Altered tissue-specific opsonic activities and opsono-recognition of liposomes in tumour-bearing rats

Reticuloendothelial phagocytic and serum opsonic activity was evaluated at terminal stages of tumour growth in rats transplanted subcutaneously with chondrosarcoma in an attempt to evaluate the role of opsonic protein(s) in governing liposome recognition and clearance by the macrophage system. The liver of the tumour-bearing animals manifested a decline in the uptake of multilamellar vesicles composed of egg phosphatidylcholine: cholesterol: dicetyl phosphate (mole ratio 7:2:1) from the blood when compared to healthy animals. In contrast, an increase in splenic clearance of liposomes was encountered in tumour-bearing rats. Studies with isolated liver non-parenchymal cells suggested that liposome recognition in both health and at terminal stages of cancer growth is influenced by a serum opsonin, which can be precipitated by 35-50% ammonium sulphate, as well as the concentration of calcium levels in serum. Serum of healthy animals equally enhanced liposome recognition by the hepatic macrophages of both normal and tumour-bearing rats. In contrast, both cell populations manifested poor liposome recognition in the presence of serum pooled from tumour-bearing animals and the results were comparable to the corresponding liposome-cell interaction in the absence of serum. The opsonic activity of serum derived from tumour-bearing rats could be demonstrated either by prior dialysis of serum against de-ionized water or by addition of EGTA. Liver phagocytes of healthy animals recognized more liposome in the presence of dialysed or EGTA-chelated tumour-serum than that of liver cells derived from tumour transplanted rats. A significant increase in serum calcium concentration was found in all tumour-bearing rats. When the concentration of calcium in the serum of normal animals was increased to the level that is encountered in tumour-bearing rats, a sharp drop in liposome recognition by liver phagocytes was observed. This drop in opsonic activity was not related to changes in the ionic strength of serum. The ammonium sulphate precipitated opsonin was also calcium-sensitive and its opsonic activity was abolished in the presence of calcium. Studies with isolated splenic phagocytes suggested that an increase in the opsonic activity of serum, but not the elevated calcium level, was responsible for hyperphagocytosis of liposomes by the splenic phagocytes of tumour-transplanted animals. The opsonic molecule which enhanced liposome recognition by liver non-parenchymal cells failed to enhance liposome clearance by the splenic phagocytes. These findings suggest that the alteration in macrophage clearance of liposomes during the terminal growth of cancer may be mediated in part by changes in the opsonic capacity of serum.

Psychoneuroimmunology: animal models of disease

OBJECTIVE

Psychoneuroimmunology, which investigates the bidirectional communication between the central nervous system and the immune system, has been greatly advanced by the use of animal models. The objective of this paper is to describe animal models of disease that can or might be utilized to elucidate neural-immune interactions that alter pathogenesis.

METHODS

This paper reviews animal studies that have demonstrated a link among the brain, behavior, immunity, and disease, highlighting models in which the potential contribution of CNS-immune interactions has not yet been explored.

RESULTS

Animal studies allow for careful control of environmental stimuli, genetic background, and immunological challenge. As such, they are an important component of psychoneuroimmunology research. Models in which one might study the role of psychosocial factors in immunologically mediated disease processes, as in the case of other pathophysiologic processes, profit from an ability to manipulate both stressful events and the magnitude of the challenge to the immune system.

CONCLUSIONS

Animal studies in psychoneuroimmunology highlight the complexity of the interactions among behavior, the brain, the immune system, and pathogen. The genetic background of the animal (both in terms of central nervous and immune system responses), its previous history, the nature of the stressor, the nature of the pathogen and the type of immune response generated are some of the interacting factors that determine the magnitude and direction of stress-induced changes in disease outcome.

Impedance spectra of tumour tissue in comparison with normal tissue; a possible clinical application for electrical impedance tomography

Electrical characteristics of living tissues have been investigated for a long time in the search for further methods to complement the traditional investigations of pathology and physiology. Tumour tissue has been shown to exhibit a larger permittivity and conductivity than normal tissues. This might be associated with the fact that tumour cells have a higher water content and sodium concentration than normal cells, as well as different electrochemical properties of their cell membranes. To our knowledge only a few contributions on this subject have been published. This study describes an additional application on measurements of the complex impedance of tumour and normal tissues, in order to compare the impedance features of the two tissue types. The tissue sample is placed in a measuring cell in which the temperature is controlled. The measuring cell is connected to an impedance meter able to measure the complex impedance in terms of real and imaginary part curves for frequencies from 1.5 kHz to 700 kHz. The four-electrode principle is used with the current injected by the outer electrodes and the voltage difference measured between the inner electrodes. The current can be altered up to 1 mA. The instrument can be calibrated with known resistance and capacitance networks connected to the input of the instrument in order to minimize the measurement errors. The calibration routine uses a polynomial adaptation and can be applied interactively. Measurements performed by the instrument show promising results. Preliminary results show that this method can be extended to a new application for detection of tumour tissue by electrical impedance tomography (EIT).

