Ultrasonic hyperthermia and drugs as therapy for human tumor xenografts

Ultrasonic energy can generate controlled, local hyperthermia (42 degrees C--43 degrees C), and ultrasonic hyperthermia results in increased cytotoxicity of chemotherapeutic drugs for the treatment of cancer. Human breast (MX-1) and lung (LX-1) tumors implanted subcutaneously in athymic nude mice were treated with a single application of ultrasonic (670 kHz, peak intensity of 5 watts/cm2) hyperthermia (43.0 degrees C +/- 0.5 degrees C) for 30 minutes in combination with suboptimal doses of cyclophosphamide, melphalan, or procarbazine. Delays in the tumor growth rate and temporary tumor regression were observed. Comparison of the tumor growth rate with single modalities, ie, drug or hyperthermia alone, shows evidence of synergistic effects of the combination of ultrasonic hyperthermia and melphalan on MX-1 and of hyperthermia and procarbazine on LX-1 tumors.     

Novel myofilament Ca2+-sensitizing property of xanthine oxidase inhibitors

To better understand the relationship of the growth characteristics of tumor tissues and their response to ionizing radiation alone and in combination with local tumor hyperthermia, we compared three different tumor sublines of the Dunning rat prostate carcinoma R3327. This report includes results obtained with the anaplastic AT1 subline (volume doubling time 5.2 days), the moderately differentiated mucin-secreting HI subline (volume doubling time about 9 days) and the well-differentiated, hormone-dependent H subline (volume doubling time about 17 days). The effects of single doses of photons (10 to 40 Gy) with and without local tumor hyperthermia (35 min immersion at 43.5 degrees C) were quantified by growth delay. The time to reach five times the volume at the time of treatment after 30 Gy alone was found to be 56.0, 134.9 and 184.0 days for the R3327-AT1, HI and H tumors, respectively. The R3327-H tumor was more radiosensitive than the AT1 or HI subline. Five of nine R3327-H tumors were controlled locally with a single dose of photons (40 Gy). Local tumor hyperthermia alone induced growth delay in both differentiated tumors, while the anaplastic tumor subline did not respond. Combined treatment modalities with heat applied directly after irradiation revealed isoeffective thermal enhancement ratios for 30 Gy which decreased from 1.59 for the AT1 tumor and 1.42 for the HI tumor to 1.23 in the well-differentiated subline R3327-H.     

Distribution of adriamycin in mice under conditions of local hyperthermia which improve systemic drug therapy

Local tumor hyperthermia (LTH) (43 degrees C for 60 minutes) enhanced the effectiveness of Adriamycin (ADR) (10 mg/kg iv) administered systemically against the 16C mouse mammary adenocarcinoma. LTH was produced by the local application of 2450 MHz microwaves to sc implanted tumors. During LTH the intratumor temperature uniformity was +/- 0.5 degrees C and the rectal temperatures were 36 degrees C--38 degrees C. The simultaneous application of LTH and ADR resulted in tumor growth delays which were greater than those expected from the addition of individual treatments. Enhanced effectiveness of these treatments did not occur if the two treatments were separated by 4 hours. Cures were observed only in the treatment groups that received drug and heat simultaneously. Measurements of the tissue distribution of ADR and its metabolites using 14C-ADR indicated that the uptake of radioactivity in the heated tumors was not increased by LTH. A greater percentage of the radioactivity in heated tumors was recovered as ADR metabolites and correspondingly less radioactivity was recovered as unchanged ADR.     

