Long-lasting gene expression by particle-mediated intramuscular transfection modified with bupivacaine: combinatorial gene therapy with IL-12 and IL-18 cDNA against rat sarcoma at a distant site

The immune response is modulated by genetic adjuvants using plasmid vectors expressing cytokines. Skeletal muscle can express a foreign gene intramuscularly administered via a needle injection, and the potential of muscle as a target tissue for somatic gene therapy in treating cancer has been explored. In the present study, we investigated the efficacy of particle-mediated intramuscular transfection modified with a local anesthetic agent, bupivacaine, on luciferase and green fluorescent protein. The results indicate that these proteins are more efficiently expressed and persist longer in muscle modified in this way compared with the needle-injection method. Using an established rat sarcoma model, particle-mediated intramuscular gene-gun therapy with a combination of IL-12 and IL-18 cDNA was conducted. Growth of the distant sarcoma was significantly inhibited by particle-mediated intramuscular combination gene therapy, and the survival rate was also improved. Furthermore, the combination gene-gun therapy maintained significant levels of interferon-gamma and induced a high activity of tumor-specific cytotoxic T lymphocytes. These results suggest that the sustained local delivery of IL-12 and IL-18 cDNA using intramuscular gene-gun therapy modified with bupivacaine can induce long-term antitumor immunity, and can provide the great advantage of inhibiting the disseminated tumor.

Renal chemoembolization with mitomycin c/Ethibloc: pharmacokinetics and efficacy in an animal model

BACKGROUND AND PURPOSE

Arterial embolization can be an alternative treatment for kidney malignancy. We investigated the efficacy of renal embolization with a combination of an occlusive agent (Ethibloc) and the cytotoxic substance mitomycin C (MMC) in an animal model.

MATERIALS AND METHODS

In 32 rats with implanted Yoshida sarcoma, nephrectomy was carried out 15, 30, 60, or 90 minutes after chemoembolization (1 mg v 2 mg of MMC/mL of Ethibloc) or chemoperfusion (1 mg of MMC/mL of NaCl) of the tumor-bearing kidney. The MMC tissue concentration was measured in the kidney specimens. Six dogs also underwent chemoembolization or chemoperfusion with monitoring of MMC serum concentration at the same intervals. We compared the survival time of rats with Yoshida sarcoma after chemoembolization (N = 15), chemoperfusion (N = 18), embolization (N = 18), nephrectomy (N = 21), and no treatment (N = 25).

RESULTS

The MMC tissue concentration in the rat model was much higher after chemoembolization than after chemoperfusion for at least 1.5 hours. The MMC serum concentration in the dogs showed a high initial peak (0.6 mg/L) after chemoperfusion, then dropped quickly to the same level seen 30 minutes after chemoembolization with 1 mg of MMC/mL of Ethibloc (0.15 mg/L). The MMC serum concentration following chemoembolization with 2 mg of MMC/mL of Ethibloc stayed higher (0.3-0.25 mg/L) for 60 minutes. The survival rates after nephrectomy were equal to those after chemoembolization (80% survival after 30 days), with poorer survival being seen after embolization (75%) and chemoperfusion (70%). In the control group, all rats were dead at the 27th day.

CONCLUSION

Chemoembolization produces persistently high tissue concentrations of MMC and avoids toxic peak serum levels. It improves the efficacy of organ ablative vasoocclusion in renal malignancies.

Immunomodulatory effects of Bacillus firmus

3-day-old miniature piglets were stimulated in vivo with Bacillus firmus by the intraperitoneal or intragastric route for 1 d. Cells containing IgA and IgG2 were detected in the ileum in all stimulated but not in control animals. The frequency of blood CD3+ cells increased after intraperitoneal administration of B. firmus, the ratio of polymorphonuclears to lymphocytes increased in all stimulated piglets. B. firmus induced antitumor immunity in rats with transplanted Yoshida sarcoma cells. Granular lymphocytes and dead tumor cells were found in peritoneal exudate of stimulated animals. B. firmus induced IFN-gamma synthesis in human blood lymphocytes stimulated in vitro for 1 d. The amount of TNF-alpha produced by these stimulated human peripheral blood mononuclears (PBMC) was lower than that of PBMC stimulated with some other bacterial immunomodulators. Cells containing TGF-beta or IL-8 were not found in human PBMC stimulated with B. firmus.

