Stress impairs the efficacy of immune stimulation by CpG-C: Potential neuroendocrine mediating mechanisms and significance to tumor metastasis and the perioperative period.

We recently reported that immune stimulation can be compromised if animals are simultaneously subjected to stressful conditions. To test the generalizability of these findings, and to elucidate neuroendocrine mediating mechanisms, we herein employed CpG-C, a novel TLR-9 immune-stimulating agent. Animals were subjected to ongoing stress (20-h of wet cage exposure) during CpG-C treatment, and antagonists to glucocorticoids, ß-adrenoceptor, COX2, or opioids were employed (RU486, nadolol, etodolac, naltrexone). In F344 rats, marginating-pulmonary NK cell numbers and cytotoxicity were studied, and the NK-sensitive MADB106 experimental metastasis model was used. In Balb/C mice, experimental hepatic metastases of the CT-26 colon tumor were studied; and in C57BL/6J mice, survival rates following excision of B16 melanoma was assessed - both mouse tumor models involved surgical stress. The findings indicated that simultaneous blockade of glucocorticoid and ß-adrenergic receptors improved CpG-C efficacy against MADB106 metastasis. In mice bearing B16 melanoma, long-term survival rate was improved by CpG-C only when employed simultaneously with blockers of glucocorticoids, catecholamines, and prostaglandins. Prolonged stress impaired CpG-C efficacy in potentiating NK activity, and in resisting MADB106 metastasis in both sexes, as also supported by in vitro studies. This latter effect was not blocked by any of the antagonists or by adrenalectomy. In the CT26 model, prolonged stress only partially reduced the efficacy of CpG-C. Overall, our findings indicate that ongoing behavioral stress and surgery can jeopardize immune-stimulatory interventions and abolish their beneficial metastasis-reducing impacts. These findings have implications for the clinical setting, which often involve psychological and physiological stress responses during immune-stimulation.

In vivo suppression of plasma IL-12 levels by acute and chronic stress paradigms: potential mediating mechanisms and sex differences.

Interleukin-12 (IL-12) is a major pro-inflammatory cytokine, which promotes cell-mediated immunity and T(H)1 differentiation. In vitro studies indicated suppression of IL-12 production by several stress-related factors, but no effects of behavioral stress were shown on plasma IL-12 levels. Therefore, in the current study we (i) examined the in vivo effects of various behavioral and pharmacological stress paradigms on baseline plasma IL-12 levels; (ii) compared these in vivo findings to those obtained following in vitro stimulation of leukocytes from the same rats; and (iii) assessed potential sexual dimorphism in these outcomes. The findings indicated that plasma IL-12 levels were significantly reduced by social confrontation, wet-cage exposure, surgery, and the administration of corticosterone, epinephrine, or prostaglandin-E(2). Notably, most in vivo impacts on plasma levels were not evident when assessed in vitro. The IL-12-reducing effects of wet-cage exposure, and of corticosterone and epinephrine administration, were significantly greater in males than in females, although females exhibited greater total corticosterone levels following stress. The duration of acute stressors predicted the degree of IL-12 reduction, but more prolonged stressors did not. Furthermore, seven days of alternating behavioral stressors reduced plasma IL-12 levels more than 14 days. These findings suggest animals' behavioral habituation to stress conditions, or a specific immune mechanism restricting the duration of IL-12 reduction. Overall, our findings indicate a generic and robust stress-induced reduction in plasma IL-12 levels, and suggest epinephrine, corticosterone, and prostaglandin-E(2), as potential mediators that should be scrutinized in vivo in the context of natural physiological stress responses.

Perceived control moderates the influence of active coping on salivary cortisol response to acute pain among women but not men.

It is generally established that active-coping strategies and greater perceived control over pain are associated with improved pain-related outcomes; however, it remains unclear whether these factors independently or interactively influence adrenocortical function in reaction to a painful stimulus. The present study examined whether active coping predicted magnitude cortisol response to acute pain, whether perceived control over pain moderated this association, and whether effects differed as a function of sex. Our findings suggest that perceived control moderates the active coping-adrenocortical relation among women but not men, such that active coping may augment the release of cortisol in response to a painful stimulus only in the presence of greater perceived control over pain. Taken together, active coping and perceived control may potentiate an adaptive neuroendocrine response to an acute painful stressor.

