Spontaneous regression of micro-metastases following primary tumor excision: a critical role for primary tumor secretome

BACKGROUND

Numerous case studies have reported spontaneous regression of recognized metastases following primary tumor excision, but underlying mechanisms are elusive. Here, we present a model of regression and latency of metastases following primary tumor excision and identify potential underlying mechanisms.

RESULTS

Using MDA-MB-231HM human breast cancer cells that express highly sensitive luciferase, we monitored early development stages of spontaneous metastases in BALB/c nu/nu mice. Removal of the primary tumor caused marked regression of micro-metastases, but not of larger metastases, and in vivo supplementation of tumor secretome diminished this regression, suggesting that primary tumor-secreted factors promote early metastatic growth. Correspondingly, MDA-MB-231HM-conditioned medium increased in vitro tumor proliferation and adhesion and reduced apoptosis. To identify specific mediating factors, cytokine array and proteomic analysis of MDA-MB-231HM secretome were conducted. The results identified significant enrichment of angiogenesis, growth factor binding and activity, focal adhesion, and metalloprotease and apoptosis regulation processes. Neutralization of MDA-MB-231HM-secreted key mediators of these processes, IL-8, PDGF-AA, Serpin E1 (PAI-1), and MIF, each antagonized secretome-induced proliferation. Moreover, their in vivo simultaneous blockade in the presence of the primary tumor arrested the development of micro-metastases. Interestingly, in the METABRIC cohort of breast cancer patients, elevated expression of Serpin E1, IL-8, or the four factors combined predicted poor survival.

CONCLUSIONS

These results demonstrate regression and latency of micro-metastases following primary tumor excision and a crucial role for primary tumor secretome in promoting early metastatic growth in MDA-MB-231HM xenografts. If generalized, such findings can suggest novel approaches to control micro-metastases and minimal residual disease.

Deleterious synergistic effects of distress and surgery on cancer metastasis: Abolishment through an integrated perioperative immune-stimulating stress-inflammatory-reducing intervention

The perioperative period holds disproportionate impact on long-term cancer outcomes. Nevertheless, perioperative interventions to improve long-term cancer outcomes are not clinical routines, including perioperative stress-reducing or immune-stimulating approaches. Here, mimicking the clinical setting of pre-operative distress, followed by surgery, we examined the separate and combined effects of these events on the efficacy of pre-operative immune stimulation in rats and mice, and on post-operative resistance to tumor metastasis of the syngeneic mammary adenocarcinoma MADB106 in F344 rats and the CT26 colon carcinoma in Balb/C mice. The novel immune stimulating agents, GLA-SE or CpG-C (TLR-4 and TLR-9 agonists, respectively), were employed pre-operatively. Sixteen hours of pre-operative behavioral stressors (i) lowered CpG-C induced plasma IL-12 levels, and reduced resistance to MADB106 and CT-26 experimental metastases, and (ii) worsened the deleterious effects of laparotomy on metastasis in both tumor models. In rats, these effects of pre-operative stress were further studied and successfully abolished by the glucocorticoid receptor antagonist RU-486. Additionally, in vitro studies indicated the dampening effect of corticosterone on immune stimulation. Last, we tested a perioperative integrated intervention in the context of pre-operative stress and laparotomy, based on (i) antagonizing the impact of glucocorticoids before surgery, (ii) activating anti-metastatic immunity perioperatively, and (iii) blocking excessive operative and post-operative adrenergic and prostanoid responses. This integrated intervention successfully and completely abolished the deleterious effects of stress and of surgery on post-operative resistance to experimental metastasis. Such and similar integrated approaches can be studied clinically in cancer patients.

Regeneration of Functional Adrenal Tissue Following Bilateral Adrenalectomy

It is assumed that after complete bilateral adrenalectomy (ADX), no adrenal tissue will redevelop and adrenal hormone levels will remain low and unaffected by stress. However, anecdotal observations in animals and in patients suggest that under some unknown circumstances the opposite can occur. Herein, we studied whether adrenalectomized rats can develop an alternative source of systemic corticosterone after complete bilateral ADX with minimal replacement therapy. Male and female rats underwent either a standard ADX, in which the glands were removed with minimal surrounding adipose tissue, or an extensive ADX, in which glands were removed with most surrounding adipose tissue. Excised glands were histologically tested for completeness, and corticosterone replacement was nullified within 1 to 3 weeks postoperatively. In four experiments and in both excision approaches, some rats gradually reestablished baseline corticosterone levels and stress response in a time-dependent manner, but differences were observed in the reestablishing rates: 80% in standard ADX vs 20% in extensive ADX. Upon searching for the source of corticosterone secretion, we were surprised to find functional macroscopic foci of adrenocortical tissue without medullary tissue, mostly proximal to the original location. Chronic stress accelerated corticosterone level reestablishment. We hypothesized that underlying this phenomenon were preexisting ectopic microscopic foci of adrenocortical-like tissue or a few adrenal cells that were pre-embedded in surrounding tissue or detached from the excised gland upon removal. We concluded that adrenalectomized animals may develop compensatory mechanisms and suggest that studies employing ADX consider additional corticosterone supplementation, minimize stress, and verify the absence of circulating corticosterone.

