Beta-Adrenergic Signaling in Tumor Immunology and Immunotherapy.

Communication between the nervous and immune systems is required for the body to regulate physiological homeostasis. Beta-adrenergic receptors expressed on immune cells mediate the modulation of immune response by neural activity. Activation of beta-adrenergic signaling results in suppression of antitumor immune response and limits the efficacy of cancer immunotherapy. Beta-adrenergic signaling is also involved in regulation of hematopoietic reconstitution, which is critical to the graft-versus-tumor (GVT) effect and to graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (HCT). In this review, the function of beta-adrenergic signaling in mediating tumor immunosuppression will be highlighted. We will also discuss the implication of targeting beta-adrenergic signaling to improve the efficacy of cancer immunotherapy including the GVT effect, and to diminish the adverse effects including GVHD.

Inhibition of indoleamine 2,3-dioxygenase by stereoisomers of 1-methyl tryptophan in an experimental graft-versus-tumor model.

Indoleamine 2,3-dioxygenase (IDO) is a rate-limiting enzyme in tryptophan catabolism that plays an important role in the induction of immune tolerance. Its role in graft-versus-tumor effect after allogeneic stem cell transplantation (allo-SCT) remains unclear. Using a murine graft-versus-tumor model of reduced-intensity allo-HSCT followed by donor leukocyte infusion (DLI), we examined the role of IDO inhibition. Two stereoisomers of 1-methyl tryptophan (1-MT), a small-molecule inhibitor of IDO, reduced the growth of inoculated tumor in the mice that received DLI and had higher expression of IDO1 and IFNγ. However, L-1MT, but not D-1MT, mitigated tumor growth in mice that did not receive DLI and did not express IDO1 and IFNγ. Accordingly, both stereoisomers reduced plasma kynurenine concentrations early after DLI and enhanced in vitro cytotoxic lymphocyte function after allogeneic mixed lymphocyte reaction. Furthermore, L-1MT was more efficient in causing direct cytotoxic effects than D-1MT. Our results suggest that IDO inhibition can benefit anti-tumor therapy in the setting of reduced-intensity allo-SCT using DLI.

Host-derived CD8+ dendritic cells are required for induction of optimal graft-versus-tumor responses after experimental allogeneic bone marrow transplantation.

The graft-versus-tumor (GVT) effect after allogeneic hematopoietic cell transplantation (allo-HCT) represents an effective form of immunotherapy against many malignancies. Meaningful separation of the potentially curative GVT responses from graft-versus-host disease (GVHD), the most serious toxicity following T-cell replete allo-HCT, has been an elusive goal. GVHD is initiated by alloantigens, although both alloantigens and tumor-specific antigens (TSAs) initiate GVT responses. Emerging data have illuminated a role for antigen-presenting cells (APCs) in inducing alloantigen-specific responses. By using multiple clinically relevant murine models, we show that a specific subset of host-derived APCs-CD8(+) dendritic cells (DCs)-enhances TSA responses and is required for optimal induction of GVT. Stimulation of TLR3, which among host hematopoietic APC subsets is predominantly expressed on CD8(+) DCs, enhanced GVT without exacerbating GVHD. Thus, strategies that modulate host APC subsets without direct manipulation of donor T cells could augment GVT responses and enhance the efficacy of allo-HCT.

Granzyme B-mediated damage of CD8+ T cells impairs graft-versus-tumor effect.

Allogeneic hematopoietic cell transplantation is an established treatment for hematologic and other malignancies. Donor-derived immune cells can identify and attack host tumor cells, producing a graft-versus-tumor (GVT) effect that is crucial to the treatment. Using multiple tumor models and diverse donor-host combinations, we have studied the role of granzyme B (GzmB) in GVT effect. We first confirmed previous findings that GzmB deficiency diminished the ability of a high dose of CD8(+) T cells to cause lethal graft-versus-host disease. However, when GVT studies were performed using a moderate cell dose that the hosts could tolerate, GzmB(-/-) CD8(+) T cells demonstrated a significantly enhanced GVT effect. GzmB-mediated, activation-induced cell death in wild-type CD8(+) T cells was found responsible for their reduced GVT activity. Conversely, GzmB(-/-) CD8(+) T cells exhibited enhanced expansion, skewed toward an effector or effector memory phenotype, and produced higher amounts of IFN-γ and Fas ligand that might contribute to GzmB-independent tumor control. These findings demonstrate for the first time, to our knowledge, that GzmB-mediated damage of CD8(+) T cells impairs the desired GVT effect. This study suggests that inhibiting donor-derived GzmB function may represent a promising strategy to improve GVT effect without exacerbating graft-versus-host disease.

