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

Harnessing cancer immunotherapy during the unexploited immediate perioperative period

The immediate perioperative period (days before and after surgery) is hypothesized to be crucial in determining long-term cancer outcomes: during this short period, numerous factors, including excess stress and inflammatory responses, tumour-cell shedding and pro-angiogenic and/or growth factors, might facilitate the progression of pre-existing micrometastases and the initiation of new metastases, while simultaneously jeopardizing immune control over residual malignant cells. Thus, application of anticancer immunotherapy during this critical time frame could potentially improve patient outcomes. Nevertheless, this strategy has rarely been implemented to date. In this Perspective, we discuss apparent contraindications for the perioperative use of cancer immunotherapy, suggest safe immunotherapeutic and other anti-metastatic approaches during this important time frame and specify desired characteristics of such interventions. These characteristics include a rapid onset of immune activation, avoidance of tumour-promoting effects, no or minimal increase in surgical risk, resilience to stress-related factors and minimal induction of stress responses. Pharmacological control of excess perioperative stress-inflammatory responses has been shown to be clinically feasible and could potentially be combined with immune stimulation to overcome the direct pro-metastatic effects of surgery, prevent immune suppression and enhance immunostimulatory responses. Accordingly, we believe that certain types of immunotherapy, together with interventions to abrogate stress-inflammatory responses, should be evaluated in conjunction with surgery and, for maximal effectiveness, could be initiated before administration of adjuvant therapies. Such strategies might improve the overall success of cancer treatment.

Impact of perioperative pain management on cancer recurrence: an ASRA/ESRA special article

Cancer causes considerable suffering and 80% of advanced cancer patients experience moderate to severe pain. Surgical tumor excision remains a cornerstone of primary cancer treatment, but is also recognized as one of the greatest risk factors for metastatic spread. The perioperative period, characterized by the surgical stress response, pharmacologic-induced angiogenesis, and immunomodulation results in a physiologic environment that supports tumor spread and distant reimplantation.In the perioperative period, anesthesiologists may have a brief and uniquewindow of opportunity to modulate the unwanted consequences of the stressresponse on the immune system and minimize residual disease. This reviewdiscusses the current research on analgesic therapies and their impact ondisease progression, followed by an evidence-based evaluation of perioperativepain interventions and medications.

Lack of immunotoxic effects of repeated exposure to atrazine associated with the adaptation of adrenal gland activation

T cell-dependent IgM antibody production and natural killer cell (NKC) activity were assessed in SD rats orally administered atrazine for 28 days to males (0, 6.5, 25, or 100 mg/kg/day) or females (0, 3, 6, or 50 mg/kg/day), or 30 or 500 ppm in diet (3 or 51 mg/kg/day). Anti-asialo GM1 antibodies (NKC) and cyclophosphamide (antibody-forming cell assay [AFC]) served as positive controls. Pituitary (ACTH, prolactin), adrenal (corticosterone, progesterone, aldosterone), and gonadal (androgens, estrogens) hormones were assessed after 1, 7, and/or 28 days of treatment. Food intake and body weights were significantly reduced in the highest dosed males, and transiently affected in females. Urinary corticosterone levels were not increased in atrazine-treated groups in either sex at any time point measured (10, 22, or 24 days). Corticosterone and progesterone were elevated in males after a single atrazine dose ≥6.5 mg/kg/day, but not after 7, 14, or 28 doses. There were no effects on adrenal, pituitary, or gonadal hormones in females. Atrazine did not suppress the AFC response or decrease NKC function after 28 days in males or females. Atrazine had no effect on spleen weights or spleen cell numbers in males or females, although thymus weights were elevated in males receiving the highest dose. The lack of immunotoxic effect of atrazine was associated with diminished adrenal activation over time in males, and no effects on adrenal hormones in females.