The association of the cortisol awakening response with experimental pain ratings.

Cortisol is a key stress hormone that is implicated in a variety of physiological responses. Attenuated Cortisol Awakening Response (CAR) is associated with many negative health outcomes, but little research has investigated CAR and pain. The current study examines the association of CAR with experimental acute-pain ratings in healthy men and women. Attenuated CAR was related to greater pain intensity and unpleasantness ratings. Future research should examine this association across various pain populations.

Medical conditions and symptoms associated with posttraumatic stress disorder in low-income urban women.

BACKGROUND: Epidemiological studies have consistently reported rates of posttraumatic stress disorder (PTSD) in women that are twice that of men. In men and women, PTSD has been associated with comorbid medical conditions, medical symptoms and lower self-rating of health. In low-income urban women, rates of PTSD are even more elevated than in suburban women and may be related to observed health disparities. METHODS: In this study, 250 women seeking healthcare at an urban clinic were interviewed for a PTSD diagnosis, major depressive disorder (MDD), the experience of traumatic events, the experience of current and past common medical conditions and symptoms, and subjective rating of health. A chart review was used to assess healthcare use in the past year. RESULTS: More current (5.2 vs. 3.8, p < 0.05) and past medical conditions (4.6 vs. 3.3, p < 0.05) were reported by women with a lifetime history of PTSD than by women without this history, after controlling for demographics and current depression. Women with lifetime PTSD also had more annual clinic appointments (5.9 vs. 3.8 p < 0.03) and were 2.4 times (p < 0.05) more likely to report lower appraisal of their physical health. CONCLUSIONS: These findings suggest that urban health-seeking women with PTSD experience health impairments that may cause increased morbidity and that healthcare providers should consider the health ramifications of PTSD when providing medical care to women.

The relationship between competence and performance: implications for assessing practice performance.

OBJECTIVE: This paper aims to describe current views of the relationship between competence and performance and to delineate some of the implications of the distinctions between the two areas for the purpose of assessing doctors in practice. METHODS: During a 2-day closed session, the authors, using their wide experiences in this domain, defined the problem and the context, discussed the content and set up a new model. This was developed further by e-mail correspondence over a 6-month period. RESULTS: Competency-based assessments were defined as measures of what doctors do in testing situations, while performance-based assessments were defined as measures of what doctors do in practice. The distinction between competency-based and performance-based methods leads to a three-stage model for assessing doctors in practice. The first component of the model proposed is a screening test that would identify doctors at risk. Practitioners who 'pass' the screen would move on to a continuous quality improvement process aimed at raising the general level of performance. Practitioners deemed to be at risk would undergo a more detailed assessment process focused on rigorous testing, with poor performers targeted for remediation or removal from practice. CONCLUSION: We propose a new model, designated the Cambridge Model, which extends and refines Miller's pyramid. It inverts his pyramid, focuses exclusively on the top two tiers, and identifies performance as a product of competence, the influences of the individual (e.g. health, relationships), and the influences of the system (e.g. facilities, practice time). The model provides a basis for understanding and designing assessments of practice performance.

When enough is enough: a conceptual basis for fair and defensible practice performance assessment.