Methionine depletion modulates the antitumor and antimetastatic efficacy of ethionine

The elevated methionine requirement for the growth of tumors, termed methionine dependence, is a potentially highly effective therapeutic target. To attack this target we are developing anti-methionine chemotherapy. In this study of anti-methionine chemotherapy we have observed that the methionine analog ethionine is synergistic with methionine depletion in arresting the growth of the Yoshida sarcoma both in vitro and when transplanted to nude mice. In contrast, ethionine in vitro in a methionine-containing medium is not effective against Yoshida sarcoma cells. Similarly, ethionine administered along with a methionine-containing diet is ineffective against the Yoshida sarcoma growing in nude mice. A methionine-depleted diet alone is only partially effective against tumor growth. The Yoshida sarcoma gave rise to metastases in 75% of the- organs observed in the mice on the methionine-containing diet, and 43 % of the organs in the mice on the methionine-free diet. In striking contrast, no metastases were observed in the ethionine-treated animals on the methionine-free diet. Anti-methionine chemotherapy consisting of dietary methionine depletion and ethionine administration caused an initial weight loss but the animals weight stabilized resulting in no animal deaths. The synergism of ethionine and methionine depletion is markedly similar in vitro and in vivo suggesting the observed efficacy is due to the specific anti-methionine targeting. Thus methionine depletion highly potentiates the anti-tumor and anti-metastatic effectiveness of ethionine suggesting that anti-methionine chemotherapy consisting of methionine depletion as a modulator of methionine analogs holds great promise as a new, tumor-selective therapeutic approach.

[Treatment of solid tumor by a small amount of direct current]

Solid tumor treatment was given in our animal laboratory to determine the mechanism of tumor disappearance by direct electric current, and clinical trials were done on 9 far advanced recurrent rectal cancers. Solid tumors of Yoshida sarcoma in Donryu rat were treated by 1 mA of constant direct current for 1 hour a day, for 4 days. The tumors disappeared in 13/16 within 21 days. Positive results of DNA Nick-end labeling and ladder patterns in the gel electrophoresis of DNA were observed in the regressing tumor specimen. It is considered that apoptosis is the one of the mechanisms of a disappearing tumor. As for the clinical trial concern, in 9 cases of rectal cancer, one CR and 5 PR were seen.

Prolonged survival of AVN Wistar rats with transplanted Yoshida sarcoma and increase of granular lymphocytes after administration of Bacillus firmus and their crude lipids

Bacillus firmus is a Gram-positive, aerobic, sporulating, nonpathogenic air contaminant which, according to earlier findings, is a strong polyclonal activator of B lymphocytes. The crude lipids of this microbe induced significant resistance of mice against listerial infection. The administration of bacterin, like that of crude lipids obtained by the extraction of cell suspension with chloroform-methanol to rats, strain AVN Wistar, transplanted later with Yoshida sarcoma, significantly prolonged the survival of the animals in comparison with the control group. At the same time the number of granular lymphocytes was increased. The destruction of tumor cells in the peritoneal exudate of immunostimulated rats was also determined.

Arginine-enriched solution induces a marked increase in muscle glutamine concentration and enhances muscle protein synthesis in tumor-bearing rats

