Specific eradication of micrometastases by transfer of tumour-immune T cells from major-histocompatibility-complex congenic mice

TGF-β neutralization attenuates tumor residency of activated T cells to enhance systemic immunity in mice

A tissue resident-like phenotype in tumor infiltrating T cells can limit systemic anti-tumor immunity. Enhanced systemic anti-tumor immunity is observed in head and neck cancer patients after neoadjuvant PD-L1 immune checkpoint blockade (ICB) and transforming growth factor β (TGF-β) neutralization. Using T cell receptor (TCR) sequencing and functional immunity assays in a syngeneic model of oral cancer, we dissect the relative contribution of these treatments to enhanced systemic immunity. The addition of TGF-β neutralization to ICB resulted in the egress of expanded and exhausted CD8+ tumor infiltrating lymphocytes (TILs) into circulation and greater systemic anti-tumor immunity. This enhanced egress associated with reduced expression of Itgae (CD103) and its upstream regulator Znf683. Circulating CD8+ T cells expressed higher Cxcr3 after treatment, an observation also made in samples from patients treated with dual TGF-β neutralization and ICB. These findings provide the scientific rationale for the use of PD-L1 ICB and TGF-β neutralization in newly diagnosed patients with carcinomas prior to definitive treatment of locoregional disease.

Complete remission of cancer in late-stage disease by radiation and transfer of allogeneic MHC-matched immune T cells: lessons from GvL studies in animals

Most immunotherapy studies in animal tumor models are performed in early stages of the disease. Reports on the studies of treatment in late stages of tumor growth and metastasis are much rarer. To guide future efforts for treatment in late-stage disease, a model of effective immune rejection of advanced metastasized cancer is reviewed and lessons therefrom are summarized. Already cachectic DBA/2 mice with a subcutaneously transplanted syngeneic tumor (ESb-MP lymphoma) of 1.5 cm diameter and with macroscopic liver and kidney metastases at 4 weeks could be successfully treated by a combination of sublethal (5 Gy) irradiation followed by a single transfer of 20 million anti-tumor immune spleen cells from tumor-resistant allogeneic MHC-B10.D2 mice. Following intravenous cell transfer, the primary tumors became encapsulated and were eventually rejected from the skin while visceral metastases gradually disappeared leaving behind only scar tissue. There was wound-healing at the site of the rejected primary tumor, and the animals survived long term without any tumor recurrence. The complete eradication of late-stage disease by adoptive cellular immunotherapy could be corroborated noninvasively by (31)P-NMR spectroscopy of primary tumors and by (1)H-NMR microimaging of liver metastases. Conclusions from functional mechanistic studies in this model are summarized and clinical implications discussed.

Nitric oxide-induced apoptosis in tumor cells

Nitric oxide (NO), an important molecule involved in neurotransmission, vascular homeostasis, immune regulation, and host defense, is generated from a guanido nitrogen of L-arginine by the family of NO synthase enzymes. Large amounts of NO produced for relatively long periods of time (days to weeks) by inducible NO synthase in macrophages and vascular endothelial cells after challenge with lipopolysaccharide or cytokines (such as interferons, tumor necrosis factor-alpha, and interleukin-1), are cytotoxic for various pathogens and tumor cells. This cytotoxic effect against tumor cells was found to be associated with apoptosis (programmed cell death). The mechanism of NO-mediated apoptosis involves accumulation of the tumor suppressor protein p53, damage of different mitochondrial functions, alterations in the expression of members of the Bcl-2 family, activation of the caspase cascade, and DNA fragmentation. Depending on the amount, duration, and the site of NO production, this molecule may not only mediate apoptosis in target cells but also protect cells from apoptosis induced by other apoptotic stimuli. In this review, we will concentrate on the current knowledge about the role of NO as an effector of apoptosis in tumor cells and discuss the mechanisms of NO-mediated apoptosis.