INTRODUCTION: An essential element of practice performance assessment involves combining the results of various procedures in order to see the whole picture. This must be derived from both objective and subjective assessment, as well as a combination of quantitative and qualitative assessment procedures. Because of the severe consequences an assessment of practice performance may have, it is essential that the procedure is both defensible to the stakeholders and fair in that it distinguishes well between good performers and underperformers. LESSONS FROM COMPETENCE ASSESSMENT: Large samples of behaviour are always necessary because of the domain specificity of competence and performance. The test content is considerably more important in determining which competency is being measured than the test format, and it is important to recognise that the process of problem-solving process is more idiosyncratic than its outcome. It is advisable to add some structure to the assessment but to refrain from over-structuring, as this tends to trivialise the measurement. IMPLICATIONS FOR PRACTICE PERFORMANCE ASSESSMENT: A practice performance assessment should use multiple instruments. The reproducibility of subjective parts should not be increased by over-structuring, but by sampling through sources of bias. As many sources of bias may exist, sampling through all of them may not prove feasible. Therefore, a more project-orientated approach is suggested using a range of instruments. At various timepoints during any assessment with a particular instrument, questions should be raised as to whether the sampling is sufficient with respect to the quantity and quality of the observations, and whether the totality of assessments across instruments is sufficient to see 'the whole picture'. This policy is embedded within a larger organisational and health care context.

Attenuation of the tumor-promoting effect of surgery by spinal blockade in rats.

BACKGROUND: The perioperative period is characterized by a state of immunosuppression, which was shown in animal studies to underlie the promotion of tumor metastasis by surgery. As this immunosuppression is partly ascribed to the neuroendocrine stress response, the authors hypothesized that spinal blockade, known to attenuate this response, may reduce the tumor-promoting effect of surgery. METHODS: Fischer-344 rats were subjected to a laparotomy during general halothane anesthesia alone or combined with either systemic morphine (10 mg/kg) or spinal block using bupivacaine (50 microg) with morphine (10 microg). Control groups were either anesthetized or undisturbed. Blood was drawn 5 h after surgery to assess number and activity of natural killer cells, or rats were inoculated intravenously with MADB106 adenocarcinoma cells, which metastasize only to the lungs. Metastatic development was assessed by quantifying lung retention of tumor cells 24 h after inoculation or by counting pulmonary metastases 3 weeks later. RESULTS: Laparotomy conducted during general anesthesia alone increased lung tumor retention up to 17-fold. The addition of spinal block reduced this effect by 70%. The number of metastases increased from 16.7 +/- 10.5 (mean +/- SD) in the control group to 37.2 +/- 24.4 after surgery and was reduced to 10.5 +/- 4.7 during spinal block. Systemic morphine also reduced the effects of surgery, but to a lesser degree. Natural killer cell activity was suppressed to a similar extent by surgery and by anesthesia alone. CONCLUSIONS: The addition of spinal blockade to general halothane anesthesia markedly attenuates the promotion of metastasis by surgery.

Evidence that postoperative pain is a mediator of the tumor-promoting effects of surgery in rats.

We have previously shown in rats that the provision of analgesic doses of morphine significantly reduces the tumor-promoting effects of undergoing and recovering from surgery. Because morphine had no effect in non-operated animals, and because a single preoperative dose given hours before tumor inoculation was effective, we have suggested that it is the pain-relieving effects of the drug that underlies its beneficial impact. To support and strengthen this suggestion, two different regimens of analgesia were employed, the systemic administration of the more selective mu-agonist, fentanyl, and the intrathecal (i.t.) administration of bupivacaine plus morphine. To assess host resistance against metastasis, we used a lung clearance assay of the MADB106 mammary adenocarcinoma, a natural killer (NK)-sensitive syngeneic cell line that metastasizes only to the lungs. Female and male Fischer 344 rats were randomly assigned to one of four groups using a 2x2 experimental design: experimental laparotomy under halothane anesthesia versus anesthesia alone, by drug treatment versus vehicle. In the first in vivo experiment, fentanyl was administered 20 min before surgery (40 microg/kg subcutaneously (s.c.)), and at the end of surgery in a slow-release suspension (20 microg/kg s.c.). In the second in vivo experiment, bupivacaine (10 microg) plus morphine (20 microg) in 50 microl was administered i.t. before surgery. Surgery resulted in a 3- to 4-fold increase in the lung retention of MADB106 cells in both males and females, and the observed surgery-induced increase in lung tumor retention was reduced by more than 65% in the fentanyl-treated animals and more than 45% in the animals receiving i.t. bupivacaine plus morphine. Neither drug regimen exerted effects in the anesthesia only animals. Surgery also resulted in a significant suppression of whole blood NK activity assessed at 5 h postoperatively, the same time point at which MADB106 tumor cells were inoculated in the in vivo studies. Unlike the in vivo study, fentanyl suppressed NK activity at this time point in non-operated rats, but had no effect in operated rats. Taken together, these findings strengthen the suggestion that the management of perioperative pain is a critical factor in preventing surgery-induced decreases in host resistance against metastasis. If similar relationships between pain and metastasis occur in humans, then pain control must become a priority in the postoperative care of individuals with cancer.

