Effects of stress on tumor growth and metastasis in mice bearing Lewis lung carcinoma

'Invisible actors'-How poor methodology reporting compromises mouse models of oncology: A cross-sectional survey

The laboratory mouse is a key player in preclinical oncology research. However, emphasis of techniques reporting at the expense of critical animal-related detail compromises research integrity, animal welfare, and, ultimately, the translation potential of mouse-based oncology models. To evaluate current reporting practices, we performed a cross-sectional survey of 400 preclinical oncology studies using mouse solid-tumour models. Articles published in 2020 were selected from 20 journals that specifically endorsed the ARRIVE (Animal Research: Reporting of In Vivo Experiments) preclinical reporting guidelines. We assessed reporting compliance for 22 items in five domains: ethical oversight assurance, animal signalment, husbandry, welfare, and euthanasia. Data were analysed using hierarchical generalised random-intercept models, clustered on journal. Overall, reporting of animal-related items was poor. Median compliance over all categories was 23%. There was little or no association between extent of reporting compliance and journal or journal impact factor. Age, sex, and source were reported most frequently, but verifiable strain information was reported for <10% of studies. Animal husbandry, housing environment, and welfare items were reported by <5% of studies. Fewer than one in four studies reported analgesia use, humane endpoints, or an identifiable method of euthanasia. Of concern was the poor documentation of ethical oversight information. Fewer than one in four provided verifiable approval information, and almost one in ten reported no information, or information that was demonstrably false. Mice are the "invisible actors" in preclinical oncology research. In spite of widespread endorsement of reporting guidelines, adherence to reporting guidelines on the part of authors is poor and journals fail to enforce guideline reporting standards. In particular, the inadequate reporting of key animal-related items severely restricts the utility and translation potential of mouse models, and results in research waste. Both investigators and journals have the ethical responsibility to ensure animals are not wasted in uninformative research.

Welfare Assessment, End-Point Refinement and the Effects of Non-Aversive Handling in C57BL/6 Mice with Lewis Lung Cancer

Cancer-bearing mice are at risk of developing anxiety, pain, or malaise. These conditions may not only harm welfare but could also undermine data quality and translational validity in studies to develop therapeutic interventions. We aimed to establish whether, or at what point mice developing lung cancer show these symptoms, what measures can best detect their onset, and if data quality and animal welfare can be enhanced by using non-aversive handling (NAH). Welfare was monitored using various daily methods. At the beginning and end of the study, we also scored behaviour for general welfare evaluation, recorded nociceptive thresholds, and applied the mouse grimace scale (MGS). Cancer caused a decline in daily welfare parameters (body weight, and food and water consumption) beginning at around 4 days prior to euthanasia. As cancer progressed, rearing and walking declined to a greater extent in cancer-bearing versus control mice, while grooming, inactive periods, and MGS scores increased. A decline in nest building capability and food consumption provided a particularly effective means of detecting deteriorating welfare. These changes suggested a welfare problem arose as cancer developed, so similar studies would benefit from refinement, with mice being removed from the study at least 4 days earlier. However, the problem of highly varied tumour growth made it difficult to determine this time-point accurately. There were no detectable beneficial effects of NAH on either data quality or in terms of enhanced welfare.

Toward prediction of abscopal effect in radioimmunotherapy: Pre-clinical investigation

PURPOSE

Immunotherapy (IT) and radiotherapy (RT) can act synergistically, enhancing antitumor response beyond what either treatment can achieve separately. Anecdotal reports suggest that these results are in part due to the induction of an abscopal effect on non-irradiated lesions. Systematic data on incidence of the abscopal effect are scarce, while the existence and the identification of predictive signatures or this phenomenon are lacking. The purpose of this pre-clinical investigational work is to shed more light on the subject by identifying several imaging features and blood counts, which can be utilized to build a predictive binary logistic model.