Blood flow, oxygenation, and bioenergetic status of tumors after erythropoietin treatment in normal and anemic rats

Growth, blood flow, oxygenation, and bioenergetic status of experimental tumors were investigated in normal (control) and anemic animals after administration of recombinant human erythropoietin (rhEPO). DS sarcomas were implanted s.c. onto the hind foot dorsum of Sprague-Dawley rats. Tumor-associated anemia was induced by the development of an i.p. hemorrhagic ascites. rhEPO (1000 IU/kg) was administered s.c. three times per week over 14 days, after which it was found to have significantly increased hematocrit values in both normal and anemic animals. Tumor growth in anemic animals was slower than in normal animals, and rhEPO administration did not influence tumor growth in either group. Tumor blood flow in anemic animals was lower than in control animals and was only increased in larger tumors in animals in which anemia was prevented by prophylactic rhEPO application. Tumor oxygenation, determined using polarographic needle electrodes and oxygen partial pressure histography, was poorer in anemic animals than in normal animals. This reduction could be reversed partially, but not compensated fully by rhEPO treatment in smaller tumors (< or = 1.4 ml). These changes suggest that rhEPO, by improving tumor oxygenation, may increase the efficacy of standard radiotherapy in anemic animals and may be of use in anemic tumor patients in whom the success of radiotherapy or O2-dependent chemotherapy might be limited by tumor hypoxia.

Relationship of mitotic arrest and apoptosis to antitumor effect of paclitaxel

BACKGROUND

Microtubules are cellular organelles with functions that include control of cell division by mitosis, cell morphology, and transport of material within the cell. The anticancer drug paclitaxel (Taxol) promotes accelerated assembly of excessively stable microtubules. Consequently, treated cells tend to become arrested in mitosis. The drug also induces apoptotic cell death in vitro and in vivo. Prior to this study, the relative contributions of mitotic arrest and apoptosis to the in vivo antitumor effect and the relationship between the two factors had not been established; moreover, it is not known whether paclitaxel-induced mitotic arrest inevitably results in cell death.

PURPOSE

Our aim was to quantify the mitotic arrest and apoptosis induced by paclitaxel in 16 murine tumors in vivo and to correlate these two factors with the drug's antitumor effect.

METHODS

Inbred C3Hf/Kam mice were implanted with one of the following 16 syngeneic tumors: seven adenocarcinomas (MCa-4, MCa-29, MCa-35, MCa-K, OCa-I, ACa-SG, and HCa-I), two squamous cell carcinomas (SCC-IV and SCC-VII), six sarcomas (FSa, FSa-II, Sa-IIa, Sa-NH, NFSa, and Sa-4020), and one lymphoma (Ly-TH). The tumor growth delay induced by paclitaxel (40 mg/kg body weight given intravenously) was measured in 163 control and 163 treated mice, and its significance was assessed by Student's t test. In a separate group of 439 mice, the percentage of cells in mitosis or apoptosis was scored micromorphometrically at various times after paclitaxel administration. The significance of correlations between paclitaxel-induced tumor growth delay and paclitaxel-induced levels of mitosis or apoptosis was determined by simple correlation and Spearman's rank correlation. P values reported represent two-sided tests of statistical significance.

RESULTS

Statistically significant tumor growth delays were found in response to paclitaxel treatment of mice for three of four murine mammary carcinomas (all P < or = .010), an ovarian carcinoma (P = .00003), a salivary gland adenocarcinoma (P = .0002), a lymphoma (P = .0002), and two of six sarcomas (both P < or = .034), but not for either of two squamous cell carcinomas or for the hepatocellular carcinoma. Paclitaxel-induced mitotic arrest was apparent in all tumor types, but to various degrees, and was not significantly correlated with growth delay (R2 = .16; P = .124). In contrast, apoptotic cell death in response to paclitaxel was not ubiquitous, but it was strongly correlated with growth delay (R2 = .59; P = .001). The pretreatment level of apoptosis was correlated with both paclitaxel-induced apoptosis (R2 = .71; P = .00004) and tumor growth delay (R2 = .55; P = .001).

CONCLUSION

The antitumor effect of paclitaxel was correlated with paclitaxel-induced apoptosis and base-line apoptosis, but not with mitotic arrest.

IMPLICATIONS

Apoptosis is an important mechanism of cell death in response to paclitaxel treatment of in vivo murine tumors. An underlying tumor type-specific propensity for apoptosis is implied by the correlation between pretreatment and paclitaxel-induced apoptosis. Both the extent of pretreatment apoptosis and the paclitaxel-induced percentage of apoptosis may be useful predictors of response to the drug.

Clinical applications of characteristic frequency measurements: preliminary in vivo study

In vivo electrical impedance tomography images have been available for some years, and most of them show variation in impedance amplitude between two different states, for example between inspiration and expiration of the lungs. A refinement of the tomography technique has made it possible to show images of the complex impedance of the body. If several frequencies are used, more information on the investigated tissues can be collected, and new areas made available for investigation. It has been shown that tissues exhibit a characteristic frequency that can be derived from the maximum magnitude of the (negative) reactance. The characteristic frequency-related images can be calculated from several imaginary part curves obtained using the back-projection technique. The paper shows in vivo impedance spectra from different parts of the body, determines the characteristic frequency of the different in vivo measurements and suggests different applications of characteristic frequency imaging. Several data sets are collected to show the reproducibility of the measurements.

Effects of blood flow modifiers on tumor metabolism observed in vivo by proton magnetic resonance spectroscopic imaging

Perfusion plays a key role in tumor proliferation and therapeutic response. Tumor heterogeneity necessitates use of the highest spatial resolution to monitor metabolic correlates of blood flow changes. This is best achieved with 1H NMR spectroscopy, which permits noninvasive acquisition of high resolution spectroscopic images (SI) of subcutaneous tumors in a relatively short scan time (e.g., 12-25 microliters voxels with signal-to-noise ratio 7:1 in 30 min at 4.7 T). This study seeks to identify 1H spectroscopic indices of tumor blood flow. Proton SI of subcutaneous murine RIF-1 tumors were recorded (a) before and after administration of nicotinamide (1 g/kg) to increase blood flow, and (b) before and after hydralazine (10 mg/kg) to decrease flow. Nicotinamide produced a significant decrease in the total choline peak amplitudes, which subsequent high resolution NMR spectroscopy of tumor extracts revealed to be due to decreases in phosphocholine and glycerophosphocholine. The deamidation of nicotinamide to nicotinic acid, which is known to have hypolipidemic effects and to stimulate the formation of prostaglandins, may have sufficiently altered lipid metabolism to affect the in vivo concentration of the NMR-visible choline-containing compounds. The main effect of hydralazine was a significant increase of lactate, which is consistent with a reduction of tumor blood flow.