Suppression of NK cell activity and of resistance to metastasis by stress: a role for adrenal catecholamines and beta-adrenoceptors.

Although acute stress has been reported to suppress natural killer cell activity (NKA) and host resistance to metastasis, it is unclear whether the sympathetic nervous system (SNS) has a role in these effects. The current study in Fischer 344 rats assessed the involvement of adrenal catecholamines and beta(1)- and beta(2)-adrenoceptors in mediating these deleterious effects of swim stress. In addition to assessing the number and activity of NK cells following swim stress, we used a tumor model based on the MADB106 mammary adenocarcinoma line: this syngeneic tumor metastasizes only to the lungs, and its lung tumor retention (LTR) and metastatic colonization are highly sensitive to NKA. The findings indicate that stress increased both LTR, assessed 24 h after inoculation, and the number of lung metastases, counted 3 weeks later. These effects were attenuated or completely abolished by the ganglionic blocker chlorisondamine (3 mg/kg i.p.), by adrenal demedullation, by a selective beta-adrenergic antagonist (nadolol, 0.4 mg/kg), and additively by a selective beta(1)- (atenolol, 1-6 mg/kg) and a selective beta(2)-antagonist (either butoxamine 4-32 mg/kg or ICI-118,551 0.3-8 mg/kg). Stress also suppressed NKA, and adrenal demedullation prevented this suppression. Administration of adrenaline (0.1-1 mg/kg) or of a beta-adrenergic agonist (metaproterenol, 0.8 mg/kg), in physiologically relevant doses, suppressed NKA in a dose-dependent manner, and increased LTR to levels characteristic of swim stress. Taken together, these findings suggest that acute stress, by releasing catecholamines from the adrenal glands and activating beta(1)- and beta(2)-adrenoceptors, suppresses NKA and consequently compromises resistance to NK-sensitive metastasis.

Natural killer cell activity and resistance to tumor metastasis in prepubescent rats: deficient baselines, but invulnerability to stress and beta-adrenergic stimulation.

Although young children and animals exhibit high rates of tumor development, little is known about natural killer (NK) cell activity in the very young. We recently provided direct evidence that reduced levels of NK activity in prepubescent rats underlie higher levels of susceptibility to metastasis. The aim of the current study was to further characterize NK activity and tumor resistance in prepubescent rats, specifically with respect to the effects of stress and sex, as these factors have been shown to modulate tumor development in adult populations. Two NK outcomes were assessed: levels of whole blood NK cytotoxicity and lung tumor retention of NK-sensitive MADB106 tumor cells which metastasize only to the lungs. The corticosterone (CS) response to surgery was also assessed. In the first set of experiments, prepubescent males and females (36 days of age) and mature males (98 days) were subjected to abdominal surgery and 5 h later were either tested for plasma CS levels or challenged with MADB106 tumor cells. The findings indicated that whereas surgery increased CS levels in the young rats to similar levels observed in mature animals, surgical stress did not increase lung tumor retention in the young animals, despite exerting marked and significant effects in the mature rats. These findings persisted when lower tumor loads were used in the young rats to compensate for the markedly reduced resistance to metastasis in this population. Because surgery involves activation of the sympathetic nervous system (SNS) which is known to regulate NK activity, we assessed the impact of the beta-adrenergic agonist, metaproterenol, on NK activity and on lung tumor retention. Metaproterenol (0.8 mg/kg, 1 h before testing) resulted in a large suppression of NK activity and resistance against MADB106 metastasis in mature males and females, but not in prepubescent animals. In mature, but not in young animals, males exhibited higher baseline levels of NK activity. Taken together, these findings indicate that NK cells of prepubescent rats are resistant to beta-adrenergic stimulation, and suggest that prepubescent rats are markedly less responsive to SNS-induced suppression of NK activity, which may underlie their invulnerability to the effects of surgery on MADB106 metastasis.