Combined treatment of inoperable carcinomas of the uterine cervix with radiotherapy and regional hyperthermia. Results of a phase II trial

AIM: The disappointing results for inoperable, advanced tumors of the uterine cervix after conventional radiotherapy alone necessitates improving of radiation therapy. Simultaneous chemotherapy or altered radiation fractionation, such as accelerated regimen, increase acute toxicity and treatment is often difficult to deliver in the planned manner. The purpose of this phase II study was to investigate the toxicity and effectiveness of a combined approach with radiotherapy and regional hyperthermia. PATIENTS AND METHODS: From January 1994 to October 1995 18 patients with advanced carcinomas of the uterine cervix were treated in combination with radiotherapy and hyperthermia. The patients were treated with 6 to 20 MV photons delivered by a linear accelerator in a 4-field-box technique to a total dose of 50.4 Gy in 28 fractions. In the first and fourth week 2 regional hyperthermia treatments were each applied with the Sigma-60 applicator from a BSD-2000 unit. After this a boost to the primary tumor was given with high-dose-rate iridium-192 brachytherapy by an afterloading technique with 4 x 5 Gy at point A to a total of 20 Gy and for the involved parametrium anterioposterior-posterioanterior to 9 Gy in 5 fractions. RESULTS: The acute toxicity was low and similar to an external radiotherapy alone treatment. No Grade III/IV acute toxicity was found. The median age was 47 years (range 34 to 67 years). In 16 of 18 patients a rapid tumor regression was observed during combined thermo-radiotherapy, which allowed the use of intracavitary high-dose-rate brachytherapy in these cases. Complete and partial remission were observed in 13 and 4 cases, respectively. One patient did not respond to the treatment. The median follow-up was 24 months (range 17 to 36 months). The local tumor control rate was 48% at 2 years. Median T20, T50 and T90 values were 41.7 degrees C (range 40.3 to 43.2 degrees C), 41.1 degrees C (range 39.2 to 42.5 degrees C) and 39.9 degrees C (range 37.7 to 41.9 degrees C), respectively. Cumulative minutes of T90 > 40 degrees C (Cum40T90) and cumulative minutes, which were isoeffective to 43 degrees C, were calculated (CEM43T90, CEM43T50, CEM43T20). CEM43T90 was found to be a significant parameter in terms of local tumor control for the 4 hyperthermia treatments (p = 0.019). CONCLUSIONS: This treatment modality has proved to be feasible and well tolerable. The rapid tumor shrinkage in the combined approach of radiotherapy with hyperthermia before beginning brachytherapy seems to be a good prerequisite for improving of the disappointing results in cure of advanced cancer of the uterine cervix.     

High cytokine production and effective antitumor activity of a recombinant vaccinia virus encoding murine interleukin 12

We have constructed a recombinant vaccinia virus (recVV), vKT0334 mIL-12, containing the genes encoding the p35 and p40 subunits of murine interleukin-12 (mIL-12). In vitro experiments demonstrated that vKT0334 mIL-12 efficiently infected a variety of murine and human tumor cell lines and produced very high amounts (1.5 micrograms/10(6) cells/24 h) of biologically active mIL-12. Mice injected s.c. with 10(6) MCA 105 sarcoma cells, followed by injection at the same site with saline or a control recVV, vKT033, containing no mIL-12 genes, all developed progressively growing tumor, whereas 60% of animals injected with vKT0334 mIL-12 remained tumor free (P < 0.0005). Furthermore, tumor growth was significantly reduced in the remaining mice treated with vKT0334 mIL-12 that did develop tumor compared with mice treated with vKT033 (P < 0.03) or saline (P < 0.0001). We conclude that recVV expressing high levels of mIL-12 offers an effective in vivo method of cytokine gene delivery and expression in tumors with subsequent antitumor effect.     

Direct evidence for bimodal DNA damage induced by tirapazamine

The ability of tirapazamine (1, 3-amino-1,2,4-benzotriazine 1, 4-dioxide, SR4233) to fix DNA radical lesions is demonstrated by studying the reaction between the antitumor drug and an oligonucleotide radical that is independently produced at a defined site within a biopolymer. Using beta-mercaptoethanol as a competitor, it was determined that tirapazamine traps a C1'-nucleotide radical with a rate constant of approximately 2 x 10(8) M-1 s-1. Product and isotopic labeling studies suggest that tirapazamine reacts with the radical via covalent adduct formation, resulting primarily from reaction at the N-oxide oxygen. Intermediate covalent adducts could not be observed, but are postulated to decompose to the alkaline labile 2'-deoxyribonolactone lesion. These experiments affirm recent proposals suggesting that tirapazamine can serve as a surrogate for O2 in converting DNA radicals into toxic strand damage events.     