Exploitation of hypoxia for radiation therapy: a lesson from phenothiazines

In experimental radiation therapy of tumours, phenothiazines are known to sensitize hypoxic cancer cells while offering protection to the normal surrounding tissue. It is hypothesized that the differential radiosensitization of tumour cells and radioprotection of normal cells by phenothiazines is related to the presence of Fe2+ and Fe3+ ion concentration respectively. As a result of changed biochemical environment such as pH, hypoxia and accumulation of ferritin, the Fe2+ ion concentration in tumours, especially in the hypoxic cells, is expected to be higher (and to be further enhanced by irradiation) than in the well-oxygenated normal cells. In normal cells, iron would predominantly be in the Fe3+ form, which might increase the protective effect of phenothiazines. A many-fold increase in radiation effect has been shown by us in vivo as well as in vitro systems in the combined presence of phenothiazines and Fe2+ ions. Our findings suggest that the hypoxic condition can be exploited for radiation therapy by employing suitable metal-based chemomodulation.

[Antithrombogenic activity of blood vessel walls in the pathogenesis of metastasis in tumor-bearing animals]

The purpose of this work was to examine the relationship between the antiaggregatory activity of the vascular wall and the metastatic spread of experimental tumors. Rats with the tumor "Myosarcoma-1" displayed, on the average, a 30% reduction in the antiaggregatory activity of the aortic wall. Three-week of the animals with a combination of the drugs dipyridamole (0.84 mg/kg per os), phytin (14 mg/kg per os), glutamic acid (28 mg/kg per os) restored the antiaggregatory properties of the vascular wall virtually up to the control values. The similar result was observed with cordarone (60 mg/kg intraperitoneally): the antiaggregatory properties of the vascular wall increased on the average by 50%. The metastatic spread of tumor cells in mice with Lewis carcinoma of the lung decreased on the average twice while treating them with these agents. The findings point to the fact that drug correction of the antiaggregatory activity of the vascular wall reduces the rate of metastatic spread.

1995 Whitaker Lecture: delivery of molecules, particles, and cells to solid tumors

To reach cancer cells in a tumor, a blood-borne therapeutic agent must make its way into the blood vessels of the tumor and across the vessel wall into the interstitium, and finally migrate through the interstitium. Unfortunately, tumors often develop in ways that hinder each of these steps. Our research goals are to analyze each of these steps experimentally and theoretically, and then to integrate the resulting information in a unified theoretical framework. This paradigm of analysis and synthesis has allowed us to obtain a better understanding of physiological barriers in solid tumors, and to develop novel strategies to exploit and/or to overcome these barriers for improved cancer detection and treatment.

Biology of a brain metastasis

The appearance of a brain metastasis is generally regarded as an ominous event in the progression of many solid tumors because it usually means that the patient will have reduced quality and length of survival. It is important to study the biology of brain metastasis because present treatments are principally palliative and new approaches to diagnosis and treatment are clearly needed.

Chemokines: a superfamily of chemotactic cytokines

Chemokines are a bipartite family of chemotactic proteins that bear the structural hallmark of four cysteine residues, the first two of which are in tandem. The spectrum of action of chemokines encompasses a large number of leukocyte populations, including monocytes, granulocytes, lymphocytes, NK and dendritic cells. Although the spectrum of action of chemokines largely overlaps, clear differences are still present. Chemokines play an important role in the recruitment of leukocytes at the site of inflammation, allergic reaction and tumors. Available information on receptor usage by MCP-1 and related chemokines and signal transduction pathways is reviewed. The better understanding of signaling mechanisms will provide a new basis for the development of therapeutic strategies.

Blockade of the estrogen induced increase in progesterone receptor caused by propylthiouracil, an anti-thyroid drug, in a transplantable pituitary tumor in rats

It is well known that estrogen (E2) induces progesterone receptor (PR) in the uterus and the mammary gland. In MtT/F84, a pituitary tumor, which was established in our laboratory and has been maintained with in vivo passages, we investigated the PR regulation by E2 in relation to the host's thyroidal status. The PR level in the tumor had increased five fold 48 h after an E2 injection. When the host rats were treated with propylthiouracil (PTU), an anti-thyroid drug, the induction of PR after an E2 injection was completely blocked. This result is consistent with our previous findings indicating that E2 responsiveness in the tumor may be under the control of thyroid hormones. The estrogen receptor (ER) level in the tumor treated with PTU was 15% of the control. This low ER level may account for the blocking of PR induction after an E2 injection. When the host animals were continuously treated with various doses of E2, the PR level in the tumor rose in correlation with the E2 doses. PTU administration, however, did not prevent long term induction of PR by continuous E2 treatment. Our findings suggest that PTU lower the ER level and suppresses the short term estrogenic actions such as PR induction after an E2 injection.