Exploiting the critical perioperative period to improve long-term cancer outcomes

Evidence suggests that the perioperative period and the excision of the primary tumour can promote the development of metastases—the main cause of cancer-related mortality. This Review first presents the assertion that the perioperative timeframe is pivotal in determining long-term cancer outcomes, disproportionally to its short duration (days to weeks). We then analyse the various aspects of surgery, and their consequent paracrine and neuroendocrine responses, which could facilitate the metastatic process by directly affecting malignant tissues, and/or through indirect pathways, such as immunological perturbations. We address the influences of surgery-related anxiety and stress, nutritional status, anaesthetics and analgesics, hypothermia, blood transfusion, tissue damage, and levels of sex hormones, and point at some as probable deleterious factors. Through understanding these processes and reviewing empirical evidence, we provide suggestions for potential new perioperative approaches and interventions aimed at attenuating deleterious processes and ultimately improving treatment outcomes. Specifically, we highlight excess perioperative release of catecholamines and prostaglandins as key deleterious mediators of surgery, and we recommend blockade of these responses during the perioperative period, as well as other low-risk, low-cost interventions. The measures described in this Review could transform the perioperative timeframe from a prominent facilitator of metastatic progression, to a window of opportunity for arresting and/or eliminating residual disease, potentially improving long-term survival rates in patients with cancer.

Chemopreventive and therapeutic potential of "naringenin," a flavanone present in citrus fruits

Cancer is one of the major causes of deaths in developed countries and is emerging as a major public health burden in developing countries too. Changes in cancer prevalence patterns have been noticed due to rapid urbanization and changing lifestyles. One of the major concerns is an influence of dietary habits on cancer rates. Approaches to prevent cancer are many and chemoprevention or dietary cancer prevention is one of them. Therefore, nutritional practices are looked at as effective types of dietary cancer prevention strategies. Attention has been given to identifying plant-derived dietary agents, which could be developed as a promising chemotherapeutic with minimal toxic side effects. Naringenin, a phytochemical mainly present in citrus fruits and tomatoes, is a frequent component of the human diet and has gained increasing interest because of its positive health effects not only in cancer prevention but also in noncancer diseases. In the last few years, significant progress has been made in studying the biological effects of naringenin at cellular and molecular levels. This review examines the cancer chemopreventive/therapeutic effects of naringenin in an organ-specific format, evaluating its limitations, and its considerable potential for development as a cancer chemopreventive/therapeutic agent.

Effects of postoperative epidural analgesia on recurrence-free and overall survival in patients with nonsmall cell lung cancer

STUDY OBJECTIVE

To determine whether postoperative epidural analgesia is associated with better recurrence-free survival and overall survival after lung cancer surgery.

DESIGN

Retrospective study.

SETTING

Academic hospital.

MEASUREMENTS

Data of patients with stage 1, stage 2, and stage 3 nonsmall cell lung cancer, who underwent tumor resection surgery, were studied. Patient data were grouped into three different postoperative pain management interventions: intravenous patient-controlled analgesia, patient-controlled epidural analgesia, and their combination. Univariate and multicovariate Cox proportional hazards models were applied to assess the effects of covariates of interest on overall survival and recurrence-free survival.

MAIN RESULTS

The type of postoperative analgesia used for patients who underwent surgery for nonsmall cell lung cancer did not affect recurrence-free survival or overall survival. However, certain variables, including age ≥ 65 years, male gender, body mass index ≥ 25 kg/m(2), ASA physical status 4, and the need for preoperative blood transfusions, pneumonectomy, and postoperative radiation, were associated with decreased recurrence-free survival and overall survival.

CONCLUSIONS

The type of postoperative analgesia used after surgery for nonsmall cell lung cancer is not associated with better 2-year or 5-year recurrence-free survival or overall survival rates.

Salivary cortisol and soluble tumor necrosis factor-α receptor II responses to multiple experimental modalities of acute pain

The present study compared cortisol and soluble tumor necrosis factor-α receptor II (sTNFαRII) responses provoked by cold pressor, hot water, ischemic, and neutral water (i.e., room temperature) modalities. Oral fluid samples were collected before, immediately after, and during recovery to assess physiological responses. From baseline, the cold pressor, but not hot water or ischemic modalities, produced a significant time-dependent elevation in cortisol, whereas cortisol significantly decreased for the neutral water task. When compared to baseline, the cold pressor, hot water, and ischemic modalities were associated with decreased sTNFαRII responses over time. The sTNFαRII response to neutral water initially decreased but returned to approximate baseline levels. Pain ratings were positively associated with cortisol increase from baseline and the overall cortisol response was negatively associated with the overall sTNFαRII response.