Phase I/II trial of combined 131I anti-CEA monoclonal antibody and hyperthermia in patients with advanced colorectal adenocarcinoma

BACKGROUND: This pilot project was undertaken to evaluate the toxicity of and tumor response to combined 131I anti-carcinoembryonic antigen monoclonal antibody (131I anti-CEA RMoAb) and hyperthermia in patients with metastatic colorectal adenocarcinoma. METHODS: Nine patients who had colorectal carcinoma with liver metastases were enrolled in this study. Intact 131I anti-CEA RMoAb was used (the specific antibody was IMMU-4, provided by Immunomedics, Inc., Morris Plains, NJ). During the diagnostic phase, dosimetry revealed that the tumor site received a higher radiation dose than the surrounding normal tissues in only six patients. These six, who were treated with radioimmunotherapy and hyperthermia, were the basis of this study. The first three patients were treated with 30 mCi/m2 of 131I anti-CEA RMoAb, and the next three received 60 mCi/m2. Pharmacokinetic clearance data were reported for all nine patients. RESULTS: Thermometry data revealed an average T90 of 40.3 (+/- 1.4 degrees C) and T50 of 41.1 (+/- 1.2 degrees C). The average thermal dose equivalent at 42.5 degrees C was 34.5 (+/- 21.5) minutes. The average Tmin, Tmax, and Tmeam were 40 (+/- 1.2 degrees C), 42.4 (+/- 0.7 degrees C), and 41.1 (+/- 1.1 degrees C), respectively. The pharmacokinetic clearance data of antibody showed monoexponential plasma clearances in all patients except one, in whom a biexponential plasma clearance was observed. In general, similar plasma and whole-body clearances as well as similar urinary excretions were observed when diagnostic and therapeutic phases for each patient were compared. Two of the six patients showed a marked improvement in their symptoms; five patients showed a drop in carcinoembryonic antigen levels. A follow-up computed tomography scan one month after treatment showed no change in tumor volume in five patients; one patient showed a partial response. Three patients developed toxicity, two developed moderate thrombocytopenia (39,000 and 58,000), and the other patient developed hematoma resulting from the insertion of a catheter for thermometry. CONCLUSIONS: It is feasible to combine hyperthermia and radiolabeled monoclonal antibodies, and the combination was well tolerated by these patients. The interaction between hyperthermia and low dose rate radioimmunotherapy is complex. Further studies are necessary to explore the use of this combined modality in the management of maligancies.     

Retroviral transfer of human cytochrome P450 genes for oxazaphosphorine-based cancer gene therapy