Growth factors in mechanisms of malignancy: roles for TGF-beta and FGF

Malignant progression is a complex process involving the accumulation of multiple genetic alterations leading to changes in many specialized cell functions. Important in this process is the loss of growth control which is frequently associated with modifications in growth factor production, and growth factor response pathways. Indeed, oncogenes have been characterized that code for polypeptide growth factors or their receptors, and many tumor cell populations release potently mitogenic growth factors which contribute to the malignant properties of tumor cells. In this review, the importance of growth factors in mechanisms of malignant progression is emphasized, using as examples the transforming growth factor-beta (TGF-beta) and fibroblast growth factor (FGF) families. We describe many of the properties and biological activities of these two families of growth factors, focusing on mechanisms of autocrine and intracrine mitogenic stimulation of tumor cell proliferation and malignant progression. The discussion includes evidence for altered growth factor expression in tumor cells, and the relationship between these changes in growth factors and alterations in the regulation of DNA synthesis, cell proliferation, protease production and cell motility required for invasion and metastasis. Recent studies are described that show that aberrant expression of TGF-beta1, bFGF or K-FGF results in dramatic changes in the genetic stability of cells, leading to increased rates of spontaneous gene amplification and the generation of drug resistant variants. These findings describe new malignancy relevant functions for altered growth factor expression.

Reoxygenation after single irradiation in rodent tumors of different types and sizes

PURPOSE

To investigate the variation of reoxygenation patterns after single irradiation in murine tumors of different types and sizes.

METHODS AND MATERIALS

Whole-body single irradiation of 13 to 15 Gy was delivered to 10 mm RIF1 tumors of C3H/He mice, 22 mm SCCVII tumors of C3H/He mice, and 16 mm EMT6 tumors of Balb/c mice. Thereafter, changes in the hypoxic fraction with time were determined by the paired survival curve method. The data were compared with the results we had ++previously obtained with 10 mm SCCVII and 10 mm EMT6 tumors.

RESULTS

The hypoxic fraction at 1 h after the priming irradiation was 26% for 10 mm RIF1 tumors, 48% for 10 mm SCCVII tumors, and 100% for 10 mm EMT6 tumors. Thus, RIF1 and SCCVII tumors, both of which have few necrotic areas, showed rapid reoxygenation, whereas EMT6 tumors, which have large necrotic areas, reoxygenated slowly. Although the hypoxic fraction returned to the pretreatment level within 72 h in 10 mm SCCVII and 10 mm EMT6 tumors, it did not in 10 mm RIF1 tumors. In contrast, the patterns of reoxygenation were similar between 22 mm and 10 mm SCCVII tumors and between 16 mm and 10 mm EMT6 tumors.

CONCLUSION

The three tumors showed different patterns of reoxygenation. Tumors that have a low proportion of necrosis may reoxygenate rapidly. However, tumor size appeared to have less influence on the pattern of reoxygenation.

Timing of cancer chemotherapy based on circadian variations in tumor tissue blood flow

Blood flows of normal tissues (subcutis, liver, kidney cortex, bone marrow) and tumor tissues (SLC) were measured during a daytime period (3-9 HALO) and a nighttime period (15-21 HALO) by the hydrogen clearance technique. Rats were subjected to an artificial light-dark cycle with light from 7 A.M. to 7 P.M. In all normal tissues, there were no significant differences between average tissue blood flows in 2 different time zones, while tumor tissue blood flow increased significantly in the nighttime. Based on this functional characteristic of tumor microcirculation, anti-tumor effects were compared between a group in which ADM was administered at 4 HALO and a group in which it was administered at 16 HALO. The therapeutic effect of ADM on rats administered at 16 HALO was significantly greater, particularly in large tumors, than that on rats administered at 4 HALO. The main reason for this therapeutic improvement may be due to the selective increase in delivery of anti-cancer drugs to tumor tissues brought about by a circadian increase in tumor tissue blood flow.

The effect of a herbicide--sodium salt of 2,4-dichlorophenoxyacetic acid on guerin carcinoma

The effect of sodium salt of 2,4-dichlorophenoxyacetic acid, being an active component of herbicide "PIELIK", upon the development of Guerin carcinoma implanted in male Wistar rats, was studied. 192 animals were divided in to 6 equal groups: I-animals which obtained physiological salt solution; II-rats exposed to the herbicide in postlactational period; III-animals with Guerin carcinoma, non exposed to the herbicide; IV- rats exposed to the herbicide in postlactational period+Guerin carcinoma; V-animals exposed to the herbicide from prenatal period to the end of an experiment, without Guerin carcinoma; VI-the same as in V group, but with Guerin carcinoma. The effect of the herbicide on tumor growth dynamism (diameters and mass), degree of tumour malignancy (metastases to lymph nodes), animals survival time and morfological changes in the primary tumour and in metastases was evaluated. Basing of the results obtained, it was stated that this herbicide accelerates the development of Guerin carcinoma and reduces the survival time in the rats exposed to it in the prenatal and postnatal period. However, it does not significantly influence the growth of the carcinoma in the rats exposed only in the postlactational period.

The Rac and Rho pathways as a source of drug targets for Ras-mediated malignancies

The small GTP-binding proteins Rac and Rho are key control elements in the reorganization of the actin cytoskeleton induced by growth factors or oncogenic Ras. It has been established recently that Rac and Rho also play a crucial role in Ras transformation. This suggests that the elements in the pathways regulated by Rac and Rho are valid targets for cancer therapy. Several important components of those signaling pathways have now have identified.

