Augmentation of antitumor immune responses after adoptive transfer of bone marrow derived from donors immunized with tumor lysate-pulsed dendritic cells

Immunotherapy for neuroblastoma by hematopoietic cell transplantation and post-transplant immunomodulation

Neuroblastoma represents a relatively common childhood tumor that imposes therapeutic difficulties. High risk neuroblastoma patients have poor prognosis, display limited response to radiochemotherapy and may be treated by hematopoietic cell transplantation. Allogeneic and haploidentical transplants have the distinct advantage of reinstitution of immune surveillance, reinforced by antigenic barriers. The key factors favorable to ignition of potent anti-tumor reactions are transition to adaptive immunity, recovery from lymphopenia and removal of inhibitory signals that inactivate immune cells at the local and systemic levels. Post-transplant immunomodulation may further foster anti-tumor reactivity, with positive but transient impact of infusions of lymphocytes and natural killer cells both from the donor, the recipient or third party. The most promising approaches include introduction of antigen-presenting cells in early post-transplant stages and neutralization of inhibitory signals. Further studies will likely shed light on the nature and actions of suppressor factors within tumor stroma and at the systemic level.

Early immunisation with dendritic cells after allogeneic bone marrow transplantation elicits graft vs tumour reactivity

Background:

Perspectives of immunotherapy to cancer mediated by bone marrow transplantation (BMT) in conjunction with dendritic cell (DC)-mediated immune sensitisation have yielded modest success so far. In this study, we assessed the impact of DC on graft vs tumour (GvT) reactions triggered by allogeneic BMT.

Methods:

H2K^a mice implanted with congenic subcutaneous Neuro-2a neuroblastoma (NB, H2K^a) tumours were irradiated and grafted with allogeneic H2K^b bone marrow cells (BMC) followed by immunisation with tumour-inexperienced or tumour-pulsed DC.

Results:

Immunisation with tumour-pulsed donor DC after allogeneic BMT suppressed tumour growth through induction of T cell-mediated NB cell lysis. Early post-transplant administration of DC was more effective than delayed immunisation, with similar efficacy of DC inoculated into the tumour and intravenously. In addition, tumour inexperienced DC were equally effective as tumour-pulsed DC in suppression of tumour growth. Immunisation of DC did not impact quantitative immune reconstitution, however, it enhanced T-cell maturation as evident from interferon-γ (IFN-γ) secretion, proliferation in response to mitogenic stimulation and tumour cell lysis in vitro. Dendritic cells potentiate GvT reactivity both through activation of T cells and specific sensitisation against tumour antigens. We found that during pulsing with tumour lysate DC also elaborate a factor that selectively inhibits lymphocyte proliferation, which is however abolished by humoral and DC-mediated lymphocyte activation.

Conclusion:

These data reveal complex involvement of antigen-presenting cells in GvT reactions, suggesting that the limited success in clinical application is not a result of limited efficacy but suboptimal implementation. Although DC can amplify soluble signals from NB lysates that inhibit lymphocyte proliferation, early administration of DC is a dominant factor in suppression of tumour growth.

Immunomodulation with dendritic cells and donor lymphocyte infusion converge to induce graft vs neuroblastoma reactions without GVHD after allogeneic bone marrow transplantation

BACKGROUND

Mounting evidence points to the efficacy of donor lymphocyte infusion (DLI) and immunisation with tumour-pulsed dendritic cells (DC) in generating graft vs leukaemia reactions after allogeneic bone marrow transplantation (BMT). We assessed the efficacy of DLI and DC in generating potent graft vs neuroblastoma tumour (GVT) reactions following allogeneic BMT.

METHODS

Mice bearing congenic (H2K(a)) Neuro-2a tumours were grafted with allogeneic (H2K(b)) T-cell-depleted bone marrow cells. Tumour-pulsed donor DC (DC(Neuro2a)) were inoculated (on day +7) in conjunction with donor (H2K(b)) and haploidentical (H2K(a/b)) lymphocytes.

RESULTS

Murine Neuro-2a cells elicit immune reactions as efficient as B lymphoma in major histocompatibility complex antigen-disparate mice. Lymphopenia induced by conditioning facilitates GVT, and transition to adaptive immunity is enhanced by simultaneous infusion of and DC(Neuro2a) and lymphocytes devoid of graft vs host (GVH) activity (H2K(a/b)). In variance, the efficacy of DC-mediated immunomodulation was diminished by severe graft vs host disease (GVHD), showing mechanistic dissociation and antagonising potential to GVT.

CONCLUSIONS

The GVHD is not a prerequisite to induce GVT reactivity after allogeneic BMT, but is rather detrimental to induction of anti-tumour immunity by DC-mediated immunomodulation. Simultaneous inoculation of tumour-pulsed donor DC and DLI synergise in stimulation of potent GVT reactions to the extent of eradication of established NB tumours.

