Allogeneic Hematopoietic Cell Transplantation as Immunotherapy for Solid Tumors

Haploidentical hematopoietic stem cell transplantation as individual treatment option in pediatric patients with very high-risk sarcomas

Background

Prognosis of children with primary disseminated or metastatic relapsed sarcomas remains dismal despite intensification of conventional therapies including high-dose chemotherapy. Since haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is effective in the treatment of hematological malignancies by mediating a graft versus leukemia effect, we evaluated this approach in pediatric sarcomas as well.

Methods

Patients with bone Ewing sarcoma or soft tissue sarcoma who received haplo-HSCT as part of clinical trials using CD3+ or TCRα/β+ and CD19+ depletion respectively were evaluated regarding feasibility of treatment and survival.

Results

We identified 15 patients with primary disseminated disease and 14 with metastatic relapse who were transplanted from a haploidentical donor to improve prognosis. Three-year event-free survival (EFS) was 18,1% and predominantly determined by disease relapse. Survival depended on response to pre-transplant therapy (3y-EFS of patients in complete or very good partial response: 36,4%). However, no patient with metastatic relapse could be rescued.

Conclusion

Haplo-HSCT for consolidation after conventional therapy seems to be of interest for some, but not for the majority of patients with high-risk pediatric sarcomas. Evaluation of its future use as basis for subsequent humoral or cellular immunotherapies is necessary.

Dissecting the biology of allogeneic HSCT to enhance the GvT effect whilst minimizing GvHD

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) was the first successful therapy for patients with haematological malignancies, predominantly owing to graft-versus-tumour (GvT) effects. Dramatic methodological changes, designed to expand eligibility for allo-HSCT to older patients and/or those with comorbidities, have led to the use of reduced-intensity conditioning regimens, in parallel with more aggressive immunosuppression to better control graft-versus-host disease (GvHD). Consequently, disease relapse has become the major cause of death following allo-HSCT. Hence, the prevention and treatment of relapse has come to the forefront and remains an unmet medical need. Despite >60 years of preclinical and clinical studies, the immunological requirements necessary to achieve GvT effects without promoting GvHD have not been fully established. Herein, we review learnings from preclinical modelling and clinical studies relating to the GvT effect, focusing on mechanisms of relapse and on immunomodulatory strategies that are being developed to overcome disease recurrence after both allo-HSCT and autologous HSCT. Emphasis is placed on discussing current knowledge and approaches predicated on the use of cell therapies, cytokines to augment immune responses and dual-purpose antibody therapies or other pharmacological agents that can control GvHD whilst simultaneously targeting cancer cells.

Selective T cell-depleted haploidentical hematopoietic stem cell transplantation for relapsed/refractory neuroblastoma

Relapsed/refractory NB carries a bleak outcome, warranting novel treatment options. HaploHSCT induces a graft-versus-NB effect via natural killer cell alloreactivity. Review of patients with relapsed/refractory NB who underwent haploHSCT with ex vivo T-cell depletion in our unit from 2013 through 2018. Ten patients were identified (male=5; median age at haploHSCT=6.45 y, range: 3.49-11.02 y). Indications were relapsed in 7 and refractoriness in 3; disease status at haploHSCT was CR in 2, PR in 6, and PD in 2. All patients received peripheral blood stem cell grafts after ex vivo T-cell depletion (CD3/CD19-depletion=1; TCR-αβ/CD19-depletion=4; CD3/CD45RA-depletion=4; and TCR-αβ/CD45RA-depletion=1). Conditioning regimens were fludarabine-based. Neutrophils engrafted on median D + 10 (range: D + 9 to +13), and platelets engrafted (≥20 × 109 /L) on median D + 8 (range: D + 5 to D + 14). Early T- and NK-cell recovery were evident. Of the 10 patients, acute rejection developed in 1 (who died of PD despite rescue HSCT), and 1 died of sepsis before engraftment; 8 experienced full donor-chimerism post-HSCT. Among the 8, 6 experienced CR, 1 died of PD, and 1 died of pulmonary hypertensive crisis before evaluation. At publication, 4 were in remission (2.8, 7.4, 28.5, and 58.9 months). No significant GvHD occurred. HaploHSCT with selective ex vivo T-cell depletion may be a safe and useful salvage strategy for relapsed/refractory NB.