Naringenin reduces lung metastasis in a breast cancer resection model

Metastasis is the main cause of death in cancer patients. To improve the outcomes of patients undergoing a surgery, new adjuvant therapies that can effectively inhibit metastases have to be developed. Studies have shown that flavonoid naringenin, a natural product that is mainly present in grapes and citrus, may contribute to cancer prevention. It has many advantages compared to traditional chemotherapeutic drugs, such as low toxicity. To determine whether naringenin can also inhibit metastases, a breast cancer resection model that mimics clinical situations was established. We found that orally administered naringenin significantly decreased the number of metastatic tumor cells in the lung and extended the life span of tumor resected mice. Flow cytometry analysis revealed that T cells displayed enhanced antitumor activity in naringenin treated mice, with an increased proportion of IFN-γ and IL-2 expressing T cells. In vitro studies further demonstrated that relief of immunosuppression caused by regulatory T cells might be the fundamental mechanism of metastasis inhibition by naringenin. These results indicate that orally administered naringenin can inhibit the outgrowth of metastases after surgery via regulating host immunity. Thus, naringenin can be an ideal surgical adjuvant therapy for breast cancer patients.

Continuous stress disrupts immunostimulatory effects of IL-12

Immune stimulation by biological response modifiers is a common approach in tumor immunotherapy. IL-12 was found effective in various animal studies, but clinical trials showed limited success. However, among other differences, animal models do not simulate psychological or physiological stress while employing IL-12, whereas cancer patients often experience distress while treated with immunostimulants. Thus, in the current study we assessed the impact of continuous stress on the efficacy of IL-12 immunostimulation. F344 rats were subjected to a pharmacological stress paradigm (continuous administration of a β-adrenergic agonist) or to a 20 h behavioral stress paradigm (wet cage exposure) commencing 2h before IL-12 administration. Twenty-six hours after stress initiation, we studied indices known to reflect IL-12 immunostimulatory impacts, including NK cell numbers and activity in different immune compartments, and in vivo resistance to MADB106 lung tumor colonization. The results indicated that both the pharmacological and behavioral stress paradigms significantly reduced the increase in the number and activity of marginating-pulmonary NK cells evident in non-stressed IL-12 treated animals. Additionally, stressed animals exhibited a lower IL-12-induced improvement of MADB106 lung clearance, an in vivo index that markedly depends on total marginating-pulmonary NK activity. These deleterious effects of stress were more prominent in males than in females. Overall, the findings demonstrate that prolonged stress exposure can disrupt the efficacy of simultaneous immunostimulatory treatments, irrespective of stress effects on baseline immune measures. Neuroendocrine and cellular mediating mechanisms are yet unknown, but the potential clinical ramifications of these findings warrant consideration in clinical trials employing immunostimulatory agents.

Ethanol withdrawal hastens the aging of cytochrome c oxidase

We investigated whether abrupt ethanol withdrawal (EW) age-specifically inhibits a key mitochondrial enzyme, cytochrome c oxidase (COX), and whether estrogen mitigates this problem. We also tested whether this possible effect of EW involves a substrate (cytochrome c) deficiency that is associated with proapoptotic Bcl2-associated X protein (BAX) and mitochondrial membrane swelling. Ovariectomized young, middle age, and older rats, with or without 17β-estradiol (E2) implantation, underwent repeated EW. Cerebelli were collected to measure COX activity and the mitochondrial membrane swelling using spectrophotometry and the mitochondrial levels of cytochrome c and BAX using an immunoblot method. The loss of COX activity and the mitochondrial membrane swelling occurred only in older rats under control diet conditions but occurred earlier, starting in the young rats under EW conditions. E2 treatment mitigated these EW effects. EW increased mitochondrial BAX particularly in middle age rats but did not alter cytochrome c. Collectively EW hastens but E2 delays the age-associated loss of COX activity. This EW effect is independent of cytochrome c but may involve the mitochondrial overload of BAX and membrane vulnerability.