A role for NK cells in greater susceptibility of young rats to metastatic formation.

Cancer is the second leading cause of death in children (after accidents) and is more prevalent in the first 5 years of life than in the subsequent 10 years. Very young animals have been shown to be more susceptible to malignant growth and whether such increased susceptibility is attributable to reduced resistance of the host to tumor development or to increased incidence of cancerous cells is, as yet, unclear. In the current study, we used 36 day old male and female rats and adult rats to specifically study the role of natural killer (NK) cell activity, as well as hormones known to regulate their activity, in mediating reduced resistance to tumor metastasis at prepubescence. A mammary adenocarcinoma cell line (MADB106) syngeneic to the Fischer 344 rat was used. Following i.v. injection, MADB106 tumor cells seed and colonize only in the lungs, a process shown in adult rats to be controlled by NK cells during the first 24 hours after tumor inoculation. As was found in our previous studies, young rats demonstrated a 10-fold higher percentage of lung tumor cell retention compared to adult rats. Importantly, this higher percentage of tumor cell retention was evident using the same number of tumor cells per kg of body weight in young and adult rats, and maintained even when young rats were challenged with 10- and 100-fold fewer MADB106 cells per kg than adults. Selective depletion of NK cells markedly increased tumor cell retention in all rats, indicating that NK cells play a crucial role in resistance against MADB106 retention in both young and adult rats. Employing in vitro assessment of whole blood NK cytotoxicity. young animals exhibited markedly less specific killing compared to the mature animals. Taken together, these findings indicate a reduced resistance of the young rats against MADB106 retention that is mediated by diminished NK activity in these rats. Factors other than NK cells appear to play a minor role determining age differences in this model. Age- and sex-related differences in plasma beta-endorphin and corticosterone levels were also found, suggesting different activation levels of the HPA axis. These differences, however, seen unlikely to underlie the reduced NK activity in young rats.

Evidence that stress and surgical interventions promote tumor development by suppressing natural killer cell activity.

Stress and surgery have been suggested to compromise host resistance to infectious and malignant diseases in experimental and clinical settings. Because stress affects numerous physiological systems, the role of the immune system in mediating such effects is unclear. In the current study, we assessed the degree to which stress-induced alterations in natural killer (NK) cell activity underlie increased susceptibility to tumor development in F344 rats. Two stress paradigms were used: forced swim and abdominal surgery. Host resistance to tumor development was studied using 3 tumor models syngeneic to inbred F344 rats: CRNK-16 leukemia and the MADB106 mammary adenocarcinoma, both sensitive to NK activity, and the NK-insensitive C4047 colon cancer. Swim stress increased CRNK-16-associated mortality and metastatic development of MADB106 but not metastasis of C4047 cells. In both stress paradigms, stress suppressed NK activity (NKA) for a duration that paralleled its metastasis-enhancing effects on the MADB106 tumor. In vivo depletion of large granular lymphocyte/NK cells abolished the metastasis-enhancing effects of swim stress but not of surgical stress. Our findings indicate that stress-induced suppression of NKA is sufficient to cause enhanced tumor development. Under certain stressful conditions, suppression of NKA is the primary mediator of the tumor-enhancing effects of stress, while under other conditions, additional factors play a significant role. Clinical circumstances in which surgical stress may induce enhanced metastatic growth are discussed.

Psychological influences on surgical recovery. Perspectives from psychoneuroimmunology.