Cyclophosphamide (CPA) and ifosfamide (IFA) are widely used anticancer prodrugs that are bioactivated in the liver by specific cytochrome P450 enzymes (CYPs). The therapeutic activity of these antitumor agents can be compromised by a low therapeutic index that is, in part, due to the systemic distribution of activated drug metabolites. Here, recombinant retroviruses were used to deliver six different CPA- or IFA-metabolizing human CYP genes to 9L gliosarcoma cells: 2B6, 2C8, 2C9, 2C18 (Met385 and Thr385 alleles), 2C19, and 3A4. Intratumoral cytochrome P450 expression conferred substantial sensitivity to CPA cytotoxicity, with the most dramatic effects seen with CYP2B6. Strong CPA chemosensitivity was also seen following transduction of CYP2C18-Met, despite a very low level of CYP protein expression (>60-fold lower than that of 2B6). In contrast to CPA, the cytotoxicity of IFA was greatest toward tumor cells transduced with CYP3A4, followed by CYPs 2B6 and 2C18-Met. A substantial further increase in chemosensitivity was achieved upon transduction of 2B6 or 2C18-Met-expressing tumor cells with P450 reductase, which provided for more efficient intratumoral prodrug activation and cytotoxicity at lower drug concentrations. With 2B6- plus P450 reductase-transduced tumor cells, CPA but not IFA conferred a strong cell contact-independent bystander cytotoxic effect on non-P450-expressing 9L cells. CPA treatment of tumors that were transduced with 2B6 or 2C18-Met together with P450 reductase and were grown s.c. in immunodeficient mice resulted in a large enhancement of the liver P450-dependent antitumor effect seen with control 9L tumors, with no apparent increase in host toxicity (growth delay of >25-50 days in P450-expressing tumors versus approximately 5-6 days without P450). CYP2B6 plus P450 reductase and CYP2C18-Met plus P450 reductase thus appear to be excellent gene combinations for use with CPA in P450/prodrug activation-based cancer gene therapy.     

Long-lasting complete inhibition of human solid tumors in SCID mice by targeting endothelial cells of tumor vasculature with antihuman endoglin immunotoxin

In the present study, we developed an antitumor immunoconjugate that appears to be promising as a novel curative antitumor agent against a variety of human solid tumors. We generated a new antihuman endoglin (EDG) monoclonal antibody (mAb) K4-2C10 (or termed SN6f) that cross-reacts with mouse endothelial cells. Such cross-reactive anti-EDG mAbs have not been reported previously. This mAb was used to target tumor-associated vasculature in SCID mice inoculated with human tumors. No anti-EDG mAb or its immunoconjugates have previously been successfully used for targeting vasculature in vivo. In this study, MCF-7 human breast cancer cells were inoculated s.c. into SCID mice. K4-2C10 did not react with the MCF-7 cells but showed a weak reactivity with mouse endothelial cells. The mAb reacted with the proliferating endothelial cells more strongly than with the quiescent endothelial cells. The mAb exhibited much stronger reactivity (>10-fold) with human endothelial cells than with mouse endothelial cells and reacted strongly with vascular endothelium of tumor-associated blood vessels in a variety of human malignant tissues. Conjugates of K4-2C10 with ricin A chain (RA) and deglycosylated ricin A chain (dgRA) showed a weak but specific cytotoxic activity against murine endothelial cells in vitro; the 50% inhibitory dose of the RA and dgRA conjugates was 54 nm and 29 nm, respectively. Remarkable antitumor efficacy was observed when a small amount (a total of 60 microgram corresponding to 24% of the LD50 dose) of the dgRA conjugate was administered i.v. into SCID mice that had been inoculated s.c. with MCF-7. Unconjugated mAb K4-2C10 was not significantly effective in the inhibition of the tumor growth. The immunotoxin (IT) completely inhibited growth of the tumor in all of the treated mice (n = 8). Furthermore, similar antitumor efficacy was observed when the IT was administered i.v. into the tumor-inoculated SCID mice that had been pretreated with unconjugated K4-2C10 to block the potentially available weak binding sites of normal tissues. The strong therapeutic effects of the IT were reproduced in another set of therapeutic experiments. No significant side effects were observed in the mice. The differences in the tumor growth between the control group and the IT-treated groups were statistically significant. The IT showed antiangiogenic activity in the dorsal air sac method. The results indicate that K4-2C10 IT effectively treated the tumor-bearing mice by selectively inhibiting the tumor-associated blood vessels and by disrupting tumor-associated angiogenesis. The strong antitumor efficacy of the K4-2C10 IT is remarkable in view of the fact that K4-2C10 and its IT showed only a weak reactivity with mouse endothelial cells, and a relatively small amount of the IT was administered i.v. to treat s.c. tumors. We anticipate that the K4-2C10 IT will show much stronger antitumor efficacy and antiangiogenic activity in patients with solid tumors and other angiogenesis-associated diseases. The present results demonstrate for the first time that an anti-EDG mAb or its immunoconjugate can effectively target tumor-associated vasculature in vivo.     