MATERIALS AND METHODS

This proof-of-principle study was performed on Lewis Lung Carcinoma in a syngeneic, subcutaneous murine model. Nineteen mice were used: four as control and the rest were subjected to combined RT plus IT regimen. Tumors were implanted on both flanks and after reaching volume of ~200 mm3 the animals were CT and MRI imaged and blood was collected. Quantitative imaging features (radiomics) were extracted for both flanks. Subsequently, the treated animals received radiation (only to the right flank) in three 8 Gy fractions followed by PD-1 inhibitor administrations. Tumor volumes were followed and animals exhibiting identical of better tumor growth delay on the non-irradiated (left) flank as compared to the irradiated flank were identified as experiencing an abscopal effect. Binary logistic regression analysis was performed to create models for CT and MRI radiomics and blood counts, which are predictive of the abscopal effect.

RESULTS

Four of the treated animals experienced an abscopal effect. Three CT and two MRI radiomics features together with the pre-treatment neutrophil-to-lymphocyte (NLR) ratio correlated with the abscopal effect. Predictive models were created by combining the radiomics with NLR. ROC analyses indicated that the CT model had AUC of 0.846, while the MRI model had AUC of 0.946.

CONCLUSIONS

The combination of CT and MRI radiomics with blood counts resulted in models with AUCs of 1 on the modeling dataset. Application of the models to the validation dataset exhibited AUCs above 0.84, indicating very good predictive power of the combination between quantitative imaging and blood counts.

Heterogeneity of circulating tumor cell dissemination and lung metastases in a subcutaneous Lewis lung carcinoma model

Subcutaneous (s.c.) tumor models are widely used in pre-clinical cancer metastasis research. Despite this, the dynamics and natural progression of circulating tumor cells (CTCs) and CTC clusters (CTCCs) in peripheral blood are poorly understood in these models. In this work, we used a new technique called 'diffuse in vivo flow cytometry' (DiFC) to study CTC and CTCC dissemination in an s.c. Lewis lung carcinoma (LLC) model in mice. Tumors were grown in the rear flank and we performed DiFC up to 31 days after inoculation. At the study endpoint, lungs were excised and bioluminescence imaging (BLI) was performed to determine the extent of lung metastases. We also used fluorescence macro-cryotome imaging to visualize infiltration and growth of the primary tumor. DiFC revealed significant heterogeneity in CTC and CTCC numbers amongst all mice studied, despite using clonally identical LLC cells and tumor placement. Maximum DiFC count rates corresponded to 0.1 to 14 CTCs per mL of peripheral blood. In general, CTC numbers did not necessarily increase monotonically over time and were poorly correlated with tumor volume. However, there was a good correlation between CTC and CTCC numbers in peripheral blood and lung metastases. We attribute the differences in CTC numbers primarily due to growth patterns of the primary tumor. This study is one of the few reports of CTC shedding dynamics in sub-cutaneous metastasis models and underscores the value of in vivo methods for continuous, non-invasive CTC monitoring.

Breast cancer: Is grief a risk factor?

Cancer is characterized by the disordered growth of cells that have high capacity of invasion to the tissues and organs. One of the types of tumour that has national incidence and high mortality is breast cancer. Studies show that in addition to hereditary factors, lifestyle and environmental factors, there are factors related to emotional distress (mourning), which interfere with the development of breast cancer. Thus, it is necessary to investigate if the experience of mourning can trigger the appearance of the tumour. For this, an integrative review was performed to verify the existence of the relationship between mourning and development of breast cancer, which presented contradictory results. Methodological errors and lack of access to important information, such as alcohol and tobacco use, were pointed out as the main causes of the contradiction found. A possible mechanism involving cortisol release has been proposed, but more research is needed to make it clear whether the association between mourning and breast cancer really exists, and by what path.

