Kinetics of the early recruitment of leukocyte subsets at the sites of tumor cells in the lungs: natural killer (NK) cells rapidly attract monocytes but not lymphocytes in the surveillance of micrometastasis

A Novel Dipeptidyl Peptidase-4 Inhibitor DA-1229 Ameliorates Tubulointerstitial Fibrosis in Cyclosporine Nephrotoxicity in Mice

Cyclosporine A (CyA) is an immunosuppressive agent that induces nephrotoxicity with long-term treatment. The roles of DPP-4 and its inhibitors in cyclosporine nephrotoxicity are not fully understood. Therefore, we investigated the effects of a novel DPP-4 inhibitor, DA-1229, on the progression of renal disease in an experimental cyclosporine nephrotoxicity model. Chronic cyclosporine nephrotoxicity was induced in six-week-old male ICR mice by subcutaneous injections of CyA at a dose of 30 mg/kg for four weeks. Animals were treated with DA-1229 at a dose of 300 mg/kg per day in food for four weeks. Although DPP-4 activity did not increase in the kidneys of mice with induced cyclosporine nephrotoxicity, DA-1229 treatment significantly suppressed DPP-4 activity in both plasma and renal tissues. DPP-4 inhibition by DA-1229 led to significantly decreased albuminuria and urinary excretion of 8-isoprosatane. DPP-4 inhibition also substantially suppressed pro-inflammatory effects, profibrotic molecules, and macrophage infiltration, and led to the improvement in renal structural changes. Our results suggest that DPP-4 inhibition by DA-1229 provides renoprotective effects in an animal model of cyclosporine nephrotoxicity via antioxidant, anti-inflammatory, and anti-fibrotic mechanisms. DPP-4 inhibition may be a useful new therapeutic approach for the management of progressive renal disease in cyclosporine nephrotoxicity.

Proteolytic degradation of neuropeptide Y (NPY) from head to toe: Identification of novel NPY-cleaving peptidases and potential drug interactions in CNS and Periphery

The bioactivity of neuropeptide Y (NPY) is either N-terminally modulated with respect to receptor selectivity by dipeptidyl peptidase 4 (DP4)-like enzymes or proteolytic degraded by neprilysin or meprins, thereby abrogating signal transduction. However, neither the subcellular nor the compartmental differentiation of these regulatory mechanisms is fully understood. Using mass spectrometry, selective inhibitors and histochemistry, studies across various cell types, body fluids, and tissues revealed that most frequently DP4-like enzymes, aminopeptidases P, secreted meprin-A (Mep-A), and cathepsin D (CTSD) rapidly hydrolyze NPY, depending on the cell type and tissue under study. Novel degradation of NPY by cathepsins B, D, L, G, S, and tissue kallikrein could also be identified. The expression of DP4, CTSD, and Mep-A at the median eminence indicates that the bioactivity of NPY is regulated by peptidases at the interphase between the periphery and the CNS. Detailed ex vivo studies on human sera and CSF samples recognized CTSD as the major NPY-cleaving enzyme in the CSF, whereas an additional C-terminal truncation by angiotensin-converting enzyme could be detected in serum. The latter finding hints to potential drug interaction between antidiabetic DP4 inhibitors and anti-hypertensive angiotensin-converting enzyme inhibitors, while it ablates suspected hypertensive side effects of only antidiabetic DP4-inhibitors application. The bioactivity of neuropeptide Y (NPY) is either N-terminally modulated with respect to receptor selectivity by dipeptidyl peptidase 4 (DP4)-like enzymes or proteolytic degraded by neprilysin or meprins, thereby abrogating signal transduction. However, neither the subcellular nor the compartmental differentiation of these regulatory mechanisms is fully understood. Using mass spectrometry, selective inhibitors and histochemistry, studies across various cell types, body fluids, and tissues revealed that most frequently DP4-like enzymes, aminopeptidases P, secreted meprin-A (Mep-A), and cathepsin D (CTSD) rapidly hydrolyze NPY, depending on the cell type and tissue under study. Novel degradation of NPY by cathepsins B, D, L, G, S, and tissue kallikrein could also be identified. The expression of DP4, CTSD, and Mep-A at the median eminence indicates that the bioactivity of NPY is regulated by peptidases at the interphase between the periphery and the CNS. Detailed ex vivo studies on human sera and CSF samples recognized CTSD as the major NPY-cleaving enzyme in the CSF, whereas an additional C-terminal truncation by angiotensin-converting enzyme could be detected in serum. The latter finding hints to potential drug interaction between antidiabetic DP4 inhibitors and anti-hypertensive angiotensin-converting enzyme inhibitors, while it ablates suspected hypertensive side effects of only antidiabetic DP4-inhibitors application.

