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

Porous ceramic titanium dioxide scaffolds promote bone formation in rabbit peri-implant cortical defect model

Titanium oxide (TiO₂) scaffolds have previously been reported to exhibit very low mechanical strength. However, we have been able to produce a scaffold that features a high interconnectivity, a porosity of 91% and a compressive strength above 1.2 MPa. This study analyzed the in vivo performance of the porous TiO₂ scaffolds in a peri-implant cortical defect model in the rabbit. After 8 weeks of healing, morphological microcomputed tomography analyses of the defects treated with the TiO₂ scaffolds had significantly higher bone volume, bone surface and bone surface-to-volume ratio when compared to sham, both in the cortical and bone marrow compartment. No adverse effects, i.e. tissue necrosis or inflammation as measured by lactate dehydrogenase activity and real-time reverse transcription polymerase chain reaction analysis, were observed. Moreover, the scaffold did not hinder bone growth onto the adjacent cortical titanium implant. Histology clearly demonstrated new bone formation in the cortical sections of the defects and the presence of newly formed bone in close proximity to the scaffold surface and the surface of the adjacent Ti implant. Bone-to-material contact between the newly formed bone and the scaffold was observed in the histological sections. Islets of new bone were also present in the marrow compartment albeit in small amounts. In conclusion, the present investigation demonstrates that TiO₂ scaffolds osseointegrate well and are a suitable scaffold for peri-implant bone healing and growth.

Chronic stress enhances progression of acute lymphoblastic leukemia via β-adrenergic signaling

Clinical studies suggest that stress-related biobehavioral factors can accelerate the progression of hematopoietic cancers such as acute lymphoblastic leukemia (ALL), but it is unclear whether such effects are causal or what biological pathways mediate such effects. Given the network of sympathetic nervous system (SNS) fibers that innervates the bone marrow to regulate normal (non-leukemic) hematopoietic progenitor cells, we tested the possibility that stress-induced SNS signaling might also affect ALL progression. In an orthotopic mouse model, Nalm-6 human pre-B ALL cells were transduced with the luciferase gene for longitudinal bioluminescent imaging and injected i.v. into male SCID mice for bone marrow engraftment. Two weeks of daily restraint stress significantly enhanced ALL tumor burden and dissemination in comparison to controls, and this effect was blocked by the β-adrenergic antagonist, propranolol. Although Nalm-6 ALL cells expressed mRNA for β1- and β3-adrenergic receptors, they showed no evidence of cAMP signaling in response to norepinephrine, and norepinephrine failed to enhance Nalm-6 proliferation in vitro. These results show that chronic stress can accelerate the progression of human pre-B ALL tumor load via a β-adrenergic signaling pathway that likely involves indirect regulation of ALL biology via alterations in the function of other host cell types such as immune cells or the bone marrow microenvironment.

Do stress responses promote leukemia progression? An animal study suggesting a role for epinephrine and prostaglandin-E2 through reduced NK activity

In leukemia patients, stress and anxiety were suggested to predict poorer prognosis. Oncological patients experience ample physiological and psychological stress, potentially leading to increased secretion of stress factors, including epinephrine, corticosteroids, and prostaglandins. Here we tested whether environmental stress and these stress factors impact survival of leukemia-challenged rats, and studied mediating mechanisms. F344 rats were administered with a miniscule dose of 60 CRNK-16 leukemia cells, and were subjected to intermittent forced swim stress or to administration of physiologically relevant doses of epinephrine, prostaglandin-E₂ or corticosterone. Stress and each stress factor, and/or their combinations, doubled mortality rates when acutely applied simultaneously with, or two or six days after tumor challenge. Acute administration of the β-adrenergic blocker nadolol diminished the effects of environmental stress, without affecting baseline survival rates. Prolonged β-adrenergic blockade or COX inhibition (using etodolac) also increased baseline survival rates, possibly by blocking tumor-related or normal levels of catecholamines and prostaglandins. Searching for mediating mechanisms, we found that each of the stress factors transiently suppressed NK activity against CRNK-16 and YAC-1 lines on a per NK basis. In contrast, the direct effects of stress factors on CRNK-16 proliferation, vitality, and VEGF secretion could not explain or even contradicted the in vivo survival findings. Overall, it seems that environmental stress, epinephrine, and prostaglandins promote leukemia progression in rats, potentially through suppressing cell mediated immunity. Thus, patients with hematological malignancies, which often exhibit diminished NK activity, may benefit from extended β-blockade and COX inhibition.

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.

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.

A Novel Ultra-porous Titanium Dioxide Ceramic with Excellent Biocompatibility

The current study compares biocompatibility, cell growth and morphology, pore diameter distribution, and interconnectivity of a novel titanium dioxide (TiO2) bone graft substitute granules with three different commercially available bone graft granules Natix®, Straumann® BoneCeramic, and Bio-Oss®. Human primary mesenchymal stem cells were cultured on the bone graft substitutes and cell viability and proliferation were evaluated after 1 and 3 days. The microstructural properties of the bone graft substitutes were evaluated by scanning electron microscopy, micro-computed tomography analysis, and mechanical testing. The cell viability and proliferation, porosity, interconnectivity, open pore size, and surface area-to-volume ratio of TiO2 granules were significantly higher than commercial bone granules (Bio-Oss® and Straumann ® BoneCeramic).

Blood transfusion promotes cancer progression: a critical role for aged erythrocytes

BACKGROUND

In cancer patients, allogeneic blood transfusion is associated with poorer prognosis, but the independent effect of the transfusion is controversial. Moreover, mediating mechanisms underlying the alleged cancer-promoting effects of blood transfusion are unknown, including the involvement of donors' leukocytes, erythrocytes, and soluble factors.

METHOD

Two syngeneic tumor models were used in Fischer 344 rats, the MADB106 mammary adenocarcinoma and the CRNK-16 leukemia. Outcomes included host ability to clear circulating cancer cells, and host survival rates. The independent impact of blood transfusion was assessed, and potential deleterious characteristics of the transfusion were studied, including blood storage duration; the role of erythrocytes, leukocyte, and soluble factors; and the kinetics of the effects.

RESULTS

Blood transfusion was found to be an independent and significant risk factor for cancer progression in both models, causing up to a fourfold increase in lung tumor retention and doubling mortality rates. Blood storage time was the critical determinant of these deleterious effects, regardless of whether the transfused blood was allogeneic or autogenic. Surprisingly, aged erythrocytes (9 days and older), rather than leukocytes or soluble factors, mediated the effects, which occurred in both operated and nonoperated animals. The effects of erythrocytes transfusion in the MADB106 model emerged immediately and dissipated within 24 h.

CONCLUSIONS

In rats, transfusion of fresh blood is less harmful than transfusion of stored blood in the context of progressing malignancies. Further studies should address mediating mechanisms through which erythrocytes' storage duration can impact the rate of complications while treating malignant diseases and potentially other pathologies.

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.