Characterisation of functional biotinylated TNF-alpha targeted to the membrane of apoptotic melanoma cells

Homing of annexin-labeled stem cells to apoptotic cells

Ischemic diseases are characterized by the presence of pro-apoptotic stimuli, which initiate a cascade of processes that lead to cell injury and death. Several molecules and events represent detectable indicators of the different stages of apoptosis. Among these indicators is phosphatidylserine (PS) translocation from the inner to the outer leaflet of the plasma membrane, which can be detected by annexinV (ANXA5) conjugation. This is a widely used in vivo and in vitro assay marking the early stages of apoptosis. We report here on an original method that employs PS-ANXA5 conjugation to target stem cells to apoptotic cells. Mesenchymal stem cells (MSCs) from GFP-positive transgenic rats were biotinylated on membrane surfaces with sulfosuccinimidyl-6-(biotinamido) hexanoate (sulfo-NHS-LC-biot) and then bound to avidin. The avidin-biotinylated MSCs were labeled with biotin conjugated ANXA5. Bovine aortic endothelial cells (BAE-1 cells) were exposed to UVC to induce caspasedependent apoptosis. Finally, we tested the ability of ANXA5-labeled MSCs to bind BAE-1 apoptotic cells: suspended ANXA5-labeled MSCs were seeded for 1 hour on a monolayer of UV-treated or control BAE-1 cells. After washing, the number of MSCs bound to BAE-1 cells was evaluated by confocal microscopy. Statistical analysis demonstrated a significant increase in the number of MSCs tagged to apoptotic BAE-1 cells. Therefore, stem cell ANXA5 tagging via biotin-avidin bridges could be a straightforward method of improving homing to apoptotic tissues.

Chimeric form of tumor necrosis factor-alpha has enhanced surface expression and antitumor activity

Tumor necrosis factor (TNF)-alpha is a type-II transmembrane protein that is cleaved by TNF-alpha-converting enzyme (TACE/ADAM-17) to release soluble TNF, a cytokine with potent antitumor properties whose use in clinical applications is limited by its severe systemic toxicity. We found that human cells transfected with vectors encoding TNF without the TACE cleavage site (DeltaTACE-TNF) still released functional cytokine at substantial levels that varied between transfected cell lines of different tissue types. Vectors encoding membrane-associated domains of CD154, another TNF-family protein, conjoined with the carboxyl-terminal domain of TNF, directed higher-level surface expression of a functional TNF that, in contrast to DeltaTACE-TNF, was resistant to cleavage in all cell types. Furthermore, adenovirus vectors encoding CD154-TNF had significantly greater in vivo biological activity in inducing regression of established, syngeneic tumors in mice than adenovirus vectors encoding TNF, and lacked toxicity associated with soluble TNF. As such, CD154-TNF is a novel TNF that appears superior for treatment of tumors in which high-level local expression of TNF is desired.

Melanoma cells interfere with the interaction of dendritic cells with NK/LAK cells

Dendritic cells (DCs) and natural killer (NK) cells are key players at the interface between innate resistance and acquired immunity. NK cells can induce DC maturation, a differentiation process whereby DCs respond to a environmental stimulus and acquire the ability of eliciting adaptive immunity. Conversely, maturing DCs promote NK functions in vivo and in vitro. This interplay has important consequences on the immune response to pathogens and possibly to neoplastic cells. Here, we show that B16 melanoma cells actively modulate the interaction between DCs derived from bone marrow precursors and NK/LAK cells propagated from the spleen of C57BL/6 mice. DCs increased in a dose-dependent manner the ability of NK/LAK cells to kill melanoma cells and to produce cytokines. This activatory cross-talk entailed the production of IL-18 by DCs and of IFN-gamma by NK/LAK cells. Melanoma cells were not a passive target of NK activity; they regulated the outcome of the interaction between DCs and NK/LAK cells, inhibiting the in vitro production of cytokines as effectively as the genetic deletion of IL-18 or IFN-gamma. Interference with the NK/DC interaction possibly represents a mechanism used by growing tumors to evade the immune response.