Surgery as a double-edged sword: a clinically feasible approach to overcome the metastasis-promoting effects of surgery by blunting stress and prostaglandin responses

Surgery remains an essential therapeutic approach for most solid malignancies, including breast cancer. However, surgery also constitutes a risk factor for promotion of pre-existing micrometastases and the initiation of new metastases through several mechanisms, including the release of prostaglandins and stress hormones (e.g., catecholamines and glucocorticoids). However, the perioperative period also presents an opportunity for cell mediated immunity (CMI) and other mechanisms to eradicate or control minimal residual disease, provided that the deleterious effects of surgery are minimized. Here, we discuss the key role of endogenous stress hormones and prostaglandins in promoting the metastatic process through their direct impact on malignant cells, and through their deleterious impact on anti-cancer CMI. We further discuss the effects of anesthetic techniques, the extent of surgery, pain alleviation, and timing within the menstrual cycle with respect to their impact on tumor recurrence and physiological stress responses. Last, we suggest an attractive perioperative drug regimen, based on a combination of a cyclooxygenase (COX)-2 inhibitor and a β-adrenergic blocker, which we found effective in attenuating immune suppression and the metastasis-promoting effects of surgery in several tumor models. This regimen is clinically applicable, and could potentially promote disease free survival in patients operated for breast and other types of cancer.

Lactation modifies stress-induced immune changes in laboratory rats

Lactation and stressor exposure both influence the activity of the immune system, but the interaction of both factors on the immune defense is poorly understood. The aim was therefore to investigate in lactating Long-Evans rats the effect of social stress on aspects of cellular immunity in the blood and mesenteric lymph nodes (MLN). Acute social stress (2h) was induced in lactating and non-lactating female intruders using a confrontation model that yielded into social defeat and increased plasma corticosterone concentrations. Stress as well as lactation had marked effects on the immune system. Acute social stress caused granulocytosis, reduced lymphocyte proliferation, and cytokine production in the blood, but had no significant effects in MLN. In the blood of lactating rats, increased numbers of granulocytes and enhanced phagocytosis, but decreased B cell numbers and reduced IL-2 production was observed. However, in MLN both lymphocyte proliferation and monocyte numbers were increased in lactating rats. The effect of stress on the immune measures was often similar in lactating and non-lactating females, but a few important differences were evident: Only non-lactating animals showed an increase in blood granulocyte numbers and a decrease in IL-2 production in response to stressor exposure. Thus, during lactation, a neuroendocrine status may exist which impedes stress-induced modulations at least of some immune parameters.

Drugs of anaesthesia and cancer

Anaesthesia represents one of the most important medical advances in history, and, nowadays, can widely be considered safe, thanks to the discovery of new drugs and the adoption of modern technologies. Nevertheless, anaesthetic practices still represent cause for concern regarding the consequences they produce. Various anaesthetics are frequently used without knowing their effects on specific diseases: despite having been reported that invasion or metastasis of cancer cells easily occurs during surgical procedures, numerous anaesthetics are used for cancer resection even if their effect on the behaviour of cancer cells is unclear. Guidelines for a proper use of anaesthetics in cancer surgery are not available, therefore, the aim of the present review is to survey available up-to-date information on the effects of the most used drugs in anaesthesia (volatile and intravenous anaesthetics, nitrous oxide, opioids, local anaesthetics and neuromuscular blocking drugs) in correlation to cancer. This kind of knowledge could be a basic valuable support to improve anaesthesia performance and patient safety.

Male--female differences in the impact of beta-adrenoceptor stimulation on resistance to experimental metastasis: exploring the effects of age and gonadal hormone involvement

We studied the development of sexual dimorphism in resistance to NK-sensitive experimental metastasis under baseline conditions and following adrenoceptor stimulation. With increasing age, baseline resistance to MADB106 lung tumor retention (LTR) increased in both sexes, but also the susceptibility to the tumor-enhancing effects of a beta-adrenergic agonist, metaproterenol. Beginning at 13 weeks, males exhibited a 2- to 3-fold greater increase in LTR than females following adrenoceptor stimulation. This adult dimorphism was robust to ovariectomy, and questionably related to androgens. The findings are consistent with reduced female responsiveness to sympathetic activation, and substantiate the importance of including both sexes when studying neuroimmunomodulation.