Allogeneic stem cell transplantation for patients with advanced rhabdomyosarcoma: a retrospective assessment

BACKGROUND

Allogeneic haematopoietic stem cell transplantation (allo-SCT) may provide donor cytotoxic T cell-/NK cell-mediated disease control in patients with rhabdomyosarcoma (RMS). However, little is known about the prevalence of graft-vs-RMS effects and only a few case experiences have been reported.

METHODS

We evaluated allo-SCT outcomes of 30 European Group for Blood and Marrow Transplantation (EBMT)-registered patients with advanced RMS regarding toxicity, progression-free survival (PFS) and overall survival (OS) after allo-SCT. Twenty patients were conditioned with reduced intensity and ten with high-dose chemotherapy. Twenty-three patients were transplanted with HLA-matched and seven with HLA-mismatched grafts. Three patients additionally received donor lymphocyte infusions (DLIs). Median follow-up was 9 months.

RESULTS

Three-year OS was 20% (s.e.±8%) with a median survival time of 12 months. Cumulative risk of progression was 67% (s.e.±10%) and 11% (s.e.±6%) for death of complications. Thirteen patients developed acute graft-vs-host disease (GvHD) and five developed chronic GvHD. Eighteen patients died of disease and four of complications. Eight patients survived in complete remission (CR) (median: 44 months). No patients with residual disease before allo-SCT were converted to CR.

CONCLUSION

The use of allo-SCT in patients with advanced RMS is currently experimental. In a subset of patients, it may constitute a valuable approach for consolidating CR, but this needs to be validated in prospective trials.

Successful allogeneic hematopoietic cell engraftment after a minimal conditioning regimen in children with relapsed or refractory solid tumors

Children with relapsed or refractory solid tumors face dismal prognoses, and novel therapies are desperately needed. Allogeneic hematopoietic cell transplantation (HCT) offers potential for cell-based therapy, but the toxicity of myeloablation limits this approach in heavily pretreated patients. We sought to determine the feasibility of HCT in a cohort of 24 children with incurable solid tumors using human leukocyte antigen-matched sibling or unrelated donors and a minimal conditioning regimen. Before stem cell infusion, all patients received 3 daily doses of 30 mg/m(2) fludarabine followed by 2 Gy of total body irradiation. Hematopoietic cell recovery was rapid and reliable. Median time to neutrophil engraftment was 13.5 days for sibling donors and 12 days for unrelated donors. Donor lymphocyte infusions were used safely in 4 patients, all of whom had either improved chimerism or apparent tumor response. Graft-versus-host disease was comparable across donor sources and did not affect survival. Relapse remains a substantial barrier, although objective graft-versus-tumor effect was observed in several patients. Four patients with detectable disease before HCT achieved a complete response for at least 30 days after HCT, and two remain long-term survivors. Three patients were in complete response before HCT and remained in remission for 3, 6, and 74 months after HCT. Early disease response was associated with improved survival. Allogeneic HCT using this conditioning regimen offers a potential platform for novel immunotherapies.

Cancer immunotherapy

Cancer immunotherapy consists of approaches that modify the host immune system, and/or the utilization of components of the immune system, as cancer treatment. During the past 25 years, 17 immunologic products have received regulatory approval based on anticancer activity as single agents and/or in combination with chemotherapy. These include the nonspecific immune stimulants BCG and levamisole; the cytokines interferon-α and interleukin-2; the monoclonal antibodies rituximab, ofatumumab, alemtuzumab, trastuzumab, bevacizumab, cetuximab, and panitumumab; the radiolabeled antibodies Y-90 ibritumomab tiuxetan and I-131 tositumomab; the immunotoxins denileukin diftitox and gemtuzumab ozogamicin; nonmyeloablative allogeneic transplants with donor lymphocyte infusions; and the anti-prostate cancer cell-based therapy sipuleucel-T. All but two of these products are still regularly used to treat various B- and T-cell malignancies, and numerous solid tumors, including breast, lung, colorectal, prostate, melanoma, kidney, glioblastoma, bladder, and head and neck. Positive randomized trials have recently been reported for idiotype vaccines in lymphoma and a peptide vaccine in melanoma. The anti-CTLA-4 monoclonal antibody ipilumumab, which blocks regulatory T-cells, is expected to receive regulatory approval in the near future, based on a randomized trial in melanoma. As the fourth modality of cancer treatment, biotherapy/immunotherapy is an increasingly important component of the anticancer armamentarium.