Perioperative treatment with the new synthetic TLR-4 agonist GLA-SE reduces cancer metastasis without adverse effects

The use of TLR agonists as an anti-cancer treatment is gaining momentum given their capacity to activate various host cellular responses through the secretion of inflammatory cytokines and type-I interferons. It is now also recognized that the perioperative period is a window of opportunity for various interventions aiming at reducing the risk of cancer metastases-the major cause of cancer related death. However, immune-stimulatory approach has not been used perioperatively given several contraindications to surgery. To overcome these obstacles, in this study, we used the newly introduced, fully synthetic TLR-4 agonist, Glucopyranosyl Lipid-A (GLA-SE), in various models of cancer metastases, and in the context of acute stress or surgery. Without exerting evident adverse effects, a single systemic administration of GLA-SE rapidly and dose dependently elevated both innate and adaptive immunity in the circulation, lungs and the lymphatic system. Importantly, GLA-SE treatment led to reduced metastatic development of a mammary adenocarcinoma and a colon carcinoma by approximately 40-75% in F344 rats and BALB/c mice, respectively, at least partly through elevating marginating-pulmonary NK cell cytotoxicity. GLA-SE is safe and well tolerated in humans, and currently is used as an adjuvant in phase-II clinical trials. Given that the TLR-4 receptor and its signaling cascade is highly conserved throughout evolution, our current results suggest that GLA-SE may be a promising immune stimulatory agent in the context of oncological surgeries, aiming to reduce long-term cancer recurrence.

Plasma IL-12 levels are suppressed in vivo by stress and surgery through endogenous release of glucocorticoids and prostaglandins but not catecholamines or opioids

IL-12 is a prominent Th1 differentiator and leukocyte activator. Ample studies showed suppression of IL-12 production by numerous stress factors, including prostaglandins, catecholamines, glucocorticoids, and opioids, but did so in vitro and in the context of artificial leukocyte activation, not simulating the in vivo setting. In a recent study we reported in vivo suppression of plasma IL-12 levels by behavioral stress and surgery. The current study aims to elucidate neuroendocrine mechanisms underlying this phenomenon in naïve F344 rats. To this end, both adrenalectomy and administration of specific antagonists were used, targeting the aforementioned stress factors. The results indicated that corticosterone and prostaglandins are prominent mediators of the IL-12-suppressing effects of stress and surgery, apparently through directly suppressing leukocyte IL-12 production. Following surgery, endogenous prostaglandins exerted their effects mainly through elevating corticosterone levels. Importantly, stress-induced release of epinephrine or opioids had no impact on plasma IL-12 levels, while pharmacological administration of epinephrine reduced plasma IL-12 levels by elevating corticosterone levels. Last, a whole blood in vitro study indicated that prostaglandins and corticosterone, but not epinephrine, suppressed IL-12 production in non-stimulated leukocytes, and only corticosterone did so in the context of CpG-C-induced IL-12 production. Overall, the findings reiterate the notion that results from in vitro or pharmacological in vivo studies cannot indicate the effects of endogenously released stress hormones under stress/surgery conditions. Herein, corticosterone and prostaglandins, but not catecholamines or opioids, were key mediators of the suppressive effect of stress and surgery on in vivo plasma IL-12 levels in otherwise naïve animals.

In vivo suppression of NK cell cytotoxicity by stress and surgery: glucocorticoids have a minor role compared to catecholamines and prostaglandins

Most in vitro and ex-vivo studies indicate a profound suppression of NK cell cytotoxicity (NKCC) by glucocorticoids; while catecholamines and prostaglandins were reported both to suppress and to enhance NKCC. However, methodological considerations hinder our ability to deduce from these findings to the impact of endogenous release of these factors on in vivo levels of NKCC and their implications to NK-dependent resistance to pathologies in living humans or animals. Here we used an in vivo approach that sensitively and specifically reflects NKCC in living F344 rats, based on lung clearance of NK-sensitive tumor cells (MADB106), and based on comparing effects between NK-intact and NK-depleted rats. To study the role of corticosterone, epinephrine, and prostaglandins, we administered these factors to rats, or antagonized their endogenous release following different stress paradigms or surgery. The results indicated that endogenous or exogenous elevated corticosterone levels can suppress in vivo NKCC levels, but only under some conditions, and mostly secondarily to the NK-suppressing impact of epinephrine. Specifically, corticosterone-induced NKCC suppression occurred (i) only under prolonged, but not short exposure to stress, and mainly in males; (ii) was smaller than the prominent impact of epinephrine; (iii) was mostly ascribed to corticosterone-induced potentiation of the effects of epinephrine or/and prostaglandins; and (iv) was completely abolished through antagonizing epinephrine or/and prostaglandins. Overall, these findings markedly limit the significance of stress/surgery-induced corticosterone release in the in vivo suppression of NKCC, and highlight the blockade of epinephrine or/and prostaglandins as effective and clinically feasible approaches to overcome such immuno-suppressive effects.