Using a transplantable Yoshida sarcoma in a rat model of total parenteral nutrition (TPN), we measured the effectiveness of an arginine-enriched amino acid solution (AI-82) on muscle glutamine concentration and muscle protein synthesis compared with that of a conventional amino acid solution (Proteamin12). After tumor-bearing rats had been given one of two isocaloric TPN regimens for 6 days, [15N]glycine (99 atom %) containing TPN solution was infused into animals at a constant rate of 8 mg of [15N]glycine per hour for 18 hours, after which the liver, skeletal muscle (gastrocnemius muscle), and tumor protein synthesis rates were measured. A significantly increased whole muscle protein synthesis rate was observed in the AI-82 group; there was no difference in the whole liver and tumor protein synthesis rates between the two groups. When each TPN solution was administered for 1 week, muscle concentrations of arginine, ornithine, glutamine, and glutamate were considerably higher in the AI-82 group than in the Proteamin12 group, and these differences were also accompanied by a decrease in the plasma branched-chain amino acid (BCAA) (leucine, isoleucine, and valine) levels in the AI-82 group. The high levels of muscle glutamine concentration in the AI-82 group were investigated in connection with the high use of exogenous branched-chain amino acids.

Therapeutic tumor-specific cell cycle block induced by methionine starvation in vivo

The ability to induce a specific cell cycle block selectively in the tumor could have many uses in chemotherapy. In the present study we have achieved this goal of inducing a tumor-specific cell cycle block in vivo by depriving Yoshida sarcoma-bearing nude mice of dietary methionine. Further, we demonstrate that methionine depletion also causes the tumor to eventually regress. The antitumor effect of methionine depletion resulted in the extended survival of the tumor-bearing mice. The mice on the methionine-deprived diets maintained their body weight for the time period studied, indicating that tumor regression was not a function of body weight loss. The data reported here support future experiments utilizing methionine depletion as a target for tumor-selective cell cycle-dependent therapy.

Glutamine antagonist with diet deficient in glutamine and aspartate reduce tumor growth

This study was designed to investigate whether a combination of a glutamine antagonist (DON) and a diet deficient in glutamate and aspartate (AG) altered glutamine metabolism in tumor tissue, and inhibited tumor growth. In experiment-1, 21 male Donryu rats were fed with AG and implanted with Yoshida's Sarcoma. Of them, 7 rats were sacrificed on the 5th day (group AG), other 7 were sacrificed next day (group AG-1) and the remaining 7 were injected with DON on the 5th day and sacrificed next day (group AG+D). The tumor weight of group AG+D was significantly lower than of group AG, or of group AG-1. In experiment-2, of 23 rats, 9 were fed with control diet and 14 were fed with AG and implanted. 12 were sacrificed on the 5th day (group C, AG), and 11 were injected with DON on the 5th day and sacrificed next day (group C+D, AG+D). The reduced ratio of tumor weight in group C+D and group AG+D were 25% and 67%, respectively. These results show that the tumor growth could be inhibited by using metabolic antagonist of glutamine, and that it had synergistic effect in conjunction with the imbalanced diet.

Antitumor effect of methionine-depleting total parenteral nutrition with doxorubicin administration on Yoshida sarcoma-bearing rats

Methionine-depleting total parenteral nutrition (methionine-depleting TPN), which infuses an amino acid solution devoid of L-methionine and L-cysteine as the sole protein source, showed enhancement of the effect of several anti-cancer agents. In this study, the combined effect of the methionine-depleting TPN with the administration of doxorubicin was examined in Yoshida sarcoma (YS)-bearing rats with regard to effects on the primary tumor growth, the extension of metastasis, and the host animal's life span. In the first experiment, immediately after receiving methionine-depleting TPN for 8 days, the animals were killed. Pathologic findings evaluated tumor growth in the implanted site and extension of the metastasis. In the second experiment, the survival period was determined after animals received methionine-depleting TPN for 10 days, with subsequent oral feeding until they died naturally. Proliferation of YS was markedly suppressed. In particular, hematogenous metastasis, which is a characteristic of YS, was suppressed, and a longer survival period (42.7 +/- 15.6 days, mean +/- SD) was attained in rats in the group treated with the methionine-depleting TPN combined with the administration of doxorubicin.