High-dose chemotherapy followed by autologous and allogeneic peripheral blood stem cell transplantation for recurrent disseminated trilateral retinoblastoma

INTRODUCTION

Trilateral retinoblastoma (TRb) is an intracranial neurogenic tumor associated with unilateral or bilateral retinoblastoma and has very poor prognosis. Patients typically die from leptomeningeal tumor dissemination.

CASE REPORT

A 3-year-old girl who had been diagnosed with TRb had a disseminated relapse after a tumorectomy, cerebrospinal irradiation, and conventional chemotherapy. The disseminated tumor disappeared after the first autologous peripheral blood stem cell transplantation (PBSCT) with high-dose melphalan and thiotepa. During the second complete remission, a second autologous PBSCT with high-dose busulfan and melphalan was performed. Seven months after the first PBSCT, the second relapse occurred, and we subsequently performed an allogeneic PBSCT with myeloablative chemotherapy consisting of melphalan, thiotepa, and cyclophosphamide. The patient showed clinical improvement after the allogeneic PBSCT.

CONCLUSION

Although high-dose chemotherapies have a curative effect for some patients with TRb, the prognoses of disseminated tumors are still poor. Further examination of the high-dose chemotherapy is necessary for the time, the conditioning drugs, and the hematopoietic stem cell sources.

Cord blood as a source of non-senescent lymphocytes for tumor immunotherapy

While proof of concept that the immune system can be harnessed to attack cancer cells has been established, only a minority of patients are cured with immunotherapeutic regimens designed to enhance host autologous immunity. Recently acquired knowledge indicates that the low response rates associated with conventional cancer immunotherapy could be attributed, at least in part, to the processes of immunosenescence and replicative senescence, which consequently render the anti-tumor T cell clones of the aged host quantitatively insufficient and qualitatively impaired to elicit an effective anti-cancer response. Therefore, it is anticipated that the efficacy of adoptive T cell cancer immunotherapy can be dramatically improved by utilizing "young" T cells with targeted antigen specificity derived from umbilical cord blood, instead of current practice using autologous senescent T cells derived usually from aged cancer patients. Functionally competent CD8(+) T cells specific against tumor antigens (e.g. Her2/neu and MAGEA3) as well as against viral antigens have been recently generated from cord blood mononuclear cells suggesting that cord blood can be a source of "young" anti-tumor T cells for adoptive cancer immunotherapy. Moreover, cord blood can give rise to antigen non-specific effector cells including NK cells and dendritic cells. Finally, umbilical cord blood anti-tumor specific T cell clones are unlikely to have participated in tumor immunoediting, making them more efficient than host T cells in eradicating tumor cells.

The immunological impact of genetic drift in the B10.BR congenic inbred mouse strain

The MHC-matched, minor histocompatibility Ag (miHA)-mismatched B10.BR-->CBA strain combination has been used to elucidate the immunobiology of graft-vs-host disease (GVHD) following allogeneic bone marrow transplantation. Studies conducted in the 1980s had established that B10.BR CD8+ T cells were capable of mediating GVHD in the absence of CD4+ T cells, and that CD4+ T cells were unable to induce lethal disease. In more recent studies with this GVHD model, we detected etiological discrepancies with the previously published results, which suggested that genetic drift might have occurred within the B10.BR strain. In particular, there was increased allorecognition of CBA miHA by B10.BR CD4+ T cells, as determined by both TCR Vbeta spectratype analysis and the induction of lethal GVHD in CBA recipients. Additionally, alloreactivity was observed between the genetically drifted mice (B10.BR/Jdrif) and mice rederived from frozen embryos of the original strain (B10.BR/Jrep) using Vbeta spectratype analysis and IFN-gamma ELISPOT assays, suggesting that new miHA differences had arisen between the mice. Furthermore, T cell-depleted B10.BR/Jdrif bone marrow cells were unable to provide long-term survival following either allogeneic or syngeneic bone marrow transplantation. Gene expression analysis revealed several genes involved in hematopoiesis that were overexpressed in the lineage-negative fraction of B10.BR/Jdrif bone marrow, as compared with B10.BR/Jrep mice. Taken together, these results suggest that genetic drift in the B10.BR strain has significantly impacted the immune alloreactive response in the GVHD model by causing altered expression of miHA and diminished capacity for survival following transplantation into lethally irradiated recipients.