PGE2 suppresses NK activity in vivo directly and through adrenal hormones: effects that cannot be reflected by ex vivo assessment of NK cytotoxicity

Surgery can suppress in vivo levels of NK cell cytotoxicity (NKCC) through various mechanisms, including catecholamine-, glucocorticoid (CORT)-, and prostaglandin (PG)-mediated responses. However, PGs are synthesized locally following tissue damage, driving proinflammatory and CORT responses, while their systemic levels are often unaffected. Thus, we herein studied the role of adrenal factors in mediating in vivo effects of PGs on NKCC, using adrenalectomized and sham-operated F344 rats subjected to surgery or PGE(2) administration. In vivo and ex vivo approaches were employed, based on intravenous administration of the NK-sensitive MADB106 tumor line, and based on ex vivo assessment of YAC-1 and MADB106 target-line lysis. Additionally, in vitro studies assessed the kinetics of the impact of epinephrine, CORT, and PGE(2) on NKCC. The results indicated that suppression of NKCC by epinephrine and PGE(2) are short lasting, and cannot be evident when these compounds are removed from the in vitro assay milieu, or in the context of ex vivo assessment of NKCC. In contrast, the effects of CORT are long-lasting and are reflected in both conditions even after its removal. Marginating-pulmonary NKCC was less susceptible to suppression than circulating NKCC, when tested against the xenogeneic YAC-1 target line, but not against the syngeneic MADB106 line, which seems to involve different cytotoxicity mechanisms. Overall, these findings indicate that elevated systemic PG levels can directly suppress NKCC in vivo, but following laparotomy adrenal hormones mediate most of the effects of endogenously-released PGs. Additionally, the ex vivo approach seems limited in reflecting the short-lasting NK-suppressive effects of catecholamines and PGs.

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.

Synergism between immunostimulation and prevention of surgery-induced immune suppression: an approach to reduce post-operative tumor progression

BACKGROUND

A unique opportunity to eradicate cancer is presented immediately after the excision of the primary tumor, but surgical procedures often induce the release of immunosuppressing factors that render cell mediated immunity ineffective. Here we tested the hypothesis that integration of peri-operative immunostimulation and blockade of immunosuppression could synergistically improve post-operative anti-metastatic immunity and long-term survival.

METHODS

Two syngeneic tumor models in F344 rats were employed, studying post-operative tumor progression. In the first model, survival following laparotomy and CRNK-16 leukemia was studied. Rats were peri-operatively treated with the immuno-stimulant poly I-C (5x0.2 mg/kg/inj), with catecholamine- and prostaglandin-blockers (shown to prevent post-operative immunosuppression: 4.5 mg/kg nadolol, 4 mg/kg indomethacin), with both interventions, or with neither. Long-term survival was assessed thereafter. The second model used the MADB106 mammary adenocarcinoma, assessing its lung tumor retention (LTR) following i.v. inoculation, as well as host marginating-pulmonary NK numbers and activity against this tumor. IL-12 was employed for immunostimulation (4x1.5 microg/kg/inj), with and without the above blockers.

RESULTS

Post-operative CRNK-16 survival rates were significantly improved only by the integrated approach of immune stimulation and endocrine blockers. Post-operative MADB106 LTR was additively reduced by the two interventions. Importantly, while IL-12 increased pulmonary NK cytotoxicity against MADB106, surgery markedly suppressed this cytotoxicity in both IL-12 and vehicle treated animals. The blockers prevented this suppression per lung and per single NK cell.

CONCLUSIONS

Immunostimulation could be rendered ineffective post-operatively due to immunosuppression; therefore integrating endocrine-blocker therapies into the realm of peri-operative immunotherapy could optimize immune control over residual disease, potentially improving clinical outcomes.

Improving survival rates in two models of spontaneous postoperative metastasis in mice by combined administration of a beta-adrenergic antagonist and a cyclooxygenase-2 inhibitor

Clinical practice does not consider perioperative paracrine and neuroendocrine stress responses as risk factors for cancer recurrence, although recent animal studies provided supportive evidence. Suggested mechanisms include the effects of stress-hormones on tumor cells and on host physiology. In this study, in mice undergoing primary tumor excision, we tested the survival-enhancing potential of perioperative blockade of catecholamines and prostaglandins, and studied potential mediating mechanisms. C57BL/6J mice were inoculated intrafootpad with syngeneic B16F10.9-melanoma or Lewis lung carcinoma, and the paw was amputated when a developing tumor exceeded 100 microl. The clinically used beta-adrenergic antagonist propranolol, and/or the cyclooxygenase-2 inhibitor etodolac, were administered once before amputation, and recurrence-free survival was monitored. In different studies, NK cytotoxicity, leukocytes' molecular functional markers, and vascular endothelial growth factor secretion by tumor cells were studied in the context of surgery and drug treatments. The findings indicated that the combination of propranolol and etodolac, but neither drug alone, significantly and markedly improved survival rates in both tumor models, and was as effective as established immunostimulatory agents (IL-12 and polyinosinic-polycytiylic acid). Surgery markedly reduced NK cytotoxicity and NK cell expression of Fas ligand and CD11a, reduced all circulating lymphocyte-subtype concentrations, and increased corticosterone levels. Propranolol and etodolac administration counteracted these perturbations. B16 and 3LL secreted vascular endothelial growth factor in vitro, but secretion was not affected by catecholamine agonists, prostaglandins, corticosterone, propranolol, or etodolac. Overall, propranolol and etodolac administration, which could be applied perioperatively in most cancer patients with minimal risk and low cost, has counteracted several immunologic and endocrinologic perturbations and improved recurrence-free survival rates in mice undergoing primary tumor excision.