Antitumor immunity induction by intracellular hyperthermia using magnetite cationic liposomes

Induction of antitumor immunity to T-9 rat glioma by intracellular hyperthermia using functional magnetic particles was investigated. Magnetite cationic liposomes (MCLs), which have a positive surface charge, were used as heating mediators for intracellular hyperthermia. Solid T-9 glioma tissues were formed subcutaneously on both femurs of female F344 rats, and MCLs were injected via a needle only into the left solid tumors (treatment side). The rats were then divided into two groups, which received no irradiation, or irradiation for 30 min given three times at 24-h intervals with an alternating magnetic field (118 kHz, 384 Oe). On the treatment side, the tumor tissue disappeared completely in many rats exposed to the magnetic field. The tumor tissue on the opposite side also disappeared completely, even though MCLs were not injected into the right solid tumors. To examine whether a long-lasting and tumor-specific immunity could be generated, the rats that had been cured by the hyperthermia treatment were rechallenged with T-9 cells 3 months later. After a period of transient growth, all tumors disappeared. Furthermore, immunocytochemical assay revealed that the immune response induced by the hyperthermia treatment was mediated by both CD8+ and CD4+ T cells and accompanied by a marked augmentation of tumor-selective cytotoxic T lymphocyte activity. These results suggest that our magnetic particles are potentially effective tools for hyperthermic treatment of solid tumors, because in addition to killing of the tumor cells by heat, a host immune response is induced.     

Tumor necrosis factor alpha-mediated tumor regression by the in vivo transfer of genes into the artery that leads to tumors

We report that tumor necrosis factor (TNF) alpha induced a strong antitumor immune reaction when it was produced in arteries leading to tumors by gene transfer in vivo. We used a mouse model carrying a sarcoma-180 tumor in the right footpad and injected the fusogenic liposomes encapsulating the human TNF-alpha gene into the right femoral artery. Under this condition, human TNF-alpha was detected only in the artery leading to the tumor and in the tumor. There was a significant regression in tumor growth when the TNF-alpha gene was delivered into the right femoral artery, with 4 of 11 mice completely cured. No regression was observed when the TNF-alpha gene was delivered into the left femoral artery or into the tumor or when the luciferase gene was administered. Tumor regression was inhibited by the injection of anti-TNF-alpha, anti-CD4, or anti-CD8 monoclonal antibody, and CD8+ T cells accumulated in the tumors of TNF-alpha-treated mice. These results suggest that TNF-alpha expressed locally in the arteries leading to tumors efficiently suppresses tumor growth through reinforcement of an antitumor immune reaction. The significance of this phenomenon for cancer gene therapy was discussed.     

Improvement of tumor oxygenation status by mild temperature hyperthermia alone or in combination with carbogen

The effects of mild temperature hyperthermia (MTH) on the oxygenation and radioresponse in rodent tumors were investigated. FSall tumors grown in the legs of C3H mice and R3230 AC tumors grown in the legs of Fischer rats were heated with a water bath and the partial pressure of oxygen (pO2) was determined using the microelectrode method. In FSall tumors, the pO2 measured immediately after heating at 41.5 degrees C for 1 hour was markedly higher than that in the control tumors, whereas heating at higher temperatures for 1 hour decreased the tumor oxygenation. In R3230 AC tumors, heating at 41.5 degrees C for 1 hour caused a moderate increase in the pO2 and heating at 42.5 degrees or 43.5 degrees C for 30 minutes markedly increased the pO2. However, heating at 42.5 degrees C or higher temperatures for 1 hour decreased the pO2 in the R3230 AC tumors. The improvement of oxygenation in FSall tumors by heating at 41.5 degrees C for 1 hour increased the radiation-induced cell death in these tumors. The combination of carbogen breathing with MTH was far more potent than carbogen breathing or MTH alone in increasing tumor oxygenation and potentiating the radiation effect in FSall tumors.     