Tumor vaccines for breast cancer

The goal of cancer vaccines and immunotherapies is to train the immune system to recognize cancer cells and destroy them. Immune responses play a dynamic role in the development of cancers, from immunosurveillance to immune escape; from in situ immune dysregulation to metastatic spread. The systematic identification and targeting of molecules involved in the immune response has led to a wide variety of potential immunotherapeutic targets for the treatment of breast cancer. Extraordinary advances in molecular immunology have led to a detailed understanding of tumor antigens, antigen presentation, innate immunity, cytokine and chemokine pathways, and immunoregulation. Many of these vaccine therapies are already in clinical development. It is the rational and rapid translation of these scientific discoveries into effective therapies for patients with breast cancer that poses the greatest challenge, and opportunity, to realize the potential of tumor vaccine therapy for breast cancer.

Large-scale production and characterization of novel CD4+ cytotoxic T cells with broad tumor specificity for immunotherapy

Immune-cell-based approaches using cytotoxic and dendritic cells are under constant scrutiny to design novel therapies for the treatment of tumors. These strategies are hampered by the lack of efficient and economical large-scale production methods for effector cells. Here we describe the propagation of large amounts of a unique population of CD4(+) cytotoxic T cells, which we termed tumor killer T cells (TKTC), because of their potent and broad antitumor cell activity. With this cultivation strategy, TKTCs from peripheral blood mononuclear cells are generated within a short period of time using a pulse with a stimulating cell line followed by continuous growth in serum-free medium supplemented with a mixture of interleukin-2 and cyclosporin A. Expression and functional profiling did not allow a classification of TKTCs to any thus far defined subtype of T cells. Cytotoxic assays showed that TKTCs kill a panel of tumor targets of diverse tissue origin while leaving normal cells unaffected. Blocking experiments revealed that TKTC killing was, to a significant extent, mediated by tumor necrosis factor-related apoptosis-inducing ligand and was independent of MHC restriction. These results suggest that TKTCs have a high potential as a novel tool in the adoptive immunotherapy of cancer.

Targeting minor histocompatibility antigens in graft versus tumor or graft versus leukemia responses

Allogeneic hematopoietic cell transplantation (alloHCT) represents the only curative therapy for several hematologic malignancies, and shows promise as a nascent treatment modality for select solid tumors. Although the original goal of alloHCT was hematopoietic reconstitution after sub-lethal chemoradiotherapy, recognition of a profound donor lymphocyte-mediated graft-versus-leukemia (GVL) or graft-versus-tumor (GVT) effect has shifted the paradigm from pre-transplant cytoreduction to tumor control via donor lymphocytes. In human leukocyte antigen (HLA)-compatible alloHCT, GVL and GVT reactions are induced primarily by donor T-cell recognition of minor histocompatibility antigens (mHAgs). Here we review the literature regarding mHAg-specific T cells in GVL and GVT reactions, and discuss the prospects of exploiting mHAgs as immunotherapeutic targets.

Adoptive transfer of allogeneic tumor-specific T cells mediates effective regression of large tumors across major histocompatibility barriers

Graft-versus-tumor effects can be achieved after allogeneic bone marrow transplantation in patients with malignancies of the kidney or hematopoietic system but are often accompanied by severe graft-versus-host-disease (GVHD). We sought to maximize graft-versus-tumor while minimizing GVHD using tumor-specific allogeneic effector T cells rather than open-repertoire T cells. We transferred allogeneic CD8(+) pmel-1 or CD4(+) TRP-1 T cells specific for the melanoma-associated antigens, glycoprotein 100 (gp100) and tyrosinase-related protein-1 (TRP-1), respectively, into B16-melanoma-bearing mice. Mice receiving a preparative regimen of nonmyeloablating (5 Gy) total body irradiation experienced the rapid rejection of tumor-specific allogeneic lymphocytes with no impact on tumor growth. However, when mice were given more intense total body irradiation conditioning regimens combined with autologous bone marrow transplantation, adoptively transferred allogeneic tumor-specific T lymphocytes persisted at detectable levels for several weeks and mediated significant regression of large, vascularized tumors. We found that the risk of GVHD was low when tumor-specific T cells were transferred and significant toxicity was observed only when substantial numbers of open repertoire allogeneic naive T cells were mixed with the tumor-specific lymphocytes. Taken together, these data indicate that the use of tumor-specific allogeneic CD8(+) T cells or CD4(+) can result in significant antitumor effects in the absence of measurable GVHD.