Ex vivo-expanded donor CD4(+) lymphocyte infusion against relapsing neuroblastoma: A transient graft-versus-tumor effect.

High-risk neuroblastoma has a poor prognosis despite multimodal treatment including high-dose chemotherapy. A 7-year-old male with neuroblastoma received ex vivo-expanded donor CD4(+) T lymphocyte infusion (CD4(+) DLI) after recurrence in the bone marrow following allogeneic hematopoietic stem cell transplantation from his HLA-identical mother. The disease transiently responded to CD4(+) DLI with reduction of tumor cells and a decrease of serum neuron-specific enolase. The response was associated with development of continued high fever and an increase of cytotoxic T lymphocytes in peripheral blood. This case suggests a possibility of a graft-versus-tumor effect against neuroblastoma.

Allogeneic haematopoietic cell transplantation for multiple myeloma: reducing transplant-related mortality while harnessing the graft-versus-myeloma effect.

Allogeneic haematopoietic cell transplantation (allo-HCT) provides effective therapy for patients with various haematological malignancies. In multiple myeloma (MM) this approach can induce response rates in 35-75% of patients. However, the outcome is hampered by high rates of treatment-related mortality (TRM). Reduced intensity conditioning to lower TRM has been successfully applied. The fact that previous clinical reports have documented graft-versus-myeloma (GVM) activity without graft-versus-host disease (GVHD) suggests that at least two distinct immunocompetent cell populations mediating GVHD and/or GVM may exist. Further characterization of effectors after allo-HCT and their targets may help to clarify the immune response that mediates the GVM effect. This review considers the clinical results with myeloablative and reduced intensity conditioning prior to allo-HCT for MM, with emphasis on attempts to prevent GVHD while preserving the GVM effect. Strategies including donor lymphocyte infusions as part of the allogeneic protocol and antigenic targets for GVM effect are reviewed.

Graft-versus-lymphoma effect in refractory cutaneous T-cell lymphoma after reduced-intensity HLA-matched sibling allogeneic stem cell transplantation.

Cutaneous T-cell lymphomas (CTCL) are rare diseases that, in their advanced stages or in transformation, have a poor prognosis. Autologous stem cell transplantation (Au-SCT) after high-dose therapy has yielded disappointing results. Allogeneic transplantation (allo-SCT) provides the potential advantage of an immune-mediated graft-versus-lymphoma (GVL) effect. Reduced-intensity allo-SCT potentially offers a GVL effect, but with diminished toxicity related to the induction regimen; however, published experience with this approach in CTCL is limited. We report a series of three patients (age 35-49) with advanced, refractory (n=2) or transformed (n=1) CTCL who underwent reduced-intensity allo-SCT in the context of active disease. All three survived the peri-transplant period and, despite later having disease relapse, all exhibited evidence of a GVL effect. Relapses of the disease were in the context of immune suppression for graft-versus-host disease (GVHD), and when immune suppression was reduced, responses were regained. A comparison is made of these results to those in a review of the published literature to date. We conclude that while a GVL can be achieved for CTCL with reduced-intensity allogeneic transplantation, the clinical benefits are short lived and novel approaches are required to obtain sustained remissions.

Donor leukocyte infusions in relapsed Hodgkin's lymphoma following allogeneic stem cell transplantation: CD3+ cell dose, GVHD and disease response.

Nine patients with advanced Hodgkin's lymphoma (HL) who had undergone allogeneic stem cell transplantation (allo-SCT) received donor leukocyte infusions (DLIs) for treatment of persistent or progressive disease (PD). A total of 15 DLIs were performed, with four patients receiving more than one DLI. In four patients, prior salvage chemotherapy was administered. The median CD3+ cell dose administered was 77.5 x 10(6)/kg (range 5-285). GVHD developed in all but one patient. The response rate was 4/9 (44%). Three of these four responders developed GVHD and 3/4 had received chemotherapy. No correlation was observed between CD3+ cell dose infused and disease response. At the latest follow-up, three patients are alive and six have expired (PD n=3, nonrelapse mortality n=3). The median response duration was 7 months (range 4-9), with one response currently ongoing. These data suggest that DLIs for immunotherapy of recurrent HL have significant activity, although they frequently leads to GVHD. The small sample size does not allow any conclusion as to whether chemotherapy administration increases the chance of response. The CD3 cell dose infused does not seem to correlate with disease response.