Anti-tumor effect of L-methionine-deprived total parenteral nutrition with 5-fluorouracil administration on Yoshida sarcoma-bearing rats

L-methionine-deprived total parenteral nutrition (methionine-deprived TPN), infusing amino acid solution devoid of L-methionine and L-cysteine by the method of TPN as an only protein source, showed enhancement of the effect of several anti-cancer agents. In this study the combined effect of the methionine-deprived TPN with administration of 5-fluorouracil (5-FU) was examined in Yoshida Sarcoma (YS)-bearing rats, from aspects of effects on the tumor metastasis and the host animal's life span, in the following four groups treated with: methionine-deprived TPN with administration of 5-FU, methionine-deprived TPN without administration of 5-FU, L-methionine-contained TPN plus 5-FU, and L-methionine-contained TPN without 5-FU. In the first experiment, TPN was continued for 8 days in the four groups, and the anti-cancer effect of methionine-deprived TPN and administration of 5-FU based on both the growth of the primary tumor at the implanted site and the tumor metastasis was studied from the view point of pathologic findings of animals killed immediately after these treatments. In experiment 2 the survival period was examined after these treatments for 10 days with subsequent oral feeding until death. The results were as follows: proliferation of YS, transplanted subcutaneously, was markedly suppressed; particularly hematogenous metastasis, characteristic in YS, was prominently blunted then obtained an apparent longer survival period in rats treated with the methionine-deprived TPN with administration of 5-FU.

[Complement behavior in rats bearing Yoshida tumors subjected to treatment with gonadotropin and PGE2]

The haemolytic activity of the total Complement (CH50) and the fractions C3 and C4 were assayed in rats transplanted with Yoshida's tumor and then treated with hCG, LH-FSH and PGE2. A relevant increase, only concerning the values of the CH50 and C3 fraction, was observed in all animals in the early days after the transplantation, probably due to a sort of stress "by transplantation". Afterwards, hCG and PGE2 induced an increase in CH50 and C3 values, but not in the C4 fraction. Treatment with LH and FSH led to a very slight increase in the CH50 and C3. In the following days, as a consequence of the cachexia, a progressive reduction of the values of the Complement was observed in all animals. Those treated with hCG also showed a little increase of survival. The authors suggest that the increase in CH50 and C3 fraction induced by the treatment with hCG and PGE2 could be an expression of increase of the aspecific humoral immunity, as a compensatory mechanism of the cell-mediated immunological depression which occurs during neoplasias.

Factors governing hyperthermia-induced pH changes in Yoshida sarcomas

The impact of various factors modulating the acidification of tumour tissue upon localized ultrasound hyperthermia (1.7 MHz) at 44 degrees C for 60 min was investigated. Yoshida sarcomas were implanted into the hind foot dorsum of Sprague-Dawley rats. Frequency distributions of tumour tissue pH values were measured with miniaturized needle glass pH electrodes (diameter of the sensitive tip: 650 microns). During normothermia the average tumour pH is 6.87 +/- 0.21. No relationship is found between tumour pH and tumour size (range: 0.6-5.4 g). A pH gradient exists from the tumour periphery (0.5-3.5 mm) to more central tissue layers (7.5-10.5 mm; delta pH = 0.17). During hyperthermia with heating-up rates greater than 1.5 degree C/min, mean tumour pH drops to 6.71 +/- 0.20 considering all tumours. The pH reduction observed is size-dependent being most pronounced in medium-sized tumours (wet weights around 2.4 g, delta pH = 0.26). Using the same tumour sizes, but heating-up rates less than 0.7 degree C/min, the tissue acidification is more severe (delta pH = 0.40). To a small extent, pH changes also depend on the tumour region investigated (e.g. central vs. peripheral tissue layers) leading to a flattening of the pH gradient from the tumour shell to the centre during heat treatment. During hyperthermia an interstitial oedema occurs, being mostly marked in small tumours (around 1.4 g). Considering systemic changes, a transient increase in perfusion pressure (leading to a change in blood flow), as well as a slight elevation of blood glucose levels (leading to a higher glucose supply), during hyperthermia may contribute to the pH drop.