The impact of the opioids fentanyl and morphine on nociception and bone destruction in a murine model of bone cancer pain

Chronic pain resulting from metastasis into skeleton of certain neoplastic diseases remains poorly understood and relatively resistant to analgesic treatment. Opioids are the principal axis in drug therapy for this type of pain, especially at the end stage of cancer. Our aim was to examine whether, fentanyl as well as morphine, two potent analgesic opioids commonly used to treat cancer pain, would inhibit pain and bone lesion-related responses in a murine model of bone cancer pain. Repeated administration of equianalgesic doses of fentanyl (0.16 mg/kg s.c. once a day) and morphine (20 mg/kg s.c. once a day) initiated at day 1 (prophylactic treatment) or at day 7 (curative treatment) after tumor cell inoculation in the femoral cavity consistently decreased bone pain symptoms and tumor growth-induced bone destruction (micro-CT bone structure parameters). Both fentanyl and morphine treatments resulted in clear antinociceptive properties as well as reductions in cancer cell-induced bone lesions. The present results demonstrate that fentanyl, and to some lesser degree morphine, has potential benefits in the treatment and development of bone cancer pain. As such, chronic administration of high doses of certain opioids like fentanyl may have clinical utility in the management of bone cancer pain.

Anxiety stress and nociceptive responses in mice

Nociception in laboratory animals appears to be influenced by physical or emotional stressors. Nevertheless, the reported data are not univocal. Discrepancies seem to be caused by some kind of stress model and/or by the timing of stressor application. The aim of the present work is to study the influence of chronic application of a well-controlled and defined anxiety stress paradigm (rotational stress) on the behavioral formalin pain responses in mice maintained in a low-stress environment. The results indicate that emotional chronic stress increases specific pain responses in the late inflammatory phase and, correspondingly, decreases self-grooming. Locomotor activity appears influenced by pain presence only. The hormonal and neural mechanisms that could be involved in the observed nonspecific and specific nociceptive responses to stress are discussed.

Intermittent hepatic ischemia-reperfusion minimizes liver metastasis in rats

BACKGROUND

Surgical stresses, including hepatic ischemia-reperfusion (I/R), promote cancer growth and metastasis. We have reported that continuous hepatic I/R increases liver damage and promoted liver metastasis from colon cancer, whereas intermittent I/R causes less liver damage. We therefore examined whether intermittent I/R could reduce liver metastasis in a rat model.

MATERIALS AND METHODS

Adult male Fischer rats was divided between three groups: group A (control), which received laparotomy for 120 min with no liver ischemia; group B (continuous I/R), which received 60 min of 70% partial liver ischemia followed by 60 min of reperfusion; and group C (intermittent I/R), which received 15 min of 70% ischemia and 15 min of reperfusion, repeated four times. Just before closing the abdomen, all animals were inoculated intrasplenically with rat colon adenocarcinoma cells (RCN-H4). Tumor nodules on the liver surface were counted 3 weeks later. In addition, expression of E-selectin mRNA in liver was examined at 1, 3, and 6 h after completing I/R by a reverse transcription-polymerase chain reaction.

RESULTS

Continuous I/R (B) greatly promoted liver metastasis in both ischemic and nonischemic liver lobes, whereas intermittent I/R (C) showed significantly fewer metastasis than group B in both lobes. Significantly less E-selectin mRNA was expressed in group C than in group B.

CONCLUSIONS

Intermittent I/R limits expression of E-selectin mRNA and liver metastasis. Intermittent hepatic I/R is less stressful than continuous I/R, minimizing liver metastasis by colon cancer cells through avoidance of E-selectin up-regulation.

Seasonal dependency of the effects of rotational stress and cyclophosphamide in mice bearing lewis lung carcinoma