Nonmyeloablative allogeneic bone marrow transplantation as immunotherapy for hematologic malignancies and metastatic solid tumors in preclinical models

OBJECTIVE

We previously demonstrated that a combination of mild total lymphoid irradiation (TLI) with selective depletion of the host's donor-reactive cells allows for stable and graft-vs-host disease (GVHD)-free engraftment of allogeneic bone marrow (BM). In this study, we investigated the efficacy of this nonmyeloablative strategy for BM transplantation (BMT) as immunotherapy for minimal residual disease.

MATERIALS AND METHODS

BALB/c mice inoculated with leukemia (BCL1) or breast carcinoma (4T1) cells were conditioned for BMT with TLI (200 cGy) followed by priming with donor (C57BL/6) BM cells on day 1, and by injection with 200 mg/kg cyclophosphamide on day 2. After conditioning (day 3), recipients were transplanted with BM cells from the same donor. Treated animals were monitored for 230 days for survival, development of leukemia/solid tumor, and GVHD.

RESULTS

BMT converted the mice to complete chimeras and prevented development of leukemia in 90% of recipients and locally growing breast carcinoma in 40% of the mice. Immunization of donors of the second BM with 4T1 cells prevented development of breast carcinoma in 80% of 4T1 inoculated mice. Fewer animals treated for malignancy by nonmyeloablative BMT died of GVHD than those treated by myeloablative BMT. However, late GVHD-related mortality in mice treated for leukemia was higher than after nonmyeloablative BMT to naive recipients (p < 0.00001). Infusion of host-type anti-donor immune lymphocytes 8 days after BMT improved the survival of recipients treated for leukemia without affecting engraftment and the graft-vs-leukemia potential of donor BM.

CONCLUSIONS

Effective eradication of malignant cells can be achieved following allogeneic BMT after nonmyeloablative conditioning.

Sialoadhesin-Positive Host Macrophages Play an Essential Role in Graft-Versus-Leukemia Reactivity in Mice

We recently established an effective immune T-cell–mediated graft-versus-leukemia (GVL) murine model system in which complete tumor remissions were achievable even in advanced metastasized cancer. We now describe that this T-cell–mediated therapy is dependent on host macrophages expressing the lymphocyte adhesion molecule sialoadhesin (Sn). Depletion of Kupffer cells in tumor-bearing mice during adoptive immunotherapy (ADI) or the treatment of these animals with anti-Sn monoclonal antibodies led to complete or partial inhibition of the immune T-cell–mediated therapeutic effect. Furthermore, Sn+ host macrophages in livers formed clusters during ADI with donor CD8 T cells. To test for a possible antigen presentation function of these macrophages, we used as an in vitro model the antigen β-galactosidase for which a dominant major histocompatibility complex (MHC) class I Ld-restricted peptide epitope is known to be recognized by specific CD8 cytotoxic T lymphocytes (CTL). We demonstrate that purified Sn+ macrophages can process exogenous β-galactosidase and stimulate MHC class I peptide-restricted CTL responses. Thus, Sn+ macrophages, which are significantly increased in the liver after ADI, may process tumor-derived proteins via the MHC class I pathway as well as via the MHC class II pathway, as shown previously, and present respective peptide epitopes to CD8 as well as to CD4 immune T cells, respectively. The synergistic interactions observed before between immune CD4 and CD8 T cells during ADI could thus occur in the observed clusters with Sn+ host macrophages.

Sialoadhesin-Positive Host Macrophages Play an Essential Role in Graft-Versus-Leukemia Reactivity in Mice

