Granzyme B; the chalk-mark of a cytotoxic lymphocyte

Monocyte Maturation Mediators Upregulate CD83, ICAM-1 and MHC Class 1 Expression on Ewing's Sarcoma, Enhancing T Cell Cytotoxicity

Ewing's sarcoma (EwS) is a pediatric solid tumor entity with low somatic mutational burden and a low rate of tumor-infiltrating T cells, indicating a low extent of immunogenicity. In EwS, immunogenicity may furthermore be significantly diminished by a predominantly M2 macrophage driven pro-tumorigenic tumor microenvironment. In the past, we demonstrated that CHM1319-specific TCR-transgenic T cells are able to control EwS growth in a preclinical mouse model as well as in a patient with metastatic disease. However, new adjuvant techniques to induce long lasting and curative CHM1319-specific TCR-transgenic T cell-mediated anti-tumor responses are needed. In this work, we sought to identify a technique to improve the cytotoxic effect of CHM1319-specific TCR-transgenic T cell by altering the immunogenic cell surface marker expression on EwS cell lines using different cytokines. We demonstrate that TNF, IL-6, IL-1β and PGE2 cause pro-immunogenic CD83, MHC class I and II as well as ICAM-1 upregulation in EwS cell lines. This observation was associated with significantly improved recognition and killing of the tumor cells by EwS-specific CHM1319/HLA-A*02:01-restricted TCR-transgenic T cells. Conclusively, we demonstrate that the induction of an inflammatory signature renders EwS more susceptible to adoptive T cell therapy. TNF, which is upregulated during inflammatory processes, is of particular translational interest as its secretion may be induced in the patients e.g., by irradiation and hyperthermia in the clinical setting. In future clinical protocols, this finding may be important to identify appropriate conditioning regimens as well as point of time for adoptive T cell-based immunotherapy in EwS patients.

Sinonasal T-cell expression of cytotoxic mediators granzyme B and perforin is reduced in patients with chronic rhinosinusitis

BACKGROUND

CD8+ T cells and natural killer (NK) cells are cytotoxic cells that use granzyme B (GrB) and perforin. Defective cytotoxic function is known to play a role in dysregulated immune response as seen in chronic sinusitis, also referred to as chronic rhinosinusitis (CRS). However, to our knowledge, in the United States, neither GrB or perforin expression has been reported in patients with CRS.

OBJECTIVE

The aim of this study was to investigate sinonasal cytotoxic cells, their mediators, and cell-specific distribution of these mediators in patients with CRS with nasal polyp (CRSwNP) and in patients with CRS without nasal polyp (CRSsNP).

METHODS

Blood and sinus tissue samples were taken from patients with CRSsNP (n = 8) and CRSwNP (n = 8) at the time of surgery. Control subjects (n = 8) underwent surgery for cerebrospinal fluid leak repair or to remove non-hormone-secreting pituitary tumors. The cells were analyzed via flow cytometry by using CD8 expression to identify cytotoxic T cells and CD56 expression to identify NK cells. Intracellular GrB and perforin expression were analyzed with flow cytometry.

RESULTS

We observed no significant differences in plasma or peripheral blood immune cell numbers or specific levels of GrB or perforin among the groups. In the sinonasal mucosa of the patients with CRSsNP and the patients with CRSwNP, there was a significant decrease in GrB and perforin levels (p < 0.05) despite similar or increased numbers of cytotoxic cells when compared with the controls. The overall decrease in GrB and perforin in the sinonasal mucosa of the patients with CRSsNP and the patients with CRSwNP was due to decreased T cell production. There was no difference in total NK cell count or expression of perforin or GrB among all the groups.

CONCLUSION

Total levels of sinonasal GrB and perforin were decreased in the sinonasal mucosa of both the patients with CRSwNP and the patients with CRSsNP compared with the controls, whereas sinonasal CD8+ T cells, (but not NK cells,), intracellular stores of GrB and perforin were reduced in the patients with CRSwNP compared with the controls.

Granzyme B cleavage of fibronectin disrupts endothelial cell adhesion, migration and capillary tube formation

Dysregulated angiogenesis contributes to the pathogenesis of chronic inflammatory diseases. Modulation of the extracellular matrix by immune-derived proteases can alter endothelial cell-matrix interactions as well as endothelial cell sprouting, migration and capillary formation. Granzyme B is a serine protease that is expressed by a variety of immune cells, and accumulates in the extracellular milieu in many chronic inflammatory disorders that are associated with dysregulated angiogenesis. Although granzyme B is known to cleave fibronectin, an essential glycoprotein in vascular morphogenesis, the role of granzyme B in modulating angiogenesis is unknown. In the present study, granzyme B cleaved both plasma fibronectin and cell-derived fibronectin, resulting in the release of multiple fibronectin fragments. Granzyme B cleavage of fibronectin resulted in a dose-dependent reduction in endothelial cell adhesion to fibronectin as well as reduced endothelial cell migration and tubular formation. These events were prevented when granzyme B activity was inhibited by a small molecule inhibitor. In summary, granzyme B-mediated cleavage of fibronectin contributes to attenuated angiogenesis through the disruption of endothelial cell - fibronectin interaction resulting in impaired endothelial cell migration and tubular formation.