The antitumor effects of cyclophosphamide were previously shown to be markedly reduced by the application of restraint stress in mice bearing Lewis lung carcinoma. The aim of this work was to determine the effects of rotational stress on the antitumor action of cyclophosphamide in the same animal-tumor system. Since the effects of rotational stress on metastasis were found to display a circannual rhythm, with a maximum in summer and a minimum in winter, the experiments were performed in June and February. Groups of 10 young female mice were kept under low stress housing conditions, with a 12-12 h light/dark cycle, starting 2 weeks before and during each experiment. Rotational stress caused an increase of metastasis volume to 361% of nonstressed controls in June and a decrease to 32.4% in February. In both seasons, the treatment with cyclophosphamide (240 mg/kg/day for 6 days) caused the absence of detectable metastasis at sacrifice in all mice; its combination with rotational stress caused the presence of metastases in similar proportions (6/10 and 10/10 for June vs February, respectively). The survival time of control mice was approximately twice as long in February as in June and was not appreciably modified by rotational stress; cyclophosphamide was similarly active in both seasons (4/10 and 6/10 long-term survivors for June vs February, respectively), and the number of long-term survivors was reduced to 0/10 in both seasons by rotational stress. The survival of the different experimental groups inversely correlated with the number of metastases as determined at sacrifice at the end of treatment and also with the number of CD3(+) and CD4(+) splenic T-lymphocyte subsets. These results do not appear to depend on the disruption of the circadian organization of the mice by rotational stress or by seasonal differences in cyclophosphamide activity. On the other hand, they can be interpreted assuming that cyclophosphamide reduces tumor metastasis and that T-lymphocyte-mediated immune responses of the host, amenable to modulation by stress and displaying seasonal differences uncoupled from circadian rhythms, further contribute to the tumor inhibitory effects of the drug. The observed differences in tumor metastasis caused by rotational stress and survival time in two different seasons, and the marked attenuation of cyclophosphamide antitumor action by rotational stress, appear of interest for their experimental and clinical implications.

Mental state as a possible independent prognostic variable for survival in patients with advanced lung carcinoma

BACKGROUND

Although psychologic factors have been reported to influence the progression of cancer, this theory remains controversial. A prospective study of patients with advanced lung carcinoma was performed to explore the influence of the patient's mental state on survival.

METHODS

The patient's mental state was assessed with the Tokyo University Egogram. In a preliminary study, the egograms of long-term survivors (survival > 3 years) with TNM Stage IIIB or Stage IV lung carcinoma were compared with the egograms of consecutive, newly diagnosed lung carcinoma patients (controls). Next, in a prospective study, 123 patients with nonsmall cell lung carcinoma and 56 patients with small cell lung carcinoma (Stage IIIB or Stage IV; Eastern Cooperative Oncology Group performance status of 0 or 1) completed the egogram. Based on the results of the preliminary study, the subjects in the prospective study were divided into Group A (Free Child [FC] >or= 50th percentile and Adapted Child [AC] < 50th percentile) and Group B (FC < 50 percentile or AC >or= 50 percentile). The survival of the two groups was compared. The Cox proportional hazards model was used to determine the joint effect of the patient's mental state and other prognostic factors.

RESULTS

In the preliminary study, the FC score of the long-term survivors was significantly higher and the AC score was significantly lower than those of the controls. In the prospective study, the survival of Group A was significantly longer than that of Group B both in the nonsmall cell lung carcinoma and small cell lung carcinoma patients (P = 0.002 and P = 0.005, respectively, by the log-rank test). Multivariate analysis demonstrated that after adjustment for clinical factors, being in Group A was a significant predictor of survival both in the nonsmall cell and small cell lung carcinoma patients.

CONCLUSIONS

The results of the current study demonstrate that the mental state of the patient as assessed by the egogram may have prognostic significance in patients with advanced lung carcinoma.

Stress and chemotherapy. Combined effects on tumor progression and immunity in animal models

In mice bearing Lewis lung carcinoma, rotational and restraint stress specifically increases the formation of lung metastasis, and restraint stress markedly attenuates the antitumor effects of cyclophosphamide. The aim of this investigation was therefore to examine the effects of restraint stress on tumor metastasis in mice bearing MCa mammary carcinoma, and on the effectiveness of CCNU and DTIC. Restraint stress increases MCa mammary carcinoma metastasis, causes a marked reduction in cyclophosphamide activity, and a minor attenuation of the effects of CCNU and DTIC. The possible occurrence of seasonal factors, observed for the increase by rotational stress of Lewis lung carcinoma metastasis, was also determined for cyclophosphamide effectiveness. The survival time of control mice is longer in February than in June, and is not appreciably modified by rotational stress. The effects of cyclophosphamide are similar in both seasonal periods, and are similarly attenuated by rotational stress. The seasonal effects of rotational stress, and the reduction of the effects of cyclophosphamide caused by rotational stress, are accompanied by corresponding variations in the number of CD3+ and CD4+ splenic T-lymphocyte subsets and in the CD4+/CD8+ ratio, respectively. The reported effects of stress on tumor progression and on the effectiveness of cyclophosphamide thus appear to occur via modulation of immune responses of the host directed against the tumor. These data appear of interest for their experimental implications, and suggest the opportunity to consider the role that the stress during treatment may play in determining the effectiveness of clinical antitumor chemotherapy.