[Increase in the generation of superoxide radicals and in the inhibitory effect on Yoshida sarcoma of anthracycline antitumor agents by ultrasound]

The antitumor effects of ultrasonic (US) irradiation in combination with the administration of an anthracycline drug, such as adriamycin and THP-adriamycin, were investigated from a viewpoint of the generation of superoxide radicals (SOR). In the in vitro experiments, the generation of SOR by US irradiation was measured by the amount of cytochrome c reduced. The addition of the drug stimulated the generation of SOR by US irradiation. In the in vivo experiments, Donryu rats inoculated subcutaneously by Yoshida sarcoma were treated with US irradiation in combination with the drug. During US irradiation, the temperature of the rat tissue irradiated was kept below 37 degrees C to avoid thermal effects. To know the optimum timing of US irradiation after the administration of the drug, the drug concentrations in the tumor and blood were determined and the time course of drug concentrations was analyzed pharmacokinetically. The effects of drugs and/or US irradiation showed antitumor activity judged by the growth of the tumor size or the survival time of rats. The combination treatments of US irradiation with the drug marked additional or synergistic effects on Yoshida sarcoma. Considering the relationship between the antitumor effect in vivo and the generation of SOR in vitro, the increase of anti-tumor effect of US irradiation by the anthracycline drug may be caused by the stimulation of the generation of SOR.

[Comparison of continuous venous infusion of 5-FU and FT-207 under total parenteral nutrition]

Yoshida sarcoma-bearing rats were continuously infused with 5-FU at a dose of 20 mg/kg/day, and FT-207 at a dose of 40 mg/kg/day, 100 mg/kg/day or 140 mg/kg/day under TPN. After 4 days, rats were sacrificed and the 5-FU and FT-207 concentrations in their organs were measured. The 5-FU level in the tumor was almost the same at when 5-FU was injected at 20 mg/kg/day and FT-207 at 140 mg/kg/day. This 5-FU level in the tumor was twice and four times higher than that of the group injected with FT-207 at 100 mg/kg/day and 40 mg/kg/day. The 5-FU level in the tumor in all four groups was almost twice as high as that in the stomach, intestine and kidney, 7-10 times higher than that in the liver, and 10-30 times higher than that in serum. The FT-207 levels in the alimentary tract, kidney, tumor and serum were almost the same. The conclusion of our preliminary research is that FT-207 is recommended for use in continuous infusion at 7 times the dose of 5-FU when injected under TPN.

Evaluation of the effect of arginine-enriched amino acid solution on tumor growth

To investigate the effect of arginine-enriched solution on tumor growth and metastasis, rats were infused with solutions containing 5.5 and 0.66% arginine for 8 days. Infusions were started at the same time of subcutaneous transplant of Yoshida sarcoma. Arginine-rich solution suppressed tumor growth at an early stage and prevented metastases to the liver and kidney. In addition, arginine supplements enhanced the phagocytic activity of alveolar macrophages. It also resulted in maintenance of a positive nitrogen balance and prevented the increases in the levels of several amino acids observed in the control group. The suppressive effect of arginine-enriched solution on tumor growth may be due to its activation of the immunologic system, in which the phagocytic activity of macrophages probably participates.

[Effect of local moderate hyperthermia in combination with chemotherapy by N-nitroso-1,3-bis-(2-chloroethyl)urea (BCNU) on the descending colon of the rat with transplanted Yoshida sarcoma. 2. Monochemotherapy in combination with subsequent hyperthermia at various time intervals]

There are numerous reports on in vitro and in vivo investigations of hyperthermia for cytostasis of malignant tumors. Combination of chemotherapy and hyperthermia is to potentiate the therapeutic effect. The time interval between the two types of therapy was the main subject of the present investigation. Local hyperthermia (43 degrees C, 60 min) following BCNU chemotherapy at intervals of 0, 3, 6, 9, 12, and 24 h, respectively, was studied in a colonic Yoshida sarcoma model in Sprague-Dawley rats. No significant increase in the curing rate resulted from hyperthermic treatment. The results suggest that the highly anticipated hyperthermic peritoneal lavages should be investigated in controlled animal experiments prior to clinical use.