Surgery-induced immunosuppression and postoperative pain management

Surgery is well-known to result in the suppression of some immune functions; however, the role of perioperative pain has only recently been studied. Pain-relieving anesthesia techniques and perioperative analgesia provide some protection against surgery-induced immune suppression and infectious surgical sequelae, although few studies also assess postoperative pain. Attributing a biological consequence to the observed immune alterations remains an issue in human studies, and the use of immune sensitive tumor models in animals enables the linking of immune changes with disease and a means by which to explore causal relationships among surgery-related pain, immune function, and metastatic development. There is strong evidence in animals that pain-relieving interventions significantly reduce the tumor-enhancing effects of undergoing and recovering from surgery. It cannot be assumed that animal findings are directly applicable to the human condition; however, if such relationships hold in humans, perioperative pain management becomes an important strategy for reducing postoperative sequelae.

Stress, stress response, and health

Components of stress and the stress response differ between men and women. The tend-and-befriend response, mediated by oxytocin and endogenous opioids, may be more applicable to women than the fight-or-flight response, which was based largely on studies of men. Even within the flight-or-flight response pattern there are sex-based differences. The HPA axis interacts with reproductive function, such as menstruation. For immune function there are sex differences as well as differences within the menstrual phase. Inclusion of men and women in stress response studies is critical. Further study is needed to clarify the influence of ovarian hormones on the stress and immune responses during the reproductive stages in women's lives, including menarche. pregnancy, and perimenopause.

Serum levels of sex hormones and corticosterone throughout 4- and 5-day estrous cycles in Fischer 344 rats and their simulation in ovariectomized females

Among inbred strains of rats, the Fischer 344 (F344) is commonly used in immunological and behavioral studies. However, little is known about patterns of sex hormones and corticosterone (CORT) secretion throughout the estrous cycle in this strain, which is characterized by a marked CORT response to stress and variable length of cycles. In the current study, using radioimmunoassays, we assessed serum levels of progesterone, estradiol, LH, testosterone, prolactin and CORT, at 1-h intervals throughout the estrous cycle in F344 female rats with 4- and 5-day cycles, as well as in males. Vaginal smears were obtained from 268 females for 15 consecutive days to determine individual length of the estrous cycle and the exact estrous phase upon blood withdrawal, which was conducted once in each rat on the 12th day of smearing. The results indicated that both 4- and 5-day cyclers have two distinct and marked surges of progesterone, one on proestrus day and the other on diestrous-1 day. Testosterone levels in 5-day cyclers peaked on diestrus-3, one day earlier than in 4-day cyclers. Daily peak levels of CORT gradually increased from estrus day to proestrous day, whereas daily nadir levels of CORT remained unchanged. To simulate the natural kinetics of specific sex hormones in ovariectomized females, different doses of estradiol, progesterone, testosterone, prolactin or CORT were injected s.c. or i.p., or 90-day sustained release pellets containing different doses of estradiol or progesterone were implanted. The findings indicated dose- and time-dependent effects, suggesting regimens for modeling the estrous cycle or replacement therapy.

The relationship between chronic pain, immune function, depression, and health behaviors

The objectives of this study were 1) to determine the relationships between pain perceptions, immune function, depression and health behaviors and 2) to examine the effects of chronic pain on immune function using depression and health behaviors as covariates. A nonexperimental cross-sectional design was used to compare 24 chronic back pain patients with 33 asymptomatic no-pain healthy subjects. Immune function measures using natural killer (NK) cell activity, percent and numbers of NK cells, and T-cell lymphocyte proliferation with mitogens concanavalin A (ConA) and pytohemagglutinin (PHA) as well as self-report measures for depression and health behaviors were collected on all subjects. Pain perceptions showed positive significant correlations with depression (P = 0.01) and total percent of NK cells (P = 0.04). Depression and health behaviors were negatively correlated (P = 0.01). Positive associations were observed for depression and 2 PHA mitogen levels (P < 0.05). Comparison of group means, controlling for depression and health behaviors, showed that chronic pain patients' immune function, as measured by the combined NK effector to target (E:T) cell ratio levels, was significantly higher than the no-pain comparison group. Pain perceptions may have a deleterious effect on enumerative NK cell measures and depression levels. However, people with chronic pain may not experience attenuation in functional immune parameters.