Metastatic-promoting effects of LPS: sexual dimorphism and mediation by catecholamines and prostaglandins

Inflammation is implicated in several medical conditions that are sexually dimorphic, including depression, cardiovascular diseases, autoimmunity, and presumably cancer progression. Here we studied the effects of the proinflammatory agent, LPS, on MADB106 lung tumor retention (LTR), and sought to elucidate underlying mechanisms and sexual dimorphism. F344 male and female rats were administered with LPS (0.001-1mg/kg i.v.) simultaneously with tumor cell inoculation, and treated with a beta-blocker (nadolol, 0.2-0.3mg/kg s.c.), a COX inhibitor (indomethacin, 4mg/kg s.c.) or both drugs. To study the role of NK cells, numbers and cytotoxicity of marginating-pulmonary NK cells were studied, and selective in vivo NK-depletion was employed. Serum levels of corticosterone, IL-6, and TNF-alpha were also assessed. The findings indicated that LPS increased LTR in both sexes, but 10-fold higher doses were needed in females to reach the increase evident in males. Additionally, nadolol and indomethacin reduced the effects of LPS, more so in males. In vivo NK-depletion and ex vivo NK activity studies suggested that LPS affected LTR through both NK-independent and NK-dependent mechanisms, the latter mediated through prostaglandin release in males. Corticosterone, IL-6, and TNF-alpha responses to LPS were sexually dimorphic, but were not associated with LPS or drugs' impacts on LTR. Overall, our findings demonstrate sexual dimorphism in LPS-induced elevated susceptibility to MADB106 experimental metastasis, and in potential humoral underlying mechanisms. Further studies are needed to elucidate additional immunological and non-immunological mediators of these dimorphisms, as well as to assess their involvement in other sexually dimorphic pathologies that are associated with inflammation.

Inducing a mode of NK-resistance to suppression by stress and surgery: a potential approach based on low dose of poly I-C to reduce postoperative cancer metastasis

Perioperative suppression of NK activity has been suggested to compromise host resistance to tumor progression. Here, we sought to develop a clinically applicable preoperative regimen to prevent immunosuppression and promotion of metastasis by stress or surgery. The synthetic ds-RNA, poly I-C, was used in vivo in F344 rats, based on its alleged in vitro ability to protect immunocytes from suppression by cAMP elevating agents. Different regimens of poly I-C were studied in controls and in rats subjected to a pharmacological stressor, swim stress, or surgical stress. Resistance to lung experimental metastasis of the syngeneic non-immunogenic MADB106 mammary adenocarcinoma was assessed. Numbers of circulating and marginating-pulmonary NK cells and their cytotoxicity against the MADB106 and YAC-1 target lines were also studied. Our findings established a regimen of repeated low-dose poly I-C administration with minimal side effects (0.2mg/kg i.p. 5, 3, and 1day before tumor inoculation). This regimen, while hardly affecting resistance levels in non-stressed animals, prevented all stressors from promoting metastases. These beneficial effects occurred in the presence of a primary tumor and in both sexes. Poly I-C increased the numbers of NK cells, and, on a per NK cell basis, while not increasing cytotoxicity, profoundly protected marginating-pulmonary NK cells from suppression by surgery. This study suggests a non-toxic clinically translatable prophylactic use of poly I-C to target the critical perioperative period. By increasing the number of marginating-pulmonary NK cells, and by transforming them into a mode of resistance to immunosuppression, this approach may reduce postoperative metastasis in cancer patients.

Immune suppression while awaiting surgery and following it: dissociations between plasma cytokine levels, their induced production, and NK cell cytotoxicity

Surgery may render patients susceptible to life-threatening complications, including infections and later metastases. Suppression of cell mediated immunity (CMI) and perturbations in the cytokine network were implicated in these outcomes. The current study assessed the effects of various surgeries on a wide array of immune indices, and compared patients' pre-operative immune status to that of control subjects. A total of 81 subjects (controls, moderate and major surgeries) provided up to five daily blood samples. Whole blood procedures were conducted within hours of blood withdrawal, assessing NK cell number and cytotoxicity, and plasma cytokine levels and induced production (IFNgamma, IL-6, IL-10, and IL-12). Our findings indicate that surgery reduced NK cell numbers/ml blood, and independently suppressed NK activity per NK cell and per ml blood. Among other perturbations in the cytokine network, pro-CMI cytokine production (IL-12 and IFNgamma) was reduced by surgery. Surprisingly, plasma levels of IFNgamma and IL-6 increased following surgery, while their in vitro induced production showed opposite effects. Patients awaiting surgery exhibited impaired IL-12 induced production and NK activity/ml, and reduced IFNgamma plasma levels. No significant associations were found between NK cytotoxicity and Th1 cytokines, although these indices showed high correlations with other variables. Overall, our findings indicate that patients exhibit impaired immune functions even before operation, which seem to contribute to the evident post-operative immune suppression. In the peri-operative context, induced cytokine production and plasma cytokines levels reflect different processes. Last, we suggest that peri-operative suppression of NK activity is mediated by neuroendocrine responses rather than Th1 cytokines.