Studies on the mechanism of sulofenur and LY295501 toxicity: effect on the regulation of cytosolic calcium in relation to cytotoxicity in normal and tumorigenic rat kidney cell lines

Treatment of NRK-52E (normal) and H/1.2-NRK-52E (Harvey-ras transfected NRK-52E) rat kidney epithelial-like cells with two Eli Lilly antitumor compounds, sulofenur and LY295501 (15.6 microM-1000 microM) resulted in concentration- and time-dependent cell killing. Cytosolic Ca2+ became elevated in both cell lines in the presence of extracellular Ca2+ but only minimally in its absence. Both drugs were more toxic to the tumorigenic cells than to the normal cells, but LY295501 was significantly more toxic to both cells. The similarity in toxic response by both cell lines suggests a similar mechanism of toxic action for both drugs. Since LY295501 is highly toxic to tumorigenic cells but has a manageable dose-limiting toxicity it shows excellent potential for use in chemotherapy.

Experimental models for carcinogenesis in the house musk shrew, Suncus murinus, Insectivora

Animal carcinogenicity studies have mainly been performed on rodents. From the phylogenetic point of view, animals closer to humans must be included in these studies. Insectivora are considered to be the most primitive placental mammals and much closer to the early primates than rodents. Among the insectivora, the house musk shrew (Suncus murinus, family Soracidae), has been bred under laboratory condition. This animal is small having a short life span, and a comparatively low incidence of spontaneous tumor provides a useful animal model for tumor induction studies. We have examined the carcinogenicity of several chemicals known to produce tumors in rodents and found shrews, in general, to be sensitive to these chemicals but often showed different targets compared to rodents, and some chemicals tested were demonstrated not to be carcinogenic. Here we describe the carcinogenic studies performed in our laboratory and review other works including the occurrence of spontaneous tumors in shrews. Shrew carcinogenesis may fill up the gap of knowledge existing between the rodents and human beings.

Lack of general correlation between interstitial fluid pressure and oxygen partial pressure in solid tumors

Several studies have shown a decrease in blood perfusion and oxygen partial pressure (pO2), and an increase in interstitial fluid pressure (IFP) with increasing tumor size. However, it is not evident if the elevated IFP is a key parameter responsible for the poor perfusion and oxygenation of solid tumors. To this end, IFP and pO2 were measured in nine human tumor xenografts in immunodeficient mice at a fixed tumor size (approximately 250 mm3). IFP and pO2 were also measured as a function of tumor volume in one human colon adenocarcinoma (LS174T) and in one human glioblastoma (HGL-9). In LS174T tumors IFP did not vary with size (P < .07); however, median pO2 decreased from approximately 35 mm Hg in 100-mm3 tumors to approximately 15 mm Hg in tumors of approximately 500 mm3 (P < 0.001). In HGL-9 tumors an inverse correlation between IFP and pO2 was found; IFP increased (P < 0.001) and pO2 decreased (P < 0.001) with increasing tumor size. At a fixed tumor size of 250 mm3 no correlation was found between mean IFP and median pO2 (P < 0.5) or between the mean IFP and the hypoxic fraction (pO2 < 2.5 mm Hg) (P < 0.7) in the nine tumors studied. The absence of a general relationship between IFP and pO2 could result in part from differences in vascular resistance between tumors. For example, a high geometric resistance to blood flow on the arterial side will lead to a low IFP and blood flow, whereas an elevation of the venous resistance will reduce blood flow and increase IFP.(ABSTRACT TRUNCATED AT 250 WORDS)

Problems involved in temperature measurements using EIT

In cancer therapy, hyperthermic treatment by microwaves requires a non-invasive and reliable method for measuring the temperature distribution inside the body. EIT seems to be able to evaluate the temperature-dependent tissue impedance for delivering the temperature profile in a cross-section of the body. Assuming a temperature coefficient of the resistivity of an electrolyte of about -2% degrees C-1 and temperature measurement to an accuracy of 0.5 degree C, the error in impedance measurement must be lower than 1%. Irrespective of the accuracy of the tomographic measuring system itself, a problem arises from the fact that the fluid content in the tissue as well as the fluid distribution between the extracellular and the intracellular compartment change with temperature. Measurements of the impedance spectra of skeletal muscle and tumours of rats during hyperthermic treatment deliver very different temperature coefficients of the resistivity from -1.3% degree C-1 to -3% degree C-1, thus questioning the feasibility of the EIT as a temperature measuring method. However, changes in the tissue caused by hyperthermia (e.g., fluid shifts, development of oedema and membrane disintegration) can be detected.

Age-related neoplasia in a lifetime study of ad libitum-fed and food-restricted B6C3F1 mice

Longevity, body weight, and age-specific neoplasia were determined in 1,064 B6C3F1 mice as part of a coordinated study of food restriction (FR). Restricted animals were offered 60% of the diet consumed by the ad libitum (AL) group. Longevity data were derived from a set of 56 animals of each sex from each diet group, which were examined whenever dead or moribund. For cross-sectional data, a parallel set of 210 animals were sacrificed in groups of 12-15 at 6-mo intervals. Lifetime body weight was reduced in the FR mice approximately proportional to restriction (i.e., 40%). Food restriction increased the age at 50% survival (median) by 36% in both sexes and increased the maximal lifespan (mean age of oldest 10%) by 21.5% in males and by 32.5% in females. In 56 males of the longevity groups, there were 89 neoplasms in the AL subgroup versus 53 in FR; 56 AL females had 100, versus 58 in 55 FR females. Increase in lifespan of the restricted animals was achieved primarily by decrease in incidence and delay of onset of fatal tumors, of which lymphoma was the most prominent. This report catalogs all of the neoplasms (1,103) observed in longevity and cross-sectional groups, by diet, sex, and age. These data add to the existing knowledge base needed for future studies of dietary restriction and aging as well to evaluate nutrition of animals used in bioassays.