Soluble DPP4 originates in part from bone marrow cells and not from the kidney

Dipeptidyl peptidase 4 (DPP4) is known to inactivate incretins as well as important chemokines and neuropeptides. DPP4 is expressed as a transmembrane protein but also occurs as a soluble enzyme circulating in the blood. However, the origin of the soluble DPP4 (sDPP4) is still unknown. In this study, DPP4 activity was quantified in plasma and extracted from different rat organs. Then, in order to see if the kidney or the bone marrow was the source of sDPP4, kidney or bone marrow transplantation was performed between wildtype (wt) Dark Agouti (DA) and DPP4 deficient congenic rats (n=6-9). Kidney was verified to have the highest DPP4 activity, followed by spleen and lung. In the following three weeks after successful kidney transplantation only transient trace plasma DPP4 activity was detected in DPP4 deficient rats receiving wt kidneys. In addition, DPP4 activity was not diminished in DA wt rats receiving DPP4 deficient kidneys. Both findings indicated that sDPP4 did not originate from the kidney. In contrast, 43±14% (compared to wt) sDPP4 activity was detected in the plasma of DPP4 deficient DA rats that were reconstituted with wt bone marrow cells. Not only leukocyte but also macrophage subpopulations express DPP4 in bone marrow as well as in blood as assessed by flow cytometry. Thus, bone marrow derived cells but not the kidney represent at least one source of sDPP4. And leukocyte or macrophage subpopulations could be potential candidates.

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.

Stimulation of pulmonary immune responses by the TLR2/6 agonist MALP-2 and effect on melanoma metastasis to the lung

Given that metastasized melanoma is a fatal disease in most cases, it is tempting to develop strategies to a priori prevent metastasis. We have stimulated the pulmonary innate immune system by macrophage-activating lipopeptide-2 (MALP-2), a specific agonist at Toll-like receptor (TLR) 2/6, and investigated its impact on experimental melanoma metastasis. In C57BL/6 mice, intratracheal application of MALP-2 induced a profound influx of neutrophils and macrophages into the lung, which peaked after 24 h (sixfold increase) and returned to baseline within 72 h. Further analysis revealed that MALP-2 also markedly induced VCAM-1 expression on pulmonary blood vessels. In vitro experiments demonstrated that this adhesion molecule mediates binding of B16F10 melanoma cells. Furthermore, in vivo or in vitro treatment with MALP-2 did not significantly affect the ability of immune cells to lyse melanoma cells. As a consequence, notwithstanding the profound pulmonary immune response induction and in contrast to conclusions drawn from some previous publications, the net extent of experimental metastasis did not change significantly, regardless of the application regimen of MALP-2 prior to, concomitant with or after tumor cell inoculation. Melanoma cells stably transfected with green fluorescent protein allowed tracking of early events after tumor cell dissemination and showed that MALP-2-mediated TLR2/6 activation did not interfere with pulmonary melanoma cell arrest. Likewise, boosting the immune induction after establishment of metastases did not change the clinical outcome. These unexpected results vividly counsel caution regarding predictions of immunomodulating therapies, as multiple intertwined effects may influence the net outcome.