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.

Timing within the oestrous cycle modulates adrenergic suppression of NK activity and resistance to metastasis: possible clinical implications

Clinical observations suggest that the rate of metastatic development and long-term mortality following surgery in breast cancer patients is influenced by the menstrual phase during which surgery is conducted. The menstrual cycle is known to modulate various physiological responses and medical conditions that involve adrenergic mechanisms (e.g., asthma). Natural killer activity (NKA), an immune function controlling metastasis, is suppressed following surgery, and in vitro by adrenaline. We therefore hypothesize that the clinical observation may be partly attributable to surgery-induced adrenergic suppression of NK-dependent resistance to metastasis, a suppression that depends on menstrual phase during surgery. To test this hypothesis in rats, 140 F344 females at different phases of their oestrous cycle were injected with a beta-adrenergic agonist, metaproterenol (MP) (0.4 or 0.8 mg kg(-1), s.c.), or with vehicle, before i.v. inoculation with MADB106 tumour cells. This syngeneic mammary adenocarcinoma line metastasizes only to the lungs, and is highly sensitive to NKA. In a second experiment, the suppression of NKA by MP was studied in vitro in blood drawn at different phases of the oestrous cycle (n = 36). Finally, the effects of stress on the number and activity of NK cells were assessed along the oestrous cycle (n = 71). The findings indicate that the suppressive effects of MP on resistance to metastasis and on NKA, are significantly greater during the oestrous phase characterized by high oestradiol levels (D3/proestrus/oestrus). Similarly, NKA per cell was suppressed by stress only during this phase. In untreated animals, in which inadvertent stress was minimized, no effects of the oestrous cycle on NKA or on resistance to metastasis were evident. These findings indicate that the oestrous cycle modulates adrenergic suppression of NKA and of resistance to metastasis. The relevance of these findings to the above clinical observation, as well as that of our related findings in women from a parallel study, is discussed.

Usefulness of positron emission tomographic visualization for examination of in vivo susceptibility to metastasis

BACKGROUND

Immune surveillance may play a role in protecting against the establishment of metastasis. The authors previously observed that the injection of as few as 10(4) lung metastatic B16BL6 melanoma cells/0.2 mL resulted in no metastasis and in a reduced rate of cell accumulation in the lung, the target organ. In the current study, the authors examined the correlation between metastatic potential and tumor cell trafficking by using a liver-metastatic model.

METHODS

The liver-metastatic potential of RAW117-H10 cells was examined by varying the number of cells injected into mice through the portal vein. To investigate the trafficking of the cells, the authors performed positron emission tomography (PET) analysis, because advances in this technology now enable the use of PET to investigate the real-time trafficking of as few as 10(4) cells/0.2 mL. Furthermore, to clarify the role of the immune defense system, metastatic potential and cell trafficking also were examined by using macrophage-depleted mice.

RESULTS

When 10(6) or 10(5) RAW117-H10 cells/0.2 mL were injected into mice, both quantities of cells caused liver metastasis, cells accumulated in the liver at a similar rate, and there was an approximately 10-fold difference in the number of accumulated cells between the two doses. However, the injection of 10(4) cells/0.2 mL did not produce metastasis, and the accumulation rate in the liver was less than one-tenth of that after the injection of 10(5) cells/0.2 mL. The treatment of mice with 2-chloroadenosine for depleting macrophages prior to the injection of 10(4) cells/0.2 mL resulted in the suppression of the fast elimination of the cells from the liver. Corresponding to this change in PET images, the injection of 10(4) cells/0.2 mL into 2-chloroadenosine-pretreated mice resulted in metastasis.