Greater fear or distress prior to surgery is associated with a slower and more complicated postoperative recovery. Although anxiety presumably interferes with recuperation through both behavioral and physiological mechanisms, the pathways have been unclear. Recent work in psychoneuroimmunology (PNI) has demonstrated that stress delays wound healing. In addition, a second line of research has illustrated the adverse effects of pain on endocrine and immune function. A biobehavioral model is described that is based on these and other data; it suggests a number of routes through which psychological and behavioral responses can influence surgery and post-surgical outcomes. Clinical and research implications are highlighted.

Pre-operative versus postoperative administration of morphine: impact on the neuroendocrine, behavioural, and metastatic-enhancing effects of surgery.

We have previously shown that the pre- and postoperative administration of an analgesic dose of morphine attenuated the tumour-enhancing effects of surgery. This study was undertaken to assess the relative role and exclusive importance of pre- versus postoperative morphine administration on neuroendocrine, metastatic, and behavioural outcomes of surgery in Fischer 344 rats. The natural killer (NK) sensitive mammary adenocarcinoma cell line, MADB106, was used in a lung clearance assay to assess host resistance to metastasis. Either morphine or its vehicle was administered to all rats at three times: (1) 30 min before surgery (8 mg kg-1, in saline); (2) immediately after surgery in a slow release suspension (SRS, 4 mg kg-1); and (3) 5 h after surgery at the time of tumour cell inoculation (2 mg kg-1, in SRS). Five surgery groups underwent an experimental laparotomy with halothane anaesthesia and received either the vehicle at all three times or morphine in one of four different regimens: before surgery only, at all three times, after surgery only at times 2 and 3, and after surgery total at times 2 and 3 with the preoperative dose added at time 2. Two control groups underwent anaesthesia alone and received either morphine or the vehicle at all three times. Surgery resulted in a twofold increase in tumour cell retention, which was significantly attenuated by all four morphine treatment regimens (P < 0.05). Furthermore, the two surgery groups that were treated with morphine preoperatively appeared to derive greater benefit; whereas the preoperatively treated groups exhibited a 65-70% attenuation of surgery-induced increases in tumour cell retention, only a 50% attenuation was evident in the two groups treated postoperatively. Surgery significantly reduced rearing behaviour and morphine reversed this effect such that most morphine-treated surgery groups exhibited similar levels of rearing behaviour as was observed in the unoperated animals throughout the 4-h postoperative observation period. Morphine treatment also significantly attenuated surgery-induced increases in plasma corticosterone concentrations assessed at 5 h after surgery. If such relationships hold in humans, these findings support the suggestion that the pre-surgical administration of morphine is key in optimizing its beneficial effects on surgery-induced increases in metastasis.

Increased surgery-induced metastasis and suppressed natural killer cell activity during proestrus/estrus in rats.

We have previously reported sex- and estrous-related differences in host resistance to the metastatic development of a mammary adenocarcinoma cell line, MADB106, in the Fischer 344 (F344) rat. In other studies, we found that surgery suppressed natural killer (NK) cell activity and increased the NK-sensitive metastatic development of MADB106 tumor cells. The current study was designed to explore whether sex or estrous phase at the time of surgery impacts the degree of such deleterious effects of surgery. Such estrous effects could be related to an ongoing clinical debate regarding the importance of the timing of breast cancer surgery with the menstrual cycle in premenopausal women. Mature F344 males and cycling females underwent either experimental laparotomy with halothane anesthesia, halothane anesthesia alone, or were untreated. Five hours after surgery, animals either were injected with radiolabeled MADB106 tumor cells and assessed for lung tumor cell retention 12 hours later, or underwent blood withdrawal for in vitro assessment of NK cell activity. MADB106 tumor cells metastasize only to the lungs, and lung tumor cell retention is: a) an early indicator of the number of metastases that would develop weeks later, and b) highly sensitive to in vivo levels of NK activity. This mammary adenocarcinoma cell line is syngeneic to the inbred F344 strain of rats used in our studies, thus constituting a model for breast cancer metastasis. The results indicated that sex, estrous phase, and surgery interacted in their effects on NK cell activity and tumor metastasis. MADB106 lung tumor cell retention was increased by surgery in both sexes (2- to 3-fold) compared to the anesthesia only and control groups. This increase, however, was significantly greater in proestrus/estrus (P/E) females than in metestrus/diestrus (M/D) females. Among the control animals, females in P/E exhibited significantly less NK cytotoxic activity compared to the males, and the NK activity exhibited by females in M/D was between these two groups. Surgery suppressed NK cytotoxic activity to a similar level in all groups. Possible implications of these findings for the surgical care of women with breast cancer are discussed.