Oncology in neuroimmunomodulation. What progress has been made?

In 1987 in Dubrovnik, Yugoslavia, N.H. Spector named a new discipline: Neuroimmunomodulation. R. Ader called this new discipline psychoneuroimmunomodulation when the major emphysis was on its behavioral aspects. Neuroimmunomodulation (NIM) is devoted to the study of the interactions at different morphologic and functional levels among the immune, nervous, and endocrine systems. In fact, this science is the modern manifestation of an old science: in the words of B.D. Jankovic (1987), "Neuroimmunomodulation is a modern reflection in neurosciences and immunosciences of the ideas and experience of philosophers and ingenious observers of ancient Egypt, Greece, China, India, and other civilizations that the mind is involved in the defense against diseases." Twelve years ago NIM was regarded by many conventional scientists almost as a form of witchcraft. Today it may be the fastest growing area of biomedical science research in the world. Important clinical applications will not be far behind. NIM research has also progressed in the field of oncology research. Topics such as treatment of hormone-dependent cancer with analogues of hypothalamic hormones, the role of opioids and T cells in cancer, stress-cancer-immune connections, the anticancer role of melatonin and cytokines, immunotherapy of cancer, and the role of psychotherapy in cancer patients represent some lines of research that have been or are being investigated by scientists. Some areas remain to be thoroughly investigated such as the influence of physical exercise (sports), music (classical or modern), and/or relaxation techniques (e.g. yoga) on the development of human cancer. This paper reviews the role of NIM in oncology and provides some perspectives for further research and development of clinical applications.

Natural killer cell tumoricidal activity and deterioration of lung tumor metastasis in silicotic mice and stressed silicotic mice

Aim of this study is to explore the role of splenic NK cells in the lung metastasis in the silicotic mice. The number of metastatic foci increased 1.5-fold and 1.8-fold in the silicotic and stressed silicotic mice compared with the control mice. Treatment with an immunomodulator reduced the rate of tumor metastasis in silicotic mice with or without stresses, while their NK cell activity was normalized. Decrease of NK cell activity on the day of tumor inoculation but not on the post-inoculation days seems to be a major factor for predicting the extent of tumor metastasis in the silicotic and stressed silicotic mice.

Time-dependent effects of stressor application on metastasis of tumor cells in the lung and its regulation by an immunomodulator in mice

The effects of the timing of stressor application on transplanted tumor cells and its possible regulation by an immunomodulator was investigated. Male C57 BL/6N mice were subjected to rotational stressor for 7 days relative to tumor cell inoculation: stressor after inoculation of Lewis lung cancer cells, stressor during inoculation and stressor before inoculation. Stressor application and tumor cell inoculation induced transient decreases in body weight, particularly in mice stressed after inoculation. The mice exposed to the stressor during inoculation or before inoculation showed significant increases in the number of metastatic foci relative to control mice. Early administration of an immunomodulator, PSK, significantly attenuated the increase of metastatic foci in stressed mice. The weights of thymus gland and spleen at 14 days after inoculation were similar in the three stressor groups and the control group. Application of the stressor reduced NK cell activity of the normal mice as well as tumor bearing mice. The lowest pre-inoculation NK cell activity was observed in mice stressed for 7 days beginning on the day of inoculation. The NK cell activity decreased in the tumor bearing mice which were stressed at the time of tumor inoculation. Decreased NK cell activity was reversed at day 14 after tumor inoculation. The mice exposed to the stressor after inoculation showed lowest level of NK cell activity relative to mice exposed to the stressor before or during inoculation. The treatment of mice with PSK reduced these changes significantly. The present results suggest that the rotational stress reduces splenic NK cell activity, which may influence the magnitude of tumor metastasis, depending on the time of tumor cell injection. Further, administration of an immunomodulator may counteract the reduction of the NK cell activity.