Prophylactic IL-12 treatment reduces postoperative metastasis: mediation by increased numbers but not cytotoxicity of NK cells

Despite a promising potential, interleukin-12 immunotherapy has yielded limited clinical success while causing perilous toxicities. Here we study a context in which IL-12 may prove clinically beneficial--the removal of the primary tumor, when cell-mediated immunity (CMI) may eradicate minimal residual disease (MRD), but is inhibited by postoperative immunosuppression, potentially leading to enhanced malignant progression. F344 rats were preoperatively treated with IL-12 and inoculated postoperatively with syngeneic MADB106 tumor cells. An optimal regimen of eight-day sustained exposure to IL-12 was developed (1 microg/rat/day), which caused mild side effects, increased baseline resistance to experimental MADB106 metastasis, and abolished the promotion of metastasis by laparotomy and other immunosuppressive paradigms. Depletion of NK cells indicated their major role in controlling MADB106 metastasis in naïve and IL-12 treated rats. Studying NK cytotoxicity, we found that IL-12 did not potentiate activity per NK cell, nor protected it from suppression by surgery. However, IL-12 increased the numbers of NK cells in the circulation and marginating pulmonary pool of naïve and operated rats, and correspondingly increased total NK activity in these compartments. Therefore, this study indicates anti-tumor effects of IL-12 based on increased numbers of strategically located NK cells, and advocates a prophylactic approach against the potential metastasis-promoting effects of surgery.

Amelioration of operation-induced suppression of marginating pulmonary NK activity using poly IC: a potential approach to reduce postoperative metastasis

BACKGROUND AND OBJECTIVES

Pulmonary metastasis is a major cause of death in cases of operable cancer, and evidence suggests that postoperative immunosuppression contributes to this complication. In this study, we aimed to circumvent this risk and identify immunocytes critical in preventing pulmonary metastases.

METHODS

F344 rats were treated with either vehicle or repeated low doses of poly I-C (0.2 mg/kg i.p., days 5, 3, and 1 preoperatively), a Th1-cytokine-inducing agent, then subjected or not to laparotomy. Using a non-immunogenic syngeneic mammary adenocarcinoma line (MADB106) we studied: (a) NK cytotoxicity (NKC) in marginating-pulmonary (MP) and in circulating leukocytes; (b) resistance to experimental lung metastasis; and (c) in vitro susceptibility of NKC to corticosterone and prostaglandin-E(2), substances thought to mediate postoperative immunosuppression.

RESULTS

MP but not circulating leukocytes showed significant NKC against MADB106 cells. Surgery suppressed this MP-NKC per NK cell and promoted MADB106 metastasis, and poly I-C treatment completely abolished both effects. Poly I-C quadrupled the numbers of MP-NK cells without causing apparent side effects, and protected MP-NKC from in vitro suppression by corticosterone and prostaglandin-E(2).

CONCLUSIONS

MP-NK cells are unique in their ability to kill this apparently immunoresistant tumor. Low doses of synthetic ds-RNA (poly I-C), and potentially Th1 cytokines, can expand this MP-NK population and protect it from immunosuppression. The novelty of such a prophylactic approach is targeting the immediate postoperative period, which is characterized by high vulnerability to residual disease, and protecting critical anti-metastatic immunity against postoperative suppression. Testing such a potentially innocuous intervention in oncology patients preparing for surgery may reduce metastatic recurrence.

Autologous control of a highly malignant syngeneic CRNK-16 leukemia in the rat: a role for NK cells

It is unclear whether autologous immunity could be recruited to restrict the progression of leukemia. Patients harboring leukemia commonly display suppressed cell mediated immunity, which may contribute to their inability to control the disease. Immune response against leukemia is evident in allogeneic HLA-mismatched bone marrow transplantation, implicating the involvement of NK cells. This graft-versus-leukemia (GVL) activity suggests that, if not suppressed, an autologous NK cell response could potentially control acute leukemia that had down-regulated HLA expression. In the current study we assessed the role of non-suppressed autologous NK cells in controlling a syngeneic highly malignant leukemia, the CRNK-16 line, that constitute a major cause of natural death in aged F344 rats. A minuscule dose of 60 CRNK-16 leukemia cells per rat was sufficient to induce 50% mortality rates, and animals that survived this challenge did not show improved survival upon a second challenge. The CRNK-16 line was found to exhibit low levels of MHC-I, and selective in vivo depletion of NK cells nullified in vitro NK activity against the CRNK-16 line and reduced survival rates from this leukemia. In vivo activation of NK cells, employing low doses of poly I-C or IL-12, increased in vitro NK activity against the leukemia and dramatically improved survival rates when treatment was initiated before, but not after leukemia inoculation. These results indicate the ability of competent autologous NK cells to restrict highly malignant non-immunogenic leukemia. Thereby, this model presents an opportunity to study specific in vivo NK-leukemia interactions.