Inhibition of experimental cancer cachexia by anti-cytokine and anti-cytokine-receptor therapy

Cachexia consists of a constellation of metabolic changes that occur in cancer patients, including the reduction of muscle and fat tissue, asthenia, anorexia, hypoglycemia and hypercalcemia. These syndromes complicate therapeutic intervention and decrease the quality of life of the patient. This review discusses the involvement of cytokines in cancer cachexia and describes the contribution of IL-6 and other cytokines to the wasting of C-26-bearing mice. The neutralization of IL-6 by antibody, or IL-6 receptor antagonism by suramin, significantly reduce the severity of key parameters of cachexia. The participation of several other factors (PGE2, IL-1, IL-10 and TNF-alpha) in the cellular communication between the C-26 tumor cell and tumor-infiltrating macrophages is also described.

Perfusion changes in the RIF-1 tumour and normal tissues after carbogen and nicotinamide, individually and combined

The strategy of combining carbogen breathing and nicotinamide to overcome chronic and acute hypoxia respectively is being evaluated clinically. The effects of both agents individually and in combination on relative perfusion of 400-700 mm3 RIF-1 tumours and normal tissues were measured by 86Rb extraction. Carbogen breathing alone for 6 min increased relative tumour perfusion by 50-70% compared with control at flow rates of 50 to 200 ml min-1, but the effect was lost at 300 ml min-1. All flow rates also produced similar increases in relative perfusion of lung, of between 36% and 58%, and smaller increases in skin, of between 20% and 34%. The minimum breathing time at 150 ml min-1 to produce a significant increase in relative tumour perfusion was 4.5 min, and the effect was maintained up to 9 min. Nicotinamide alone at 1000 mg kg-1 60 min before assay did not alter relative tumour perfusion. Comparing the combination of nicotinamide with 6 min carbogen breathing at 150 ml min-1 with carbogen breathing alone showed no difference in relative tumour perfusion; increases were of 36% and 42% respectively. Nicotinamide-induced alterations in microcirculation associated with reduction of acute hypoxia have therefore not been detected by 86Rb extraction. The perfusion-enhancing effect of carbogen in this tumour is probably an important component of its radiosensitising ability, in addition to its known ability to increase the oxygen-carrying capacity of the blood, and should be taken into consideration in clinical studies.

Membrane ruffling of cancer cells: a parameter of tumour cell motility and invasion

Membrane ruffling of cells is a dynamic and rapid movement with irregular fluctuation of protrusion and withdrawal of the margin of the cell surface membrane. The ruffling can be seen in two major types: ruffling around the periphery and leading edge of an adherent cell and circular ruffling on the dorsal surface. A number of cytokines have been shown to increase membrane ruffling, and methods of decreasing ruffling are now being reported. Membrane ruffling has been shown to relate to metastatic status in tumour cells obtained by fine needle aspiration, while in-vitro and animal tumour studies show it to be an indicator of tumour cell motility and metastatic potential. If these latter findings can be confirmed as applicable to clinical tumours as well, the establishment of such a relationship may be useful in predicting invasion and metastasis in human tumours, as well as providing a model to study methods of inhibiting or reversing metastatic potential.

Dynamic scaling in the dielectric response of excised EMT-6 tumours undergoing hyperthermia

A constant-phase-angle response (CPA) has been identified in the dielectric spectrum of EMT-6 tissues undergoing hyperthermia. A dynamic scaling relationship between the static permittivity and conductivity using the CPA frequency exponent n has been shown to occur during the destructive phase of hyperthermia. This behaviour has been attributed to the self-similar structure of the internal membrane compartments of the cells and described by means of a hierarchical circuit model. In this way the CPA exponent has been related to the convolution of internal membrane surfaces lying in between the mitochondria and the outer cell wall. The dynamic scaling is assigned to the progressive destruction of cell membranes in sequence from the outside inwards.

Physiologic mechanisms of therapeutic resistance. Blood flow and hypoxia

The tools now are available to characterize oxygenation/hypoxia in the clinic. The clinical investigations conducted thus far have shown that significant regions of hypoxia exist in solid tumors in patients. Of the various strategies developed in the laboratory for reducing (or eliminating) hypoxia in tumors, the intravenous administration of nontoxic oxygen-carrying materials is probably the most generally applicable in a clinical setting.

Anti-tumor action of dietary restriction is lesion-dependent in male Fischer 344 rats

The effects of dietary restriction (DR) on spontaneous oncogenesis in male Fischer 344 rats were analyzed. Previously reported analyses of studies carried out in our laboratory demonstrated that DR reduces the incidence and delays the onset, but not the progression, of leukemia in male F344 rats. In this report, the influence of DR on pituitary tumors, adrenal pheochromocytoma, pancreatic islet cell tumors, and interstitial cell tumors of the testis was analyzed. DR reduced the relative incidence (relative onset rates) and delayed the onset of the four tumors. DR also retarded the progression (duration from onset to death) of pituitary tumors and pheochromocytoma. DR has delayed the onset of all tumors of the male F344 rat so far analyzed, but its effect on tumor progression appears to be lesion-dependent.