Diet-induced obesity, exogenous leptin-, and MADB106 tumor cell challenge affect tissue leukocyte distribution and serum levels of cytokines in F344 rats

The adipocyte-derived catabolic protein leptin alters cell-mediated immunity and cytokine crosstalk. This may provide new insights into the altered immune response, seen in obese individuals. Therefore, we determined the tissue distribution of immune cells in diet-induced obese (dio) and normal weight F344 rats challenged with MADB106 tumor cells or leptin. Immune cell distribution in blood (by FACS analysis) and tissues (NK cells in spleen and liver, immunohistologically) as well as pro-inflammatory cytokines (IL-6, TNF-α; by flow cytometry) were investigated in 28 normal weight and 28 dio rats (n = 4-6/group). Pro-inflammatory cytokines were increased 3-fold for IL-6 and 7-fold for TNF-α in obese animals. Higher numbers of blood monocytes and NK cells were found in obese as compared to normal weight animals. In dio rats challenged with leptin and MADB106 tumor cells, monocyte numbers were decreased as compared to the obese control animals. Immunohistochemistry revealed an altered NK cell distribution in a compartment-, treatment-, and bodyweight-specific manner. In conclusion, our data reveal a distinct distribution pattern of monocytes and NK cells in dio rats as compared to normal weight littermates and an additional modulatory effect of a leptin- and MADB106 tumor cell challenge.

Age-dependent stimulatory effect of desipramine and fluoxetine pretreatment on metastasis formation by B16F10 melanoma in male C57BL/6 mice

Although recent data may provide theoretical support for the preventive use of antidepressants in cancer patients, so far no study has demonstrated the clinical benefits of such strategies in the general population of cancer patients [39, 41]. Moreover, an association between antidepressant use and the risk of tumor promotion could neither be excluded nor established. The aim of this study was to compare the effect of desipramine (a tricyclic antidepressant, TCA) and fluoxetine (a selective serotonin reuptake inhibitor, SSRI) on tumor growth of the mouse B16F10 transplanted melanoma in "young" 6-9 month old and "aged" 18-23 month old male C57BL/6 mice. Drugs were administered daily at a dose of 10 mg/kg, ip, for two weeks and tumor cells were inoculated 2 h after the last antidepressant administration. Control animals were treated with saline. Tumor growth was significantly slower in aged than in young saline-treated control animals. Pretreatment with desipramine dramatically promoted metastasis formation and increased mortality rate but inhibited primary tumor growth in young males. On the other hand, both antidepressants increased primary tumor growth in aged animals, whereas metastasis was only moderately promoted. To determine the effect of antidepressant drug pretreatment and tumor progress on some parameters of cell-mediated immunity (proliferative activity and cytokine production by splenocytes) and angiogenesis, vascular endothelial growth factor (VEGF) and metalloproteinase (MMP)-9 plasma levels were established. The prometastatic effect of desipramine in young animals was connected with an increase of VEGF and MMP-9 plasma levels.

The marginating-pulmonary immune compartment in rats: characteristics of continuous inflammation and activated NK cells

A significant role has been indicated for cellular immunity in controlling circulating cancer cells, but most autologous tumor cells seem resistant, in vitro, to natural killer cell (NKC) and cytotoxic T lymphocytes cytotoxicity. Addressing this apparent contradiction, we recently identified a unique leukocyte population, marginating-pulmonary (MP)-leukocytes, which exhibit potent natural killer (NK) cytotoxicity. Here, we characterize the MP-compartment in naive and immunostimulated rats, and assessed its cytotoxicity against "NK-resistant" tumors cells. Animals were treated with poly I-C (3x0.2 mg/kg) or saline, and circulating-leukocytes and MP-leukocytes were collected and analyzed in terms of cellular composition, cellular activation markers, and NK cytotoxicity of leukocytes and purified NKCs. Compared with circulating-leukocytes, MP-leukocytes showed greater proportion of granulocytes, monocytes, NKCs, and large NKCs; higher expression of activation and adhesion markers (CD25, CD11a, CD11b, and NKR-P1, IFN-gamma); and elevated NK cytotoxicity of leukocytes and purified NKCs against several syngeneic and xenogeneic NK-resistant target cells (from both F344 and BDX inbred rats). In immunostimulated animals (treated with poly I-C), but not in naive animals, purified NKCs from the MP-compartment showed markedly superior cytotoxicity, suggesting that poly I-C immunostimulation uniquely affect MP-NKCs, and that in naive animals other MP-leukocytes support NK cytotoxicity. Overall, the results suggest that the MP-compartment is characterized by a continuous activated inflammatory microenvironment uniquely affected by immunostimulation. If similarly potent MP-NKCs exist in patients, then circulating autologous tumor cells that are considered "NK-resistant" could actually be controlled by MP-NKCs. Innate immunity may assume greater role in controlling malignant spread, especially after immunostimulation.