Measurement of ultrasound energy density distributions in vivo

Thermocouple junctions coated with absorbing material have been used for measurement of ultrasound energy density distribution in vivo. The response of this type of probe has been measured in tumours implanted in rats, in ox liver, and in a water bath, using 1 and 3 MHz focussed ultrasound, and these measurements are reported in this paper. The initial rapid rate of temperature rise during the first 60 ms after the ultrasound is switched on provides a reliable index of ultrasound energy density. The coating material increases the magnitude of the temperature rise and reduces variations caused by differences in tissue properties and changes in blood flow. The response is a linear function of ultrasound energy density over the range of interest for therapeutic applications. Thus probes calibrated in known ultrasound fields in water tanks can be used to estimate energy densities in tissue directly.

"In vivo" anti-hCG antibodies and Yoshida's tumor development

The anti-hCG antibodies, obtained from the rats immunized with hCG and tetanus toxoid causes slight delay in the formation of ascites liquid and increase of the survival rate in various groups of rats transplanted with Yoshida's tumor.

Physiological factors in hyperthermia

The blood flow in normal tissues, i.e., skin and muscle, increases remarkably when heated at temperatures commonly used in hyperthermia (42 degrees -45 degrees C), whereas that in tumor appears to increase slightly when heated at temperatures below 41 degrees -42 degrees C but drastically decreases at temperatures above 42 degrees C. Histopathological studies of the heated tumors demonstrated a pronounced hyperemia, vascular occlusion, and hemorrhage. Due to the vascular occlusion, the dissipation of heat in the tumors becomes inefficient, and the temperatures in the tumor rise higher than those in normal tissues during hyperthermia at temperatures above 42 degrees C. The pH in tumors significantly decreases upon heating. The acidic conditions in the tumors enhances the thermal killing of tumor cells and inhibits the repair of thermal damage and development of tolerance to heat. The mechanism of the decrease in blood flow and pH in the heated tumors is not clear, but these two phenomena seem closely related. The preferential effect of hyperthermia on tumors may be attributed to the higher temperature relative to normal tissue temperature during heating and also to the decrease in the pH upon heating.

Thermal interactions between normal and neoplastic tissues in the rat, rabbit, swine, and dog during hyperthermia

Thermal interactions between normal and neoplastic tissues in mammalian species are modeled by a set of simultaneous first order nonlinear differential equations. Thermal regulation is introduced in the model, accounting for increases in the rates of metabolism, blood flow, and respiration of the normal tissues, taking under consideration the modes of reaction of the specific animals to thermal stress. The model adequately simulated the available temperature distributions data for localized hyperthermia in the rat and is also used for predictions of temperature distributions during localized and whole body hyperthermia in the rat, rabbit, swine, and dog.

Influence of tumour volume and cell kinetics on the response of the solid Yoshida sarcoma to hyperthermia (42 degrees C)

The cytokinetic response of the solid Yoshida sarcoma to hyperthermia was examined at two tumour volumes, 1.0-1.5 ml and 3.0-3.5 ml. The tumour, growing on the feet of rats, was heated at 42 degrees C for 1 h by water-bath immersion. The larger tumour grew more slowly than the smaller one (doubling time 144 h vs 36 h) due to a halving in growth fraction from 67.8 to 39.6% and an increase in cell-loss factor from 59 to 75.9%. Cell cycle and phase times were similar at both volumes. The effect of heat on the population kinetics at both volumes was similar but complex, and involved delayed cell death after up to 10 mitoses. Initial cell killing and blockade of cell-cycle progression (0-24 h) was followed by recovery of proliferation due to recruitment of cells from the non-proliferative compartment, cell cycle and phase times remaining unaltered. From 48 h, the proliferation rate declined progressively, and tumours were completely necrotic 7-8 days after heat. The damaging effects of heat were at least as severe in the large tumours with a low labelling index and small growth fraction as in the smaller tumours with a much larger compartment of proliferating cells and shorter doubling time. The results imply that there may be no simple relationship between proliferative status and thermosensitivity of a tumour, and illustrate the difficulty in predicting tumour response to heat on the basis of cytokinetic studies.