We recently established an effective immune T-cell–mediated graft-versus-leukemia (GVL) murine model system in which complete tumor remissions were achievable even in advanced metastasized cancer. We now describe that this T-cell–mediated therapy is dependent on host macrophages expressing the lymphocyte adhesion molecule sialoadhesin (Sn). Depletion of Kupffer cells in tumor-bearing mice during adoptive immunotherapy (ADI) or the treatment of these animals with anti-Sn monoclonal antibodies led to complete or partial inhibition of the immune T-cell–mediated therapeutic effect. Furthermore, Sn+ host macrophages in livers formed clusters during ADI with donor CD8 T cells. To test for a possible antigen presentation function of these macrophages, we used as an in vitro model the antigen β-galactosidase for which a dominant major histocompatibility complex (MHC) class I Ld-restricted peptide epitope is known to be recognized by specific CD8 cytotoxic T lymphocytes (CTL). We demonstrate that purified Sn+ macrophages can process exogenous β-galactosidase and stimulate MHC class I peptide-restricted CTL responses. Thus, Sn+ macrophages, which are significantly increased in the liver after ADI, may process tumor-derived proteins via the MHC class I pathway as well as via the MHC class II pathway, as shown previously, and present respective peptide epitopes to CD8 as well as to CD4 immune T cells, respectively. The synergistic interactions observed before between immune CD4 and CD8 T cells during ADI could thus occur in the observed clusters with Sn+ host macrophages.

Role of cytokines in GVL (ESb lymphoma) and GVHD after adoptive transfer of allogeneic T lymphocytes in mice

ESb lymphoma cells injected i.v. into DBA/2 (H-2d) mice multiply rapidly in the liver and kill all mice in a few days. Adoptive transfer of allogeneic C57B1/6 (H-2b) tumor-immune or normal splenic lymphocytes to sublethally irradiated DBA/2 mice induced a marked antitumor state, graft-versus-leukemia (GVL), increasing the mean survival time 2-3-fold, but also induced an acute and lethal graft-versus host disease (GVHD). We have undertaken experiments to try to dissociate GVL from GVHD. Transfer of immune spleen cells induced a greater GVL than transfer of normal spleen cells with an equivalent to GVHD. Three to five million immune or normal CD8+ T lymphocytes were sufficient to induce both GVL and GVHD. Individual DBA/2 mice were labeled and followed. In mice undergoing GVHD, the spleens were repopulated by donor (H-2b) lymphocytes, and tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were present in the sera of 26 of 27 and 18 of 20 mice, respectively, together with increased amounts of TNF-alpha and IL-6 mRNA in their spleens. This was in contrast to DBA/2 mice receiving allogeneic cells but not developing GVHD. Both interferon-alpha/beta (IFN-alpha/beta) and IL-12, which had proven very effective in association with adoptive transfer of syngeneic immune T lymphocytes in inhibiting ESb metastases, enhanced GVHD when administered with allogeneic immune or normal spleen cells, and >90% of mice died. Intensive IL-2 treatment inhibited GVHD while maintaining GVL.

Loss of Endogenous Mouse Mammary Tumor Virus Superantigen Increases Tumor Resistance

From a cross between a tumor-susceptible mouse strain (DBA/2; D) and a tumor-resistant MHC-identical strain (B10.D2; D2) new recombinant inbred mouse strains were established over many generations of inbreeding and tumor resistance selection. Since resistance to the highly metastatic DBA/2 lymphoma variant ESb had an immunologic basis, and the two parental strains differed in endogenous viral superantigens (vSAGs), DNA of three D2×D recombinant inbred mouse lines was typed for endogenous mouse mammary tumor viruses using mouse mammary tumor virus long terminal repeat- and env gene-specific probes. The resistant D2×D mice were very similar to the susceptible parental strain D in their Mtv Southern blots, except for the lack of a single band corresponding to Mtv-7, the provirus coding for the strong DBA/2 superantigen Mls-1a. A backcross analysis revealed that Mtv-7-negative F2 mice were significantly more resistant than Mtv-7-positive F2 mice. When Mtv-7 was reintroduced into the resistant lines by crossing them with either CBA/J or BALB/D2.Mls-1a, the mice became again more tumor susceptible. Finally, we demonstrate the ability to transfer immunoresistance and graft-vs-leukemia reactivity from tumor-resistant to tumor-susceptible mice.