Optimized systemic dosing with CpG DNA enhances dendritic cell-mediated rejection of a poorly immunogenic mammary tumor in BALB/c mice

To model a clinical trial of dendritic cell (DC) therapy of a poorly immunogenic mammary tumor, we treated BALB/c mice bearing an established TS/A mammary tumor with lysate-pulsed DCs and CpG DNA. We observed that the dose of CpG DNA required to activate DCs in vitro was insufficient to mediate tumor rejection in vivo. We therefore undertook in vivo studies to identify an optimized dose of CpG DNA for tumor therapy, defined as the lowest and least frequently administered dose of CpG DNA that mediated complete tumor rejection. We show that one priming dose of 15 nanomoles and one booster dose of 10 nanomoles of CpG DNA given 7 days apart, respectively, with lysate-loaded DCs were sufficient to mediate complete tumor rejection in vivo. This dose of CpG DNA was 42-fold higher than that required to activate DCs in vitro but was not associated with any toxicity in mice. Also, the cured mice rejected a subsequent challenge with fresh TS/A tumor, and both CD4(+) and CD8(+) T cells were required for tumor rejection. We conclude that effective DC-based therapy of a poorly immunogenic TS/A tumor is enhanced by optimized dosing of CpG DNA. Our data have important implications for DC-based clinical trials of breast cancer immunotherapy.

Blockade of programmed death ligand 1 enhances the therapeutic efficacy of combination immunotherapy against melanoma

Inhibition of antitumor T cell responses can be mediated by the productive interaction between the programmed death-1 (PD-1) receptor on T cells and its ligand PD-L1. PD-L1 is highly expressed on both murine bone marrow-derived dendritic cells (DCs) and B16 melanoma. In this study, in vitro blockade of PD-L1 interaction on DCs led to enhanced IFN-gamma production and cytotoxicity by Ag-specific T cells. In vivo, the systemic administration of anti-PD-L1 Ab plus melanoma peptide-pulsed DCs resulted in a higher number of melanoma peptide-specific CD8(+) T cells, but this combination was insufficient to delay the growth of established B16 melanoma. Although the addition of 600 rad of total body irradiation delayed tumor growth, further adoptive transfer of Ag-specific CD8(+) T cells was needed to achieve tumor regression and long-term survival of the treated mice. Lymphopenic mice treated with anti-PD-L1 Ab demonstrated increased activation and persistence of adoptively transferred T cells, including a higher number of CD8(+) T cells infiltrating the tumor mass. Together, these studies support the blocking of PD-L1 signaling as a means to enhance combined immunotherapy approaches against melanoma.

To ablate or not to ablate? HSCs in the T cell driver's seat

The combination of the induction of lymphopenia and vaccination and/or T cell transfer is garnering much attention for cancer treatment. Preclinical studies have shown that the induction of lymphopenia by chemotherapy or radiation can enhance the antitumor efficacy of several distinct, cell-based immunotherapeutic approaches. The mechanism(s) by which such enhancement is achieved are being intensively studied, yet there is much opportunity for improvement. The animal studies reported by Wrzesinski and colleagues in this issue of the JCI are a promising and timely step in this direction (see the related article beginning on page 492). The authors have evaluated both the effect of increasing the intensity of lymphodepletion and the influence of HSC transfer on the in vivo function of adoptively transferred CD8(+) T cells. We discuss their results in light of the evolving field and their implications for advancing cell-based immunotherapies for cancer.

Peritransplantation vaccination with chaperone-rich cell lysate induces antileukemia immunity

We have reported that chaperone-rich cell lysate (CRCL) is an effective anticancer vaccine in immunocompetent mice. In this study, we explored the therapeutic applicability of CRCL in the context of syngeneic hematopoietic cell transplantation (HCT) to treat preexisting leukemia. Our results demonstrate that tumor growth is significantly delayed in mice receiving syngeneic HCT from 12B1 tumor CRCL-immunized donors compared with animals receiving HCT from nonimmunized donors. CRCL immunization after immune HCT further hindered tumor growth when compared with immune HCT without posttransplantation vaccination. The magnitude of the immune response was consistent with the antitumor effects observed in vivo. Rechallenge of surviving mice with 12B1 or A20 cells in opposite groins confirmed that mice had developed long-term tumor-specific immunity against 12B1 tumor cells. In addition, we documented that both T cells and natural killer cells contributed to the antitumor effect of CRCL vaccination, because depletion of either subset hampered tumor growth delay. Thus, our results indicate that CRCL is a promising vaccine capable of generating specific immune responses. This antitumor immunity can be effectively transferred to a host via HCT and further enhanced after HCT with additional tumor CRCL immunizations.

Biological response modifiers as adjuncts to stem cell transplantation

Cytokines produced by immune and non-immune cells serve as potent mediators with the properties of signal cells that coordinate the immune response. They are delivered by cells either to the systemic circulation or to the local environment. They are being used at present in the field of stem cell transplantation (SCT) in order to improve transplant outcome. This paper reviews the existing data on pre-, peri- and post-SCT treatment with cytokines.

Vaccine strategies to treat lymphoproliferative disorders

Lymphoproliferative disorders, including follicular lymphoma (FL), multiple myeloma (MM) and chronic lymphatic leukaemia (CLL), are slowly progressive malignancies which remain incurable despite advances in therapy. Harnessing the immune system to recognise and destroy tumours is a promising new approach to treating these diseases. Dendritic cells (DC) are unique antigen-presenting cells that play a central role in the initiation and direction of immune responses. DC loaded ex vivo with tumour-associated antigens and administered as a vaccine have already shown promise in early clinical trials for a number of lymphoproliferative disorders, but the need for improvement is widely agreed. Recent advances in the understanding of basic DC biology and lessons from early clinical trials have provided exciting new insights into the generation of anti-tumour immune responses and the design of vaccine strategies. In this review we provide an overview of our current understanding of DC biology and their function in patients with lymphoproliferative disorders. We discuss the current status of clinical trials and new approaches to exploit the antigen presenting capacity of DC to design vaccines of the future.