High NK cell activity in recurrent miscarriage: what are we really measuring?

BACKGROUND

Several studies have shown that women with unexplained recurrent miscarriage (RM) have increased numbers and activity of peripheral blood NK cells and that elevated levels of these cells predict subsequent miscarriages in women with RM. Because catecholamines rapidly mobilize NK cells into the circulation, such increases may not reflect a steady state of overactive immunity but may result from a transient increase in the number of NK cells because of the stress associated with blood withdrawal.

METHODS

Blood was drawn from 22 controls and 38 RM patients immediately after vein cannulation, and again 20 min later. The percentage of NK cells within lymphocytes, their concentration per microlitre of blood and their activity were assessed.

RESULTS

All three indices of NK cells did not change in the controls across the two samples. However, women with RM had elevated levels in all three NK indices in the first blood sample, but these levels declined to values similar to those seen in the controls. This decline was mainly observed in primary aborters whose NK activity was highest in the first blood withdrawal. Accordingly, there was a high correlation between the magnitude of the decline and the initial NK cell indices in women with RM. The change in activity highly correlated with the change in the concentration of NK cells.

CONCLUSION

The increased NK number and activity previously observed in RM patients may result from a transient stress response at the time of blood withdrawal. Patients with primary RM may be characterized by exaggerated acute stress responses in other circumstances.

Marginating pulmonary-NK activity and resistance to experimental tumor metastasis: suppression by surgery and the prophylactic use of a beta-adrenergic antagonist and a prostaglandin synthesis inhibitor

Surgery is imperative for cancer treatment, but was suggested to suppress immunity and facilitate metastasis. Here we study the involvement of catecholamines and prostaglandins (PG) in such outcomes, and the role played by marginating-pulmonary (MP)-NK cells in controlling MADB106 metastasis. Non-operated and laparotomized F344 rats were injected postoperatively with a PG synthesis inhibitor (indomethacin, 4 mg/kg i.p.), a beta-blocker (nadolol, 0.6 mg/kg s.c.), both drugs, or vehicle. Rats were then inoculated intravenously with non-immunogenic syngeneic MADB106 cells, and 24 h later lung tumor retention was assessed, or 3 weeks later lung metastases were counted. Additionally, 12 h after surgery we harvested MP-NK cells and circulating-NK cells and compared their numbers and cytotoxicity against MADB106 cells and standard YAC-1 target cells. Surgery significantly increased MADB106 metastasis. Nadolol and indomethacin reduced this effect by approximately 50% when used alone, and significantly more (75%) when used together. Only MP-leukocytes exhibited NK cytotoxicity against MADB106 cells. Surgery markedly suppressed it, and nadolol and indomethacin additively restored it. Similar effects were observed assessing MP-NK and circulating-NK cytotoxicity against YAC-1 target cells. Alterations in the numbers of NK cells were partly associated with alterations in total MP-NK activity, but not with circulating-NK activity. Last, administrating nai ve rats with physiologically relevant doses of a beta-adrenergic agonist (metaproterenol), and/or with PGE2, additively and independently of each other promoted MADB106 metastasis, simulating the effects of surgery. These findings point at potential prophylactic measures in cancer patients undergoing surgery, and suggest a role for MP-NK cells in resisting metastasis of apparently insensitive tumors.

Differences in number and activity of peripheral natural killer cells in primary versus secondary recurrent miscarriage

OBJECTIVE

To compare peripheral natural-killer (NK) cell numbers and activity in women with primary recurrent miscarriage, secondary recurrent miscarriage and controls.

DESIGN

Observational study. Academic medical center.

PATIENT(S)

Thirty-eight women with primary recurrent miscarriage, 29 women with secondary recurrent miscarriage, and 25 control women.

INTERVENTION(S)

None.[1] The proportion of NK cells in the total lymphocyte population, [2] the concentration of NK cells per microliter of blood, and [3] NK activity (NKA), using both standard and whole-blood assays.

RESULT(S)

Primary aborters had the highest proportion and concentration of NK cells and had the highest activity using the standard assay. Secondary aborters had an intermediate level of these NK cell indices, whereas the control patients had the lowest levels. Using the whole-blood NKA assay, the differences between primary and secondary aborters were most apparent: primary aborters had significantly higher NKA than did either secondary aborters or control women (72, 40, and 35 lytic units, respectively). Approximately 50% of the variability in NKA could be attributed to differences in concentrations of NK cell per microliter of blood.

CONCLUSION(S)

The higher NKA evident in primary recurrent miscarriage and the reported higher efficacy of immunotherapy in primary aborters support the involvement of NK cells in the etiology of primary recurrent miscarriage.