Multiple myeloma: role of allogeneic transplantation.

An estimated 14,600 new cases of multiple myeloma will be diagnosed in the United States in 2002. Multiple myeloma remains an incurable disease despite significant improvements in complete response rates and overall survival through the use of autologous stem cell transplantation. Allogeneic transplantation offers the advantage of a tumor-free graft and a graft-vs-myeloma effect but has been associated with a high mortality rate from transplant-related complications-primarily graft-vs-host disease (GVHD). As immunotherapy for patients with relapsed myeloma, donor lymphocyte infusion has resulted in response rates of over 50%, but many of these responses are not durable. In addition, donor lymphocyte infusion is associated with a significant risk of moderate-to-severe GVHD. In an attempt to decrease the high transplant-related mortality of conventional allogeneic transplants and to employ the proven efficacy of immunoreactive donor T lymphocytes, the use of nonmyeloablative transplants or "mini-transplants" is increasing. This approach has succeeded in significantly reducing transplant-related mortality but still may not be sufficient in producing long-term remissions or cures in myeloma patients. A combination of an autologous transplant (to achieve maximal cytoreduction) and a mini-transplant with donor lymphocyte infusion (for the immunoablative effect of alloreactive T lymphocytes) followed by maintenance therapy (thalidomide [Thalomid], steroids, cytokines, vaccines) for long-term immunomodulation is being investigated as a potential cure for this challenging disease.

A graft-versus-tumor effect in a patient with ependymoma who received an allogenic bone marrow transplant for therapy-related leukemia. Case report.

Graft-versus-leukemia effect is an immune-mediated antitumor phenomenon associated with allogenic bone marrow transplants (BMTs) for hematological malignancies, and recent findings have indicated that a similar effect could occur in some solid tumors such as breast cancers. The authors report on a 42-year-old man with a recurrent ependymoma who received an allogenic BMT for therapy-related leukemia. After transplantation, the patient developed chronic graft-versus-host disease, which was controlled with steroid agents. Interestingly, the recurrent ependymoma regressed steadily over the next 21 months posttransplant, until the tumor became almost undetectable on magnetic resonance images. This case indicates that the graft-versus-tumor effect, mediated by cytotoxic T cells, may be able to target intraparenchymal neuroepithelial tumors, despite the brain's generally recognized status as an immunoprivileged organ.

Allogeneic hematopoietic cell transplantation for multiple myeloma.

At the present time, allogeneic hematopoetic stem cell transplantation (AHSCT) is the only proven treatment for multiple myeloma (MM) that is potentially curative. This conclusion is based on observations of patients who have undergone AHSCT and are living disease-free for 5-15 years. While patients who receive either allogeneic or autologous stem cell transplants for MM have similar 3-5 year survival, only allograft recipients appear to enjoy long-term disease free survival. This is most likely due to an allogeneic graft-versus-myeloma effect, demonstrated most dramatically by complete responses observed after the simple infusion of donor lymphocytes for patients who have relapsed after a prior allograft. The very high transplant related mortality associated with standard allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative treatment modality. Complications are age-related and thus standard AHSCT is offered only to patients under age 55; further limiting the utility of this treatment. The challenge for clinical investigators will be to reduce the incidence of post-transplant complications for patients receiving AHSCT for MM. These strategies include the use of non-ablative conditioning regimens, the use of peripheral blood stem cells rather than bone marrow, graft engineering and targeted conditioning therapies such as bone-seeking radioisotopes. In one such approach, tandem autologous/non-ablative allogeneic transplants have been shown to result in relatively low mortality, high complete response rates and 1-year survivals of 81%. Further follow-up and randomized trials will help to define the utility of this strategy.

T-cell--depleted allogeneic bone marrow transplantation followed by donor lymphocyte infusion in patients with multiple myeloma: induction of graft-versus-myeloma effect.