Melatonin administration in tumor-bearing mice (intact and pinealectomized) in relation to stress, zinc, thymulin and IL-2

Melatonin (MEL) may counteract tumors through a direct oncostatic role. MEL is also an antistress agent with immunoenhancing properties against tumors due to a suppressive role of MEL on corticosterone release. Rotational stress (RS) (spatial disorientation) facilitates metastasis progression in mice. Also, MEL counteracts tumors because of its influence on immune responses via the metabolic zinc pool, which, is reduced in tumors and stress. Zinc is required for normal thymic endocrine activity (i.e. thymulin) and interleukin-2 (IL-2) production. Because in vivo data is still controversial, exogenous MEL treatment (22 days in drinking water) in both intact and pinealectomized (px) mice bearing Lewis lung carcinoma leads to significant decrements of metastasis volume, restoration of the negative crude zinc balance, recovery of thymulin activity and increment of IL-2 exclusively in intact and px tumor bearing mice subjected to RS. Significant inverse correlations are found in both stressed intact and px tumor bearing mice after MEL treatment between zinc and corticosterone (r = 0.78, P < 0.01; r = 0.80, P < 0.01, respectively). Positive correlations between zinc and IL-2 (r = 0.75, P < 0.01; r = 0.73, P < 0.01, respectively) or thymulin (r = 0.75, P < 0.01; r = 0.82, P < 0.01, respectively) are observed in same models of mice. These findings suggest a MEL action to decrease metastasis mediated by a possible interplay between zinc and MEL, via corticosterone, with consequent restoration of thymic efficiency and IL-2 production. MEL as an antistress agent with immunoenhancing properties in cancer deserves further consideration.nuclear factor-kb; POMC, proopiomelanocortin; Px, pinealectomized mice; RIA, radioimmunoassay; RS, rotational stress; SDI, stressed intact mice; SDPx, stressed pinealectomized mice; TNF-alpha, tumor necrosis factor-alpha; ZnFTS, active zinc-bound thymulin; ZnFTS + FTS, total thymulin.

Seasonal effects of rotational stress on Lewis lung carcinoma metastasis and T-lymphocyte subsets in mice

Rotational stress specifically increases the formation of spontaneous lung metastasis in mice bearing Lewis lung carcinoma, without significantly modifying the growth of primary tumor. The increase in metastasis number and volume caused by rotational stress varies in magnitude with a highly significant circannual rhythm; the acrophase approximately coincides with summer solstice. Rotational stress causes a significant reduction in the number of CD3+ and CD4+ T-lymphocyte subsets in summer, whereas in winter the number of CD3+ subset is significantly increased; the CD4+/CD8+ ratio and the number of NK 1.1 antigen positive cells are not significantly modified by rotational stress in both periods considered. The increase in metastasis formation by rotational stress thus appears to negatively correlate with the number of splenic CD3+ and CD4+ T-lymphocyte subsets. This seasonal behavior occurs in spite of the control of light cycle, temperature and humidity in the animal housing, suggesting the existence in the host of an endogenous oscillator with a circannual period. These data indicate the opportunity to consider endogenous rhythms within the host, as well as seasonal factors, in studies on stress and neuroimmunomodulation in experimental oncology.