The immune-suppressive nature of pain.

OBJECTIVES: To review evidence that the immune system plays a role in controlling the spread of cancer and findings that perioperative pain relief improves immune status and health outcomes. DATA SOURCES: Research studies and review articles pertaining to immunity, immune function, stress, and immune-suppressive nature of pain. CONCLUSIONS: Pain not only results in suffering but is a pathogen itself, capable of facilitating the progression of metastatic disease. Adequate pain relief decreases these risks. IMPLICATIONS FOR NURSING PRACTICE: Adequate pain relief is not only a primary concern in caring for individuals in pain but may be a matter of physiologic necessity as further studies reveal the immune-suppressive nature of pain.

Increased susceptibility to metastasis during pro-oestrus/oestrus in rats: possible role of oestradiol and natural killer cells.

It has been suggested that tumour development and immunocompetence are affected by the menstrual and the oestrous cycle, and sex hormones have been shown to modulate lymphokine production, neuroendocrine activity and immunity. In this study, we assessed natural killer cell activity and host susceptibility to metastasis during the oestrous cycle in the Fischer 344 inbred rat strain. Females were inoculated intravenously with MADB106 tumour cells, a syngeneic mammary adenocarcinoma cell line that metastasises only to the lungs. The susceptibility to metastatic development of this tumour was found to be significantly higher during pro-oestrus and oestrus than during metoestrus and dioestrus. Two days of exposure to oestradiol benzoate caused similar effects in ovariectomised females, and a single administration of progesterone reduced this effect of oestradiol to a statistically non-significant level. The tumour was found to be negative for oestradiol receptors, and its in vitro proliferation rate was not affected by oestradiol or progesterone, suggesting that the effects of sex hormones on the metastatic process are not attributable to a direct effect on tumour cells. Because the metastatic process of MADB106 tumour cells is known, and confirmed here, to be highly controlled by large granular lymphocyte/natural killer (LGL/NK) cell activity, we assessed their role in mediating the effects of the oestrous cycle. The number and activity levels of circulating blood LG/NK cells (NKR-PI+ bright) were studied. Findings indicated oestrous-dependent alterations in the number of LGL/NK cells and suggested a diminished NK activity per LGL/NK cell during pro-oestrus/ oestrus, the same phases that were characterised by higher susceptibility to metastatic development. These findings provide the first empirical evidence for a causal relationship between a short-term exposure to elevated oestradiol/low progesterone levels and decreased resistance to tumour metastasis, and it is hypothesised that an alteration in LGL/NK cell activity underlies these effects. Homologies and relevance to clinical phenomena are discussed.

Acute alcohol intoxication suppresses natural killer cell activity and promotes tumor metastasis.

Alcohol consumption is associated with increased morbidity and mortality related to infectious diseases and malignancy (1-5), although immune mediation of these relationships is controversial. Specifically, the activity of natural killer (NK) cells, which are involved in the resistance to infections and metastasis, can be suppressed in the presence of ethanol in vitro. However, acute consumption or infusion of ethanol in vivo exerts no effects on NK activity assessed in vitro thereafter. Therefore, we have developed and used a method to study the effects of ethanol on NK activity in living rats by using an NK-sensitive metastatic process and selective depletion of NK cells in vivo. Acute ethanol intoxication caused a marked suppression of NK activity in vivo and a tenfold increase in the number of MADB106 tumor metastases. Ethanol had no effect in rats selectively depleted of NK cells or when an NK-insensitive tumor (C4047) was used. These findings suggest that even acute ethanol intoxication markedly suppresses NK activity in the living organism. This suppression may underlie some aspects of the association between alcoholism, infectious disease and malignancies.