An innovative triple immunogold labeling method to investigate the hemopoietic stem cell niche in situ

The ultrastructural study of rare cells within their niche in situ is very difficult. We have developed a method for locating individual transplanted cells and simultaneously identifying and analyzing the molecules and cellular phenotypes surrounding them in situ using transmission electron microscopy. This innovative method involves triple immunogold labeling combined with serial ultrathin sectioning. We demonstrate the validity of this approach by examining the niche of individual transplanted cells from a population highly enriched for hemopoietic stem cells and the ultrastructural expression of two key stem cell regulatory molecules, hyaluronic acid and osteopontin. In addition, we describe the phenotypes of the surrounding cells.

Phenotyping of congenic dipeptidyl peptidase 4 (DP4) deficient Dark Agouti (DA) rats suggests involvement of DP4 in neuro-, endocrine, and immune functions

BACKGROUND

Treatment of diabetes type 2 using chronic pharmacological inhibition of dipeptidyl peptidase 4 (DP4) still requires an in-depth analysis of models for chronic DP4 deficiency, because adverse reactions induced by some DP4 inhibitors have been described.

METHODS

In the present study, a novel congenic rat model of DP4 deficiency on a "DP4-high" DA rat genetic background was generated (DA.F344-Dpp4(m)/ SvH rats) and comprehensively phenotyped.

RESULTS

Similar to chronic pharmacological inhibition of DP4, DP4 deficient rats exhibited a phenotype involving reduced diet-induced body weight gain and improved glucose tolerance associated with increased levels of glucagon-like peptide-1 (GLP-1) and bound leptin as well as decreased aminotransferases and triglycerides. Additionally, DA.F344-Dpp4(m)/SvH rats showed anxiolytic-like and reduced stress-like responses, a phenomenon presently not targeted by DP4 inhibitors. However, several immune alterations, such as differential leukocyte subset composition at baseline, blunted natural killer cell and T-cell functions, and altered cytokine levels were observed.

CONCLUSIONS

While this animal model confirms a critical role of DP4 in GLP-1-dependent glucose regulation, genetically induced chronic DP4 deficiency apparently also affects stress-regulatory and immuneregulatory systems, indicating that the use of chronic DP4 inhibitors might have the potential to interfere with central nervous system and immune functions in vivo.

NK-dependent increases in CCL22 secretion selectively recruits regulatory T cells to the tumor microenvironment

Tumor-induced immune suppression involves the accumulation of immune-suppressive infiltrates in the microenvironment. This study demonstrates increased numbers of CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) in the lungs of C57BL/6 mice bearing a metastatic Lewis lung carcinoma (LLC) variant. These Tregs suppressed the proliferation of endogenous CD4(+)CD25(-) cells and expressed higher levels of the chemokine receptor CCR4 than other types of T cells. LLC-bearing lungs secreted elevated levels of the CCR4-associated chemokine CCL22 compared with normal lungs. However, CCL22 was not secreted by LLC or normal epithelial controls, suggesting that CCL22 is secreted by a nonepithelial component of the microenvironment. Migration assays revealed that medium conditioned by LLC-bearing lungs selectively recruited Tregs at higher frequencies than did medium conditioned by normal lungs. Neutralization of CCL22 significantly reduced this selective recruitment toward both conditioned media. A series of immunomagnetic isolations, FACS, and flow cytometric analyses were used to isolate different cellular fractions from both normal and LLC-bearing lungs. When isolated, only the NK-containing fractions secreted CCL22, and the same fraction isolated from LLC-bearing lungs secreted higher levels. Depletion of NK cells from both normal and LLC-bearing lung tissue significantly reduced CCL22 secretion, suggesting that a large portion of secreted CCL22 is NK cell dependent. Flow cytometric analysis of the lung NK compartments revealed no significant increase in NK cell numbers across LLC-bearing lung tissue as a whole as compared with normal tissue. However, immunofluorescent staining revealed an increased frequency of NK cells at the tumor periphery that were closely associated with the elevated FoxP3(+) infiltrate.