Restraint stress reduces the antitumor efficacy of cyclophosphamide in tumor-bearing mice

Treatment with the cytotoxic antitumor drug cyclophosphamide is highly effective in mice bearing Lewis lung carcinoma, causing the absence of macroscopically detectable tumors at necroscopy after sacrifice. When the effects of the treatment on survival are determined, a significant increase in survival time and in the proportion of long-term survivors is observed. When restraint stress is further applied, tumors develop in all of the mice treated with cyclophosphamide, and survival time and the fraction of long-term survivors are significantly reduced. Flow cytometry of splenic T-lymphocyte subsets in normal mice indicates a significant decrease in the number of CD3+, CD4+, and CD8+ subsets after treatment with cyclophosphamide and after application of restraint stress; the interaction of the two treatments is significant for CD3+ and marginally significant for CD4+ subsets. The attenuation by restraint stress which was observed for the effects of cyclophosphamide on the presence of tumors at necroscopy and for the survival of the treated mice might thus be interpreted as follows: restraint stress attenuates the immune functions of the host directed toward the weakly immunogenic tumor, an effect which, in the absence of restraint stress, interacts effectively with the cytotoxic action of cyclophosphamide toward tumor cells. The results obtained using this animal model thus indicate that experimental stress reduces the therapeutic efficacy of a cytotoxic antitumor drug; experimental and clinical implications are discussed.

Enhancement of tumor growth under short light/dark cycle in mouse lung

We examined whether a change in daily light/dark cycle affected DNA synthesis and tumor growth in mouse lung. Both CD-1 and A/J mice, which were treated with urethane and maintained under the short light/dark cycle (6 h light, 6 h dark), developed significantly larger sizes of lung tumors than the mice maintained under the standard light/dark cycle (12 h light, 12 h dark), indicating that short and frequent light/dark cycles enhanced tumor growth. When 3H-labeled thymidine was injected and incorporated radioactivity in the lung tissue was measured, two peaks of DNA synthesis in the lung were observed in a day under the short light/dark cycle, and both peaks were during light periods, while only one peak was observed during the dark period under the standard light/dark cycle. Although the level of [3H]thymidine incorporation into the lung tissue in the short light/dark cycle is lower than that in the standard cycle, frequent or unbalanced DNA synthesis may have promoted the growth of lung tumors.

Psychosocial factors in the development and progression of breast cancer

The factors responsible for the genesis of breast cancer remain unclear. Emerging, although controversial, evidence suggests that factors related to life-style, such as dietary fat or alcohol intake, or exposure to various forms of stressors, are associated with mammary tumorigenesis. The possible role of life-style factors in breast cancer is important in light of the fact that mortality to this disease is increasing in most countries and that development of curative therapies for breast cancer has not been forthcoming. Thus, determining the role of life-style factors in the onset and progression of breast cancer, particularly among individuals genetically vulnerable to breast cancer or women with breast cancer in remission, is critical to prevent this disease. We will review the three main hypotheses which have been suggested to link psychosocial factors to the etiology of cancer, emphasizing data obtained through animal models. Interpretation of the existing data suggests that the number of stressful life-events does not predict vulnerability to develop breast cancer or survival from it; a certain level of stress appears to protect from malignancies. The crucial factor affecting tumor growth is the interaction among stress, an individual's personality, and available psychosocial support, and the effect of this interaction on an individual's ability to cope with stress. In addition, other risk factors for breast cancer known to be closely associated with psychosocial factors, namely dietary fat and alcohol consumption, may interact with the effects of psychosocial factors on breast cancer.

Metastasis and neuroendocrine system in stressed mice

The effects of experimental stressors have been examined for their differential effects on primary tumor growth and spontaneous lung metastasis in syngeneic mice bearing the weakly immunogenic tumor Lewis lung carcinoma. The effects caused by the early weaning, physical restraint and foot-shock are in general small, and affected by a high variability. On the contrary, spatial disorientation reproducibly causes a specific increase in tumor metastases. The effects of spatial disorientation are sensitive to the inhibition by treatment with bromocryptine and guanethidine, and particularly by a central and peripheral adrenergic neuron blocking agent reserpine. The use of different lighting conditions and assay of urinary melatonin excretion reveal an association between pineal gland function and effects of spatial disorientation on metastasis.