Prostaglandin e(2) suppresses NK activity in vivo and promotes postoperative tumor metastasis in rats

BACKGROUND

Prostaglandins (PGs) were shown in vitro to suppress several functions of cellular immunity. It is unclear, however, whether physiological levels of PGs can suppress cellular immunity in vivo and whether such suppression would compromise postoperative host resistance to metastasis.

METHODS

Fischer 344 rats were administered PGE(2) in doses (18 to 300 micro g/kg subcutaneously) that increased the serum levels approximately 2- to 4-fold. We then assessed the number and activity of circulating natural killer (NK) cells, as well as rats' resistance to experimental metastasis of a syngeneic NK-sensitive tumor (MADB106). To study whether endogenously released PGs after surgery compromise these indices, we tested whether laparotomy adversely affects them and whether a cyclooxygenase-synthesis inhibitor, indomethacin (4 mg/kg), attenuates these effects.

RESULTS

PGE(2) dose-dependently suppressed NK activity per NK cell and dose-dependently increased 4- and 24-hour MADB106 lung tumor retention (LTR); 240 micro g/kg of PGE(2) quadrupled the number of lung metastases counted 3 weeks later. Selective depletion of NK cells abrogated the promotion of LTR by PGE(2). Surgery significantly suppressed NK activity and increased MADB106 LTR, and indomethacin halved these effects without affecting nonoperated rats.

CONCLUSIONS

PGE(2) is a potent in vivo suppressor of NK activity, and its postoperative release may promote tumor recurrence.

The effects of a Chinese herb formula, anti-cancer number one (ACNO), on NK cell activity and tumor metastasis in rats

The effects of anti-cancer number one (ACNO), a 19-herb Chinese formula used to treat cancer patients, were studied in F344 rats. In the first study, the number and activity of circulating NK cells were evaluated following 18 days of oral consumption of 0.1, 0.5, or 2 g/kg/day. The second study assessed the effect of ACNO on resistance to metastasis of the MADB106 tumor line, a syngeneic mammary adenocarcinoma that metastasizes only to the lungs and is highly sensitive to NK activity (NKA) in vivo. Resistance to metastasis was assessed under baseline conditions and following the administration of a beta-adrenergic agonist, metaproterenol (MP). MP was used to simulate sympathetic response to stressful conditions, and was previously shown to suppress resistance to MADB 106 metastasis. The results of the first study indicated a dose-dependent increase in NKA per ml of blood and per NK cell, with no significant changes in blood concentration of NK cells. In the second study, whereas MP caused a 4.5-fold increase in the number of metastases in untreated rats, only a 2.3-fold increase occurred in rats treated with ACNO. No significant improvement in baseline levels of resistance to metastasis was observed. These findings indicate the importance of studying ACNO under stressful conditions in patients with potentially metastasizing tumors. This may prove particularly important during the perioperative period, spanning from the detection of the primary tumor to postoperative treatment. During this critical period, psychological and physiological stress responses are known to cause massive immunosuppression, which was suggested to promote metastatic development.

Timing within the menstrual cycle, sex, and the use of oral contraceptives determine adrenergic suppression of NK cell activity

Physiological responses that involve adrenergic mechanisms, such as stress-induced changes in cardiovascular indices, were reported to fluctuate along the menstrual cycle. Metastatic development following surgery was also reported to vary according to the menstrual phase during which a primary breast tumour was removed. Natural killer (NK) cells are believed to play an important role in controlling metastases. Our recent studies in rats demonstrated that adrenergic suppression of NK activity and of resistance to metastasis is more profound during oestrous phases characterized by high levels of oestradiol. In the current study in humans, we examined the in vitro impact of a beta-adrenergic agonist, metaproterenol (MP), on NK activity, comparing blood drawn from (a) women tested at 3-4 different phases of their menstrual cycle (n = 10), (b) women using oral contraceptives (OC) (n = 10), and (c) men (n = 7). NK activity in each blood sample was assessed in the presence of 5 different concentrations of MP (10(-8)M to 10(-6)M), and in its absence (baseline). The results indicated marked group differences in the magnitude of NK suppression by MP: EC(50)was 2. 6-fold lower in the luteal phase compared to the follicular phase, and 1.8-fold lower in OC users compared to men, who were least susceptible to the effects of MP. No significant group differences or menstrual effects in baseline levels of NK activity were evident. These findings provide the first empirical evidence for menstrual regulation of adrenergic impact on cellular immune competence. Relevance of these findings to the relation between the timing of breast cancer excision within the menstrual cycle and survival rates is discussed.

