Cell-free chromatin: A newly described mediator of systemic inflammation.

Recent research has shown that cell-free chromatin (cfCh) particles that are released from the billions of cells that die in the body everyday can enter into healthy cells, integrate into their genomes and induce dsDNA breaks and apoptotic responses. Genomic integration of cfCh activates NF κ B suggesting a novel mechanism of induction of systemic inflammation. Since DNA damage and inflammation are underlying pathologies in multiple devastating acute and chronic disease conditions, the discovery of agents that can inactivate cfCh may provide therapeutic possibilities.

The proteasome inhibitor bortezomib interacts synergistically with the histone deacetylase inhibitor suberoylanilide hydroxamic acid to induce T-leukemia/lymphoma cells apoptosis.

Interactions between inhibitors of the proteasome and histone deacetylases have been examined in human T-leukemia/lymphoma cells both in vitro and in vivo. Co-exposure of cells to bortezomib and suberoylanilide hydroxamic acid (SAHA) synergistically induces T-leukemia/lymphoma cells to undergo apoptosis, consistent with a significant increase in mitochondrial injury and caspase activation. These events are accompanied by inhibition of cyto-protective signaling pathways, including the nuclear factor (NF)-kappaB, Raf-1/mitogen-induced extracellular kinase (MEK)/extracellular signal-related kinase (ERK) and AKT pathways, and activation of stress-related cascades, including the stress-activated kinases c-jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK). Moreover, bortezomib in conjunction with SAHA efficiently induces apoptosis of primary T-leukemia/lymphoma cells and inhibits tumor growth in a murine xenograft model established with subcutaneous injection of Jurkat cells. Taken together, these findings confirm the synergistic anti-tumor effect of the proteasome and histone deacetylase inhibitors, and provide an insight into the future clinical applications of bortezomib-SAHA combining regimen in treating T-cell malignancies.

Pharmacologically regulated production of targeted retrovirus from T cells for systemic antitumor gene therapy.

We aimed to use cell-based carriers to direct vector production to target sites for systemic therapy. We used T cells engineered to express a chimeric T cell receptor that can specifically recognize target cells expressing the tumor-associated carcinoembryonic antigen (CEA). These T cells were modified to produce a retrovirus under tight pharmacological control using the rapamycin-inducible transcriptional regulatory system. The retroviral vectors produced were transcriptionally targeted to CEA-expressing target cells. We found that vector production and transgene expression from these T cells in vitro was dependent on pharmacological induction and expression of CEA in target cells, respectively. Mice bearing metastatic tumors that received cell carriers delivering the HSVtk gene demonstrated a significant increase in survival, but only in response to pharmacological induction of vector production. Interestingly, the therapeutic effect required the presence of the tumor-specific chimeric receptor on T cells. Further studies demonstrated that systemic delivery of tumor-specific T cells to mice bearing metastatic tumors caused recruitment of nonspecific T cells to the tumor site. We hypothesize that this enhanced targeting to tumor sites is responsible for the efficiency of T cell-mediated retroviral gene transfer and that this principle can be used to enhance systemic therapies using immune-cell carriers.

Specific tumoricidal activity of a secreted proapoptotic protein consisting of HER2 antibody and constitutively active caspase-3.

In this study, a novel approach to antitumor therapy was devised by generating a chimeric tumor-targeted killer protein, referred to as immunocasp-3, that comprises a single-chain anti-erbB2/HER2 antibody with a NH(2)-terminal signal sequence, a Pseudomonas exotoxin A translocation domain, and a constitutively active caspase-3 molecule. In principle, cells transfected with the immunocasp-3 gene would express and secrete the chimeric protein, which then binds to HER2-overexpressing tumor cells. Subsequent cleavage of the constitutively active capase-3 domain from the immunocasp-3 molecule and its release from internalized vesicles would lead to apoptotic tumor cell death. To test this strategy, we transduced human lymphoma Jurkat cells with a chimeric immunocasp-3 gene expression vector and showed that they not only expressed and secreted the fusion protein but also selectively killed tumor cells overexpressing HER2 in vitro. i.v. injection of the transduced Jurkat cells led to tumor regression in a mouse xenograft model because of continuous secretion of immunocasp-3 by the transduced cells. The growth of HER2-positive tumor cells in this model was inhibited by i.m. as well as intratumor injection of immunocasp-3 expression plasmid DNA, indicating that the immunocasp-3 molecules secreted by transfected cells have systematic antitumor activity. We conclude that the immunocasp-3 molecule, combining the properties of a tumor-specific antibody with the proapoptotic activity of a caspase, has potent and selective antitumor activity, either as cell-based therapy or as a DNA vaccine. These findings provide a compelling rationale for therapeutic protocols designed for erbB2/HER2-positive tumors.

Imaging TCR-dependent NFAT-mediated T-cell activation with positron emission tomography in vivo.

A noninvasive method for molecular imaging of T-cell activity in vivo would be of considerable value. It would aid in understanding the role of specific genes and signal transduction pathways in the course of normal and pathologic immune responses, and could elucidate temporal dynamics and immune regulation at different stages of disease and following therapy. We developed and assessed a novel method for monitoring the T-cell receptor (TCR)-dependent nuclear factor of activated T cells (NFAT)-mediated activation of T cells by optical fluorescence imaging (OFI) and positron emission tomography (PET). The herpes simplex virus type 1 thymidine kinase/green fluorescent protein [HSV1-tk/GFP (TKGFP)] dual reporter gene was used to monitor NFAT-mediated transcriptional activation in human Jurkat cells. A recombinant retrovirus bearing the NFAT-TKGFP reporter system was constructed in which the TKGFP reporter gene was placed under control of an artificial cis-acting NFAT-specific enhancer. Transduced Jurkat cells were used to establish subcutaneous infiltrates in nude rats. We demonstrated that noninvasive OFI and nuclear imaging of T-cell activation is feasible using the NFAT-TKGFP reporter system. PET imaging with [(124)I]FIAU using the NFAT-TKGFP reporter system is sufficiently sensitive to detect T-cell activation in vivo. PET images were confirmed by independent measurements of T-cell activation (e.g., CD69) and induction of GFP fluorescence. PET imaging of TCR-induced NFAT-dependent transcriptional activity may be useful in the assessment of T cell responses, T-cell-based adoptive therapies, vaccination strategies and immunosuppressive drugs.