Circulatory and metabolic responses of malignant tumors during localized hyperthermia

The effect of localized hyperthermia on the circulatory responses and on the oxygen and glucose supply has been evaluated in tissue-isolated rat tumors utilizing an in situ perfusion system. On the average, localized hyperthermia caused a significant increase in total tumor blood flow after raising of the mean tumor temperature from 37 degrees C to 39.5 degrees C. At higher temperatures (42 degrees C) total tumor blood flow decreased to a level somewhat below the flow during normothermia. However, there were great interindividual differences in the response of blood flow to temperature. The changes in blood flow were paralleled by variations of the O2-consumption and of the glucose uptake of the tumor tissue. The alteration of the oxygen and glucose supply seem to be predominantly mediated through changes of tumor blood flow with temperature. Tumor microcirculation appears to be improved at moderate hyperthermic temperatures (39 degrees C -40 degrees C) and deteriorated at higher temperatures. Whereas a vasodilation of tumor vessels seems to be a paramount factor for flow improvements, a reduction of red blood cell flexibility due to severe tissue acidosis, multiple microthromboses as well as occlusions of microvessels should be taken into consideration as factors for flow impairments at higher tumor temperatures.     

Lysosomal exocytosis induced by hyperthermia: a new model of cancer cell death. II. Effect on peritoneal macrophages

Recently we described the "macrophagic lysosomal exocytosis" (MLE) as a possible new mode of cancer cell death induced by hyperthermia (HT) [1]. In order to confirm this first report, HT was applied at the peritoneum level with perfusional procedure, after catheter insertion under local anesthesia. We evaluated the subcellular changes of peritoneal macrophages in human gastric tumor, before and after hyperthermic treatment at 42 degrees C for 90 minutes. Transmission electron microscopy showed that treatment produced the disappearance of the cytoplasmic granules, with a consequent extracellular scavenger action of the phagocytic cells, the proliferation of some organelles such as mitochondria, endoplasmic reticulum and Golgi complex that may be addressed to a subsequent restoration of the granular pool in the degranulated macrophages. This phenomenon can enhance the already documented effect of hyperthermic perfusional chemotherapy in peritoneal tumors.     

Sex-related difference in the growth of prolactinomas: a clinical and proliferation marker study

Prolactinomas in women commonly present as small intrasellar tumors, but are usually much larger in men. This discrepancy has generally been attributed to differences in the delay before diagnosis. However, studies comparing clinical and pathological correlates of growth of these tumors in both sexes are lacking. We conducted a retrospective study comparing 45 men and 51 women bearing prolactinoma to determine whether the predominance of large tumors in men was due to a delay in diagnosis or, rather, to a fundamental sex-related difference in tumor growth. Basal PRL levels (mean +/- SEM, 2789 +/- 573 ng/mL) and mean tumor diameter (26 +/- 2 mm) were significantly higher in men than in women (292 +/- 74 ng/mL and 10 +/- 1 mm, respectively; P < 0.001), but were not correlated to the age at diagnosis or the duration of symptoms. Giant tumors (n = 8) occurred in males only. The frequencies of bromocriptine-resistant tumors (30 vs.5%; P < 0.01) and invasive macroadenomas (52 vs.27%; P < 0.001) were significantly greater in men than those in women. Lastly, macroprolactinomas in males exhibited higher indexes of proliferating cells by Ki-67 immunoreactivity (2.6 +/- 1.1% of positive nuclei) than did similar tumors in female patients (0.4 +/- 0.2%; P = 0.08). We conclude that the predominance of large prolactinomas in men is due to a high frequency of rapidly growing tumors, which are often invasive and frequently bromocriptine resistant.     