Previous trials of allogeneic bone marrow transplantation (BMT) in patients with multiple myeloma (MM) have demonstrated high response rates but also high transplantation-related mortality (TRM) and high relapse rates. Exploitation of this strategy remains of interest because donor lymphocyte infusions (DLIs) can induce a potent graft-versus-myeloma (GVM) effect. CD6 T-cell--depleted allogeneic BMT was combined with prophylactic CD4(+) DLI administered 6 to 9 months after BMT in an effort to reduce TRM and to induce a GVM response after BMT. Twenty-four patients with matched sibling donors and chemotherapy-sensitive disease underwent BMT. CD6 T-cell depletion of donor bone marrow was the sole method of graft-versus-host disease (GVHD) prophylaxis. GVHD after BMT was minimal, 1 (4%) grade III and 4 (17%) grade II GVHD. Fourteen patients received DLI, 3 in complete response and 11 with persistent disease after BMT. Significant GVM responses were noted after DLI in 10 patients with persistent disease, resulting in 6 complete responses and 4 partial responses. After DLI, 50% of patients developed acute (> or = II) or extensive chronic GVHD. Two-year estimated overall survival and current progression-free survival (PFS) for all 24 patients is 55% and 42%, respectively. The 14 patients receiving DLI had an improved 2-year current PFS (65%) when compared with a historical cohort of MM patients who underwent CD6-depleted BMT survived 6 months with no GVHD and did not receive DLI (41%) (P =.13). Although this study suggests that prophylactic DLI induces significant GVM responses after allogeneic BMT, only 58% of patients were able to receive DLI despite T-cell--depleted BMT. Therefore, less toxic transplantation strategies are needed to allow a higher proportion of patients to receive DLI and the benefit from the GVM effect after transplantation. (Blood. 2001;98:934-939)

Allogeneic stem cell transplantation reduces disease progression compared to autologous transplantation in patients with multiple myeloma.

This study compares the probability of disease progression, progression-free survival, and overall survival between patients undergoing an allogeneic or autologous transplant for multiple myeloma using an identical preparative regimen. Patients received a preparative regimen of TBI, busulfan, and cyclophosphamide followed by an allogeneic or autologous transplant. In the allogeneic group (n = 21), six patients received bone marrow and 15 received G-CSF mobilized PBSC; all autologous patients (n = 35) received PBSC mobilized with cyclophosphamide and G-CSF. Allogeneic donors were HLA-identical (n = 20) or one-antigen mismatched (n = 1) siblings. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus (n = 10), tacrolimus/methotrexate (n = 6), cyclosporine/methotrexate (n = 4), or cyclosporine (n = 1). The groups were evenly matched for gender, pretransplant therapy, disease status at time of transplant, myeloma subtype, and time from diagnosis to transplant. The median age was significantly lower in the allogeneic group (48 vs 55 years, P < 0.01). In the allogeneic group the probabilities of developing acute GVHD grade II-IV and chronic GVHD were 55% and 82%, respectively. The Kaplan-Meier probability of disease progression was significantly lower in the allogeneic group (11% vs 64%, P < 0.001) compared to the autologous group. Although progression-free (60% vs 30%, P = 0.19) and overall survival at 2 years (60% vs 42%, P = 0.39) favored the allogeneic group, this did not reach statistical significance. Within the allogeneic transplant group, patients age 50 years or under had a 3-year overall survival significantly higher when compared to older patients (79% vs 29%, P = 0.03). Using identical preparative regimens, allogeneic transplantation reduced disease progression compared to autologous transplantation for myeloma. This suggests that allogeneic transplantation induces a graft-versus-myeloma (GVM) effect.

The graft-versus-leukemia effects of allogeneic cell therapy.

Until recently, the only cure for relapse after allogeneic bone marrow transplantation (BMT) has been a second BMT. Recently, infusions of leukocytes collected from the original transplant donor have been used to induce a direct graft-versus-leukemia (GVL) reaction in patients with relapsed disease. Adoptive immunotherapy with donor leukocyte infusions (DLI) results in complete remission for 60-80% of patients with relapsed chronic-phase CML; therapy is also effective for relapse of diseases other than CML, although response rates are lower. Adoptive immunotherapy induces remissions for the majority of patients with post-transplantation Epstein-Barr virus-related lymphomas and other viral-associated illnesses. The extraordinary success of DLI demonstrates that it is now possible to harness the GVL potential of the human immune system for clinical benefit. The necessary effector cells and target antigens required for GVL reactivity are poorly defined but are the subject of intensive investigation. Future trials will investigate strategies that retain and enhance the GVL effects while limiting toxicity from this therapy, and they may define methods of successful allogeneic adoptive immunotherapy outside the setting of allogeneic BMT.