CONCLUSIONS

The current study suggests that immune surveillance suppresses accumulation of tumor cells to the target and suppresses metastasis, and this effect is obvious when small numbers of tumor cells are used for the challenge. Furthermore, the immune defense system plays a role in the early stage of the metastatic process.

Stereological quantification of carboxyfluorescein-labeled rat lung metastasis: a new method for the assessment of natural killer cell activity and tumor adhesion in vivo and in situ

The function of natural killer (NK) cells is often studied by assessing in vitro levels of NK cell mediated lysis of target cells, or by assessing in vivo levels of lung tumor cell retention or metastatic colonization of intravenously injected tumor cells. However, these methods do not permit direct quantification and visualization of NK cells and their targets in vivo and in situ. Here, a new approach is described to visualize effector-to-target interactions as well as to estimate total numbers of targets in the lung, in vivo and in situ. MADB106 tumor cells were vitally labeled using carboxyfluorescein (CFSE) and intravenously (i.v.) injected into Fischer 344 rats (10(6) cells/rat). This mammary adenocarcinoma derived cell line is syngeneic to the inbred Fischer 344 rat and highly sensitive to NK cell activity in vivo. Effector-to-target interactions were visualized by immunostaining. Using the optical fractionator method, total numbers of CFSE-labeled MADB106 tumor cells were estimated in the left lung of the animals 5 min after tumor inoculation. To further demonstrate the usefulness of this approach in reflecting in vivo processes, rats were inoculated with MADB106 cells and simultaneously with a single i.v. bolus of either 1 microg/kg adrenaline or saline. Both lungs were removed 5 min later. Adrenaline caused a significant 80% reduction in the total number of lung CFSE-labeled MADB106 tumor cells, suggesting a rapid modulation of metastasis by stress hormones. This new approach facilitates the monitoring of effector-to-target interactions and the quantification of immune cell function or tumor adhesion in vivo and in situ.

Possible role of immune surveillance at the initial phase of metastasis produced by B16BL6 melanoma cells

The relationship among the real-time trafficking of lung metastatic B16BL6 cells, metastatic potential, and the injected number of the cells was examined, since the smaller the number of tumor cells injected, the more clearly the immune defense may be observed. When 1x10(6) or 1x10(5) B16BL6 cells were injected into mice via the tail vein, both numbers of cells accumulated in the lung at a similar rate: there was an approximately 10-fold difference in the number of accumulated cells between the two doses. Elimination from the lung was not dependent on the cell number but on the proportion of accumulated cells. However, the injection of 1x10(4) cells resulted in lung accumulation less than one-tenth of that obtained with 1x10(5) cell injection. Metastasis was observed when 1x10(5) or 1x10(6) B16BL6 cells were injected, but not after injection of 1x10(4) cells. To clarify the roles of the immune defense system at the initial phase of metastasis, we challenged macrophage-depleted mice with 1x10(4) tumor cells. Treatment of mice with 2-chloroadenosine prior to the tumor cell challenge cancelled the suppression of not only metastasis but also the lung accumulation. Furthermore, the administration of 2-chloroadenosine following the tumor cell challenge had little effect on the metastatic potential. These results suggest that the immune surveillance whose action was obvious at the low dose of challenged tumor cells functions strongly at the initial phase but not at the advanced stages of the metastatic process, and that macrophages play an important role in the suppression of metastasis.

Basic science research in pain

Pain is not simply a physiologic event, but a dynamic process that involves continuous interaction among complex systems. Nurses have the unique disciplinary background to envision the pain process within the context of the whole dynamic human being. Understanding the human condition in this holistic manner prepares nurses to develop clinically relevant research questions. Many of these research questions can best be answered initially through basic science research. Basic science research by a nurse will be distinct from other disciplines from the inception of the hypothesis through the conclusions drawn to the delineation of areas for further research. This article provides a few examples of basic science research in the area of pain by nurse researchers. The research includes both cellular and animal models and describes the relationship of the research to clinical practice. Patient care will ultimately benefit from clinically relevant research whether the methodology used is basic science or other methods.

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.