A non-invasive simple method for measurement of urinary excretion of melatonin in undisturbed mice

Melatonin is a hormone involved in neuroendocrine responses; its plasma concentrations display a circadian pattern which is modified by stress. Studies for determining the effects of stressors on melatonin levels in laboratory animals present the difficulty that the procedures for blood sampling are by themselves potential stressors capable of influencing the levels of the hormone measured. A simple non-stressful method for measuring urinary excretion of melatonin has been consequently developed. The method is applicable to single undisturbed mice kept in conventional cages, and consists of urine collection on chromatographic paper followed by extraction and melatonin assay by radioimmunoassay. The use of this method with BD2F1 mice indicates nocturnal excretion of melatonin significantly higher than during the day; nighttime melatonin levels were shown to be suppressed by constant illumination. A significant increase in nocturnal melatonin excretion was caused by the application of rotational stress applied as a mild experimental stressor.

Does the direct measurement of oxygen tension in tumors have any adverse effects?

A new polarographic histograph was tested in tumors to assess its potential adverse effects in mice. The tumor cell lines used were: the lewis lung carcinoma (3LL) and two human xenografts (Na11+ and HRT18). The C57BL/6 mice survival and number of pulmonary metastases were not altered after pO2 measurements. Whatever the cell line, tumor doubling times were not changed after pO2 measurements. The new polarographic histograph was found to be reliable.

Effects of rotational stress on the effectiveness of cyclophosphamide and razoxane in mice bearing Lewis lung carcinoma

The effects of conventional vs protected housing, and those caused by the periodic application of a psychological stressor (rotational stress, spatial disorientation) on mice kept in a protected housing, with spontaneous tumor metastasis have been determined in mice implanted with Lewis lung carcinoma as a function of tumor inoculum size and response to treatment with cyclophosphamide and razoxane. With a reduced inoculum size, tumor takes do not occur in mice kept in the protected housing, but do occur with spatial disorientation. With a larger inoculum size, tumor takes occur in all untreated mice, and the weight of spontaneous lung metastasis is significantly increased by spatial disorientation. For mice in protected housing, cyclophosphamide results in the absence of macroscopically detectable tumors in all of the treated mice, whereas the use of spatial disorientation abolishes this therapeutic action. The antimetastatic effects of razoxane are also reduced by rotational stress. These results indicate that housing conditions and a psychological stressor can control tumor takes and metastasis formation. They also indicate that host's antitumor resistance effectors, which are susceptible to neuroendocrine modulation by environmental and psychological stressors, participate to determine the effectiveness of the treatment with a cytotoxic (cyclophosphamide) and antimetastatic (razoxane) antitumor drug.

Paediatric oncology in developing countries

Paediatric oncology in developing countries is a specialty in its own right that has so far been largely neglected by the western medical profession. It has specific features of genetic cancer predisposition and of external factors influencing phenotypic cancer manifestations. We point out here some of the specific features of cancer presentation in children of developing countries.

A review of cancer induction by extremely low frequency electromagnetic fields. Is there a plausible mechanism?

A body of epidemiological evidence suggests an association between residential or occupational exposure to extremely low frequency (ELF) electromagnetic fields (EMF) and an increased incidence of cancer in children and adults. Experimental studies at the whole-animal and cellular level are ambiguous; bioeffects suggestive of a carcinogenic effect have been reported, but a similar volume of negative reports can also be assembled. This literature is critically reviewed based on the hypothesis that the epidemiological results are correct, and asking what plausible mechanism could explain a small increase in the incidence of a range of tumors with a non-specific increased exposure to ELF EMF? We focus on four likely mechanisms: 1) disruption of cell communication, 2) modulation of cell growth via changes in calcium ion flux, 3) activation of specific oncogenic gene sequences, and 4) action as a stress factor operating through disruption of hormonal and immune system tumor control mechanisms. We discuss the implications of epidemiologic and experimental results in the context of hypothetical mechanisms of cancer induction, and suggest experiments likely to help define putative EMF hazards.