Natural history of metastatic renal cell carcinoma in patients who underwent consultation for allogeneic hematopoietic stem cell transplantation

We characterized the natural history of metastatic renal cell carcinoma (RCC) and identified prognostic factors among patients who did or did not undergo allogeneic hematopoietic stem cell transplantation (HSCT). A total of 99 patients (23 who underwent HSCT and 76 who did not) were included in the study. Overall survival rates were comparable between the HSCT and no-HSCT groups (excluding patients with poor performance status or brain metastasis from the latter group) at a median 17.4 months of follow-up (P=.92). In univariate analyses, Fuhrman's nuclear grade 4 (P=.05), high serum calcium (P=.002), or low hemoglobin levels (P=.02), 3 or more metastatic sites (P=.02), and <12 months from diagnosis to initial recurrence (P=.04) were identified as poor prognostic factors. In multivariate analyses, 3 or more metastatic sites (P=.005) and low hemoglobin levels (P=.02) were poor prognostic factors. In the HSCT group, median survival times from consultation and from transplant were 25 and 19 months for those with 0 prognostic factors (n=7) and 11 and 7 months for those with 1 or more prognostic factors (n=16). In conclusion, previous concerns that HSCT would negatively affect long-term outcome of patients with metastatic RCC were not confirmed. Patients with any of these poor prognostic factors should not consider HSCT for metastatic RCC. The role of allogeneic HSCT for patients with no prognostic factors should be explored in clinical trials for patients with targeted therapy-resistant metastatic RCC.

IFN-gamma and Fas ligand are required for graft-versus-tumor activity against renal cell carcinoma in the absence of lethal graft-versus-host disease

To determine the mechanisms of graft-versus-tumor (GVT) activity in the absence of graft-versus-host disease (GVHD) against a solid tumor, we established two allogeneic bone marrow transplantation models with a murine renal cell carcinoma (RENCA). The addition of 0.3 x 10(6) donor CD8(+) T cells to the allograft increased the survival of tumor-bearing mice without causing GVHD. The analysis of CD8(+) T cells deficient in cytotoxic molecules demonstrated that anti-RENCA activity is dependent on IFN-gamma and Fas ligand (FasL), but does not require soluble or membrane-bound TNF-alpha, perforin, or TRAIL. Recipients of IFN-gamma(-/-) CD8(+) T cells are unable to reject RENCA compared with recipients of wild-type CD8(+) T cells and, importantly, neither group develops severe GVHD. IFN-gamma(-/-) CD8(+) T cells derived from transplanted mice are less able to kill RENCA cells in vitro, while pretreatment of RENCA cells with IFN-gamma enhances class I and FasL expression and rescues the lytic capacity of IFN-gamma(-/-) CD8(+) T cells. These results demonstrate that the addition of low numbers of selected donor CD8(+) T cells to the allograft can mediate GVT activity without lethal GVHD against murine renal cell carcinoma, and this GVT activity is dependent on IFN-gamma and FasL.

Reduced intensity conditioning for allogeneic hematopoietic cell transplantation: current perspectives

Allogeneic HCT after myeloablative conditioning is an effective therapy for patients with hematologic malignancies. In an attempt to extend this therapy to older patients or those with comorbidities, reduced intensity or truly nonmyeloablative regimens have been developed over the past decade. The principle underlying reduced intensity regimens is to provide some tumor kill with lessened regimen-related morbidity and mortality and then rely on graft-versus-tumor (GVT) effects to eradicate remaining malignant cells, whereas nonmyeloablative regimens rely primarily on GVT effects. In this article, 3 representative approaches are described, demonstrating the clinical application for hematopoietic and nonhematopoietic malignancies. Current challenges include controlling GVHD while allowing GVT to occur. In the future, clinical trials using reduced intensity and nonmyeloablative conditioning will be compared with myeloablative conditioning in selected malignancies to extend the application to standard-risk patients.