The effect of feeding piglets up to the 100th day of their life with peat preparation on their growth and physiological and biochemical indices

As judged by alkaline elution, exposure of Walker cells to either 3-amino-1,2,4-benzotriazine-1,4-dioxide (SR 4233) or nitromin results in a dose-dependent increase in DNA damage due to single-strand breaks. With nitromin or SR 4233 there was little difference in the extent of DNA single-strand breaks between Walker cells incubated either hypoxically or aerobically. In contrast, there was a 24-fold enhancement in the differential hypoxic/aerobic response to SR 4233 in clonogenic studies. Following incubation of cells with nitrogen mustard, DNA cross-linking is observed. Bioreduction of nitromin would be expected to yield nitrogen mustard as the putative reactive metabolite. However, only DNA strand-breaks could be detected in Walker cells incubated with nitromin, suggesting that reduction of this pro-drug to nitrogen mustard was not a major activation pathway. In cells incubated under aerobic conditions, SR 4233 induces oxidative DNA damage, as indicated by the formation of 8-hydroxydeoxyguanosine, suggesting the involvement of futile redox cycling. In rats dosed with SR 4233 in vivo, significantly higher levels of 8-hydroxydeoxyguanosine could be detected in liver, compared to vehicle-dosed controls.     

How to heal a wound fast

PURPOSE: To correlate patient-, tumor-, and treatment-related factors with subsequent local tumor control. METHODS AND MATERIALS: From 1977 to 1990, 196 subcutaneous/superficial lesions (179 measurable, 17 microscopic) in 151 patients with recurrent breast carcinoma of the chest wall were treated with superficial 915-MHz microwave hyperthermia and irradiation. The definition of min t43 > or = 10 min is that all monitored tumor catheters had a minimum of 1 hyperthermia session with temperatures > 43 degrees C for at least 10 min. RESULTS: Factors correlating with local control on univariate analysis included length of survival (> or = 1 year vs. < 1 year) (p < 0.0001), specific absorption rate (SAR) (> or = 25% vs. < 25%) (p = 0.0001), minimum t43 > 10 min (p < 0.0001), tumor volume (p < 0.0001), tumor surface area (p < 0.0001), tumor depth (p = 0.0002), number of hyperthermia sessions (p = 0.0003), and current radiation dose (p = 0.0012). On multivariate analysis, the factors best correlated with ultimate local control were SAR (p < 0.001) and number of hyperthermia sessions (p = 0.003). CONCLUSIONS: Multivariate analysis supports the importance of adequate specific absorption rate (SAR) coverage as a better predictor of local control than tumor volume, surface area, or depth. The explanation is that SAR can be correlated with the tumor surface area and depth, depending on the hyperthermia applicator characteristics. It is recommended that future clinical trials stratify study lesions into either SAR > or = 25% or < 25% because this can be readily estimated prior to initiating treatment. It is also recommended that future clinical trials attempt to have adequate lengths of follow-up after therapy to assess the results in long-term survivors.     

Cytotoxicity of alpha-particle-emitting astatine-211-labelled antibody in tumour spheroids: no effect of hyperthermia

The high linear energy transfer, alpha-particle-emitting radionuclide astatine-211 (211At) is of interest for certain therapeutic applications; however, because of the 55- to 70-microm path length of its alpha-particles, achieving homogeneous tracer distribution is critical. Hyperthermia may enhance the therapeutic efficacy of alpha-particle endoradiotherapy if it can improve tracer distribution. In this study, we have investigated whether hyperthermia increased the cytotoxicity of an 211At-labelled monoclonal antibody (MAb) in tumour spheroids with a radius (approximately 100 microm) greater than the range of 211At alpha-particles. Hyperthermia for 1 h at 42 degrees C was used because this treatment itself resulted in no regrowth delay. Radiolabelled chimeric MAb 81C6 reactive with the extracellular matrix antigen tenascin was added to spheroids grown from the D-247 MG human glioma cell line at activity concentrations ranging from 0.125 to 250 kBq ml(-1). A significant regrowth delay was observed at 125 and 250 kBq ml(-1) in both hyperthermia-treated and untreated spheroids. For groups receiving hyperthermia, no increase in cytotoxicity was seen compared with normothermic controls at any activity concentration. These results and those from autoradiographs indicate that hyperthermia at 42 degrees C for 1 h had no significant effect on the uptake or distribution of this antitenascin MAb in D-247 MG spheroids.     