Inhibition of CD26/dipeptidyl peptidase IV enhances CCL11/eotaxin-mediated recruitment of eosinophils in vivo

Chemokines mediate the recruitment of leukocytes to the sites of inflammation. N-terminal truncation of chemokines by the protease dipeptidyl peptidase IV (DPPIV) potentially restricts their activity during inflammatory processes such as allergic reactions, but direct evidence in vivo is very rare. After demonstrating that N-terminal truncation of the chemokine CCL11/eotaxin by DPPIV results in a loss of CCR3-mediated intracellular calcium mobilization and CCR3 internalization in human eosinophils, we focused on the in vivo role of CCL11 and provide direct evidence for specific kinetic and rate-determining effects by DPPIV-like enzymatic activity on CCL11-mediated responses of eosinophils. Namely, it is demonstrated that i.v. administration of CCL11 in wild-type F344 rats leads to mobilization of eosinophils into the blood, peaking at 30 min. This mobilization is significantly increased in DPPIV-deficient F344 rats. Intradermal administration of CCL11 is followed by a dose-dependent recruitment of eosinophils into the skin and is significantly more effective in DPPIV-deficient F344 mutants as well as after pharmacological inhibition of DPPIV. Interestingly, CCL11 application leads to an up-regulation of DPPIV, which is not associated with negative feedback inhibition via DPPIV-cleaved CCL11((3-74)). These findings demonstrate regulatory effects of DPPIV for the recruitment of eosinophils. Furthermore, they illustrate that inhibitors of DPPIV have the potential to interfere with chemokine-mediated effects in vivo including but not limited to allergy.

Postnatal life events affect the severity of asthmatic airway inflammation in the adult rat

Genetic and hygienic factors influence susceptibility to asthma. In autoimmune and inflammatory diseases, additional effects of the psychosocial environment have been demonstrated that might also play a role in asthma. In this study, the impact of different early postnatal stressors on an OVA-induced model of asthma was tested in adulthood. Fischer 344 rats were subjected to either repeated handling stimulation (HA), maternal separation (MS), or were left undisturbed in their first 4 wk of life. Behavioral differences were characterized at the age of 4 mo. At 5 mo of age, immunological cellular and serologic changes were investigated and experimental asthma was induced. Results show significantly increased exploratory behavior and reduced anxiety in HA rats compared with MS and controls. Without further behavioral or immunological challenges, HA animals exhibited an increased ex vivo NK cell cytotoxicity but no other obvious immunological differences. After induction of asthma, in contrast, MS animals exhibited proinflammatory effects in leukocyte subset composition including increased eosinophil numbers, whereas levels of IgE and the allergy-specific cytokine IL-13 were reduced compared with HA. There was a most remarkable increase of adrenocorticotropin in HA animals, comparing pre- to postchallenge plasma levels. These data demonstrate for the first time that early postnatal stimulative or adverse experiences exert long-lasting changes of the "neuroendocrinoimmune" interface in adulthood, resulting in either protective or aggravating mechanisms in allergic airway disease. Thus, in addition to genetic and hygienic factors, nongenetically acquired individual differences contribute to the pathobiology of asthma.

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.

NK cells rapidly remove B16F10 tumor cells in a perforin and interferon-gamma independent manner in vivo

Natural killer (NK) cells have been shown critical in reducing tumor lung metastasis in various murine cancer models. Effector molecules such as perforin and IFN-gamma may play important roles in inhibition of metastasis. However, most of these conclusions were based on experiments that involved quantitation of metastatic colonies several weeks after tumor challenge. The roles of NK cells and their effector molecules (perforin and IFN-gamma) in the initial immune responses against tumor metastasis in lungs are still unknown. By using the B16F10 melanoma tumor model combined with confocal microscopy, we observed an increase in numbers of B16F10 cells in NK-depleted mice at 60 min post tumor inoculation, but this effect was independent of perforin or IFN-gamma. In addition, NK cell numbers in lungs after tumor injection rapidly increased suggesting a redistribution of NK cells in the lungs. However, NK cells were not found in contact with tumor cells until day 6 or later. Our data indicate that during early responses against B16F10 cells, NK cells use another mechanism(s) besides perforin and IFN-gamma to prevent tumor metastasis.

