeutic agent.In all, 214 patients with different sites and types of advanced and recurrent, inoperable, histologically verified malignant tumours including reticuloses have been treated with doses of at least 1 Ci of the various preparations. Among the 203 evaluable treated cases, some form of response was observed in 23 out of 151 (15·2%) receiving the drug by intravenous injections and 13 out of 52 (25%) after intra-arterial injections. For the sites and types of malignant diseases which showed responses after either intravenous or intra-arterial administration among the 55 patients surviving at least 3 months after the first injection, some form of response was observed in 32 but only 5 of these showed either a "complete" or a "partial" response.It is concluded that further investigation is desirable. It is suggested that clinical trials with randomization should be carried out for inoperable cases of carcinoma of the colon and of the pancreas.