Antitumor response of genetically engineered IL-2 expression to human esophageal carcinoma cells in mature T cell-defective condition

We examined whether antitumor effect could be produced by retrovirally expressed human interleukin-2 (hIL-2) gene in human esophageal cancer cells (T.Tn) using immunocompromised nude mice. Loss of tumorigenicity of hIL-2-producing T.Tn (T.Tn/hIL-2) cells inoculated subcutaneously was observed in contrast to continuous tumor growth of wild-type cells, although in vitro proliferation of T.Tn/hIL-2 cells remained the same as that of wild-type cells. The antitumor effect was also evidenced by the injection of T.Tn/hIL-2 cells into established tumors of wild-type cells. The injection significantly retarded the subsequent growth of wild-type tumors. Histological examination of regressing T.Tn/hIL-2 cells revealed necrotic areas and infiltration of several types of inflammatory cells. Treatment of nude mice with anti-asialoGM1 antibody did not influence the IL-2-mediated tumor rejection. Vaccination of nude mice with irradiated T.Tn/hIL-2 cells whose secretion of hIL-2 in amount was comparable to that of unirradiated cells did not develop protective immunity. Taken together, the antitumor effect achieved in nude mice by the inoculation of T.Tn/hIL-2 cells is mediated by non-T non-natural killer cells.     

Interactions between hypothermia and the latency to ischemic depolarization: implications for neuroprotection

BACKGROUND: The authors postulated that hypothermic neuroprotection can be attributed to a delayed onset of ischemic depolarization. METHODS: Halothane-anesthetized rats were prepared for near-complete forebrain ischemia. Direct current (DC) potential microelectrodes were placed in hippocampal CA1. The pericranial temperature was maintained at 31 degrees C, 33 degrees C, 35 degrees C, or 37 degrees C (n = 6 per group). Bilateral carotid occlusion with systemic hypotension was initiated for 10 min. The time to onset of the DC shift was recorded. In a second experiment, rats were assigned to 37 degrees C or 31 degrees C for 10 min of ischemia, or to 31 degrees C for 14 min of ischemia (n = 8 per group). These durations of ischemia were defined to allow 9 min of ischemic depolarization in the 37 degrees C-10 min and 31 degrees C-14 min groups. Neurologic and histologic outcomes were examined 7 days later. RESULTS: Hippocampal CA1 time to depolarization increased with decreasing temperature (P < 0.0001). Time to depolarization was increased by approximately 4 min in the rats maintained at 31 degrees C compared with those at 37 degrees C. Time to repolarization during reperfusion was not affected by temperature. Increasing the duration of ischemia from 10 min to 14 min with the pericranial temperature maintained at 31 degrees C resulted in a duration of depolarization that was equivalent in the 37 degrees C-10 min and 31 degrees C-14 min groups. However, hippocampal CA1 damage was not increased (31 degrees C-10 min = 4 +/- 1% dead neurons; 31 degrees C-14 min = 6 +/- 1% dead neurons, 95% CI, -1% to 3%; 37 degrees C-10 min = 90 +/- 17% dead neurons). CONCLUSIONS: Despite similar durations of DC depolarization, outcome in hypothermic rats was markedly improved compared with normothermic rats. This indicates that hypothermic neuroprotection can be attributed to mechanisms other than the delay in time to onset of ischemic depolarization.