Effects of propyl gallate on interaction between TNF-alpha and sTNFR-I using an affinity biosensor

AIM

To study the effects of propyl gallate on the interaction of tumor necrosis factor-alpha (TNF-alpha) with its soluble receptor, sTNFR-I.

METHODS

Interactions between TNF-alpha and sTNFR-I were analyzed using an IAsys biosensor. sTNFR-I was immobilized on the carboxymethyl dextran (CMD) surface of the IAsys biosensor cuvettes, and TNF-alpha preincubated with different concentrations of propyl gallate was added to the cuvettes. The resonant angle shift caused by the binding between TNF-alpha and sTNFR-I was then recorded.

RESULTS

sTNFR-I was immobilized on the CMD surface at a density of 2.76 ng/mm(2). TNF-alpha then bound the immobilized sTNFR-I specifically, and propyl gallate was able to enhance the binding between TNF-alpha and sTNFR-I in a dose-dependent manner.

CONCLUSION

The binding between TNF-alpha and sTNFR-I is one of the targets that propyl gallate can act on in vivo. The IAsys biosensor offers a new clue as to the study on the mechanisms of action of propyl gallate.

Inhibition of phosphatidylserine recognition heightens the immunogenicity of irradiated lymphoma cells in vivo

Strategies to enhance the immunogenicity of tumors are urgently needed. Although vaccination with irradiated dying lymphoma cells recruits a tumor-specific immune response, its efficiency as immunogen is poor. Annexin V (AxV) binds with high affinity to phosphatidylserine on the surface of apoptotic and necrotic cells and thereby impairs their uptake by macrophages. Here, we report that AxV preferentially targets irradiated lymphoma cells to CD8⁺ dendritic cells for in vivo clearance, elicits the release of proinflammatory cytokines and dramatically enhances the protection elicited against the tumor. The response was endowed with both memory, because protected animals rejected living lymphoma cells after 72 d, and specificity, because vaccinated animals failed to reject unrelated neoplasms. Finally, AxV–coupled irradiated cells induced the regression of growing tumors. These data indicate that endogenous adjuvants that bind to dying tumor cells can be exploited to target tumors for immune rejection.

Accumulation of plasma nucleosomes upon treatment with anti-tumour necrosis factor-alpha antibodies

OBJECTIVE

Patients undergoing anti-tumour necrosis factor-alpha (TNF-alpha) treatment often develop autoantibodies. Apoptotic cell antigens are a potential initiating stimulus for autoantibodies. Our goal was to verify whether anti-cytokine therapy causes the release of nucleosomes, a major autoantigen generated during cell death.

DESIGN

Laboratory research study with comparison group.

SETTING

Clinical Immunology Unit and Lab, H San Raffaele University Hospital, Italy.

SUBJECTS

Eleven healthy controls and 87 rheumatic patients were studied, including 51 with rheumatoid arthritis (RA) and 33 patients with systemic lupus erythematosus (SLE).

INTERVENTIONS

Vein blood samples were taken via the antecubital vein. Blood was retrieved from 11 patients before and after injection of anti-TNF-alpha humanized antibodies. Nucleosomes were measured with an enzyme-linked immunosorbent assay. Cell death induced by anti-TNF-alpha antibodies and by the soluble cytokine was assessed in vitro.

MAIN OUTCOME MEASURES

Nucleosome level by treatment.

RESULTS

Enzyme-linked immunosorbent assay effectively detected nucleosomes either released by dying cells in vitro or circulating in the plasma. SLE but not RA patients had circulating nucleosomes at the steady state. Eight of 11 patients had significantly higher levels of plasma nucleosomes after infliximab. Minute amounts of TNF-alpha enabled infliximab to induce cell death in vitro.

CONCLUSIONS

The accumulation of nucleosomes possibly fosters the development of autoantibodies in subjects with appropriate genetic backgrounds.