Higher natural killer cell activity in schizophrenic patients: the impact of serum factors, medication, and smoking

Schizophrenia has been associated with altered immunity and reduced occurrence of autoimmune diseases and malignancies. A few studies in schizophrenic patients have assessed natural killer cell activity (NKA), but no consistent findings have emerged. However, NKA was assessed using standard procedures and in the absence of autologous serum and the various cytokines that modulate NKA and appear to be abnormal in schizophrenic patients. In the current study, therefore, the number of NK cells and the activity of the individual NK cell were assessed in whole blood shortly after blood withdrawal, in both the presence and the absence of autologous serum. Twenty-nine schizophrenic patients (11 nonmedicated), 8 nonschizophrenic control patients (bipolar and personality disorders), and 31 age-matched healthy controls were studied. Schizophrenic patients showed higher NKA per NK cell than controls and nonschizophrenic patients. This difference remained significant even when the nonmedicated schizophrenics, who showed the highest levels of NKA, were excluded. However, the increase in NKA was more pronounced in the presence of serum and was reduced to an insignificant level when serum was removed from the same samples. In both schizophrenic patients and controls, smokers and women showed lower NKA. Numbers of NK cells did not differ among groups, although medication affected blood concentration of other leukocytes. These findings indicate that the effects of serum factors, psychiatric medication, gender, and smoking should be considered when assessing NKA in schizophrenic patients. The observed higher NKA may help explain the surprising reports of low incidence of lung cancer and other malignancies in schizophrenic patients, despite their higher rate of smoking.

Hypothermia in barbiturate-anesthetized rats suppresses natural killer cell activity and compromises resistance to tumor metastasis: a role for adrenergic mechanisms

BACKGROUND

Clinical studies have implicated surgery in promoting infections and compromising immune functions, including natural killer cell activity. Animal studies indicate that surgery-induced suppression of natural killer cell activity also promotes tumor metastasis. Hypothermia, a common surgical complication, has been suggested to underlie some of the deleterious consequences of surgery. This study evaluated the effect of hypothermia on the activity and number of blood natural killer cells and on host susceptibility to metastasis. The involvement of adrenergic mechanisms was also considered.

METHODS

Fischer-344 rats remained awake in their cages (control group) or were anesthetized with 70 mg/kg thiopental and maintained for 2.5 h at core body temperatures of 30-32 degrees C (hypothermia group) or 38 degrees C (normothermia group). Thereafter, at several time points, blood was drawn so natural killer cell activity could be assessed, or rats were injected with syngeneic MADB106 tumor cells that metastasize only to the lungs. Lungs were removed 9 h later for assessment of lung tumor retention, or 4 weeks later for counting of metastases.

RESULTS

Normothermic anesthesia reduced natural killer cell activity (lytic units at 30% specific killing, mean +/- SEM) to 39+/-6.2% of control levels and hypothermia further reduced it to 15+/-6.6%. These changes were not accompanied by alterations in the numbers of circulating natural killer cells. Hypothermia increased tumor retention to 250% of control levels, and the number of metastases increased from 1.1+/-0.4 to 4.7+/-1.2. Normothermia had no significant effects on this index. Nadolol (0.4 mg/kg), a beta-adrenergic antagonist, significantly attenuated the effect of hypothermia on tumor retention.

CONCLUSIONS

Hypothermia under thiopental anesthesia suppresses natural killer cell activity and compromises host resistance to metastatic formation, possibly via adrenergic mechanisms. Such suppression may place patients with metastasizing tumors or dormant viral infections at greater risk for complications after intraoperative hypothermia.

Derangement in stress response of apolipoprotein E-deficient mice

Apolipoprotein E (apoE) is associated with familial and sporadic Alzheimer's disease (AD). Stress has been identified as a putative risk factor of AD. Thus, in the present study we examined the susceptibility of apoE-deficient mice to stress. The results obtained revealed that the elevation of corticosterone levels in apoE-deficient mice following restraint stress is markedly lower than in controls, and that these mice differ in their behavioral pain response to noxious stimuli in both stress and non-stress conditions. These findings suggest an interplay between apoE and the response to stressful stimuli and provide a model for elucidating the relationship between apoE and susceptibility to stress.

Developmental and age-related alterations in rat brain presynaptic dopaminergic mechanisms

Age-related changes in both pre- and post-synaptic components of dopamine neurons have been demonstrated in humans as well as in animals. Our study was designed to examine the effects of age on presynaptic DA neurons. To assess the developmental changes in rat striatal dopamine carrier, we used [3H]GBR 12935, which binds selectively to this transporter. In addition we monitored changes in amphetamine- and KCl-induced [3H]DA release from rat striatal slices. We were able to demonstrate age dependent changes in DA transporter density, which reached a peak at age 3 months. Amphetamine-induced released of stored DA was exactly reversed, with a nadir at age 3 months. We assumed that the combination of low DA transporter level with increased transporter-mediated DA release may have a major compensatory role with respect to the maintenance of dopaminergic transmission during normal development, aging and neuro-degenerative diseases.

Long-term effects of amygdaloid kindling on striatal dopaminergic terminals

The present study assessed the effects of kindling on striatal DA terminals. Kindled and control rats were tested for DA transporter density using [3H]GBR-12935 binding to striatal membranes and for amphetamine and KCl-induced [3H]DA release from striatal slices. Kindling decreased the maximal number of [3H]GBR-12935 binding sites in the dorsal striatum of rats sacrificed either 2 h or 4 weeks after the last seizure but had no effect on stimulated fractional [3H]DA release. These findings suggest a minor damage to DA terminals in the dorsal striatum. At the same postseizure time points, kindling augmented the hyperlocomotion associated with novel environment. Explanation of this effect requires in vivo measures of striatal DA functioning.