Matrix nonenzymatic glycosylation leads to altered cellular phenotype and intracellular tyrosine phosphorylation

The effect of matrix nonenzymatic glycosylation on signal transduction and the cellular phenotype was examined. Human microvascular endothelial cells were plated on control or glycated basement membrane-like matrix. Cells exhibited a decrease in their ability to adhere and spread on modified matrix. The pattern of intracellular tyrosine phosphorylation was examined by Western Immunoblotting; a band with 65 kDa mobility exhibited a marked reduction of tyrosine phosphorylation in cells adherent to modified matrix. Immunoprecipitation experiments provided evidence that this band is paxillin, a member of focal adhesion proteins. Immunoprecipitation with antibodies against focal adhesion kinase (pp125FAK), the enzyme that is thought to regulate paxillin tyrosine phosphorylation, also demonstrated a reduction in tyrosine phosphorylation of pp125FAK. To confirm these biochemical data, adherent cells were examined for the distribution of paxillin, using immunofluorescence microscopy; paxillin was seen in focal points peripherally located in cells on normal matrix, but lacked this pattern in cells on modified matrix. Actin filaments were also disorganized in cells plated on modified matrix. These data suggest that matrix nonenzymatic glycosylation can interfere with and potentially alter cellular phenotype and intracellular signaling.

Nitric oxide in inflammation and immunity

Few discoveries have had as comprehensive an impact on the understanding of cellular physiology as the production of nitric oxide (NO.) from the terminal guanido amino group of L-arginine through nitric oxide synthases. The sheer volume of data presently coming forth on the physiology and pathophysiology of NO. ensures that any attempt at a comprehensive review will result in a simple snapshot of the event, soon to be outdated.

Survival factors, intracellular signal transduction, and the activation of endonucleases in apoptosis

Cell survival is normally mediated by factors in the extracellular environment, whereas genetic changes that constitutively activate intracellular survival pathways often occur in cancer. It is suggested that a Ras/Raf/MAP kinase-dependent pathway is critical for cell survival. Apoptosis results from loss of these survival factors or deregulation of survival pathways. If protein kinase cascades mediate survival, then it is likely that phosphatases mediate apoptosis. Potential targets for dephosphorylation include regulators of ion homeostasis as these have been implicated in the regulation of endonucleases associated with apoptosis. Survival factors also modulate anticancer drug response and understanding these pathways may improve therapy.

Negative growth control of HeLa cells by connexin genes: connexin species specificity

In order to examine whether different connexin gene species exert different degrees of tumor-suppressing activity, we characterized growth characteristics of a gap junction-deficient human cancer cell line, HeLa cells, before and after transfection with cDNA for three different connexins, connexin (cx) 26, cx 40, and cx 43. All transfected cell lines (3 clones transfected with the cx 26 gene, 2 clones with cx 40, and 1 with cx 43) showed establishment of gap junctional intercellular communication (GJIC). Two of the cx 26-transfected clones showed significantly slower growth compared with the parental HeLa cells. When transfectants were grown in soft agar, the three cx 26-transfected clones grew much less than the other transfectants and parent HeLa cells. When injected into nude mice, the two cx 26 clones which exhibited the highest amount of cx 26 transcript induced almost no tumors, whereas other transfectants, including the cx 26 clone which exhibited the lowest amount of cx 26 transcript, were tumorigenic. Among transfectants of various connexin genes, there was no good inverse correlation between their GJIC and tumorigenicity. GJIC levels were significantly higher in tumors induced in nude mice by clone cx 26 A and E transfectants. These results suggest that all of the connexin genes examined could induce recovery of GJIC of HeLa cells, but only the cx 26 gene exerts strong negative growth control on HeLa cells; thus, this connexin gene may have different functions from other connexin genes.

The effect of body weight on tumor incidence and carcinogenicity testing in B6C3F1 mice and F344 rats

Associations between animal body weights and tumor incidence were examined using individual control animal data from 55 mouse and 53 rat studies conducted by the National Toxicology Program. Several statistically significant associations were found, the strongest of which were positive relationships between body weight and risk of liver tumors in both sexes of mice, pituitary gland tumors in both sexes of rats, and mammary gland tumors in female rats. The most compelling evidence that these relationships were causal in nature was the replication of the correlations across individual experiments. In addition, significant correlations between tumor occurrence and body weights occurred in animals as young as 9 weeks of age. Logistic regression models relating 12-month body weight to tumor risk were developed for the strongest relationships, and utilized in the reanalysis of tumor data from two National Toxicology Program studies with treatment-related decreases in body weight. A simulation study based on the logistic regression models indicated that statistical power to detect a treatment-related increase in tumor incidence can be seriously diminished when mean body weight in treated animals is depressed by as little as 10%. Conversely, when mean body weight in control animals is 10% lower than that of treated animals, false positive rates can increase to 20-30%. The severity of the effects of such commonly observed treatment-related disparities in body weight suggests that alternative data analysis methods or experimental designs should be considered to address this potential problem in carcinogenicity testing.

Consequences of angiogenesis for tumor progression, metastasis and cancer therapy

The growth of solid tumors to a clinically relevant size is dependent upon an adequate blood supply. This is achieved by the process of tumor stroma generation where the formation of new capillaries is a central event. Progressive recruitment of blood vessels to the tumor site and reciprocal support of tumor expansion by the resulting neovasculature are thought to result in a self-perpetuating loop helping to drive the growth of solid tumors. The development of new vasculature also allows an 'evacuation route' for metastatically-competent tumor cells, enabling them to depart from the primary site and colonize initially unaffected organs. Several molecular and cellular mechanisms have been identified by which tumor parenchyma may exert its angiogenic effect on host endothelial cells. As a result of this paracrine influence, tumor-associated endothelial cells acquire an 'immature' phenotype manifested by rapid proliferation, migration, release of proteases and expression of cytokines, endothelial-specific tyrosine kinases (e.g. flk-1, tek and others) as well as numerous other molecular alterations. Consequently a network of structurally and functionally aberrant blood vessels is formed within the tumor mass. There is also evidence that endothelial cells themselves, and likewise other stromal cells, may act reciprocally to alter the behavior of adjacent tumor cells in a paracrine or cell contact mediated fashion. For example, production of interleukin 6(IL-6) by endothelial cells may have a differential effect on human melanoma cells expressing different degrees of aggressiveness. In this manner endothelial derived cytokines could conceivably contribute to tumor progression by suppressing the growth of the less aggressive tumor cells and promoting dominance of their malignant counterparts in 'strategic' perivascular zones. Distinct biological features expressed by tumor-associated vasculature may serve as potential prognostic markers of disease progression as well as novel targets for therapeutic intervention.