Treatment combining RU486 and Ad5IL-12 vector attenuates the growth of experimentally formed prostate tumors and induces changes in the sentinel lymph nodes of mice

BACKGROUND

Tumor immune responses are first generated and metastases often begin in tumor sentinel lymph nodes (TSLN). Therefore, it is important to promote tumor immunity within this microenvironment. Mifepristone (RU486) treatment can interfere with cortisol signaling that can lead to suppression of tumor immunity. Here, we assessed whether treatment with RU486 in conjunction with an intratumor injection of Ad5IL-12 vector (a recombinant adenovirus expressing IL-12) could impact the TSLN microenvironment and prostate cancer progression.

METHODS

The human PC3, LNCaP or murine TRAMP-C1 prostate cancer cell lines were used to generate subcutaneous tumors in NOD.scid and C57BL/6 mice, respectively. Adjuvant effects of RU486 were looked for in combination therapy with intratumor injections (IT) of Ad5IL-12 vector in comparison to PBS, DL70-3 vector, DL70-3 + RU486, RU486 and Ad5IL-12 vector treatment controls. Changes in tumor growth, cell cytotoxic activity and populations of CD4+/FoxP3+ T regulatory cells (Treg) in the TSLN were evaluated.

RESULTS

Treatment of human PC3 prostate xenograft or TRAMP-C1 tumors with combination Ad5IL-12 vector and RU486 produced significantly better therapeutic efficacy in comparison to controls. In addition, we found that combination therapy increased the capacity of TSLN lymphocytes to produce Granzyme B in response to tumor cell targets. Finally, combination therapy tended towards decreases of CD4+/FoxP3+ T regulatory cell populations to be found in the TSLN.

CONCLUSION

Inclusion of RU486 may serve as a useful adjuvant when combined with proinflammatory tumor killing agents by enhancement of the immune response and alteration of the TSLN microenvironment.

Measuring cell death mediated by cytotoxic lymphocytes or their granule effector molecules

Cytotoxic lymphocytes (CL) are highly motile cells that utilize granule exocytosis to kill virus-infected or transformed targets. Isolated CL and purified granule proteins have been used to investigate the molecular processes that CL use to kill their targets and to investigate the basis of human disease. We have set out various methods that are routinely used to isolate CL and characterize the cell death pathways they induce. As cell death mediated through TNF-superfamily members and their respective receptors is covered elsewhere, this manuscript will deal specifically with cytotoxic granule-mediated cell death.

Identification and characterization of equine granzyme B

In the present study we describe the isolation and characterization of putative equine granzyme B for which we propose the designation 'eqGrzmB'. Sequence analysis revealed characteristic features of a GrzmB protease such as the presence of a signal (leader-) peptide and an activation di-peptide. The isolated eqGrzmB is functionally active when expressed in human or in insect cells. Furthermore, exchange of any of three putative active site amino acids, which are highly conserved along granzyme B enzymes, led to a complete loss of enzymatic activity in the newly identified eqGrzmB. Phylogenetic analysis places eqGrzmB in the chymase-locus within the large family of granzymes in close proximity to putative equine mast cell protease and to granzyme B from mouse, rat, and human. eqGrzmB proteolytic activity has been kinetically characterized and can be specifically inhibited by granzyme B inhibitors. Taken together, we conclude that we have isolated a new member of the granzyme B family, the first granzyme identified in Equidae. The description of equine granzyme B might facilitate the development of immunological assays for the activity of equine lymphocytes.

Identification of interleukin-13 receptor alpha2 peptide analogues capable of inducing improved antiglioma CTL responses

Restricted and high-level expression of interleukin-13 receptor alpha2 (IL-13Ralpha2) in a majority of human malignant gliomas makes this protein an attractive vaccine target. We have previously described the identification of the IL-13Ralpha2(345-353) peptide as a human leukocyte antigen-A2 (HLA-A2)-restricted CTL epitope. However, as it remains unclear how efficiently peptide-based vaccines can induce specific CTLs in patients with malignant gliomas, we have examined whether analogue epitopes could elicit heteroclitic antitumor T-cell responses versus wild-type peptides. We have created three IL-13Ralpha2 analogue peptides by substitutions of the COOH-terminal isoleucine (I) for valine (V) and the NH(2)-terminal tryptophan (W) for either alanine (A), glutamic acid (E), or nonsubstituted (W; designated as 1A9V, 1E9V, and 9V, respectively). In comparison with the native IL-13Ralpha2 epitope, the analogue peptides 9V and 1A9V displayed higher levels of binding affinity and stability in HLA-A2 complexes and yielded an improved stimulatory index for patient-derived, specific CTLs against the native epitope expressed by HLA-A2(+) glioma cells. In HLA-A2-transgenic HHD mice, immunization with the peptides 9V and 1A9V induced enhanced levels of CTL reactivity and protective immunity against an intracranial challenge with IL13Ralpha2-expressing syngeneic tumors when compared with vaccines containing the native IL-13Ralpha2 epitope. These findings indicate highly immunogenic IL-13Ralpha2 peptide analogues may be useful for the development of vaccines capable of effectively expanding IL-13Ralpha2-specific, tumor-reactive CTLs in glioma patients.

Ex vivo analysis of T-cell function

Our ability to analyze T-cell function in vitro has progressed in recent years to include analysis of early signaling events, such as specific protein phosphorylation, intermediate functions, such as degranulation and cytokine production, and later functions, such as proliferation. Many assays are now available to monitor these events, and comparative studies of some of these assays have been published. Major recent developments in this area include the ability to measure T-cell degranulation via cell surface exposure of CD107 and the use of polychromatic flow cytometry to examine multiple phenotypes and functions of responding T cells.