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.

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.

K-19 mRNA RT-PCR in detecting micrometastasis in regional lymph nodes of gastric cancer

AIM: To investigate the value and prospect of RT-PCR in detecting micrometastasis in regional lymph nodes of gastric cancer.

METHODS: Histopathology was used and K19 mRNA expression was detected by RT-PCR in tumor tissues and lymph nodes from gastric cancer patients undergoing radical resection of gastric carcinoma.

RESULTS: K19 mRNA was expressed in all tumor specimens of 30 cases; of the 126 lymph nodes, 26 were histopathologically positive (20.6%), and 42 positive (33.3%) by RT-PCR. Amplification fragments of 460 and 540 bp were shown in all the tumor tissues and metastatic lymph nodes after K19 and β-actin RT-PCR, while only a 540 bp fragment appeared in the lymph nodes of non-tumor patients.

CONCLUSION: K19 mRNA RT-PCR is sensitive and specific in testing micrometastasis in regional lymph nodes of gastric cancer, and it is superior to routine histopathology.

Tumor angiogenesis and metastasis formation are associated with individual differences in behavior of inbred Lewis rats

There are large individual differences in cancer progression and it has been suggested that behavioral and psychological characteristics of cancer patients may contribute to the course of the disease. To get more insight in the contribution of behavioral characteristics to cancer progression, we investigated in rats, whether a stable behavioral trait characteristic is associated with NK cell activity, tumor angiogenesis, and tumor metastasis formation. Lewis rats were characterized based on locomotor activity in an open field. Rats in the upper and lower quartile were designated as high and low active rats. Low active animals had higher NK cell activity compared to their high active counterparts. In addition, we examined tumor angiogenesis by using a subcutaneous Matrigel implant containing MADB106 adenocarcinoma cells. Tumor Matrigel implants from low active animals contained significantly more hemoglobin compared to implants from high active animals, indicating a more pronounced angiogenic response in the low active animals. Finally, experimental lung metastasis formation was investigated by injecting MADB106 cells into the tail vein. Low active animals tended to develop more metastases. Moreover, low active animals developed significantly more tumors with a diameter larger than 2 mm, which is in line with higher angiogenic capacity. In conclusion, we demonstrated that individual differences in a stable behavioral trait are linked to individual differences in angiogenic capacity and tumor progression.

Reduced splenic natural killer cell activity in rats with a hyperreactive dopaminergic system

Interactions between the nervous system and the immune system have been recognized as important regulatory processes in determining the activity of the immune response. We have previously shown that rats, which differ in the reactivity of the dopaminergic system (APO-SUS and APO-UNSUS rats), also differ in experimental metastasis formation and in susceptibility to autoimmunity. APO-SUS rats have a high response to administration of apomorphine and can be characterized as hyperdopaminergic, whereas their APO-UNSUS counterparts show low susceptibility to apomorphine and have a hypodopaminergic phenotype. In this study we investigated whether the decreased experimental metastasis formation of APO-SUS rats compared to APO-UNSUS rats is associated with higher natural killer cell activity in APO-SUS rats. Surprisingly, splenic NK cell activity of hyperdopaminergic APO-SUS female as well as male rats is significantly lower than NK cell activity of their hypodopaminergic APO-UNSUS counterparts. The reduced splenic NK activity of female APO-SUS rats is associated with lower percentages of NK cells in the spleen cell population. In contrast, male APO-SUS and APO-UNSUS rats show similar numbers of NK cells in the spleen. There was no difference in plasma dopamine levels between APO-SUS and APO-UNSUS rats and i.p. treatment of rats with the dopaminergic agonist quinpirole did not alter NK cell activity. In conclusion, our data demonstrate that differences in the reactivity of the dopaminergic system are associated with differences in splenic NK cell activity. Moreover, our data demonstrate that in this model lower splenic NK cell activity is not related to increased experimental lung metastasis formation.