Effects of hyperglycemia and hyperthermia on the pH, glycolysis, and respiration of the Yoshida sarcoma in vivo

Tissue (extracellular) pH (pHe) and intracellular pH (pHi) were measured together in vivo in the solid Yoshida sarcoma and normal organs (liver, gastrocnemius muscle) of noninbred Wistar rats. pHe was monitored by insertion of a miniature capillary glass electrode, and pHi was measured indirectly by equilibrium partitioning of the weak organic acid 5,5-dimethyloxazolidine-2,4-dione across the cell membrane. Under normal conditions, tumor, liver, and gastrocnemius had a similar pHe of 7.05--7.30; tumor pHi was consistently higher (7.2) than that of the normal tissues (6.8--7.1). Curative hyperthermia (42 degrees C for 1 hr) did not significantly change tumor pHe or pHi. After ip glucose injection [6 g/kg body wt; blood glucose level greater than 400 mg/100 ml (22 mmoles/liter) for 4 hr], tumor pHe decreased markedly to 6.6 within 4 hours and did not return to normal for a further 12--14 hours, whereas tumor pHi was hardly affected. No marked change was noted in pHe or pHi of the normal organs following glucose loading of the host. In tumor slices removed from hyperglycemic hosts, marked reduction of both respiration and glycolysis was observed. Hyperglycemia (4 hr) plus hyperthermia at 40 degrees C (1 hr) had a synergistic inhibitory effect on metabolism that was equivalent to heat alone at 42 degrees C, and respiration and glycolysis almost ceased after 3--4 hours. However, tumor heating at 40 degrees C in hyperglycemic hosts was not equivalent to hyperthermia at 42 degrees C: With the former treatment, tumor regression did not occur, and animal survival did not differ from that of control untreated rats. The data do not support the postulate that the effects of heat on tumor cells are mediated via low pHi or that hyperglycemia leads to a lowered pHi which sensitizes the tumor to destruction at 40 degrees C instead of 42 degrees C.

Induction of transplantation immunity by dansylated tumor cells

Tumor cells were coupled with fluorecent dansyl group in aqueous medium by dansyl chloride-cycloheptaamylose complex (CDC) without destruction of the cells. C57BL/6 mice and Donryu rats pretreated respectively with dansylated EL4 leukemia cells and with dansylated Yoshida sarcoma cells acquired transplantation immunity to the corresponding tumor cells. Serum and spleen cells obtained from EL4 immune mice showed cytotoxicity to EL4 cells but not to other allogeneic leukemia cells. Hapten-specific cytotoxicity of immune serum and spleen cells was not observed in the present immune system.

The influence of tumor volume and the degree of heating on the response of the solid Yoshida sarcoma to hyperthermia (40-42 degrees)

The solid Yoshida sarcoma implanted on the feet of rats was subjected to local hyperthermia by water bath immersion. Tumor response was governed by the temperature and duration of heating (i.e., the degree of heating) and by tumor volume. With small tumors (1.0- to 1.5-ml volume) an intratumor temperature of 42 degrees maintained for 1 hr led to tumor regression in 11 to 13 days, and the tumor volume was halved every 2.6 days. Following 2 hr hyperthermia (42 degrees) the tumors disappeared in 6 to 7 days, and tumor volume was halved every 1.2 days. Tumors of 2 to 3-mol volume had left the exponential phase of the growth curve and required 2 hr at 42 degrees for cure. Following heating at 40 degrees for 1 hr, there was a 50% increase in O2 uptake and anaerobic CO2 production by the tumor, accompanied by enhanced dissemination by lymphatic, vascular, and direct routes, and tumor was found in organs not usually the site of metastases (e.g., testis and stomach). With large tumors (3.0 to 4.5 ml), the survival time of the rats was significantly reduced. These results occurred in the absence of a rise in body temperature of the animals. It is concluded that in this animal-tumor system, hyperthermia at a temperature inadequate for tumor destruction (40 degrees) can result in changes in the tumor that represent a hazard to the host.