Shamgar Ben-Eliyahu

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. Int. J. Cancer 80:880–888, 1999.

Excitatory amino acid antagonists (kynurenic acid and MK-801) attenuate the development of morphine tolerance in the rat

To investigate the possible role of excitatory amino acids (EAAs) in the mechanisms of morphine tolerance, rats were treated either with the wide-spectrum EAA antagonist, kynurenic acid (150 mg/kg), or the specific N-methyl-D-aspartic acid (NMDA) receptor antagonist. MK-801 (0.05 mg/kg), during a four-day induction period of morphine tolerance. Morphine was given once daily at a dose of 15 mg kg. On the fifth day rats were injected only with morphine (15 mg/kg), and analgesia was assessed using the hot-plate test. Morphine tolerance was significantly reduced by both EAA antagonists. Control experiments showed that at the same doses neither acute nor chronic administration of these antagonists affected morphine analgesia itself in a manner that can explain these findings. The possible involvement of EAAs in the mechanisms of morphine tolerance is discussed.

Potential Prophylactic Measures Against Postoperative Immunosuppression: Could They Reduce Recurrence Rates in Oncological Patients?

Background: Removing the primary tumor is indispensable for eliminating the major pool of metastasizing cells, but the surgical procedure itself is suspected of promoting metastases. This adverse effect is attributed to several mechanisms acting in synergy, including mechanical release of tumor cells, enhanced angiogenesis, secretion of growth factors, and immunosuppression. Here we provide new insights into mechanisms of postoperative immunosuppression and assess the assumptions underlying the hypothesis that, by suppressing cell-mediated immunity (CMI), surgery may render the patient vulnerable to metastases that otherwise could have been controlled.Methods: An extensive review of relevant articles in English identified by using the MEDLINE database and cross-referencing.Results: Current literature suggests that (1) CMI can control minimal residual disease, especially if surgery is performed early; (2) major surgery transiently but markedly suppresses CMI through multiple mechanisms now better understood; (3) surgical stress promotes experimental metastasis through immunosuppression, but the clinical evidence remains indirect because of ethical limitations.Conclusions: Minimizing postoperative immunosuppression seems feasible, may limit recurrence, and should be introduced into the broader array of considerations when planning oncological surgeries. In the short run, physicians could try to avoid immunosuppressive anesthetic approaches, inadvertent hypothermia, excessive blood transfusions, and untended postoperative pain. When feasible, minimally invasive surgery should be considered. In the long run, clinical trials should evaluate prophylactic measures, including perioperative immunostimulation and several antagonists to cytokines and hormones specified herein.

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 &mgr;g) with morphine (10 &mgr;g). 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.

Stress increases metastatic spread of a mammary tumor in rats: Evidence for mediation by the immune system

Causal relationships among stress, immune suppression, and enhanced tumor development have often been suggested, but direct evidence is scant. We studied stress effects in Fischer 344 rats using a tumor model in which lung metastases of a syngeneic mammary tumor (MADB106) are controlled by natural killer (NK) cells. Animals exposed to acute stress showed a substantial decrease in NK cell cytotoxicity against this tumor in an in vitro assay and, when intravenously injected with this tumor, showed a twofold increase in surface lung metastases. The critical period during which stress increases metastases appears to be the same as that during which this tumor is known to be controlled by NK cells. These findings support the hypothesis that stress can facilitate the metastatic process via suppression of the immune system.

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

&NA; 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 &mgr;‐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 2×2 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 &mgr;g/kg subcutaneously (s.c.)), and at the end of surgery in a slow‐release suspension (20 &mgr;g/kg s.c.). In the second in vivo experiment, bupivacaine (10 &mgr;g) plus morphine (20 &mgr;g) in 50 &mgr;l 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.