Differences Between Graft-Versus-Leukemia and Graft-Versus-Host Reactivity. I. Interaction of Donor Immune T Cells With Tumor and/or Host Cells

Graft-versus-leukemia (GVL) and Graft-versus-host (GVH) reactions were compared after systemic transfer of allogeneic antitumor immune T lymphocytes from B10.D2 (H-2d; MIsb) into DBA/2 (H-2d; MIsa) mice. Before immune cell transfer, recipient DBA/2 mice were sublethally irradiated with 5 Gy to prevent host-versus-graft reactivity. Recipients were either bearing syngeneic metastatic ESb lymphomas (GVL system) or were normal, non–tumor-bearing mice (GVH system). We previously reported that this adoptive immunotherapy protocol (ADI) had pronounced GVL activity and led to immune rejection of even advanced metastasized cancer. In this study, monoclonal antibodies were used for immunohistochemical analysis of native frozen tissue sections from either spleen or liver to distinguish donor from host cells, to differentiate between CD4 and CD8 T lymphocytes, and to stain sialoadhesin-positive macrophages at different time points after cell transfer. The kinetics of donor cell infiltration in spleen and liver differed in that the lymphoid organ was infiltrated earlier (days 1 to 5 after transfer) than the nonlymphoid organ (days 5 to 20). After reaching a peak, donor cell infiltration decreased gradually and was not detectable in the spleen after day 20 and in the liver after day 30. The organ-infiltrating donor immune cells were mostly T lymphocytes and stained positive for CD4 or CD8 T-cell markers. A remarkable GVL-associated observation was made with regard to a subset of macrophages bearing the adhesion molecule sialoadhesin (SER+ macrophages). In the livers of tumor-bearing mice, their numbers increased between days 1 and 12 after ADI by a factor greater than 30. Double-staining for donor cell marker and SER showed that the sialoadhesin-expressing macrophages were of host origin. The SER+ host macrophages from GVL livers were isolated by enzyme perfusion and rosetting 12 days after ADI, when they reached peak values of about 60 cells per liver lobule, and were tested, without further antigen addition, for their capacity to stimulate an antitumor CD8 T-cell response. The results of this immunologic analysis suggest that these cells in the liver function as scavengers of the destroyed metastases and as antigen-processing and -presenting cells for antitumor immune T cells.

Characterization of a murine lymphoma cell line by 31P-NMR spectroscopy: in vivo monitoring of the local anti-tumor effects of systemic immune cell transfer

The intradermal ESb-MP murine T-cell lymphoma in syngeneic DBA/2 mice has been used as a model for adoptive immunotherapy (ADI). Cultured ESb-MP cells were characterized in suspension by 31P-NMR spectroscopy (MRS) at 11.7 T, and solid primary tumors were examined by 31P-MRS in vivo at 7.0 Tesla using surface-coil techniques. Growing tumors contained relatively high levels of phosphomonoesters (PME, predominantly phosphoethanolamine), nucleotides (NTP) and Pi, low levels of phosphodiesters (PDE) and no phosphocreatine. Mean tissue pH was found to be 6.7-6.9. The spectra of ESb-MP cells cultured in RPMI medium (containing choline but no ethanolamine) also showed low PDE and no phosphocreatine at an intracellular pH of 7.4; however, only a trace amount of phosphoethanolamine was detected and significant levels of nucleoside mono- and diphosphates were observed. The complete ADI treatment protocol involved low-dose irradiation (5 Gy) followed by i.v. transfer of immune spleen cells from allogeneic B10.D2 donors and resulted in 100% remission (responders); no treatment or incomplete ADI (irradiation or immune cell transfer alone) resulted in no remissions (nonresponders). In vivo MRS could best discriminate between responders and non-responders on the basis of tissue pH, which increased in responders to 7.0 by day 5-6 after complete ADI. Following therapy, the sum of PME + Pi (both absolute and as a percent of total phosphates) decreased significantly only for responders but only after a visible decrease in tumor volume was apparent.