Decreases in macrophage mediated antitumor activity with aging

We have demonstrated that immunotherapy of young (6-10 weeks old), and aged, (greater than 24 months old), tumor bearing mice with biological response modifiers enhanced survival and inhibited tumor growth, while treatment of aged mice had little or no effect. We hypothesized that the antitumor activity in young mice was principally mediated by activated macrophages (M phi) and predicted that the change in aged mice was caused by an intrinsic M phi defect which develops with advancing age. To directly test our hypothesis, we examined the antitumor activity of resident peritoneal M phi, purified and activated in vitro with IFN gamma plus LPS. Paralleling the results seen in vivo, M phi from aged mice exhibited reduced antitumor activity in comparison with M phi from younger mice. Moreover, there was reduced capacity of in vitro activated M phi from aged mice to produce TNF, IL-1 and nitric oxide, which are critical monokines and effector molecules that have been established to either directly inhibit tumor growth or cause tumor cell destruction. These studies establish that peritoneal M phi from aged mice have an intrinsic defect which prevents them from fully expressing their antitumor potential.

Stimulation and regulation of tumor cell motility in invasion and metastasis

In this review, the role of extracellular factors in the stimulation and regulation of tumor cell motility are discussed. Tumor cells respond in a motile fashion to a variety of external ligands including autocrine motility factors, growth factors, and components of the extracellular matrix. Since tumor cell motility is a necessary component of tumor invasion and metastasis, we speculate that these protein factors could play important regulatory roles in tumor motility at different stages of the metastatic cascade.

Inhibition of the growth of a murine and various human tumor cell lines in culture and in mice by mixture of certain substances of the circulatory system

It is well documented that despite global abnormalities of the immune system in AIDS and other immune deficiency diseases or in immunosuppressed patients, the incidence of only a few kinds of tumor increases, and that the degree of immunosuppression seems not to be a critical factor in the development of even these tumors. The fact that tumors do not develop in the majority of population during their lifetime, despite the ineffectiveness of the known immune system against the majority of tumors, can only be explained by hypothesizing that the living system has an additional defense mechanism against tumors. On the bases of literary data, it can be assumed that the effective agents of this defense mechanism are certain substances of the circulatory system. We proved this hypothesis by being able to select thirteen substances of the circulatory system from 71 compounds tested, using the synergistic tumor cell-killing effect as criteria. The mixture containing the thirteen substances (L-tryptophan, L-tyrosine, L-methionine, L(-)-malate, L-ascorbate, L-arginine, L-phenylalanine, L-histidine, 2-deoxy-D-ribose, d-biotin, pyridoxine, adenine and riboflavin) had a cytotoxic effect against Sp2/0-Ag14 mouse and K562, HEp-2, HeLa and Caco-2 human tumor cell lines in well-controlled conditions, but it was not cytotoxic against Vero normal cell line. The mixture of the above substances increased significantly the survival time of mice (T/C% 148.1) injected i.p. with Sp2/0-Ag14 mouse myeloma cells by killing more than 2 logs (99%) of the cells. Approximately the same 2 logs cell kill was found counting the Sp2/0-Ag14 cells in the ascitic fluid of control and treated animals after finishing treatment. The above mixture slowed down the growth of HeLa solid tumor significantly (T/C%, the least value 35.7). The weight loss of control and treated group during treatment did not differ significantly.

Radiation-induced DNA damage in tumors and normal tissues. II. Influence of dose, residual DNA damage and physiological factors in oxygenated cells

Detection and quantification of hypoxic cells in solid tumors is important for many experimental and clinical situations. Several laboratories, including ours, have suggested that assays which measure radiation-induced DNA strand breaks and DNA-protein crosslinks (DPCs) might be used to detect or quantify hypoxic cells in tumors and normal tissues. Recently, we demonstrated the feasibility of using an alkaline elution assay that measures strand breaks and DPCs to detect and/or quantify hypoxic cells in tissues. For this approach to be valid, DPCs must not be formed to any great extent in irradiated oxygenated cells, and the formation and repair of strand breaks and DPCs in oxygenated cells must not be modified appreciably by physiological factors (e.g. temperature, pH and nutrient depletion) that are often found in solid tumors. To address these issues, two sets of experiments were performed. In one set of experiments, oxygenated 9L cells in tissue culture, subcutaneous 9L tumors and rat cerebella were irradiated with doses of 15 or 50 Gy and allowed to repair until the residual strand break damage was low enough to detect DPCs. In another set of experiments, oxygenated exponentially growing or plateau-phase 9L cells in tissue culture were irradiated with a dose of 15 Gy at 37 or 20 degrees C, while the cells were maintained at a pH of either 6.6 or 7.3. DNA-protein crosslinks were formed in oxygenated cells about 100 times less efficiently than in hypoxic cells. In addition, temperature, pH, nutrient depletion and growth phase did not appreciably alter the formation and repair of strand breaks or the formation of DPCs in oxygenated 9L cells. These results support the use of this DNA damage assay for the detection and quantification of hypoxic cells in solid tumors.