Regulation of Dendritic Cell Function by NK Cells: Mechanisms Underlying the Synergism in the Combination Therapy of IL-12 and 4-1BB Activation

The interactions between NK cells and dendritic cells (DCs) have been previously demonstrated in vitro. In this report, the in vivo cross-regulation between NK cells and DCs was studied in tumor-bearing mice treated with adenoviral vector expressing IL-12 and agonistic anti-4-1BB Abs. NK cells are essential for both tumor rejection and CTL development in the combination therapy (IL-12 plus anti-4-1BB). The numbers and functional activities of both NK cells and DCs in tumor-infiltrating leukocytes were synergistically increased in the IL-12 plus anti-4-1BB-treated mice compared with treatment with either reagent alone. NK depletion in vivo resulted in a significant decrease in the number of DCs in tumor-infiltrating leukocytes, strongly suggesting that NK cells are involved in the activation and expansion of DCs. The mechanism by which IL-12-activated NK cells regulate DC functions is, in part, mediated through the secretion of IFN-gamma that leads to the up-regulation of 4-1BB by DCs. Furthermore, 4-1BB activation in conjunction with IL-12 gene delivery increased tumor infiltration of green fluorescence protein-labeled DCs and enhanced their MHC class II expression. The activation of DCs by NK cells and the subsequent development of antitumoral CTL responses facilitated by 4-1BB-activated DCs may account for the synergistic effects observed in the combination therapy in comparison to adenoviral vector expressing IL-12 or anti-4-1BB treatment alone.

Localization, transmission, spontaneous mutations, and variation of function of the Dpp4 (Dipeptidyl-peptidase IV; CD26) gene in rats

Dipeptidyl-peptidase IV (DPPIV) is involved in endocrine and immune functions via cleavage of regulatory peptides with a N-terminal proline or alanine such as incretins, neuropeptide Y, or several chemokines. So far no systematic investigations on the localization and transmission of the Dpp4 gene or the natural variations of DPPIV-like enzymatic function in different rat strains have been conducted. Here we mapped the Dpp4 gene to rat chromosome 3 and describe a semi-dominant mode of inheritance for Dpp4 in a mutant F344/DuCrj(DPPIV-) rat substrain lacking endogenous DPPIV-like activity. This mutant F344/DuCrj(DPPIV-) rat substrain constantly exhibits a nearly complete lack of DPPIV-like enzymatic activity, while segregation of DPPIV-like enzymatic activity was observed in another DPPIV-negative F344/Crl(Ger/DPPIV-) rat substrain. Screening of 12 different inbred laboratory rat strains revealed dramatic differences in DPPIV-like activity ranging from 11 mU/microl (LEW/Ztm rats) to 40 mU/microl (BN/Ztm and DA/Ztm rats). A lack of DPPIV-like activity in F344 rats was associated with an improved glucose tolerance and blunted natural killer cell function, which indicates the pleiotropic functional role of DPPIV in vivo. Overall, the variations in DPPIV-like enzymatic activity probably represent important confounding factors in studies using rat models for research on regulatory peptides.

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.

Intratracheal macrophage-activating lipopeptide-2 reduces metastasis in the rat lung

Primary surgery of tumors bears the risk of metastasis to organs such as the lungs. In order to prevent such metastatic processes, in the present study, local intratracheal instillation of macrophage-activating lipopeptide-2 (MALP-2) as a bacterial-derived immunomodulator of cellular host defense responses was performed, and the effects on tumor cell clearance as well as tumor colonization were investigated in the lungs of Fischer 344 (F344) rats. Compared with vehicle controls, local administration of MALP-2 parallel to intravenous inoculation of MADB106 mammary adenocarcinoma tumor cells resulted in a significant reduction of lung colony numbers, whereas MALP-2 application 1 or 3 d afterwards was not effective. Quantification of leukocyte subsets in the lung tissue by immunohistochemistry revealed a significant increase of the number of monocytes in situ, as well as an increased co-localization of Natural Killer (NK) cells with tumor cells. Synthetic MALP-2 is easily available, with virtually no limitation to the amount of compound, and easily applicable by inhalation. Therefore, as local immunostimulative effects of the bacterial antigen MALP-2 have successfully been demonstrated, its use as an immunotherapeutic agent is worth further investigation.