Rapid immune reconstitution after a reduced-intensity conditioning regimen and a CD3-depleted haploidentical stem cell graft for paediatric refractory haematological malignancies

The main obstacles to successful haploidentical haematopoietic stem cell transplantation from a mismatched family member donor are delayed immune reconstitution, vulnerability to infections and severe graft-versus-host disease (GvHD). We designed a reduced-intensity conditioning regimen that excluded total body irradiation and anti-thymocyte globulin in order to expedite immune reconstitution after a CD3-depleted haploidentical stem cell transplant. This protocol was used to treat 22 paediatric patients with refractory haematological malignancies. After transplantation, 91% of the patients achieved full donor chimaerism. They also showed rapid recovery of CD3(+) T-cells, T-cell receptor (TCR) excision circle counts, TCRbeta repertoire diversity and natural killer (NK)-cells during the first 4 months post-transplantation, compared with those results from a group of patients treated with a myeloablative conditioning regimen. The incidence and extent of viremia were limited and no lethal infection was seen. Only 9% of patients had grade 3 acute GvHD, while 27% patients had grade 1 and another 27% had grade 2 acute GvHD. This well-tolerated regimen appears to accelerate immune recovery and shorten the duration of early post-transplant immunodeficiency, thereby reducing susceptibility to viral infections. Rapid T-cell reconstitution, retention of NK-cells in the graft and induction of low grade GvHD may also enhance the potential anti-cancer immune effect.

Inflammatory cytokines predominate in cases of tumor regression after hematopoietic stem cell transplantation for solid cancer

Allogeneic hematopoietic stem cell transplantation (SCT) has recently been presented as promising immunotherapy against renal cell, colon, ovarian, breast, and primary liver cancer. Because clinical results demonstrate a variable effect on metastases, we studied whether there is an association between the clinical response and free cytokines in serum. Two patients with metastatic colorectal and 4 with renal cell cancer underwent allogeneic SCT. Conditioning included fludarabine (30 mg/m2) for 3 or 5 days, using sibling or matched unrelated donors, respectively, followed by 2 Gy total body irradiation (n=5) or cyclophosphamide (60 mg/kg) for 2 days (n=1). Antithymoglobuline (4 mg/kg) was given to patients with matched unrelated donors (n=3). Immunosuppression was cyclosporin A, combined with mycophenolate mofetil (n=5) or methotrexate (n=1). The tumor load was examined by computer tomography of the thorax and abdomen before and 3, 6, 9, and 12 months after SCT. Free cytokines in serum were analyzed using enzyme-linked immunosorbent assay. In each patient, the ratio between inflammatory (I) and anti-I cytokines was calculated. No statistical significance was found between the cytokine ratio in correlation to the tumor load according to international response evaluation criteria in solid tumors criteria. In contrast, tumor regression was found to correlate with dominating I cytokine levels in 5/7 occasions, compared with 1/12 of cases with anti-I cytokines using our local method focusing on metastases in lungs, lymph nodes, and liver (P=.01). Thus, an increased level of I cytokines possibly mirrors tumor killing induced by type 1 T-cell response. Furthermore, anti-I cytokines might inhibit cytotoxic cells from exerting the antitumor effect of allogeneic SCT.

Adoptive T‐cell transfer in cancer immunotherapy

Adoptive T-cell therapy has definite clinical benefit in relapsed leukaemia after allogeneic transplant and in Epstein-Barr virus-associated post-transplant lymphoproliferative disease. However, the majority of tumour targets are weakly immunogenic self-antigens and success has been limited in part by inadequate persistence and expansion of transferred T cells and by tumour-evasion strategies. Adoptive immunotherapy presents the opportunity to activate, expand and genetically modify T cells outside the tolerising environment of the host and a number of strategies to optimize the cellular product, including gene modification and modulation of the host environment, in particular by lymphodepletion, have been developed.