Perioperative Use of β-blockers and COX-2 Inhibitors May Improve Immune Competence and Reduce the Risk of Tumor Metastasis

BackgroundCOX inhibitors and β-blockers were recently suggested to reduce cancer progression through inhibition of tumor proliferation and growth factor secretion, induction of tumor apoptosis, and prevention of cellular immune suppression during the critical perioperative period. Here we evaluated the perioperative impact of clinically applicable drugs from these categories in the context of surgery, studying natural killer (NK) cell activity and resistance to experimental metastases.MethodsF344 rats were treated with COX-1 inhibitors (SC560), COX-2 inhibitors (indomethacin, etodolac, or celecoxib), a β-blocker (propranolol), or a combination of a COX-2 inhibitor and a β-blocker (etodolac and propranolol). Rats underwent laparotomy, and were inoculated intravenously with syngeneic MADB106 tumor cells for the assessment of lung tumor retention (LTR). Additionally, the impact of these drug regimens on postoperative levels of NK cytotoxicity was studied in peripheral blood and marginating-pulmonary leukocytes.ResultsSurgery increased MADB106 LTR. COX-2 inhibition, but not COX-1 inhibition, reduced postoperative LTR. Etodolac and propranolol both attenuated the deleterious impact of surgery, and their combined use abolished it. Surgery decreased NK cytotoxicity per NK cell in both immune compartments, and only the combination of etodolac and propranolol significantly attenuated these effects. Lastly, the initiation of drug treatment three days prior to surgery yielded the same beneficial effects as a single pre-operative administration, but, as discussed, prolonged treatment may be more advantageous clinically.ConclusionsExcess prostaglandin and catecholamine release contributes to postoperative immune-suppression. Treatment combining perioperative COX-2 inhibition and β-blockade is practical in operated cancer patients, and our study suggests potential immunological and clinical benefits.

The NMDA receptor antagonist MK-801 prevents long-lasting non-associative morphine tolerance in the rat

Several studies have demonstrated that the N-methyl-D-aspartate (NMDA) antagonist MK-801 attenuates the development of morphine tolerance and withdrawal. These studies employed repeated morphine injections to induce tolerance, a procedure in which learning has been suggested to play a significant role in tolerance development. MK-801 has been reported to block some types of learning, and it is unclear, therefore, whether the effect of MK-801 on tolerance development is due to its antagonism of associative (learning) or non-associative factors. Moreover, previous studies have tested the effects of MK-801 on morphine tolerance only up to 48 h after its induction; yet morphine tolerance can persist for many months, and it is not known whether MK-801 can block long-lasting tolerance. In the present study, therefore, we adopted a model of morphine tolerance in which the involvement of learning is minimized by using a single injection of morphine in a sustained-release preparation, and we tested tolerance for up to 56 days. In the first experiment, simultaneously administering MK-801 (0.2 mg/kg, s.c.) and morphine (60 mg/kg, s.c.), each in a sustained-release preparation, abolished tolerance that lasted at least 12 days. Analgesia was measured in the hot-plate test following a test dose of morphine (15 mg/kg, i.p.). In the second experiment, delivering MK-801 and morphine as before, the duration of morphine-induced catalepsy and analgesia was prolonged. Nevertheless, 24 h later one symptom of naloxone-precipitated withdrawal was significantly attenuated in these same animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of NK cell activity and of resistance to metastasis by stress: A role for adrenal catecholamines and β-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 β1- and β2-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 β-adrenergic antagonist (nadolol, 0.4 mg/kg), and additively by a selective β1- (atenolol, 1–6 mg/kg) and a selective β2-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 β-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 β1- and β2-adrenoceptors, suppresses NKA and consequently compromises resistance to NK-sensitive metastasis.

Morphine attenuates surgery-induced enhancement of metastatic colonization in rats

&NA; Painful Stressors such as surgery have been shown both to suppress immune function and to enhance tumor development. Whether the immune system mediates the tumor‐enhancing effects of surgery remains unclear. Moreover, the role of postoperative pain has been largely ignored in such studies. To explore these issues, we used the MADB106 tumor, a mammary adenocarcinoma syngeneic to the subjects of this study (Fischer 344 rats) and known to be sensitive to natural killer (NK) cell activity. We found that surgery enhanced metastatic colonization and that this tumor‐enhancing effect occurred only during the time in which the MADB106 tumor is sensitive to NK control. These results support the hypothesis that suppression of NK cell activity mediates the surgery‐induced enhancement of metastatic colonization. Further, we found that an analgesic dose of morphine blocked the surgery‐induced increase in metastasis without affecting metastasis in unoperated animals. These findings suggest that postoperative pain is a critical factor in promoting metastatic spread. If a similar relationship between pain and metastasis occurs in humans, then pain control must be considered a vital component of postoperative care.